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313 lines
8.4 KiB
313 lines
8.4 KiB
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* wuf.S: Window underflow trap handler for the Sparc.
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*
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* Copyright (C) 1995 David S. Miller
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*/
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#include <asm/contregs.h>
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#include <asm/page.h>
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#include <asm/ptrace.h>
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#include <asm/psr.h>
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#include <asm/smp.h>
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#include <asm/asi.h>
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#include <asm/winmacro.h>
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#include <asm/asmmacro.h>
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#include <asm/thread_info.h>
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/* Just like the overflow handler we define macros for registers
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* with fixed meanings in this routine.
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*/
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#define t_psr l0
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#define t_pc l1
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#define t_npc l2
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#define t_wim l3
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/* Don't touch the above registers or else you die horribly... */
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/* Now macros for the available scratch registers in this routine. */
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#define twin_tmp1 l4
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#define twin_tmp2 l5
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#define curptr g6
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.text
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.align 4
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/* The trap entry point has executed the following:
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*
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* rd %psr, %l0
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* rd %wim, %l3
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* b fill_window_entry
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* andcc %l0, PSR_PS, %g0
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*/
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/* Datum current_thread_info->uwinmask contains at all times a bitmask
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* where if any user windows are active, at least one bit will
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* be set in to mask. If no user windows are active, the bitmask
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* will be all zeroes.
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*/
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/* To get an idea of what has just happened to cause this
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* trap take a look at this diagram:
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*
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* 1 2 3 4 <-- Window number
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* ----------
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* T O W I <-- Symbolic name
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*
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* O == the window that execution was in when
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* the restore was attempted
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*
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* T == the trap itself has save'd us into this
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* window
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*
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* W == this window is the one which is now invalid
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* and must be made valid plus loaded from the
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* stack
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*
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* I == this window will be the invalid one when we
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* are done and return from trap if successful
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*/
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/* BEGINNING OF PATCH INSTRUCTIONS */
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/* On 7-window Sparc the boot code patches fnwin_patch1
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* with the following instruction.
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*/
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.globl fnwin_patch1_7win, fnwin_patch2_7win
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fnwin_patch1_7win: srl %t_wim, 6, %twin_tmp2
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fnwin_patch2_7win: and %twin_tmp1, 0x7f, %twin_tmp1
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/* END OF PATCH INSTRUCTIONS */
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.globl fill_window_entry, fnwin_patch1, fnwin_patch2
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fill_window_entry:
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/* LOCATION: Window 'T' */
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/* Compute what the new %wim is going to be if we retrieve
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* the proper window off of the stack.
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*/
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sll %t_wim, 1, %twin_tmp1
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fnwin_patch1: srl %t_wim, 7, %twin_tmp2
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or %twin_tmp1, %twin_tmp2, %twin_tmp1
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fnwin_patch2: and %twin_tmp1, 0xff, %twin_tmp1
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wr %twin_tmp1, 0x0, %wim /* Make window 'I' invalid */
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andcc %t_psr, PSR_PS, %g0
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be fwin_from_user
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restore %g0, %g0, %g0 /* Restore to window 'O' */
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/* Trapped from kernel, we trust that the kernel does not
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* 'over restore' sorta speak and just grab the window
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* from the stack and return. Easy enough.
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*/
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fwin_from_kernel:
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/* LOCATION: Window 'O' */
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restore %g0, %g0, %g0
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/* LOCATION: Window 'W' */
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LOAD_WINDOW(sp) /* Load it up */
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/* Spin the wheel... */
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save %g0, %g0, %g0
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save %g0, %g0, %g0
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/* I'd like to buy a vowel please... */
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/* LOCATION: Window 'T' */
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/* Now preserve the condition codes in %psr, pause, and
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* return from trap. This is the simplest case of all.
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*/
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wr %t_psr, 0x0, %psr
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WRITE_PAUSE
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jmp %t_pc
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rett %t_npc
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fwin_from_user:
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/* LOCATION: Window 'O' */
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restore %g0, %g0, %g0 /* Restore to window 'W' */
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/* LOCATION: Window 'W' */
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/* Branch to the stack validation routine */
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b srmmu_fwin_stackchk
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andcc %sp, 0x7, %g0
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#define STACK_OFFSET (THREAD_SIZE - TRACEREG_SZ - STACKFRAME_SZ)
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fwin_user_stack_is_bolixed:
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/* LOCATION: Window 'W' */
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/* Place a pt_regs frame on the kernel stack, save back
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* to the trap window and call c-code to deal with this.
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*/
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LOAD_CURRENT(l4, l5)
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sethi %hi(STACK_OFFSET), %l5
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or %l5, %lo(STACK_OFFSET), %l5
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add %l4, %l5, %l5
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/* Store globals into pt_regs frame. */
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STORE_PT_GLOBALS(l5)
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STORE_PT_YREG(l5, g3)
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/* Save current in a global while we change windows. */
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mov %l4, %curptr
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save %g0, %g0, %g0
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/* LOCATION: Window 'O' */
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rd %psr, %g3 /* Read %psr in live user window */
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mov %fp, %g4 /* Save bogus frame pointer. */
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save %g0, %g0, %g0
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/* LOCATION: Window 'T' */
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sethi %hi(STACK_OFFSET), %l5
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or %l5, %lo(STACK_OFFSET), %l5
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add %curptr, %l5, %sp
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/* Build rest of pt_regs. */
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STORE_PT_INS(sp)
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STORE_PT_PRIV(sp, t_psr, t_pc, t_npc)
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/* re-set trap time %wim value */
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wr %t_wim, 0x0, %wim
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/* Fix users window mask and buffer save count. */
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mov 0x1, %g5
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sll %g5, %g3, %g5
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st %g5, [%curptr + TI_UWINMASK] ! one live user window still
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st %g0, [%curptr + TI_W_SAVED] ! no windows in the buffer
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wr %t_psr, PSR_ET, %psr ! enable traps
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nop
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call window_underflow_fault
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mov %g4, %o0
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b ret_trap_entry
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clr %l6
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fwin_user_stack_is_ok:
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/* LOCATION: Window 'W' */
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/* The users stack area is kosher and mapped, load the
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* window and fall through to the finish up routine.
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*/
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LOAD_WINDOW(sp)
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/* Round and round she goes... */
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save %g0, %g0, %g0 /* Save to window 'O' */
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save %g0, %g0, %g0 /* Save to window 'T' */
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/* Where she'll trap nobody knows... */
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/* LOCATION: Window 'T' */
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fwin_user_finish_up:
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/* LOCATION: Window 'T' */
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wr %t_psr, 0x0, %psr
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WRITE_PAUSE
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jmp %t_pc
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rett %t_npc
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/* Here come the architecture specific checks for stack.
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* mappings. Note that unlike the window overflow handler
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* we only need to check whether the user can read from
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* the appropriate addresses. Also note that we are in
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* an invalid window which will be loaded, and this means
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* that until we actually load the window up we are free
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* to use any of the local registers contained within.
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*
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* On success these routine branch to fwin_user_stack_is_ok
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* if the area at %sp is user readable and the window still
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* needs to be loaded, else fwin_user_finish_up if the
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* routine has done the loading itself. On failure (bogus
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* user stack) the routine shall branch to the label called
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* fwin_user_stack_is_bolixed.
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*
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* Contrary to the arch-specific window overflow stack
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* check routines in wof.S, these routines are free to use
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* any of the local registers they want to as this window
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* does not belong to anyone at this point, however the
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* outs and ins are still verboten as they are part of
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* 'someone elses' window possibly.
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*/
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.globl srmmu_fwin_stackchk
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srmmu_fwin_stackchk:
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/* LOCATION: Window 'W' */
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/* Caller did 'andcc %sp, 0x7, %g0' */
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bne fwin_user_stack_is_bolixed
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sethi %hi(PAGE_OFFSET), %l5
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/* Check if the users stack is in kernel vma, then our
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* trial and error technique below would succeed for
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* the 'wrong' reason.
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*/
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mov AC_M_SFSR, %l4
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cmp %l5, %sp
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bleu fwin_user_stack_is_bolixed
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LEON_PI( lda [%l4] ASI_LEON_MMUREGS, %g0) ! clear fault status
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SUN_PI_( lda [%l4] ASI_M_MMUREGS, %g0) ! clear fault status
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/* The technique is, turn off faults on this processor,
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* just let the load rip, then check the sfsr to see if
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* a fault did occur. Then we turn on fault traps again
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* and branch conditionally based upon what happened.
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*/
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LEON_PI(lda [%g0] ASI_LEON_MMUREGS, %l5) ! read mmu-ctrl reg
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SUN_PI_(lda [%g0] ASI_M_MMUREGS, %l5) ! read mmu-ctrl reg
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or %l5, 0x2, %l5 ! turn on no-fault bit
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LEON_PI(sta %l5, [%g0] ASI_LEON_MMUREGS) ! store it
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SUN_PI_(sta %l5, [%g0] ASI_M_MMUREGS) ! store it
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/* Cross fingers and go for it. */
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LOAD_WINDOW(sp)
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/* A penny 'saved'... */
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save %g0, %g0, %g0
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save %g0, %g0, %g0
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/* Is a BADTRAP earned... */
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/* LOCATION: Window 'T' */
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LEON_PI(lda [%g0] ASI_LEON_MMUREGS, %twin_tmp1) ! load mmu-ctrl again
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SUN_PI_(lda [%g0] ASI_M_MMUREGS, %twin_tmp1) ! load mmu-ctrl again
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andn %twin_tmp1, 0x2, %twin_tmp1 ! clear no-fault bit
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LEON_PI(sta %twin_tmp1, [%g0] ASI_LEON_MMUREGS) ! store it
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SUN_PI_(sta %twin_tmp1, [%g0] ASI_M_MMUREGS) ! store it
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mov AC_M_SFAR, %twin_tmp2
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LEON_PI(lda [%twin_tmp2] ASI_LEON_MMUREGS, %g0) ! read fault address
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SUN_PI_(lda [%twin_tmp2] ASI_M_MMUREGS, %g0) ! read fault address
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mov AC_M_SFSR, %twin_tmp2
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LEON_PI(lda [%twin_tmp2] ASI_LEON_MMUREGS, %twin_tmp2) ! read fault status
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SUN_PI_(lda [%twin_tmp2] ASI_M_MMUREGS, %twin_tmp2) ! read fault status
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andcc %twin_tmp2, 0x2, %g0 ! did fault occur?
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bne 1f ! yep, cleanup
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nop
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wr %t_psr, 0x0, %psr
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nop
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b fwin_user_finish_up + 0x4
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nop
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/* Did I ever tell you about my window lobotomy?
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* anyways... fwin_user_stack_is_bolixed expects
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* to be in window 'W' so make it happy or else
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* we watchdog badly.
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*/
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1:
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restore %g0, %g0, %g0
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b fwin_user_stack_is_bolixed ! oh well
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restore %g0, %g0, %g0
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