diff options
Diffstat (limited to 'arch/sparc/kernel/wof.S')
| -rw-r--r-- | arch/sparc/kernel/wof.S | 366 |
1 files changed, 366 insertions, 0 deletions
diff --git a/arch/sparc/kernel/wof.S b/arch/sparc/kernel/wof.S new file mode 100644 index 0000000000..96a3a11242 --- /dev/null +++ b/arch/sparc/kernel/wof.S @@ -0,0 +1,366 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * wof.S: Sparc window overflow handler. + * + * Copyright (C) 1995 David S. Miller (davem@caip.rutgers.edu) + */ + +#include <asm/contregs.h> +#include <asm/page.h> +#include <asm/ptrace.h> +#include <asm/psr.h> +#include <asm/smp.h> +#include <asm/asi.h> +#include <asm/winmacro.h> +#include <asm/asmmacro.h> +#include <asm/thread_info.h> + +/* WARNING: This routine is hairy and _very_ complicated, but it + * must be as fast as possible as it handles the allocation + * of register windows to the user and kernel. If you touch + * this code be _very_ careful as many other pieces of the + * kernel depend upon how this code behaves. You have been + * duly warned... + */ + +/* We define macro's for registers which have a fixed + * meaning throughout this entire routine. The 'T' in + * the comments mean that the register can only be + * accessed when in the 'trap' window, 'G' means + * accessible in any window. Do not change these registers + * after they have been set, until you are ready to return + * from the trap. + */ +#define t_psr l0 /* %psr at trap time T */ +#define t_pc l1 /* PC for trap return T */ +#define t_npc l2 /* NPC for trap return T */ +#define t_wim l3 /* %wim at trap time T */ +#define saved_g5 l5 /* Global save register T */ +#define saved_g6 l6 /* Global save register T */ +#define curptr g6 /* Gets set to 'current' then stays G */ + +/* Now registers whose values can change within the handler. */ +#define twin_tmp l4 /* Temp reg, only usable in trap window T */ +#define glob_tmp g5 /* Global temporary reg, usable anywhere G */ + + .text + .align 4 + /* BEGINNING OF PATCH INSTRUCTIONS */ + /* On a 7-window Sparc the boot code patches spnwin_* + * instructions with the following ones. + */ + .globl spnwin_patch1_7win, spnwin_patch2_7win, spnwin_patch3_7win +spnwin_patch1_7win: sll %t_wim, 6, %glob_tmp +spnwin_patch2_7win: and %glob_tmp, 0x7f, %glob_tmp +spnwin_patch3_7win: and %twin_tmp, 0x7f, %twin_tmp + /* END OF PATCH INSTRUCTIONS */ + + /* The trap entry point has done the following: + * + * rd %psr, %l0 + * rd %wim, %l3 + * b spill_window_entry + * andcc %l0, PSR_PS, %g0 + */ + + /* Datum current_thread_info->uwinmask contains at all times a bitmask + * where if any user windows are active, at least one bit will + * be set in to mask. If no user windows are active, the bitmask + * will be all zeroes. + */ + .globl spill_window_entry + .globl spnwin_patch1, spnwin_patch2, spnwin_patch3 +spill_window_entry: + /* LOCATION: Trap Window */ + + mov %g5, %saved_g5 ! save away global temp register + mov %g6, %saved_g6 ! save away 'current' ptr register + + /* Compute what the new %wim will be if we save the + * window properly in this trap handler. + * + * newwim = ((%wim>>1) | (%wim<<(nwindows - 1))); + */ + srl %t_wim, 0x1, %twin_tmp +spnwin_patch1: sll %t_wim, 7, %glob_tmp + or %glob_tmp, %twin_tmp, %glob_tmp +spnwin_patch2: and %glob_tmp, 0xff, %glob_tmp + + /* The trap entry point has set the condition codes + * up for us to see if this is from user or kernel. + * Get the load of 'curptr' out of the way. + */ + LOAD_CURRENT(curptr, twin_tmp) + + andcc %t_psr, PSR_PS, %g0 + be,a spwin_fromuser ! all user wins, branch + save %g0, %g0, %g0 ! Go where saving will occur + + /* See if any user windows are active in the set. */ + ld [%curptr + TI_UWINMASK], %twin_tmp ! grab win mask + orcc %g0, %twin_tmp, %g0 ! check for set bits + bne spwin_exist_uwins ! yep, there are some + andn %twin_tmp, %glob_tmp, %twin_tmp ! compute new uwinmask + + /* Save into the window which must be saved and do it. + * Basically if we are here, this means that we trapped + * from kernel mode with only kernel windows in the register + * file. + */ + save %g0, %g0, %g0 ! save into the window to stash away + wr %glob_tmp, 0x0, %wim ! set new %wim, this is safe now + +spwin_no_userwins_from_kernel: + /* LOCATION: Window to be saved */ + + STORE_WINDOW(sp) ! stash the window + restore %g0, %g0, %g0 ! go back into trap window + + /* LOCATION: Trap window */ + mov %saved_g5, %g5 ! restore %glob_tmp + mov %saved_g6, %g6 ! restore %curptr + wr %t_psr, 0x0, %psr ! restore condition codes in %psr + WRITE_PAUSE ! waste some time + jmp %t_pc ! Return from trap + rett %t_npc ! we are done + +spwin_exist_uwins: + /* LOCATION: Trap window */ + + /* Wow, user windows have to be dealt with, this is dirty + * and messy as all hell. And difficult to follow if you + * are approaching the infamous register window trap handling + * problem for the first time. DON'T LOOK! + * + * Note that how the execution path works out, the new %wim + * will be left for us in the global temporary register, + * %glob_tmp. We cannot set the new %wim first because we + * need to save into the appropriate window without inducing + * a trap (traps are off, we'd get a watchdog wheee)... + * But first, store the new user window mask calculated + * above. + */ + st %twin_tmp, [%curptr + TI_UWINMASK] + save %g0, %g0, %g0 ! Go to where the saving will occur + +spwin_fromuser: + /* LOCATION: Window to be saved */ + wr %glob_tmp, 0x0, %wim ! Now it is safe to set new %wim + + /* LOCATION: Window to be saved */ + + /* This instruction branches to a routine which will check + * to validity of the users stack pointer by whatever means + * are necessary. This means that this is architecture + * specific and thus this branch instruction will need to + * be patched at boot time once the machine type is known. + * This routine _shall not_ touch %curptr under any + * circumstances whatsoever! It will branch back to the + * label 'spwin_good_ustack' if the stack is ok but still + * needs to be dumped (SRMMU for instance will not need to + * do this) or 'spwin_finish_up' if the stack is ok and the + * registers have already been saved. If the stack is found + * to be bogus for some reason the routine shall branch to + * the label 'spwin_user_stack_is_bolixed' which will take + * care of things at that point. + */ + b spwin_srmmu_stackchk + andcc %sp, 0x7, %g0 + +spwin_good_ustack: + /* LOCATION: Window to be saved */ + + /* The users stack is ok and we can safely save it at + * %sp. + */ + STORE_WINDOW(sp) + +spwin_finish_up: + restore %g0, %g0, %g0 /* Back to trap window. */ + + /* LOCATION: Trap window */ + + /* We have spilled successfully, and we have properly stored + * the appropriate window onto the stack. + */ + + /* Restore saved globals */ + mov %saved_g5, %g5 + mov %saved_g6, %g6 + + wr %t_psr, 0x0, %psr + WRITE_PAUSE + jmp %t_pc + rett %t_npc + +spwin_user_stack_is_bolixed: + /* LOCATION: Window to be saved */ + + /* Wheee, user has trashed his/her stack. We have to decide + * how to proceed based upon whether we came from kernel mode + * or not. If we came from kernel mode, toss the window into + * a special buffer and proceed, the kernel _needs_ a window + * and we could be in an interrupt handler so timing is crucial. + * If we came from user land we build a full stack frame and call + * c-code to gun down the process. + */ + rd %psr, %glob_tmp + andcc %glob_tmp, PSR_PS, %g0 + bne spwin_bad_ustack_from_kernel + nop + + /* Oh well, throw this one window into the per-task window + * buffer, the first one. + */ + st %sp, [%curptr + TI_RWIN_SPTRS] + STORE_WINDOW(curptr + TI_REG_WINDOW) + restore %g0, %g0, %g0 + + /* LOCATION: Trap Window */ + + /* Back in the trap window, update winbuffer save count. */ + mov 1, %twin_tmp + st %twin_tmp, [%curptr + TI_W_SAVED] + + /* Compute new user window mask. What we are basically + * doing is taking two windows, the invalid one at trap + * time and the one we attempted to throw onto the users + * stack, and saying that everything else is an ok user + * window. umask = ((~(%t_wim | %wim)) & valid_wim_bits) + */ + rd %wim, %twin_tmp + or %twin_tmp, %t_wim, %twin_tmp + not %twin_tmp +spnwin_patch3: and %twin_tmp, 0xff, %twin_tmp ! patched on 7win Sparcs + st %twin_tmp, [%curptr + TI_UWINMASK] + +#define STACK_OFFSET (THREAD_SIZE - TRACEREG_SZ - STACKFRAME_SZ) + + sethi %hi(STACK_OFFSET), %sp + or %sp, %lo(STACK_OFFSET), %sp + add %curptr, %sp, %sp + + /* Restore the saved globals and build a pt_regs frame. */ + mov %saved_g5, %g5 + mov %saved_g6, %g6 + STORE_PT_ALL(sp, t_psr, t_pc, t_npc, g1) + + sethi %hi(STACK_OFFSET), %g6 + or %g6, %lo(STACK_OFFSET), %g6 + sub %sp, %g6, %g6 ! curptr + + /* Turn on traps and call c-code to deal with it. */ + wr %t_psr, PSR_ET, %psr + nop + call window_overflow_fault + nop + + /* Return from trap if C-code actually fixes things, if it + * doesn't then we never get this far as the process will + * be given the look of death from Commander Peanut. + */ + b ret_trap_entry + clr %l6 + +spwin_bad_ustack_from_kernel: + /* LOCATION: Window to be saved */ + + /* The kernel provoked a spill window trap, but the window we + * need to save is a user one and the process has trashed its + * stack pointer. We need to be quick, so we throw it into + * a per-process window buffer until we can properly handle + * this later on. + */ + SAVE_BOLIXED_USER_STACK(curptr, glob_tmp) + restore %g0, %g0, %g0 + + /* LOCATION: Trap window */ + + /* Restore globals, condition codes in the %psr and + * return from trap. Note, restoring %g6 when returning + * to kernel mode is not necessarily these days. ;-) + */ + mov %saved_g5, %g5 + mov %saved_g6, %g6 + + wr %t_psr, 0x0, %psr + WRITE_PAUSE + + jmp %t_pc + rett %t_npc + +/* Undefine the register macros which would only cause trouble + * if used below. This helps find 'stupid' coding errors that + * produce 'odd' behavior. The routines below are allowed to + * make usage of glob_tmp and t_psr so we leave them defined. + */ +#undef twin_tmp +#undef curptr +#undef t_pc +#undef t_npc +#undef t_wim +#undef saved_g5 +#undef saved_g6 + +/* Now come the per-architecture window overflow stack checking routines. + * As noted above %curptr cannot be touched by this routine at all. + */ + + /* This is a generic SRMMU routine. As far as I know this + * works for all current v8/srmmu implementations, we'll + * see... + */ + .globl spwin_srmmu_stackchk +spwin_srmmu_stackchk: + /* LOCATION: Window to be saved on the stack */ + + /* Because of SMP concerns and speed we play a trick. + * We disable fault traps in the MMU control register, + * Execute the stores, then check the fault registers + * to see what happens. I can hear Linus now + * "disgusting... broken hardware...". + * + * But first, check to see if the users stack has ended + * up in kernel vma, then we would succeed for the 'wrong' + * reason... ;( Note that the 'sethi' below assumes the + * kernel is page aligned, which should always be the case. + */ + /* Check results of callers andcc %sp, 0x7, %g0 */ + bne spwin_user_stack_is_bolixed + sethi %hi(PAGE_OFFSET), %glob_tmp + cmp %glob_tmp, %sp + bleu spwin_user_stack_is_bolixed + mov AC_M_SFSR, %glob_tmp + + /* Clear the fault status and turn on the no_fault bit. */ +LEON_PI(lda [%glob_tmp] ASI_LEON_MMUREGS, %g0) ! eat SFSR +SUN_PI_(lda [%glob_tmp] ASI_M_MMUREGS, %g0) ! eat SFSR + +LEON_PI(lda [%g0] ASI_LEON_MMUREGS, %glob_tmp) ! read MMU control +SUN_PI_(lda [%g0] ASI_M_MMUREGS, %glob_tmp) ! read MMU control + or %glob_tmp, 0x2, %glob_tmp ! or in no_fault bit +LEON_PI(sta %glob_tmp, [%g0] ASI_LEON_MMUREGS) ! set it +SUN_PI_(sta %glob_tmp, [%g0] ASI_M_MMUREGS) ! set it + + /* Dump the registers and cross fingers. */ + STORE_WINDOW(sp) + + /* Clear the no_fault bit and check the status. */ + andn %glob_tmp, 0x2, %glob_tmp +LEON_PI(sta %glob_tmp, [%g0] ASI_LEON_MMUREGS) +SUN_PI_(sta %glob_tmp, [%g0] ASI_M_MMUREGS) + + mov AC_M_SFAR, %glob_tmp +LEON_PI(lda [%glob_tmp] ASI_LEON_MMUREGS, %g0) +SUN_PI_(lda [%glob_tmp] ASI_M_MMUREGS, %g0) + + mov AC_M_SFSR, %glob_tmp +LEON_PI(lda [%glob_tmp] ASI_LEON_MMUREGS, %glob_tmp) +SUN_PI_(lda [%glob_tmp] ASI_M_MMUREGS, %glob_tmp) + andcc %glob_tmp, 0x2, %g0 ! did we fault? + be,a spwin_finish_up + 0x4 ! cool beans, success + restore %g0, %g0, %g0 + + rd %psr, %glob_tmp + b spwin_user_stack_is_bolixed + 0x4 ! we faulted, ugh + nop |