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/*
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* Kernel Probes (KProbes)
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* arch/x86_64/kernel/kprobes.c
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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*
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* Copyright (C) IBM Corporation, 2002, 2004
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*
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* 2002-Oct Created by Vamsi Krishna S <vamsi_krishna@in.ibm.com> Kernel
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* Probes initial implementation ( includes contributions from
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* Rusty Russell).
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* 2004-July Suparna Bhattacharya <suparna@in.ibm.com> added jumper probes
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* interface to access function arguments.
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* 2004-Oct Jim Keniston <kenistoj@us.ibm.com> and Prasanna S Panchamukhi
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* <prasanna@in.ibm.com> adapted for x86_64
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* 2005-Mar Roland McGrath <roland@redhat.com>
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* Fixed to handle %rip-relative addressing mode correctly.
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[PATCH] x86_64 specific function return probes
The following patch adds the x86_64 architecture specific implementation
for function return probes.
Function return probes is a mechanism built on top of kprobes that allows
a caller to register a handler to be called when a given function exits.
For example, to instrument the return path of sys_mkdir:
static int sys_mkdir_exit(struct kretprobe_instance *i, struct pt_regs *regs)
{
printk("sys_mkdir exited\n");
return 0;
}
static struct kretprobe return_probe = {
.handler = sys_mkdir_exit,
};
<inside setup function>
return_probe.kp.addr = (kprobe_opcode_t *) kallsyms_lookup_name("sys_mkdir");
if (register_kretprobe(&return_probe)) {
printk(KERN_DEBUG "Unable to register return probe!\n");
/* do error path */
}
<inside cleanup function>
unregister_kretprobe(&return_probe);
The way this works is that:
* At system initialization time, kernel/kprobes.c installs a kprobe
on a function called kretprobe_trampoline() that is implemented in
the arch/x86_64/kernel/kprobes.c (More on this later)
* When a return probe is registered using register_kretprobe(),
kernel/kprobes.c will install a kprobe on the first instruction of the
targeted function with the pre handler set to arch_prepare_kretprobe()
which is implemented in arch/x86_64/kernel/kprobes.c.
* arch_prepare_kretprobe() will prepare a kretprobe instance that stores:
- nodes for hanging this instance in an empty or free list
- a pointer to the return probe
- the original return address
- a pointer to the stack address
With all this stowed away, arch_prepare_kretprobe() then sets the return
address for the targeted function to a special trampoline function called
kretprobe_trampoline() implemented in arch/x86_64/kernel/kprobes.c
* The kprobe completes as normal, with control passing back to the target
function that executes as normal, and eventually returns to our trampoline
function.
* Since a kprobe was installed on kretprobe_trampoline() during system
initialization, control passes back to kprobes via the architecture
specific function trampoline_probe_handler() which will lookup the
instance in an hlist maintained by kernel/kprobes.c, and then call
the handler function.
* When trampoline_probe_handler() is done, the kprobes infrastructure
single steps the original instruction (in this case just a top), and
then calls trampoline_post_handler(). trampoline_post_handler() then
looks up the instance again, puts the instance back on the free list,
and then makes a long jump back to the original return instruction.
So to recap, to instrument the exit path of a function this implementation
will cause four interruptions:
- A breakpoint at the very beginning of the function allowing us to
switch out the return address
- A single step interruption to execute the original instruction that
we replaced with the break instruction (normal kprobe flow)
- A breakpoint in the trampoline function where our instrumented function
returned to
- A single step interruption to execute the original instruction that
we replaced with the break instruction (normal kprobe flow)
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
20 years ago
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* 2005-May Rusty Lynch <rusty.lynch@intel.com>
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* Added function return probes functionality
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*/
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#include <linux/config.h>
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#include <linux/kprobes.h>
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#include <linux/ptrace.h>
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#include <linux/string.h>
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#include <linux/slab.h>
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#include <linux/preempt.h>
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#include <asm/cacheflush.h>
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#include <asm/pgtable.h>
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#include <asm/kdebug.h>
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void jprobe_return_end(void);
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static void __kprobes arch_copy_kprobe(struct kprobe *p);
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DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
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DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
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/*
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* returns non-zero if opcode modifies the interrupt flag.
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*/
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static inline int is_IF_modifier(kprobe_opcode_t *insn)
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{
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switch (*insn) {
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case 0xfa: /* cli */
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case 0xfb: /* sti */
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case 0xcf: /* iret/iretd */
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case 0x9d: /* popf/popfd */
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return 1;
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}
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if (*insn >= 0x40 && *insn <= 0x4f && *++insn == 0xcf)
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return 1;
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return 0;
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}
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int __kprobes arch_prepare_kprobe(struct kprobe *p)
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{
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/* insn: must be on special executable page on x86_64. */
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p->ainsn.insn = get_insn_slot();
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if (!p->ainsn.insn) {
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return -ENOMEM;
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}
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arch_copy_kprobe(p);
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return 0;
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}
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/*
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* Determine if the instruction uses the %rip-relative addressing mode.
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* If it does, return the address of the 32-bit displacement word.
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* If not, return null.
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*/
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static inline s32 *is_riprel(u8 *insn)
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{
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#define W(row,b0,b1,b2,b3,b4,b5,b6,b7,b8,b9,ba,bb,bc,bd,be,bf) \
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(((b0##UL << 0x0)|(b1##UL << 0x1)|(b2##UL << 0x2)|(b3##UL << 0x3) | \
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(b4##UL << 0x4)|(b5##UL << 0x5)|(b6##UL << 0x6)|(b7##UL << 0x7) | \
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(b8##UL << 0x8)|(b9##UL << 0x9)|(ba##UL << 0xa)|(bb##UL << 0xb) | \
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(bc##UL << 0xc)|(bd##UL << 0xd)|(be##UL << 0xe)|(bf##UL << 0xf)) \
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<< (row % 64))
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static const u64 onebyte_has_modrm[256 / 64] = {
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/* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
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/* ------------------------------- */
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W(0x00, 1,1,1,1,0,0,0,0,1,1,1,1,0,0,0,0)| /* 00 */
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W(0x10, 1,1,1,1,0,0,0,0,1,1,1,1,0,0,0,0)| /* 10 */
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W(0x20, 1,1,1,1,0,0,0,0,1,1,1,1,0,0,0,0)| /* 20 */
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W(0x30, 1,1,1,1,0,0,0,0,1,1,1,1,0,0,0,0), /* 30 */
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W(0x40, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* 40 */
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W(0x50, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* 50 */
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W(0x60, 0,0,1,1,0,0,0,0,0,1,0,1,0,0,0,0)| /* 60 */
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W(0x70, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0), /* 70 */
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W(0x80, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 80 */
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W(0x90, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* 90 */
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W(0xa0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* a0 */
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W(0xb0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0), /* b0 */
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W(0xc0, 1,1,0,0,1,1,1,1,0,0,0,0,0,0,0,0)| /* c0 */
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W(0xd0, 1,1,1,1,0,0,0,0,1,1,1,1,1,1,1,1)| /* d0 */
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W(0xe0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* e0 */
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W(0xf0, 0,0,0,0,0,0,1,1,0,0,0,0,0,0,1,1) /* f0 */
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/* ------------------------------- */
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/* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
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};
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static const u64 twobyte_has_modrm[256 / 64] = {
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/* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
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/* ------------------------------- */
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W(0x00, 1,1,1,1,0,0,0,0,0,0,0,0,0,1,0,1)| /* 0f */
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W(0x10, 1,1,1,1,1,1,1,1,1,0,0,0,0,0,0,0)| /* 1f */
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W(0x20, 1,1,1,1,1,0,1,0,1,1,1,1,1,1,1,1)| /* 2f */
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W(0x30, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0), /* 3f */
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W(0x40, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 4f */
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W(0x50, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 5f */
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W(0x60, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 6f */
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W(0x70, 1,1,1,1,1,1,1,0,0,0,0,0,1,1,1,1), /* 7f */
|
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W(0x80, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* 8f */
|
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W(0x90, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 9f */
|
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W(0xa0, 0,0,0,1,1,1,1,1,0,0,0,1,1,1,1,1)| /* af */
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W(0xb0, 1,1,1,1,1,1,1,1,0,0,1,1,1,1,1,1), /* bf */
|
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W(0xc0, 1,1,1,1,1,1,1,1,0,0,0,0,0,0,0,0)| /* cf */
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W(0xd0, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* df */
|
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W(0xe0, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* ef */
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W(0xf0, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,0) /* ff */
|
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|
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/* ------------------------------- */
|
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|
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/* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
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};
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#undef W
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|
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int need_modrm;
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|
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/* Skip legacy instruction prefixes. */
|
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while (1) {
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switch (*insn) {
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|
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case 0x66:
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case 0x67:
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|
case 0x2e:
|
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case 0x3e:
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case 0x26:
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case 0x64:
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case 0x65:
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case 0x36:
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case 0xf0:
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case 0xf3:
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case 0xf2:
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++insn;
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continue;
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}
|
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|
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break;
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}
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|
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/* Skip REX instruction prefix. */
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if ((*insn & 0xf0) == 0x40)
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++insn;
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if (*insn == 0x0f) { /* Two-byte opcode. */
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++insn;
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need_modrm = test_bit(*insn, twobyte_has_modrm);
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} else { /* One-byte opcode. */
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|
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need_modrm = test_bit(*insn, onebyte_has_modrm);
|
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|
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}
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|
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if (need_modrm) {
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|
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u8 modrm = *++insn;
|
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|
|
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if ((modrm & 0xc7) == 0x05) { /* %rip+disp32 addressing mode */
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|
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/* Displacement follows ModRM byte. */
|
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|
|
return (s32 *) ++insn;
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|
|
}
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|
|
}
|
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|
|
|
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|
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|
|
/* No %rip-relative addressing mode here. */
|
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|
|
return NULL;
|
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|
|
}
|
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|
|
static void __kprobes arch_copy_kprobe(struct kprobe *p)
|
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|
|
{
|
|
|
|
|
s32 *ripdisp;
|
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|
|
|
memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE);
|
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|
|
ripdisp = is_riprel(p->ainsn.insn);
|
|
|
|
|
if (ripdisp) {
|
|
|
|
|
/*
|
|
|
|
|
* The copied instruction uses the %rip-relative
|
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|
|
|
* addressing mode. Adjust the displacement for the
|
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|
|
|
* difference between the original location of this
|
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|
|
|
* instruction and the location of the copy that will
|
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|
|
|
* actually be run. The tricky bit here is making sure
|
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|
|
* that the sign extension happens correctly in this
|
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|
|
|
* calculation, since we need a signed 32-bit result to
|
|
|
|
|
* be sign-extended to 64 bits when it's added to the
|
|
|
|
|
* %rip value and yield the same 64-bit result that the
|
|
|
|
|
* sign-extension of the original signed 32-bit
|
|
|
|
|
* displacement would have given.
|
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|
|
|
*/
|
|
|
|
|
s64 disp = (u8 *) p->addr + *ripdisp - (u8 *) p->ainsn.insn;
|
|
|
|
|
BUG_ON((s64) (s32) disp != disp); /* Sanity check. */
|
|
|
|
|
*ripdisp = disp;
|
|
|
|
|
}
|
|
|
|
|
p->opcode = *p->addr;
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
void __kprobes arch_arm_kprobe(struct kprobe *p)
|
|
|
|
|
{
|
|
|
|
|
*p->addr = BREAKPOINT_INSTRUCTION;
|
|
|
|
|
flush_icache_range((unsigned long) p->addr,
|
|
|
|
|
(unsigned long) p->addr + sizeof(kprobe_opcode_t));
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
void __kprobes arch_disarm_kprobe(struct kprobe *p)
|
|
|
|
|
{
|
|
|
|
|
*p->addr = p->opcode;
|
|
|
|
|
flush_icache_range((unsigned long) p->addr,
|
|
|
|
|
(unsigned long) p->addr + sizeof(kprobe_opcode_t));
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
void __kprobes arch_remove_kprobe(struct kprobe *p)
|
|
|
|
|
{
|
|
|
|
|
mutex_lock(&kprobe_mutex);
|
|
|
|
|
free_insn_slot(p->ainsn.insn);
|
|
|
|
|
mutex_unlock(&kprobe_mutex);
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
static inline void save_previous_kprobe(struct kprobe_ctlblk *kcb)
|
|
|
|
|
{
|
|
|
|
|
kcb->prev_kprobe.kp = kprobe_running();
|
|
|
|
|
kcb->prev_kprobe.status = kcb->kprobe_status;
|
|
|
|
|
kcb->prev_kprobe.old_rflags = kcb->kprobe_old_rflags;
|
|
|
|
|
kcb->prev_kprobe.saved_rflags = kcb->kprobe_saved_rflags;
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
static inline void restore_previous_kprobe(struct kprobe_ctlblk *kcb)
|
|
|
|
|
{
|
|
|
|
|
__get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp;
|
|
|
|
|
kcb->kprobe_status = kcb->prev_kprobe.status;
|
|
|
|
|
kcb->kprobe_old_rflags = kcb->prev_kprobe.old_rflags;
|
|
|
|
|
kcb->kprobe_saved_rflags = kcb->prev_kprobe.saved_rflags;
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
static inline void set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
|
|
|
|
|
struct kprobe_ctlblk *kcb)
|
|
|
|
|
{
|
|
|
|
|
__get_cpu_var(current_kprobe) = p;
|
|
|
|
|
kcb->kprobe_saved_rflags = kcb->kprobe_old_rflags
|
|
|
|
|
= (regs->eflags & (TF_MASK | IF_MASK));
|
|
|
|
|
if (is_IF_modifier(p->ainsn.insn))
|
|
|
|
|
kcb->kprobe_saved_rflags &= ~IF_MASK;
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
|
|
|
|
|
{
|
|
|
|
|
regs->eflags |= TF_MASK;
|
|
|
|
|
regs->eflags &= ~IF_MASK;
|
|
|
|
|
/*single step inline if the instruction is an int3*/
|
|
|
|
|
if (p->opcode == BREAKPOINT_INSTRUCTION)
|
|
|
|
|
regs->rip = (unsigned long)p->addr;
|
|
|
|
|
else
|
|
|
|
|
regs->rip = (unsigned long)p->ainsn.insn;
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
/* Called with kretprobe_lock held */
|
|
|
|
|
void __kprobes arch_prepare_kretprobe(struct kretprobe *rp,
|
|
|
|
|
struct pt_regs *regs)
|
[PATCH] x86_64 specific function return probes
The following patch adds the x86_64 architecture specific implementation
for function return probes.
Function return probes is a mechanism built on top of kprobes that allows
a caller to register a handler to be called when a given function exits.
For example, to instrument the return path of sys_mkdir:
static int sys_mkdir_exit(struct kretprobe_instance *i, struct pt_regs *regs)
{
printk("sys_mkdir exited\n");
return 0;
}
static struct kretprobe return_probe = {
.handler = sys_mkdir_exit,
};
<inside setup function>
return_probe.kp.addr = (kprobe_opcode_t *) kallsyms_lookup_name("sys_mkdir");
if (register_kretprobe(&return_probe)) {
printk(KERN_DEBUG "Unable to register return probe!\n");
/* do error path */
}
<inside cleanup function>
unregister_kretprobe(&return_probe);
The way this works is that:
* At system initialization time, kernel/kprobes.c installs a kprobe
on a function called kretprobe_trampoline() that is implemented in
the arch/x86_64/kernel/kprobes.c (More on this later)
* When a return probe is registered using register_kretprobe(),
kernel/kprobes.c will install a kprobe on the first instruction of the
targeted function with the pre handler set to arch_prepare_kretprobe()
which is implemented in arch/x86_64/kernel/kprobes.c.
* arch_prepare_kretprobe() will prepare a kretprobe instance that stores:
- nodes for hanging this instance in an empty or free list
- a pointer to the return probe
- the original return address
- a pointer to the stack address
With all this stowed away, arch_prepare_kretprobe() then sets the return
address for the targeted function to a special trampoline function called
kretprobe_trampoline() implemented in arch/x86_64/kernel/kprobes.c
* The kprobe completes as normal, with control passing back to the target
function that executes as normal, and eventually returns to our trampoline
function.
* Since a kprobe was installed on kretprobe_trampoline() during system
initialization, control passes back to kprobes via the architecture
specific function trampoline_probe_handler() which will lookup the
instance in an hlist maintained by kernel/kprobes.c, and then call
the handler function.
* When trampoline_probe_handler() is done, the kprobes infrastructure
single steps the original instruction (in this case just a top), and
then calls trampoline_post_handler(). trampoline_post_handler() then
looks up the instance again, puts the instance back on the free list,
and then makes a long jump back to the original return instruction.
So to recap, to instrument the exit path of a function this implementation
will cause four interruptions:
- A breakpoint at the very beginning of the function allowing us to
switch out the return address
- A single step interruption to execute the original instruction that
we replaced with the break instruction (normal kprobe flow)
- A breakpoint in the trampoline function where our instrumented function
returned to
- A single step interruption to execute the original instruction that
we replaced with the break instruction (normal kprobe flow)
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
20 years ago
|
|
|
{
|
|
|
|
|
unsigned long *sara = (unsigned long *)regs->rsp;
|
|
|
|
|
struct kretprobe_instance *ri;
|
|
|
|
|
|
|
|
|
|
if ((ri = get_free_rp_inst(rp)) != NULL) {
|
|
|
|
|
ri->rp = rp;
|
|
|
|
|
ri->task = current;
|
|
|
|
|
ri->ret_addr = (kprobe_opcode_t *) *sara;
|
[PATCH] x86_64 specific function return probes
The following patch adds the x86_64 architecture specific implementation
for function return probes.
Function return probes is a mechanism built on top of kprobes that allows
a caller to register a handler to be called when a given function exits.
For example, to instrument the return path of sys_mkdir:
static int sys_mkdir_exit(struct kretprobe_instance *i, struct pt_regs *regs)
{
printk("sys_mkdir exited\n");
return 0;
}
static struct kretprobe return_probe = {
.handler = sys_mkdir_exit,
};
<inside setup function>
return_probe.kp.addr = (kprobe_opcode_t *) kallsyms_lookup_name("sys_mkdir");
if (register_kretprobe(&return_probe)) {
printk(KERN_DEBUG "Unable to register return probe!\n");
/* do error path */
}
<inside cleanup function>
unregister_kretprobe(&return_probe);
The way this works is that:
* At system initialization time, kernel/kprobes.c installs a kprobe
on a function called kretprobe_trampoline() that is implemented in
the arch/x86_64/kernel/kprobes.c (More on this later)
* When a return probe is registered using register_kretprobe(),
kernel/kprobes.c will install a kprobe on the first instruction of the
targeted function with the pre handler set to arch_prepare_kretprobe()
which is implemented in arch/x86_64/kernel/kprobes.c.
* arch_prepare_kretprobe() will prepare a kretprobe instance that stores:
- nodes for hanging this instance in an empty or free list
- a pointer to the return probe
- the original return address
- a pointer to the stack address
With all this stowed away, arch_prepare_kretprobe() then sets the return
address for the targeted function to a special trampoline function called
kretprobe_trampoline() implemented in arch/x86_64/kernel/kprobes.c
* The kprobe completes as normal, with control passing back to the target
function that executes as normal, and eventually returns to our trampoline
function.
* Since a kprobe was installed on kretprobe_trampoline() during system
initialization, control passes back to kprobes via the architecture
specific function trampoline_probe_handler() which will lookup the
instance in an hlist maintained by kernel/kprobes.c, and then call
the handler function.
* When trampoline_probe_handler() is done, the kprobes infrastructure
single steps the original instruction (in this case just a top), and
then calls trampoline_post_handler(). trampoline_post_handler() then
looks up the instance again, puts the instance back on the free list,
and then makes a long jump back to the original return instruction.
So to recap, to instrument the exit path of a function this implementation
will cause four interruptions:
- A breakpoint at the very beginning of the function allowing us to
switch out the return address
- A single step interruption to execute the original instruction that
we replaced with the break instruction (normal kprobe flow)
- A breakpoint in the trampoline function where our instrumented function
returned to
- A single step interruption to execute the original instruction that
we replaced with the break instruction (normal kprobe flow)
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
20 years ago
|
|
|
|
|
|
|
|
/* Replace the return addr with trampoline addr */
|
|
|
|
|
*sara = (unsigned long) &kretprobe_trampoline;
|
|
|
|
|
|
|
|
|
|
add_rp_inst(ri);
|
|
|
|
|
} else {
|
|
|
|
|
rp->nmissed++;
|
|
|
|
|
}
|
[PATCH] x86_64 specific function return probes
The following patch adds the x86_64 architecture specific implementation
for function return probes.
Function return probes is a mechanism built on top of kprobes that allows
a caller to register a handler to be called when a given function exits.
For example, to instrument the return path of sys_mkdir:
static int sys_mkdir_exit(struct kretprobe_instance *i, struct pt_regs *regs)
{
printk("sys_mkdir exited\n");
return 0;
}
static struct kretprobe return_probe = {
.handler = sys_mkdir_exit,
};
<inside setup function>
return_probe.kp.addr = (kprobe_opcode_t *) kallsyms_lookup_name("sys_mkdir");
if (register_kretprobe(&return_probe)) {
printk(KERN_DEBUG "Unable to register return probe!\n");
/* do error path */
}
<inside cleanup function>
unregister_kretprobe(&return_probe);
The way this works is that:
* At system initialization time, kernel/kprobes.c installs a kprobe
on a function called kretprobe_trampoline() that is implemented in
the arch/x86_64/kernel/kprobes.c (More on this later)
* When a return probe is registered using register_kretprobe(),
kernel/kprobes.c will install a kprobe on the first instruction of the
targeted function with the pre handler set to arch_prepare_kretprobe()
which is implemented in arch/x86_64/kernel/kprobes.c.
* arch_prepare_kretprobe() will prepare a kretprobe instance that stores:
- nodes for hanging this instance in an empty or free list
- a pointer to the return probe
- the original return address
- a pointer to the stack address
With all this stowed away, arch_prepare_kretprobe() then sets the return
address for the targeted function to a special trampoline function called
kretprobe_trampoline() implemented in arch/x86_64/kernel/kprobes.c
* The kprobe completes as normal, with control passing back to the target
function that executes as normal, and eventually returns to our trampoline
function.
* Since a kprobe was installed on kretprobe_trampoline() during system
initialization, control passes back to kprobes via the architecture
specific function trampoline_probe_handler() which will lookup the
instance in an hlist maintained by kernel/kprobes.c, and then call
the handler function.
* When trampoline_probe_handler() is done, the kprobes infrastructure
single steps the original instruction (in this case just a top), and
then calls trampoline_post_handler(). trampoline_post_handler() then
looks up the instance again, puts the instance back on the free list,
and then makes a long jump back to the original return instruction.
So to recap, to instrument the exit path of a function this implementation
will cause four interruptions:
- A breakpoint at the very beginning of the function allowing us to
switch out the return address
- A single step interruption to execute the original instruction that
we replaced with the break instruction (normal kprobe flow)
- A breakpoint in the trampoline function where our instrumented function
returned to
- A single step interruption to execute the original instruction that
we replaced with the break instruction (normal kprobe flow)
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
20 years ago
|
|
|
}
|
|
|
|
|
|
|
|
|
|
int __kprobes kprobe_handler(struct pt_regs *regs)
|
|
|
|
|
{
|
|
|
|
|
struct kprobe *p;
|
|
|
|
|
int ret = 0;
|
|
|
|
|
kprobe_opcode_t *addr = (kprobe_opcode_t *)(regs->rip - sizeof(kprobe_opcode_t));
|
|
|
|
|
struct kprobe_ctlblk *kcb;
|
|
|
|
|
|
|
|
|
|
/*
|
|
|
|
|
* We don't want to be preempted for the entire
|
|
|
|
|
* duration of kprobe processing
|
|
|
|
|
*/
|
|
|
|
|
preempt_disable();
|
|
|
|
|
kcb = get_kprobe_ctlblk();
|
|
|
|
|
|
|
|
|
|
/* Check we're not actually recursing */
|
|
|
|
|
if (kprobe_running()) {
|
|
|
|
|
p = get_kprobe(addr);
|
|
|
|
|
if (p) {
|
|
|
|
|
if (kcb->kprobe_status == KPROBE_HIT_SS &&
|
|
|
|
|
*p->ainsn.insn == BREAKPOINT_INSTRUCTION) {
|
|
|
|
|
regs->eflags &= ~TF_MASK;
|
|
|
|
|
regs->eflags |= kcb->kprobe_saved_rflags;
|
|
|
|
|
goto no_kprobe;
|
|
|
|
|
} else if (kcb->kprobe_status == KPROBE_HIT_SSDONE) {
|
|
|
|
|
/* TODO: Provide re-entrancy from
|
|
|
|
|
* post_kprobes_handler() and avoid exception
|
|
|
|
|
* stack corruption while single-stepping on
|
|
|
|
|
* the instruction of the new probe.
|
|
|
|
|
*/
|
|
|
|
|
arch_disarm_kprobe(p);
|
|
|
|
|
regs->rip = (unsigned long)p->addr;
|
|
|
|
|
reset_current_kprobe();
|
|
|
|
|
ret = 1;
|
|
|
|
|
} else {
|
|
|
|
|
/* We have reentered the kprobe_handler(), since
|
|
|
|
|
* another probe was hit while within the
|
|
|
|
|
* handler. We here save the original kprobe
|
|
|
|
|
* variables and just single step on instruction
|
|
|
|
|
* of the new probe without calling any user
|
|
|
|
|
* handlers.
|
|
|
|
|
*/
|
|
|
|
|
save_previous_kprobe(kcb);
|
|
|
|
|
set_current_kprobe(p, regs, kcb);
|
|
|
|
|
kprobes_inc_nmissed_count(p);
|
|
|
|
|
prepare_singlestep(p, regs);
|
|
|
|
|
kcb->kprobe_status = KPROBE_REENTER;
|
|
|
|
|
return 1;
|
|
|
|
|
}
|
|
|
|
|
} else {
|
|
|
|
|
if (*addr != BREAKPOINT_INSTRUCTION) {
|
|
|
|
|
/* The breakpoint instruction was removed by
|
|
|
|
|
* another cpu right after we hit, no further
|
|
|
|
|
* handling of this interrupt is appropriate
|
|
|
|
|
*/
|
|
|
|
|
regs->rip = (unsigned long)addr;
|
|
|
|
|
ret = 1;
|
|
|
|
|
goto no_kprobe;
|
|
|
|
|
}
|
|
|
|
|
p = __get_cpu_var(current_kprobe);
|
|
|
|
|
if (p->break_handler && p->break_handler(p, regs)) {
|
|
|
|
|
goto ss_probe;
|
|
|
|
|
}
|
|
|
|
|
}
|
|
|
|
|
goto no_kprobe;
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
p = get_kprobe(addr);
|
|
|
|
|
if (!p) {
|
|
|
|
|
if (*addr != BREAKPOINT_INSTRUCTION) {
|
|
|
|
|
/*
|
|
|
|
|
* The breakpoint instruction was removed right
|
|
|
|
|
* after we hit it. Another cpu has removed
|
|
|
|
|
* either a probepoint or a debugger breakpoint
|
|
|
|
|
* at this address. In either case, no further
|
|
|
|
|
* handling of this interrupt is appropriate.
|
|
|
|
|
* Back up over the (now missing) int3 and run
|
|
|
|
|
* the original instruction.
|
|
|
|
|
*/
|
|
|
|
|
regs->rip = (unsigned long)addr;
|
|
|
|
|
ret = 1;
|
|
|
|
|
}
|
|
|
|
|
/* Not one of ours: let kernel handle it */
|
|
|
|
|
goto no_kprobe;
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
set_current_kprobe(p, regs, kcb);
|
|
|
|
|
kcb->kprobe_status = KPROBE_HIT_ACTIVE;
|
|
|
|
|
|
|
|
|
|
if (p->pre_handler && p->pre_handler(p, regs))
|
|
|
|
|
/* handler has already set things up, so skip ss setup */
|
|
|
|
|
return 1;
|
|
|
|
|
|
|
|
|
|
ss_probe:
|
|
|
|
|
prepare_singlestep(p, regs);
|
|
|
|
|
kcb->kprobe_status = KPROBE_HIT_SS;
|
|
|
|
|
return 1;
|
|
|
|
|
|
|
|
|
|
no_kprobe:
|
|
|
|
|
preempt_enable_no_resched();
|
|
|
|
|
return ret;
|
|
|
|
|
}
|
|
|
|
|
|
[PATCH] x86_64 specific function return probes
The following patch adds the x86_64 architecture specific implementation
for function return probes.
Function return probes is a mechanism built on top of kprobes that allows
a caller to register a handler to be called when a given function exits.
For example, to instrument the return path of sys_mkdir:
static int sys_mkdir_exit(struct kretprobe_instance *i, struct pt_regs *regs)
{
printk("sys_mkdir exited\n");
return 0;
}
static struct kretprobe return_probe = {
.handler = sys_mkdir_exit,
};
<inside setup function>
return_probe.kp.addr = (kprobe_opcode_t *) kallsyms_lookup_name("sys_mkdir");
if (register_kretprobe(&return_probe)) {
printk(KERN_DEBUG "Unable to register return probe!\n");
/* do error path */
}
<inside cleanup function>
unregister_kretprobe(&return_probe);
The way this works is that:
* At system initialization time, kernel/kprobes.c installs a kprobe
on a function called kretprobe_trampoline() that is implemented in
the arch/x86_64/kernel/kprobes.c (More on this later)
* When a return probe is registered using register_kretprobe(),
kernel/kprobes.c will install a kprobe on the first instruction of the
targeted function with the pre handler set to arch_prepare_kretprobe()
which is implemented in arch/x86_64/kernel/kprobes.c.
* arch_prepare_kretprobe() will prepare a kretprobe instance that stores:
- nodes for hanging this instance in an empty or free list
- a pointer to the return probe
- the original return address
- a pointer to the stack address
With all this stowed away, arch_prepare_kretprobe() then sets the return
address for the targeted function to a special trampoline function called
kretprobe_trampoline() implemented in arch/x86_64/kernel/kprobes.c
* The kprobe completes as normal, with control passing back to the target
function that executes as normal, and eventually returns to our trampoline
function.
* Since a kprobe was installed on kretprobe_trampoline() during system
initialization, control passes back to kprobes via the architecture
specific function trampoline_probe_handler() which will lookup the
instance in an hlist maintained by kernel/kprobes.c, and then call
the handler function.
* When trampoline_probe_handler() is done, the kprobes infrastructure
single steps the original instruction (in this case just a top), and
then calls trampoline_post_handler(). trampoline_post_handler() then
looks up the instance again, puts the instance back on the free list,
and then makes a long jump back to the original return instruction.
So to recap, to instrument the exit path of a function this implementation
will cause four interruptions:
- A breakpoint at the very beginning of the function allowing us to
switch out the return address
- A single step interruption to execute the original instruction that
we replaced with the break instruction (normal kprobe flow)
- A breakpoint in the trampoline function where our instrumented function
returned to
- A single step interruption to execute the original instruction that
we replaced with the break instruction (normal kprobe flow)
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
20 years ago
|
|
|
/*
|
|
|
|
|
* For function-return probes, init_kprobes() establishes a probepoint
|
|
|
|
|
* here. When a retprobed function returns, this probe is hit and
|
|
|
|
|
* trampoline_probe_handler() runs, calling the kretprobe's handler.
|
|
|
|
|
*/
|
|
|
|
|
void kretprobe_trampoline_holder(void)
|
|
|
|
|
{
|
|
|
|
|
asm volatile ( ".global kretprobe_trampoline\n"
|
|
|
|
|
"kretprobe_trampoline: \n"
|
|
|
|
|
"nop\n");
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
/*
|
|
|
|
|
* Called when we hit the probe point at kretprobe_trampoline
|
|
|
|
|
*/
|
|
|
|
|
int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
|
[PATCH] x86_64 specific function return probes
The following patch adds the x86_64 architecture specific implementation
for function return probes.
Function return probes is a mechanism built on top of kprobes that allows
a caller to register a handler to be called when a given function exits.
For example, to instrument the return path of sys_mkdir:
static int sys_mkdir_exit(struct kretprobe_instance *i, struct pt_regs *regs)
{
printk("sys_mkdir exited\n");
return 0;
}
static struct kretprobe return_probe = {
.handler = sys_mkdir_exit,
};
<inside setup function>
return_probe.kp.addr = (kprobe_opcode_t *) kallsyms_lookup_name("sys_mkdir");
if (register_kretprobe(&return_probe)) {
printk(KERN_DEBUG "Unable to register return probe!\n");
/* do error path */
}
<inside cleanup function>
unregister_kretprobe(&return_probe);
The way this works is that:
* At system initialization time, kernel/kprobes.c installs a kprobe
on a function called kretprobe_trampoline() that is implemented in
the arch/x86_64/kernel/kprobes.c (More on this later)
* When a return probe is registered using register_kretprobe(),
kernel/kprobes.c will install a kprobe on the first instruction of the
targeted function with the pre handler set to arch_prepare_kretprobe()
which is implemented in arch/x86_64/kernel/kprobes.c.
* arch_prepare_kretprobe() will prepare a kretprobe instance that stores:
- nodes for hanging this instance in an empty or free list
- a pointer to the return probe
- the original return address
- a pointer to the stack address
With all this stowed away, arch_prepare_kretprobe() then sets the return
address for the targeted function to a special trampoline function called
kretprobe_trampoline() implemented in arch/x86_64/kernel/kprobes.c
* The kprobe completes as normal, with control passing back to the target
function that executes as normal, and eventually returns to our trampoline
function.
* Since a kprobe was installed on kretprobe_trampoline() during system
initialization, control passes back to kprobes via the architecture
specific function trampoline_probe_handler() which will lookup the
instance in an hlist maintained by kernel/kprobes.c, and then call
the handler function.
* When trampoline_probe_handler() is done, the kprobes infrastructure
single steps the original instruction (in this case just a top), and
then calls trampoline_post_handler(). trampoline_post_handler() then
looks up the instance again, puts the instance back on the free list,
and then makes a long jump back to the original return instruction.
So to recap, to instrument the exit path of a function this implementation
will cause four interruptions:
- A breakpoint at the very beginning of the function allowing us to
switch out the return address
- A single step interruption to execute the original instruction that
we replaced with the break instruction (normal kprobe flow)
- A breakpoint in the trampoline function where our instrumented function
returned to
- A single step interruption to execute the original instruction that
we replaced with the break instruction (normal kprobe flow)
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
20 years ago
|
|
|
{
|
|
|
|
|
struct kretprobe_instance *ri = NULL;
|
|
|
|
|
struct hlist_head *head;
|
|
|
|
|
struct hlist_node *node, *tmp;
|
|
|
|
|
unsigned long flags, orig_ret_address = 0;
|
|
|
|
|
unsigned long trampoline_address =(unsigned long)&kretprobe_trampoline;
|
[PATCH] x86_64 specific function return probes
The following patch adds the x86_64 architecture specific implementation
for function return probes.
Function return probes is a mechanism built on top of kprobes that allows
a caller to register a handler to be called when a given function exits.
For example, to instrument the return path of sys_mkdir:
static int sys_mkdir_exit(struct kretprobe_instance *i, struct pt_regs *regs)
{
printk("sys_mkdir exited\n");
return 0;
}
static struct kretprobe return_probe = {
.handler = sys_mkdir_exit,
};
<inside setup function>
return_probe.kp.addr = (kprobe_opcode_t *) kallsyms_lookup_name("sys_mkdir");
if (register_kretprobe(&return_probe)) {
printk(KERN_DEBUG "Unable to register return probe!\n");
/* do error path */
}
<inside cleanup function>
unregister_kretprobe(&return_probe);
The way this works is that:
* At system initialization time, kernel/kprobes.c installs a kprobe
on a function called kretprobe_trampoline() that is implemented in
the arch/x86_64/kernel/kprobes.c (More on this later)
* When a return probe is registered using register_kretprobe(),
kernel/kprobes.c will install a kprobe on the first instruction of the
targeted function with the pre handler set to arch_prepare_kretprobe()
which is implemented in arch/x86_64/kernel/kprobes.c.
* arch_prepare_kretprobe() will prepare a kretprobe instance that stores:
- nodes for hanging this instance in an empty or free list
- a pointer to the return probe
- the original return address
- a pointer to the stack address
With all this stowed away, arch_prepare_kretprobe() then sets the return
address for the targeted function to a special trampoline function called
kretprobe_trampoline() implemented in arch/x86_64/kernel/kprobes.c
* The kprobe completes as normal, with control passing back to the target
function that executes as normal, and eventually returns to our trampoline
function.
* Since a kprobe was installed on kretprobe_trampoline() during system
initialization, control passes back to kprobes via the architecture
specific function trampoline_probe_handler() which will lookup the
instance in an hlist maintained by kernel/kprobes.c, and then call
the handler function.
* When trampoline_probe_handler() is done, the kprobes infrastructure
single steps the original instruction (in this case just a top), and
then calls trampoline_post_handler(). trampoline_post_handler() then
looks up the instance again, puts the instance back on the free list,
and then makes a long jump back to the original return instruction.
So to recap, to instrument the exit path of a function this implementation
will cause four interruptions:
- A breakpoint at the very beginning of the function allowing us to
switch out the return address
- A single step interruption to execute the original instruction that
we replaced with the break instruction (normal kprobe flow)
- A breakpoint in the trampoline function where our instrumented function
returned to
- A single step interruption to execute the original instruction that
we replaced with the break instruction (normal kprobe flow)
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
20 years ago
|
|
|
|
|
|
|
|
spin_lock_irqsave(&kretprobe_lock, flags);
|
|
|
|
|
head = kretprobe_inst_table_head(current);
|
[PATCH] x86_64 specific function return probes
The following patch adds the x86_64 architecture specific implementation
for function return probes.
Function return probes is a mechanism built on top of kprobes that allows
a caller to register a handler to be called when a given function exits.
For example, to instrument the return path of sys_mkdir:
static int sys_mkdir_exit(struct kretprobe_instance *i, struct pt_regs *regs)
{
printk("sys_mkdir exited\n");
return 0;
}
static struct kretprobe return_probe = {
.handler = sys_mkdir_exit,
};
<inside setup function>
return_probe.kp.addr = (kprobe_opcode_t *) kallsyms_lookup_name("sys_mkdir");
if (register_kretprobe(&return_probe)) {
printk(KERN_DEBUG "Unable to register return probe!\n");
/* do error path */
}
<inside cleanup function>
unregister_kretprobe(&return_probe);
The way this works is that:
* At system initialization time, kernel/kprobes.c installs a kprobe
on a function called kretprobe_trampoline() that is implemented in
the arch/x86_64/kernel/kprobes.c (More on this later)
* When a return probe is registered using register_kretprobe(),
kernel/kprobes.c will install a kprobe on the first instruction of the
targeted function with the pre handler set to arch_prepare_kretprobe()
which is implemented in arch/x86_64/kernel/kprobes.c.
* arch_prepare_kretprobe() will prepare a kretprobe instance that stores:
- nodes for hanging this instance in an empty or free list
- a pointer to the return probe
- the original return address
- a pointer to the stack address
With all this stowed away, arch_prepare_kretprobe() then sets the return
address for the targeted function to a special trampoline function called
kretprobe_trampoline() implemented in arch/x86_64/kernel/kprobes.c
* The kprobe completes as normal, with control passing back to the target
function that executes as normal, and eventually returns to our trampoline
function.
* Since a kprobe was installed on kretprobe_trampoline() during system
initialization, control passes back to kprobes via the architecture
specific function trampoline_probe_handler() which will lookup the
instance in an hlist maintained by kernel/kprobes.c, and then call
the handler function.
* When trampoline_probe_handler() is done, the kprobes infrastructure
single steps the original instruction (in this case just a top), and
then calls trampoline_post_handler(). trampoline_post_handler() then
looks up the instance again, puts the instance back on the free list,
and then makes a long jump back to the original return instruction.
So to recap, to instrument the exit path of a function this implementation
will cause four interruptions:
- A breakpoint at the very beginning of the function allowing us to
switch out the return address
- A single step interruption to execute the original instruction that
we replaced with the break instruction (normal kprobe flow)
- A breakpoint in the trampoline function where our instrumented function
returned to
- A single step interruption to execute the original instruction that
we replaced with the break instruction (normal kprobe flow)
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
20 years ago
|
|
|
|
|
|
|
|
/*
|
|
|
|
|
* It is possible to have multiple instances associated with a given
|
|
|
|
|
* task either because an multiple functions in the call path
|
|
|
|
|
* have a return probe installed on them, and/or more then one return
|
|
|
|
|
* return probe was registered for a target function.
|
|
|
|
|
*
|
|
|
|
|
* We can handle this because:
|
|
|
|
|
* - instances are always inserted at the head of the list
|
|
|
|
|
* - when multiple return probes are registered for the same
|
|
|
|
|
* function, the first instance's ret_addr will point to the
|
|
|
|
|
* real return address, and all the rest will point to
|
|
|
|
|
* kretprobe_trampoline
|
|
|
|
|
*/
|
|
|
|
|
hlist_for_each_entry_safe(ri, node, tmp, head, hlist) {
|
|
|
|
|
if (ri->task != current)
|
|
|
|
|
/* another task is sharing our hash bucket */
|
|
|
|
|
continue;
|
|
|
|
|
|
|
|
|
|
if (ri->rp && ri->rp->handler)
|
|
|
|
|
ri->rp->handler(ri, regs);
|
|
|
|
|
|
|
|
|
|
orig_ret_address = (unsigned long)ri->ret_addr;
|
[PATCH] x86_64 specific function return probes
The following patch adds the x86_64 architecture specific implementation
for function return probes.
Function return probes is a mechanism built on top of kprobes that allows
a caller to register a handler to be called when a given function exits.
For example, to instrument the return path of sys_mkdir:
static int sys_mkdir_exit(struct kretprobe_instance *i, struct pt_regs *regs)
{
printk("sys_mkdir exited\n");
return 0;
}
static struct kretprobe return_probe = {
.handler = sys_mkdir_exit,
};
<inside setup function>
return_probe.kp.addr = (kprobe_opcode_t *) kallsyms_lookup_name("sys_mkdir");
if (register_kretprobe(&return_probe)) {
printk(KERN_DEBUG "Unable to register return probe!\n");
/* do error path */
}
<inside cleanup function>
unregister_kretprobe(&return_probe);
The way this works is that:
* At system initialization time, kernel/kprobes.c installs a kprobe
on a function called kretprobe_trampoline() that is implemented in
the arch/x86_64/kernel/kprobes.c (More on this later)
* When a return probe is registered using register_kretprobe(),
kernel/kprobes.c will install a kprobe on the first instruction of the
targeted function with the pre handler set to arch_prepare_kretprobe()
which is implemented in arch/x86_64/kernel/kprobes.c.
* arch_prepare_kretprobe() will prepare a kretprobe instance that stores:
- nodes for hanging this instance in an empty or free list
- a pointer to the return probe
- the original return address
- a pointer to the stack address
With all this stowed away, arch_prepare_kretprobe() then sets the return
address for the targeted function to a special trampoline function called
kretprobe_trampoline() implemented in arch/x86_64/kernel/kprobes.c
* The kprobe completes as normal, with control passing back to the target
function that executes as normal, and eventually returns to our trampoline
function.
* Since a kprobe was installed on kretprobe_trampoline() during system
initialization, control passes back to kprobes via the architecture
specific function trampoline_probe_handler() which will lookup the
instance in an hlist maintained by kernel/kprobes.c, and then call
the handler function.
* When trampoline_probe_handler() is done, the kprobes infrastructure
single steps the original instruction (in this case just a top), and
then calls trampoline_post_handler(). trampoline_post_handler() then
looks up the instance again, puts the instance back on the free list,
and then makes a long jump back to the original return instruction.
So to recap, to instrument the exit path of a function this implementation
will cause four interruptions:
- A breakpoint at the very beginning of the function allowing us to
switch out the return address
- A single step interruption to execute the original instruction that
we replaced with the break instruction (normal kprobe flow)
- A breakpoint in the trampoline function where our instrumented function
returned to
- A single step interruption to execute the original instruction that
we replaced with the break instruction (normal kprobe flow)
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
20 years ago
|
|
|
recycle_rp_inst(ri);
|
|
|
|
|
|
|
|
|
|
if (orig_ret_address != trampoline_address)
|
|
|
|
|
/*
|
|
|
|
|
* This is the real return address. Any other
|
|
|
|
|
* instances associated with this task are for
|
|
|
|
|
* other calls deeper on the call stack
|
|
|
|
|
*/
|
|
|
|
|
break;
|
[PATCH] x86_64 specific function return probes
The following patch adds the x86_64 architecture specific implementation
for function return probes.
Function return probes is a mechanism built on top of kprobes that allows
a caller to register a handler to be called when a given function exits.
For example, to instrument the return path of sys_mkdir:
static int sys_mkdir_exit(struct kretprobe_instance *i, struct pt_regs *regs)
{
printk("sys_mkdir exited\n");
return 0;
}
static struct kretprobe return_probe = {
.handler = sys_mkdir_exit,
};
<inside setup function>
return_probe.kp.addr = (kprobe_opcode_t *) kallsyms_lookup_name("sys_mkdir");
if (register_kretprobe(&return_probe)) {
printk(KERN_DEBUG "Unable to register return probe!\n");
/* do error path */
}
<inside cleanup function>
unregister_kretprobe(&return_probe);
The way this works is that:
* At system initialization time, kernel/kprobes.c installs a kprobe
on a function called kretprobe_trampoline() that is implemented in
the arch/x86_64/kernel/kprobes.c (More on this later)
* When a return probe is registered using register_kretprobe(),
kernel/kprobes.c will install a kprobe on the first instruction of the
targeted function with the pre handler set to arch_prepare_kretprobe()
which is implemented in arch/x86_64/kernel/kprobes.c.
* arch_prepare_kretprobe() will prepare a kretprobe instance that stores:
- nodes for hanging this instance in an empty or free list
- a pointer to the return probe
- the original return address
- a pointer to the stack address
With all this stowed away, arch_prepare_kretprobe() then sets the return
address for the targeted function to a special trampoline function called
kretprobe_trampoline() implemented in arch/x86_64/kernel/kprobes.c
* The kprobe completes as normal, with control passing back to the target
function that executes as normal, and eventually returns to our trampoline
function.
* Since a kprobe was installed on kretprobe_trampoline() during system
initialization, control passes back to kprobes via the architecture
specific function trampoline_probe_handler() which will lookup the
instance in an hlist maintained by kernel/kprobes.c, and then call
the handler function.
* When trampoline_probe_handler() is done, the kprobes infrastructure
single steps the original instruction (in this case just a top), and
then calls trampoline_post_handler(). trampoline_post_handler() then
looks up the instance again, puts the instance back on the free list,
and then makes a long jump back to the original return instruction.
So to recap, to instrument the exit path of a function this implementation
will cause four interruptions:
- A breakpoint at the very beginning of the function allowing us to
switch out the return address
- A single step interruption to execute the original instruction that
we replaced with the break instruction (normal kprobe flow)
- A breakpoint in the trampoline function where our instrumented function
returned to
- A single step interruption to execute the original instruction that
we replaced with the break instruction (normal kprobe flow)
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
20 years ago
|
|
|
}
|
|
|
|
|
|
|
|
|
|
BUG_ON(!orig_ret_address || (orig_ret_address == trampoline_address));
|
|
|
|
|
regs->rip = orig_ret_address;
|
|
|
|
|
|
|
|
|
|
reset_current_kprobe();
|
|
|
|
|
spin_unlock_irqrestore(&kretprobe_lock, flags);
|
|
|
|
|
preempt_enable_no_resched();
|
|
|
|
|
|
|
|
|
|
/*
|
|
|
|
|
* By returning a non-zero value, we are telling
|
|
|
|
|
* kprobe_handler() that we don't want the post_handler
|
|
|
|
|
* to run (and have re-enabled preemption)
|
|
|
|
|
*/
|
|
|
|
|
return 1;
|
[PATCH] x86_64 specific function return probes
The following patch adds the x86_64 architecture specific implementation
for function return probes.
Function return probes is a mechanism built on top of kprobes that allows
a caller to register a handler to be called when a given function exits.
For example, to instrument the return path of sys_mkdir:
static int sys_mkdir_exit(struct kretprobe_instance *i, struct pt_regs *regs)
{
printk("sys_mkdir exited\n");
return 0;
}
static struct kretprobe return_probe = {
.handler = sys_mkdir_exit,
};
<inside setup function>
return_probe.kp.addr = (kprobe_opcode_t *) kallsyms_lookup_name("sys_mkdir");
if (register_kretprobe(&return_probe)) {
printk(KERN_DEBUG "Unable to register return probe!\n");
/* do error path */
}
<inside cleanup function>
unregister_kretprobe(&return_probe);
The way this works is that:
* At system initialization time, kernel/kprobes.c installs a kprobe
on a function called kretprobe_trampoline() that is implemented in
the arch/x86_64/kernel/kprobes.c (More on this later)
* When a return probe is registered using register_kretprobe(),
kernel/kprobes.c will install a kprobe on the first instruction of the
targeted function with the pre handler set to arch_prepare_kretprobe()
which is implemented in arch/x86_64/kernel/kprobes.c.
* arch_prepare_kretprobe() will prepare a kretprobe instance that stores:
- nodes for hanging this instance in an empty or free list
- a pointer to the return probe
- the original return address
- a pointer to the stack address
With all this stowed away, arch_prepare_kretprobe() then sets the return
address for the targeted function to a special trampoline function called
kretprobe_trampoline() implemented in arch/x86_64/kernel/kprobes.c
* The kprobe completes as normal, with control passing back to the target
function that executes as normal, and eventually returns to our trampoline
function.
* Since a kprobe was installed on kretprobe_trampoline() during system
initialization, control passes back to kprobes via the architecture
specific function trampoline_probe_handler() which will lookup the
instance in an hlist maintained by kernel/kprobes.c, and then call
the handler function.
* When trampoline_probe_handler() is done, the kprobes infrastructure
single steps the original instruction (in this case just a top), and
then calls trampoline_post_handler(). trampoline_post_handler() then
looks up the instance again, puts the instance back on the free list,
and then makes a long jump back to the original return instruction.
So to recap, to instrument the exit path of a function this implementation
will cause four interruptions:
- A breakpoint at the very beginning of the function allowing us to
switch out the return address
- A single step interruption to execute the original instruction that
we replaced with the break instruction (normal kprobe flow)
- A breakpoint in the trampoline function where our instrumented function
returned to
- A single step interruption to execute the original instruction that
we replaced with the break instruction (normal kprobe flow)
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
20 years ago
|
|
|
}
|
|
|
|
|
|
|
|
|
|
/*
|
|
|
|
|
* Called after single-stepping. p->addr is the address of the
|
|
|
|
|
* instruction whose first byte has been replaced by the "int 3"
|
|
|
|
|
* instruction. To avoid the SMP problems that can occur when we
|
|
|
|
|
* temporarily put back the original opcode to single-step, we
|
|
|
|
|
* single-stepped a copy of the instruction. The address of this
|
|
|
|
|
* copy is p->ainsn.insn.
|
|
|
|
|
*
|
|
|
|
|
* This function prepares to return from the post-single-step
|
|
|
|
|
* interrupt. We have to fix up the stack as follows:
|
|
|
|
|
*
|
|
|
|
|
* 0) Except in the case of absolute or indirect jump or call instructions,
|
|
|
|
|
* the new rip is relative to the copied instruction. We need to make
|
|
|
|
|
* it relative to the original instruction.
|
|
|
|
|
*
|
|
|
|
|
* 1) If the single-stepped instruction was pushfl, then the TF and IF
|
|
|
|
|
* flags are set in the just-pushed eflags, and may need to be cleared.
|
|
|
|
|
*
|
|
|
|
|
* 2) If the single-stepped instruction was a call, the return address
|
|
|
|
|
* that is atop the stack is the address following the copied instruction.
|
|
|
|
|
* We need to make it the address following the original instruction.
|
|
|
|
|
*/
|
|
|
|
|
static void __kprobes resume_execution(struct kprobe *p,
|
|
|
|
|
struct pt_regs *regs, struct kprobe_ctlblk *kcb)
|
|
|
|
|
{
|
|
|
|
|
unsigned long *tos = (unsigned long *)regs->rsp;
|
|
|
|
|
unsigned long next_rip = 0;
|
|
|
|
|
unsigned long copy_rip = (unsigned long)p->ainsn.insn;
|
|
|
|
|
unsigned long orig_rip = (unsigned long)p->addr;
|
|
|
|
|
kprobe_opcode_t *insn = p->ainsn.insn;
|
|
|
|
|
|
|
|
|
|
/*skip the REX prefix*/
|
|
|
|
|
if (*insn >= 0x40 && *insn <= 0x4f)
|
|
|
|
|
insn++;
|
|
|
|
|
|
|
|
|
|
switch (*insn) {
|
|
|
|
|
case 0x9c: /* pushfl */
|
|
|
|
|
*tos &= ~(TF_MASK | IF_MASK);
|
|
|
|
|
*tos |= kcb->kprobe_old_rflags;
|
|
|
|
|
break;
|
|
|
|
|
case 0xc3: /* ret/lret */
|
|
|
|
|
case 0xcb:
|
|
|
|
|
case 0xc2:
|
|
|
|
|
case 0xca:
|
|
|
|
|
regs->eflags &= ~TF_MASK;
|
|
|
|
|
/* rip is already adjusted, no more changes required*/
|
|
|
|
|
return;
|
|
|
|
|
case 0xe8: /* call relative - Fix return addr */
|
|
|
|
|
*tos = orig_rip + (*tos - copy_rip);
|
|
|
|
|
break;
|
|
|
|
|
case 0xff:
|
|
|
|
|
if ((*insn & 0x30) == 0x10) {
|
|
|
|
|
/* call absolute, indirect */
|
|
|
|
|
/* Fix return addr; rip is correct. */
|
|
|
|
|
next_rip = regs->rip;
|
|
|
|
|
*tos = orig_rip + (*tos - copy_rip);
|
|
|
|
|
} else if (((*insn & 0x31) == 0x20) || /* jmp near, absolute indirect */
|
|
|
|
|
((*insn & 0x31) == 0x21)) { /* jmp far, absolute indirect */
|
|
|
|
|
/* rip is correct. */
|
|
|
|
|
next_rip = regs->rip;
|
|
|
|
|
}
|
|
|
|
|
break;
|
|
|
|
|
case 0xea: /* jmp absolute -- rip is correct */
|
|
|
|
|
next_rip = regs->rip;
|
|
|
|
|
break;
|
|
|
|
|
default:
|
|
|
|
|
break;
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
regs->eflags &= ~TF_MASK;
|
|
|
|
|
if (next_rip) {
|
|
|
|
|
regs->rip = next_rip;
|
|
|
|
|
} else {
|
|
|
|
|
regs->rip = orig_rip + (regs->rip - copy_rip);
|
|
|
|
|
}
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
int __kprobes post_kprobe_handler(struct pt_regs *regs)
|
|
|
|
|
{
|
|
|
|
|
struct kprobe *cur = kprobe_running();
|
|
|
|
|
struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
|
|
|
|
|
|
|
|
|
|
if (!cur)
|
|
|
|
|
return 0;
|
|
|
|
|
|
|
|
|
|
if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
|
|
|
|
|
kcb->kprobe_status = KPROBE_HIT_SSDONE;
|
|
|
|
|
cur->post_handler(cur, regs, 0);
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
resume_execution(cur, regs, kcb);
|
|
|
|
|
regs->eflags |= kcb->kprobe_saved_rflags;
|
|
|
|
|
|
|
|
|
|
/* Restore the original saved kprobes variables and continue. */
|
|
|
|
|
if (kcb->kprobe_status == KPROBE_REENTER) {
|
|
|
|
|
restore_previous_kprobe(kcb);
|
|
|
|
|
goto out;
|
|
|
|
|
}
|
|
|
|
|
reset_current_kprobe();
|
|
|
|
|
out:
|
|
|
|
|
preempt_enable_no_resched();
|
|
|
|
|
|
|
|
|
|
/*
|
|
|
|
|
* if somebody else is singlestepping across a probe point, eflags
|
|
|
|
|
* will have TF set, in which case, continue the remaining processing
|
|
|
|
|
* of do_debug, as if this is not a probe hit.
|
|
|
|
|
*/
|
|
|
|
|
if (regs->eflags & TF_MASK)
|
|
|
|
|
return 0;
|
|
|
|
|
|
|
|
|
|
return 1;
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
|
|
|
|
|
{
|
|
|
|
|
struct kprobe *cur = kprobe_running();
|
|
|
|
|
struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
|
|
|
|
|
|
|
|
|
|
if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
|
|
|
|
|
return 1;
|
|
|
|
|
|
|
|
|
|
if (kcb->kprobe_status & KPROBE_HIT_SS) {
|
|
|
|
|
resume_execution(cur, regs, kcb);
|
|
|
|
|
regs->eflags |= kcb->kprobe_old_rflags;
|
|
|
|
|
|
|
|
|
|
reset_current_kprobe();
|
|
|
|
|
preempt_enable_no_resched();
|
|
|
|
|
}
|
|
|
|
|
return 0;
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
/*
|
|
|
|
|
* Wrapper routine for handling exceptions.
|
|
|
|
|
*/
|
|
|
|
|
int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
|
|
|
|
|
unsigned long val, void *data)
|
|
|
|
|
{
|
|
|
|
|
struct die_args *args = (struct die_args *)data;
|
|
|
|
|
int ret = NOTIFY_DONE;
|
|
|
|
|
|
|
|
|
|
switch (val) {
|
|
|
|
|
case DIE_INT3:
|
|
|
|
|
if (kprobe_handler(args->regs))
|
|
|
|
|
ret = NOTIFY_STOP;
|
|
|
|
|
break;
|
|
|
|
|
case DIE_DEBUG:
|
|
|
|
|
if (post_kprobe_handler(args->regs))
|
|
|
|
|
ret = NOTIFY_STOP;
|
|
|
|
|
break;
|
|
|
|
|
case DIE_GPF:
|
|
|
|
|
case DIE_PAGE_FAULT:
|
|
|
|
|
/* kprobe_running() needs smp_processor_id() */
|
|
|
|
|
preempt_disable();
|
|
|
|
|
if (kprobe_running() &&
|
|
|
|
|
kprobe_fault_handler(args->regs, args->trapnr))
|
|
|
|
|
ret = NOTIFY_STOP;
|
|
|
|
|
preempt_enable();
|
|
|
|
|
break;
|
|
|
|
|
default:
|
|
|
|
|
break;
|
|
|
|
|
}
|
|
|
|
|
return ret;
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
|
|
|
|
|
{
|
|
|
|
|
struct jprobe *jp = container_of(p, struct jprobe, kp);
|
|
|
|
|
unsigned long addr;
|
|
|
|
|
struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
|
|
|
|
|
|
|
|
|
|
kcb->jprobe_saved_regs = *regs;
|
|
|
|
|
kcb->jprobe_saved_rsp = (long *) regs->rsp;
|
|
|
|
|
addr = (unsigned long)(kcb->jprobe_saved_rsp);
|
|
|
|
|
/*
|
|
|
|
|
* As Linus pointed out, gcc assumes that the callee
|
|
|
|
|
* owns the argument space and could overwrite it, e.g.
|
|
|
|
|
* tailcall optimization. So, to be absolutely safe
|
|
|
|
|
* we also save and restore enough stack bytes to cover
|
|
|
|
|
* the argument area.
|
|
|
|
|
*/
|
|
|
|
|
memcpy(kcb->jprobes_stack, (kprobe_opcode_t *)addr,
|
|
|
|
|
MIN_STACK_SIZE(addr));
|
|
|
|
|
regs->eflags &= ~IF_MASK;
|
|
|
|
|
regs->rip = (unsigned long)(jp->entry);
|
|
|
|
|
return 1;
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
void __kprobes jprobe_return(void)
|
|
|
|
|
{
|
|
|
|
|
struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
|
|
|
|
|
|
|
|
|
|
asm volatile (" xchg %%rbx,%%rsp \n"
|
|
|
|
|
" int3 \n"
|
|
|
|
|
" .globl jprobe_return_end \n"
|
|
|
|
|
" jprobe_return_end: \n"
|
|
|
|
|
" nop \n"::"b"
|
|
|
|
|
(kcb->jprobe_saved_rsp):"memory");
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
|
|
|
|
|
{
|
|
|
|
|
struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
|
|
|
|
|
u8 *addr = (u8 *) (regs->rip - 1);
|
|
|
|
|
unsigned long stack_addr = (unsigned long)(kcb->jprobe_saved_rsp);
|
|
|
|
|
struct jprobe *jp = container_of(p, struct jprobe, kp);
|
|
|
|
|
|
|
|
|
|
if ((addr > (u8 *) jprobe_return) && (addr < (u8 *) jprobe_return_end)) {
|
|
|
|
|
if ((long *)regs->rsp != kcb->jprobe_saved_rsp) {
|
|
|
|
|
struct pt_regs *saved_regs =
|
|
|
|
|
container_of(kcb->jprobe_saved_rsp,
|
|
|
|
|
struct pt_regs, rsp);
|
|
|
|
|
printk("current rsp %p does not match saved rsp %p\n",
|
|
|
|
|
(long *)regs->rsp, kcb->jprobe_saved_rsp);
|
|
|
|
|
printk("Saved registers for jprobe %p\n", jp);
|
|
|
|
|
show_registers(saved_regs);
|
|
|
|
|
printk("Current registers\n");
|
|
|
|
|
show_registers(regs);
|
|
|
|
|
BUG();
|
|
|
|
|
}
|
|
|
|
|
*regs = kcb->jprobe_saved_regs;
|
|
|
|
|
memcpy((kprobe_opcode_t *) stack_addr, kcb->jprobes_stack,
|
|
|
|
|
MIN_STACK_SIZE(stack_addr));
|
|
|
|
|
preempt_enable_no_resched();
|
|
|
|
|
return 1;
|
|
|
|
|
}
|
|
|
|
|
return 0;
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
static struct kprobe trampoline_p = {
|
|
|
|
|
.addr = (kprobe_opcode_t *) &kretprobe_trampoline,
|
|
|
|
|
.pre_handler = trampoline_probe_handler
|
|
|
|
|
};
|
|
|
|
|
|
|
|
|
|
int __init arch_init_kprobes(void)
|
|
|
|
|
{
|
|
|
|
|
return register_kprobe(&trampoline_p);
|
|
|
|
|
}
|
