Use fixmaps instead of vmap/vunmap in text_poke() for avoiding
page allocation and delayed unmapping.
At the result of above change, text_poke() becomes atomic and can be called
from stop_machine() etc.
Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Acked-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
LKML-Reference: <49B14352.2040705@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Use the mutual exclusion provided by the text edit lock in alternatives code.
Since alternative_smp_* will be called from module init code, etc,
we'd better protect it from other subsystems.
Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
LKML-Reference: <49B14332.9030109@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: low priority bug fix
This removes part of a a patch I added myself some time ago. After some
consideration the patch was a bad idea. In particular it stopped machine check
exceptions during code patching.
To quote the comment:
* MCEs only happen when something got corrupted and in this
* case we must do something about the corruption.
* Ignoring it is worse than a unlikely patching race.
* Also machine checks tend to be broadcast and if one CPU
* goes into machine check the others follow quickly, so we don't
* expect a machine check to cause undue problems during to code
* patching.
So undo the machine check related parts of
8f4e956b31 NMIs are still disabled.
This only removes code, the only additions are a new comment.
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
num_possible_cpus() can be > 1 when disabled CPUs have been accounted.
Disabled CPUs are not in the cpu_present_map, so we can use
num_present_cpus() as a safe indicator to switch to UP alternatives.
Reported-by: Chuck Ebbert <cebbert@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: <stable@kernel.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Use X86_FEATURE_NOPL to determine if it is safe to use P6 NOPs in
alternatives. Also, replace table and loop with simple if statement.
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Use X86_FEATURE_NOPL to determine if it is safe to use P6 NOPs in
alternatives. Also, replace table and loop with simple if statement.
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
If a kernel thread is preempted in single-cpu mode right after the NOP (nop
about to be turned into a lock prefix), then we CPU hotplug a CPU, and then the
thread is scheduled back again, a SMP-unsafe atomic operation will be used on
shared SMP variables, leading to corruption. No corruption would happen in the
reverse case : going from SMP to UP is ok because we split a bit instruction
into tiny pieces, which does not present this condition.
Changing the 0x90 (single-byte nop) currently used into a 0x3E DS segment
override prefix should fix this issue. Since the default of the atomic
instructions is to use the DS segment anyway, it should not affect the
behavior.
The exception to this are references that use ESP/RSP and EBP/RBP as
the base register (they will use the SS segment), however, in Linux
(a) DS == SS at all times, and (b) we do not distinguish between
segment violations reported as #SS as opposed to #GP, so there is no
need to disassemble the instruction to figure out the suitable segment.
This patch assumes that the 0x3E prefix will leave atomic operations as-is (thus
assuming they normally touch data in the DS segment). Since there seem to be no
obvious ill-use of other segment override prefixes for atomic operations, it
should be safe. It can be verified with a quick
grep -r LOCK_PREFIX include/asm-x86/
grep -A 1 -r LOCK_PREFIX arch/x86/
Taken from
This source :
AMD64 Architecture Programmer's Manual Volume 3: General-Purpose and System
Instructions
States
"Instructions that Reference a Non-Stack Segment—If an instruction encoding
references any base register other than rBP or rSP, or if an instruction
contains an immediate offset, the default segment is the data segment (DS).
These instructions can use the segment-override prefix to select one of the
non-default segments, as shown in Table 1-5."
Therefore, forcing the DS segment on the atomic operations, which already use
the DS segment, should not change.
This source :
http://wiki.osdev.org/X86_Instruction_Encoding
States
"In 64-bit the CS, SS, DS and ES segment overrides are ignored."
Confirmed by "AMD 64-Bit Technology" A.7
http://www.amd.com/us-en/assets/content_type/white_papers_and_tech_docs/x86-64_overview.pdf
"In 64-bit mode, the DS, ES, SS and CS segment-override prefixes have no effect.
These four prefixes are no longer treated as segment-override prefixes in the
context of multipleprefix rules. Instead, they are treated as null prefixes."
This patch applies to 2.6.27-rc2, but would also have to be applied to earlier
kernels (2.6.26, 2.6.25, ...).
Performance impact of the fix : tests done on "xaddq" and "xaddl" shows it
actually improves performances on Intel Xeon, AMD64, Pentium M. It does not
change the performance on Pentium II, Pentium 3 and Pentium 4.
Xeon E5405 2.0GHz :
NR_TESTS 10000000
test empty cycles : 162207948
test test 1-byte nop xadd cycles : 170755422
test test DS override prefix xadd cycles : 170000118 *
test test LOCK xadd cycles : 472012134
AMD64 2.0GHz :
NR_TESTS 10000000
test empty cycles : 146674549
test test 1-byte nop xadd cycles : 150273860
test test DS override prefix xadd cycles : 149982382 *
test test LOCK xadd cycles : 270000690
Pentium 4 3.0GHz
NR_TESTS 10000000
test empty cycles : 290001195
test test 1-byte nop xadd cycles : 310000560
test test DS override prefix xadd cycles : 310000575 *
test test LOCK xadd cycles : 1050103740
Pentium M 2.0GHz
NR_TESTS 10000000
test empty cycles : 180000523
test test 1-byte nop xadd cycles : 320000345
test test DS override prefix xadd cycles : 310000374 *
test test LOCK xadd cycles : 480000357
Pentium 3 550MHz
NR_TESTS 10000000
test empty cycles : 510000231
test test 1-byte nop xadd cycles : 620000128
test test DS override prefix xadd cycles : 620000110 *
test test LOCK xadd cycles : 800000088
Pentium II 350MHz
NR_TESTS 10000000
test empty cycles : 200833494
test test 1-byte nop xadd cycles : 340000130
test test DS override prefix xadd cycles : 340000126 *
test test LOCK xadd cycles : 530000078
Speed test modules can be found at
http://ltt.polymtl.ca/svn/trunk/tests/kernel/test-prefix-speed-32.chttp://ltt.polymtl.ca/svn/trunk/tests/kernel/test-prefix-speed.c
Macro-benchmarks
2.0GHz E5405 Core 2 dual Quad-Core Xeon
Summary
* replace smp lock prefixes with DS segment selector prefixes
no lock prefix (s) with lock prefix (s) Speedup
make -j1 kernel/ 33.94 +/- 0.07 34.91 +/- 0.27 2.8 %
hackbench 50 2.99 +/- 0.01 3.74 +/- 0.01 25.1 %
* replace smp lock prefixes with 0x90 nops
no lock prefix (s) with lock prefix (s) Speedup
make -j1 kernel/ 34.16 +/- 0.32 34.91 +/- 0.27 2.2 %
hackbench 50 3.00 +/- 0.01 3.74 +/- 0.01 24.7 %
Detail :
1 CPU, replace smp lock prefixes with DS segment selector prefixes
make -j1 kernel/
real 0m34.067s
user 0m30.630s
sys 0m2.980s
real 0m33.867s
user 0m30.582s
sys 0m3.024s
real 0m33.939s
user 0m30.738s
sys 0m2.876s
real 0m33.913s
user 0m30.806s
sys 0m2.808s
avg : 33.94s
std. dev. : 0.07s
hackbench 50
Time: 2.978
Time: 2.982
Time: 3.010
Time: 2.984
Time: 2.982
avg : 2.99
std. dev. : 0.01
1 CPU, noreplace-smp
make -j1 kernel/
real 0m35.326s
user 0m30.630s
sys 0m3.260s
real 0m34.325s
user 0m30.802s
sys 0m3.084s
real 0m35.568s
user 0m30.722s
sys 0m3.168s
real 0m34.435s
user 0m30.886s
sys 0m2.996s
avg.: 34.91s
std. dev. : 0.27s
hackbench 50
Time: 3.733
Time: 3.750
Time: 3.761
Time: 3.737
Time: 3.741
avg : 3.74
std. dev. : 0.01
1 CPU, replace smp lock prefixes with 0x90 nops
make -j1 kernel/
real 0m34.139s
user 0m30.782s
sys 0m2.820s
real 0m34.010s
user 0m30.630s
sys 0m2.976s
real 0m34.777s
user 0m30.658s
sys 0m2.916s
real 0m33.924s
user 0m30.634s
sys 0m2.924s
real 0m33.962s
user 0m30.774s
sys 0m2.800s
real 0m34.141s
user 0m30.770s
sys 0m2.828s
avg : 34.16
std. dev. : 0.32
hackbench 50
Time: 2.999
Time: 2.994
Time: 3.004
Time: 2.991
Time: 2.988
avg : 3.00
std. dev. : 0.01
I did more runs (20 runs of each) to compare the nop case to the DS
prefix case. Results in seconds. They actually does not seems to show a
significant difference.
NOP
34.155
33.955
34.012
35.299
35.679
34.141
33.995
35.016
34.254
33.957
33.957
34.008
35.013
34.494
33.893
34.295
34.314
34.854
33.991
34.132
DS
34.080
34.304
34.374
35.095
34.291
34.135
33.940
34.208
35.276
34.288
33.861
33.898
34.610
34.709
33.851
34.256
35.161
34.283
33.865
35.078
Used http://www.graphpad.com/quickcalcs/ttest1.cfm?Format=C to do the
T-test (yeah, I'm lazy) :
Group Group One (DS prefix) Group Two (nops)
Mean 34.37815 34.37070
SD 0.46108 0.51905
SEM 0.10310 0.11606
N 20 20
P value and statistical significance:
The two-tailed P value equals 0.9620
By conventional criteria, this difference is considered to be not statistically significant.
Confidence interval:
The mean of Group One minus Group Two equals 0.00745
95% confidence interval of this difference: From -0.30682 to 0.32172
Intermediate values used in calculations:
t = 0.0480
df = 38
standard error of difference = 0.155
So, unless these calculus are completely bogus, the difference between the nop
and the DS case seems not to be statistically significant.
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Acked-by: H. Peter Anvin <hpa@zytor.com>
CC: Linus Torvalds <torvalds@linux-foundation.org>
CC: Jeremy Fitzhardinge <jeremy@goop.org>
CC: Roland McGrath <roland@redhat.com>
CC: Ingo Molnar <mingo@elte.hu>
Cc: Steven Rostedt <rostedt@goodmis.org>
CC: Steven Rostedt <srostedt@redhat.com>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: Peter Zijlstra <peterz@infradead.org>
CC: Andrew Morton <akpm@linux-foundation.org>
CC: David Miller <davem@davemloft.net>
CC: Ulrich Drepper <drepper@redhat.com>
CC: Rusty Russell <rusty@rustcorp.com.au>
CC: Gregory Haskins <ghaskins@novell.com>
CC: Arnaldo Carvalho de Melo <acme@redhat.com>
CC: "Luis Claudio R. Goncalves" <lclaudio@uudg.org>
CC: Clark Williams <williams@redhat.com>
CC: Christoph Lameter <cl@linux-foundation.org>
CC: Andi Kleen <andi@firstfloor.org>
CC: Harvey Harrison <harvey.harrison@gmail.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
text_poke is sleepable.
The original fix by Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>.
Signed-off-by: Pekka Paalanen <pq@iki.fi>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This patch patches the call to mcount with nops instead
of a jmp over the mcount call.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Clean up the codepath, remove alignment restrictions and do sanity
checking of the end result, to make sure we patched the right site.
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
kernel_text_address returns true even for modules which is not wanted
in text_poke. Use core_kernel_text instead.
This is a regression introduced in e587cadd8f
which caused occasionaly crashes after suspend/resume.
Signed-off-by: Jiri Slaby <jirislaby@gmail.com>
CC: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
CC: Andi Kleen <andi@firstfloor.org>
CC: pageexec@freemail.hu
CC: H. Peter Anvin <hpa@zytor.com>
CC: Jeremy Fitzhardinge <jeremy@goop.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
* Ingo Molnar (mingo@elte.hu) wrote:
>
> * Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> wrote:
>
> > The shadow vmap for DEBUG_RODATA kernel text modification uses
> > virt_to_page to get the pages from the pointer address.
> >
> > However, I think vmalloc_to_page would be required in case the page is
> > used for modules.
> >
> > Since only the core kernel text is marked read-only, use
> > kernel_text_address() to make sure we only shadow map the core kernel
> > text, not modules.
>
> actually, i think we should mark module text readonly too.
>
Yes, but in the meantime, the x86 tree would need this patch to make
kprobes work correctly on modules.
I suspect that without this fix, with the enhanced hotplug and kprobes
patch, kprobes will use text_poke to insert breakpoints in modules
(vmalloced pages used), which will map the wrong pages and corrupt
random kernel locations instead of updating the correct page.
Work that would write protect the module pages should clearly be done,
but it can come in a later time. We have to make sure we interact
correctly with the page allocation debugging, as an example.
Here is the patch against x86.git 2.6.25-rc5 :
The shadow vmap for DEBUG_RODATA kernel text modification uses virt_to_page to
get the pages from the pointer address.
However, I think vmalloc_to_page would be required in case the page is used for
modules.
Since only the core kernel text is marked read-only, use kernel_text_address()
to make sure we only shadow map the core kernel text, not modules.
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
CC: akpm@linux-foundation.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Fix a memcpy that should be a text_poke (in apply_alternatives).
Use kernel_wp_save/kernel_wp_restore in text_poke to support DEBUG_RODATA
correctly and so the CPU HOTPLUG special case can be removed.
Add text_poke_early, for alternatives and paravirt boot-time and module load
time patching.
Changelog:
- Fix text_set and text_poke alignment check (mixed up bitwise and and or)
- Remove text_set
- Export add_nops, so it can be used by others.
- Document text_poke_early.
- Remove clflush, since it breaks some VIA architectures and is not strictly
necessary.
- Add kerneldoc to text_poke and text_poke_early.
- Create a second vmap instead of using the WP bit to support Xen and VMI.
- Move local_irq disable within text_poke and text_poke_early to be able to
be sleepable in these functions.
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
CC: Andi Kleen <andi@firstfloor.org>
CC: pageexec@freemail.hu
CC: H. Peter Anvin <hpa@zytor.com>
CC: Jeremy Fitzhardinge <jeremy@goop.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
gcc expects all toplevel assembly to return to the original section type.
The code in alteranative.c does not do this. This caused some strange bugs
in sched-devel where code would end up in the .rodata section and when
the kernel sets the NX bit on all .rodata, the kernel would crash when
executing this code.
This patch adds a .previous marker to return the code back to the
original section.
Credit goes to Andrew Pinski for telling me it wasn't a gcc bug but a
bug in the toplevel asm code in the kernel. ;-)
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
An older binutils bug caused us to not fix up alternatives.
This problem involved mutex.c but we dont do lockdep section tricks
there anymore, so this workaround is moot. Keep the printk nevertheless,
just in case ... We can remove that later on.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
On VMs implemented using JITs that cache translated code changing the lock
prefixes is a quite costly operation that forces the JIT to throw away and
retranslate a lot of code.
Previously a SMP kernel would rewrite the locks once for each CPU which
is quite unnecessary. This patch changes the code to never switch at boot in
the normal case (SMP kernel booting with >1 CPU) or only once for SMP kernel
on UP.
This makes a significant difference in boot up performance on AMD SimNow!
Also I expect it to be a little faster on native systems too because a smp
switch does a lot of text_poke()s which each synchronize the pipeline.
v1->v2: Rename max_cpus
v1->v2: Fix off by one in UP check (Thomas Gleixner)
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
The patch to suppress bitops-related warnings added a pile of ugly
casts. Many of these were related to the management of x86 CPU
capabilities. Clean these up by adding specific set/clear_cpu_cap
macros, and use them consistently.
Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
cpu_data is currently an array defined using NR_CPUS. This means that
we overallocate since we will rarely really use maximum configured cpus.
When NR_CPU count is raised to 4096 the size of cpu_data becomes
3,145,728 bytes.
These changes were adopted from the sparc64 (and ia64) code. An
additional field was added to cpuinfo_x86 to be a non-ambiguous cpu
index. This corresponds to the index into a cpumask_t as well as the
per_cpu index. It's used in various places like show_cpuinfo().
cpu_data is defined to be the boot_cpu_data structure for the NON-SMP
case.
Signed-off-by: Mike Travis <travis@sgi.com>
Acked-by: Christoph Lameter <clameter@sgi.com>
Cc: Andi Kleen <ak@suse.de>
Cc: James Bottomley <James.Bottomley@steeleye.com>
Cc: Dmitry Torokhov <dtor@mail.ru>
Cc: "Antonino A. Daplas" <adaplas@pol.net>
Cc: Mark M. Hoffman <mhoffman@lightlink.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Add support for and use the multi-byte NOPs recently documented to be
available on all PentiumPro and later processors.
This patch only applies cleanly on top of the "x86: misc.
constifications" patch sent earlier.
[ tglx: arch/x86 adaptation ]
Signed-off-by: Jan Beulich <jbeulich@novell.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
arch/x86/kernel/alternative.c | 23 ++++++++++++++++++++++-
include/asm-x86/processor_32.h | 22 ++++++++++++++++++++++
include/asm-x86/processor_64.h | 22 ++++++++++++++++++++++
3 files changed, 66 insertions(+), 1 deletion(-)
Miscellaneous x86 stuff that can live in .rodata.
[ tglx: arch/x86 adaptation ]
Signed-off-by: Jan Beulich <jbeulich@novell.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This patch refactors the paravirt_ops structure into groups of
functionally related ops:
pv_info - random info, rather than function entrypoints
pv_init_ops - functions used at boot time (some for module_init too)
pv_misc_ops - lazy mode, which didn't fit well anywhere else
pv_time_ops - time-related functions
pv_cpu_ops - various privileged instruction ops
pv_irq_ops - operations for managing interrupt state
pv_apic_ops - APIC operations
pv_mmu_ops - operations for managing pagetables
There are several motivations for this:
1. Some of these ops will be general to all x86, and some will be
i386/x86-64 specific. This makes it easier to share common stuff
while allowing separate implementations where needed.
2. At the moment we must export all of paravirt_ops, but modules only
need selected parts of it. This allows us to export on a case by case
basis (and also choose which export license we want to apply).
3. Functional groupings make things a bit more readable.
Struct paravirt_ops is now only used as a template to generate
patch-site identifiers, and to extract function pointers for inserting
into jmp/calls when patching. It is only instantiated when needed.
Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Andi Kleen <ak@suse.de>
Cc: Zach Amsden <zach@vmware.com>
Cc: Avi Kivity <avi@qumranet.com>
Cc: Anthony Liguory <aliguori@us.ibm.com>
Cc: "Glauber de Oliveira Costa" <glommer@gmail.com>
Cc: Jun Nakajima <jun.nakajima@intel.com>
> Maybe I just picked a bad time to try, but...
>
> arch/x86/kernel/alternative.c: In function 'apply_alternatives':
> arch/x86/kernel/alternative.c:191: error: 'VSYSCALL_START' undeclared (first use in this function)
> arch/x86/kernel/alternative.c:191: error: (Each undeclared identifier is reported only once
> arch/x86/kernel/alternative.c:191: error: for each function it appears in.)
> arch/x86/kernel/alternative.c:191: error: 'VSYSCALL_END' undeclared (first use in this function)
> make[1]: *** [arch/x86/kernel/alternative.o] Error 1
> make: *** [arch/x86/kernel] Error 2
Try this.
Include missing header for vsyscall.
Signed-off-by: Dave Jones <davej@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
The CLFLUSH for the modified code line in text_poke was supposed
to speed up CPU recovery. Unfortunately it seems to cause hangs
on some VIA C3s (at least on VIA Esther Model 10 Stepping 9)
Remove it.
Thanks to Stefan Becker for reporting/testing.
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
With commit ab144f5ec6 the patching code
now collects the complete new instruction stream into a temp buffer
before finally patching in the new insns. In some cases the paravirt
patchers will choose to leave the patch site unpatched (length mismatch,
clobbers mismatch, etc).
This causes the new patching code to copy an uninitialized temp buffer,
i.e. garbage, to the callsite. Simply make sure to always initialize
the buffer with the original instruction stream. A better fix is to
audit all the patchers and return proper length so that apply_paravirt()
can skip copies when we leave the patch site untouched.
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Commit 19d36ccdc3 "x86: Fix alternatives
and kprobes to remap write-protected kernel text" uses code which is
being patched for patching.
In particular, paravirt_ops does patching in two stages: first it
calls paravirt_ops.patch, then it fills any remaining instructions
with nop_out(). nop_out calls text_poke() which calls
lookup_address() which calls pgd_val() (aka paravirt_ops.pgd_val):
that call site is one of the places we patch.
If we always do patching as one single call to text_poke(), we only
need make sure we're not patching the memcpy in text_poke itself.
This means the prototype to paravirt_ops.patch needs to change, to
marshal the new code into a buffer rather than patching in place as it
does now. It also means all patching goes through text_poke(), which
is known to be safe (apply_alternatives is also changed to make a
single patch).
AK: fix compilation on x86-64 (bad rusty!)
AK: fix boot on x86-64 (sigh)
AK: merged with other patches
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This reverts most of commit 19d36ccdc3.
The way to DEBUG_RODATA interactions with KPROBES and CPU hotplug is to
just not mark the text as being write-protected in the first place.
Both of those facilities depend on rewriting instructions.
Having "helpful" debug facilities that just cause more problem is not
being helpful. It just adds complexity and bugs. Not worth it.
Reported-by: Rafael J. Wysocki <rjw@sisk.pl>
Cc: Andi Kleen <ak@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
When a machine check or NMI occurs while multiple byte code is patched
the CPU could theoretically see an inconsistent instruction and crash.
Prevent this by temporarily disabling MCEs and returning early in the
NMI handler.
Based on discussion with Mathieu Desnoyers.
Cc: Mathieu Desnoyers <compudj@krystal.dyndns.org>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Reenable kprobes and alternative patching when the kernel text is write
protected by DEBUG_RODATA
Add a general utility function to change write protected text. The new
function remaps the code using vmap to write it and takes care of CPU
synchronization. It also does CLFLUSH to make icache recovery faster.
There are some limitations on when the function can be used, see the
comment.
This is a newer version that also changes the paravirt_ops code.
text_poke also supports multi byte patching now.
Contains bug fixes from Zach Amsden and suggestions from Mathieu
Desnoyers.
Cc: Jan Beulich <jbeulich@novell.com>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Mathieu Desnoyers <compudj@krystal.dyndns.org>
Cc: Zach Amsden <zach@vmware.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Hence remove its handling in the opposite case.
Signed-off-by: Jan Beulich <jbeulich@novell.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This was broken. It adds complexity, for no good reason. Rather than
separate __pa() and __pa_symbol(), we should deprecate __pa_symbol(),
and preferably __pa() too - and just use "virt_to_phys()" instead, which
is more readable and has nicer semantics.
However, right now, just undo the separation, and make __pa_symbol() be
the exact same as __pa(). That fixes the bugs this patch introduced,
and we can do the fairly obvious cleanups later.
Do the new __phys_addr() function (which is now the actual workhorse for
the unified __pa()/__pa_symbol()) as a real external function, that way
all the potential issues with compile/link-time optimizations of
constant symbol addresses go away, and we can also, if we choose to, add
more sanity-checking of the argument.
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Vivek Goyal <vgoyal@in.ibm.com>
Cc: Andi Kleen <ak@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The other symbols used to delineate the alt-instructions sections have the
form __foo/__foo_end. Rename parainstructions to match.
Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Cc: Andi Kleen <ak@suse.de>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Implement the actual patching machinery. paravirt_patch_default()
contains the logic to automatically patch a callsite based on a few
simple rules:
- if the paravirt_op function is paravirt_nop, then patch nops
- if the paravirt_op function is a jmp target, then jmp to it
- if the paravirt_op function is callable and doesn't clobber too much
for the callsite, call it directly
paravirt_patch_default is suitable as a default implementation of
paravirt_ops.patch, will remove most of the expensive indirect calls
in favour of either a direct call or a pile of nops.
Backends may implement their own patcher, however. There are several
helper functions to help with this:
paravirt_patch_nop nop out a callsite
paravirt_patch_ignore leave the callsite as-is
paravirt_patch_call patch a call if the caller and callee
have compatible clobbers
paravirt_patch_jmp patch in a jmp
paravirt_patch_insns patch some literal instructions over
the callsite, if they fit
This patch also implements more direct patches for the native case, so
that when running on native hardware many common operations are
implemented inline.
Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Zachary Amsden <zach@vmware.com>
Cc: Anthony Liguori <anthony@codemonkey.ws>
Acked-by: Ingo Molnar <mingo@elte.hu>
Rename struct paravirt_patch to paravirt_patch_site, so that it
clearly refers to a callsite, and not the patch which may be applied
to that callsite.
Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Zachary Amsden <zach@vmware.com>
Remove CONFIG_DEBUG_PARAVIRT. When inlining code, this option
attempts to trash registers in the patch-site's "clobber" field, on
the grounds that this should find bugs with incorrect clobbers.
Unfortunately, the clobber field really means "registers modified by
this patch site", which includes return values.
Because of this, this option has outlived its usefulness, so remove
it.
Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Cc: Rusty Russell <rusty@rustcorp.com.au>
The .smp_altinstructions section and its corresponding symbols are
completely unused, so remove them.
Also, remove stray #ifdef __KENREL__ in asm-i386/alternative.h
Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Cc: Andi Kleen <ak@suse.de>
Currently __pa_symbol is for use with symbols in the kernel address
map and __pa is for use with pointers into the physical memory map.
But the code is implemented so you can usually interchange the two.
__pa which is much more common can be implemented much more cheaply
if it is it doesn't have to worry about any other kernel address
spaces. This is especially true with a relocatable kernel as
__pa_symbol needs to peform an extra variable read to resolve
the address.
There is a third macro that is added for the vsyscall data
__pa_vsymbol for finding the physical addesses of vsyscall pages.
Most of this patch is simply sorting through the references to
__pa or __pa_symbol and using the proper one. A little of
it is continuing to use a physical address when we have it
instead of recalculating it several times.
swapper_pgd is now NULL. leave_mm now uses init_mm.pgd
and init_mm.pgd is initialized at boot (instead of compile time)
to the physmem virtual mapping of init_level4_pgd. The
physical address changed.
Except for the for EMPTY_ZERO page all of the remaining references
to __pa_symbol appear to be during kernel initialization. So this
should reduce the cost of __pa in the common case, even on a relocated
kernel.
As this is technically a semantic change we need to be on the lookout
for anything I missed. But it works for me (tm).
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Vivek Goyal <vgoyal@in.ibm.com>
Signed-off-by: Andi Kleen <ak@suse.de>
noreplacement is dangerous on modern systems because it will not replace the
context switch FNSAVE with SSE aware FXSAVE. But other places in the kernel still assume
SSE and do FXSAVE and the CPU will then access FXSAVE information with
FNSAVE and cause corruption.
Easiest way to avoid this is to remove the option. It was mostly for paranoia
reasons anyways and alternative()s have been stable for some time.
Thanks to Jeremy F. for reporting and helping debug it.
Signed-off-by: Andi Kleen <ak@suse.de>
It turns out that the most called ops, by several orders of magnitude,
are the interrupt manipulation ops. These are obvious candidates for
patching, so mark them up and create infrastructure for it.
The method used is that the ops structure has a patch function, which
is called for each place which needs to be patched: this returns a
number of instructions (the rest are NOP-padded).
Usually we can spare a register (%eax) for the binary patched code to
use, but in a couple of critical places in entry.S we can't: we make
the clobbers explicit at the call site, and manually clobber the
allowed registers in debug mode as an extra check.
And:
Don't abuse CONFIG_DEBUG_KERNEL, add CONFIG_DEBUG_PARAVIRT.
And:
AK: Fix warnings in x86-64 alternative.c build
And:
AK: Fix compilation with defconfig
And:
^From: Andrew Morton <akpm@osdl.org>
Some binutlises still like to emit references to __stop_parainstructions and
__start_parainstructions.
And:
AK: Fix warnings about unused variables when PARAVIRT is disabled.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Signed-off-by: Zachary Amsden <zach@vmware.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Interrupts must be disabled during alternative instruction patching. On
systems with high timer IRQ rates, or when running in an emulator, timing
differences can result in random kernel panics because of running partially
patched instructions. This doesn't yet fix NMIs, which requires extricating
the patch code from the late bug checking and is logically separate (and also
less likely to cause problems).
Signed-off-by: Zachary Amsden <zach@vmware.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Disable SMP alternatives fixups (the patching in of NOPs on 1-CPU systems) if
the lock validator is enabled: there is a binutils section handling bug that
causes corrupted instructions when UP instructions are patched in.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Masami Hiramatsu