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Diffstat (limited to 'arch/sparc/kernel/wuf.S')
| -rw-r--r-- | arch/sparc/kernel/wuf.S | 313 |
1 files changed, 313 insertions, 0 deletions
diff --git a/arch/sparc/kernel/wuf.S b/arch/sparc/kernel/wuf.S new file mode 100644 index 000000000..1a4ca490e --- /dev/null +++ b/arch/sparc/kernel/wuf.S @@ -0,0 +1,313 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * wuf.S: Window underflow trap handler for the Sparc. + * + * Copyright (C) 1995 David S. Miller + */ + +#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> + +/* Just like the overflow handler we define macros for registers + * with fixed meanings in this routine. + */ +#define t_psr l0 +#define t_pc l1 +#define t_npc l2 +#define t_wim l3 +/* Don't touch the above registers or else you die horribly... */ + +/* Now macros for the available scratch registers in this routine. */ +#define twin_tmp1 l4 +#define twin_tmp2 l5 + +#define curptr g6 + + .text + .align 4 + + /* The trap entry point has executed the following: + * + * rd %psr, %l0 + * rd %wim, %l3 + * b fill_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. + */ + + /* To get an idea of what has just happened to cause this + * trap take a look at this diagram: + * + * 1 2 3 4 <-- Window number + * ---------- + * T O W I <-- Symbolic name + * + * O == the window that execution was in when + * the restore was attempted + * + * T == the trap itself has save'd us into this + * window + * + * W == this window is the one which is now invalid + * and must be made valid plus loaded from the + * stack + * + * I == this window will be the invalid one when we + * are done and return from trap if successful + */ + + /* BEGINNING OF PATCH INSTRUCTIONS */ + + /* On 7-window Sparc the boot code patches fnwin_patch1 + * with the following instruction. + */ + .globl fnwin_patch1_7win, fnwin_patch2_7win +fnwin_patch1_7win: srl %t_wim, 6, %twin_tmp2 +fnwin_patch2_7win: and %twin_tmp1, 0x7f, %twin_tmp1 + /* END OF PATCH INSTRUCTIONS */ + + .globl fill_window_entry, fnwin_patch1, fnwin_patch2 +fill_window_entry: + /* LOCATION: Window 'T' */ + + /* Compute what the new %wim is going to be if we retrieve + * the proper window off of the stack. + */ + sll %t_wim, 1, %twin_tmp1 +fnwin_patch1: srl %t_wim, 7, %twin_tmp2 + or %twin_tmp1, %twin_tmp2, %twin_tmp1 +fnwin_patch2: and %twin_tmp1, 0xff, %twin_tmp1 + + wr %twin_tmp1, 0x0, %wim /* Make window 'I' invalid */ + + andcc %t_psr, PSR_PS, %g0 + be fwin_from_user + restore %g0, %g0, %g0 /* Restore to window 'O' */ + + /* Trapped from kernel, we trust that the kernel does not + * 'over restore' sorta speak and just grab the window + * from the stack and return. Easy enough. + */ +fwin_from_kernel: + /* LOCATION: Window 'O' */ + + restore %g0, %g0, %g0 + + /* LOCATION: Window 'W' */ + + LOAD_WINDOW(sp) /* Load it up */ + + /* Spin the wheel... */ + save %g0, %g0, %g0 + save %g0, %g0, %g0 + /* I'd like to buy a vowel please... */ + + /* LOCATION: Window 'T' */ + + /* Now preserve the condition codes in %psr, pause, and + * return from trap. This is the simplest case of all. + */ + wr %t_psr, 0x0, %psr + WRITE_PAUSE + + jmp %t_pc + rett %t_npc + +fwin_from_user: + /* LOCATION: Window 'O' */ + + restore %g0, %g0, %g0 /* Restore to window 'W' */ + + /* LOCATION: Window 'W' */ + + /* Branch to the stack validation routine */ + b srmmu_fwin_stackchk + andcc %sp, 0x7, %g0 + +#define STACK_OFFSET (THREAD_SIZE - TRACEREG_SZ - STACKFRAME_SZ) + +fwin_user_stack_is_bolixed: + /* LOCATION: Window 'W' */ + + /* Place a pt_regs frame on the kernel stack, save back + * to the trap window and call c-code to deal with this. + */ + LOAD_CURRENT(l4, l5) + + sethi %hi(STACK_OFFSET), %l5 + or %l5, %lo(STACK_OFFSET), %l5 + add %l4, %l5, %l5 + + /* Store globals into pt_regs frame. */ + STORE_PT_GLOBALS(l5) + STORE_PT_YREG(l5, g3) + + /* Save current in a global while we change windows. */ + mov %l4, %curptr + + save %g0, %g0, %g0 + + /* LOCATION: Window 'O' */ + + rd %psr, %g3 /* Read %psr in live user window */ + mov %fp, %g4 /* Save bogus frame pointer. */ + + save %g0, %g0, %g0 + + /* LOCATION: Window 'T' */ + + sethi %hi(STACK_OFFSET), %l5 + or %l5, %lo(STACK_OFFSET), %l5 + add %curptr, %l5, %sp + + /* Build rest of pt_regs. */ + STORE_PT_INS(sp) + STORE_PT_PRIV(sp, t_psr, t_pc, t_npc) + + /* re-set trap time %wim value */ + wr %t_wim, 0x0, %wim + + /* Fix users window mask and buffer save count. */ + mov 0x1, %g5 + sll %g5, %g3, %g5 + st %g5, [%curptr + TI_UWINMASK] ! one live user window still + st %g0, [%curptr + TI_W_SAVED] ! no windows in the buffer + + wr %t_psr, PSR_ET, %psr ! enable traps + nop + call window_underflow_fault + mov %g4, %o0 + + b ret_trap_entry + clr %l6 + +fwin_user_stack_is_ok: + /* LOCATION: Window 'W' */ + + /* The users stack area is kosher and mapped, load the + * window and fall through to the finish up routine. + */ + LOAD_WINDOW(sp) + + /* Round and round she goes... */ + save %g0, %g0, %g0 /* Save to window 'O' */ + save %g0, %g0, %g0 /* Save to window 'T' */ + /* Where she'll trap nobody knows... */ + + /* LOCATION: Window 'T' */ + +fwin_user_finish_up: + /* LOCATION: Window 'T' */ + + wr %t_psr, 0x0, %psr + WRITE_PAUSE + + jmp %t_pc + rett %t_npc + + /* Here come the architecture specific checks for stack. + * mappings. Note that unlike the window overflow handler + * we only need to check whether the user can read from + * the appropriate addresses. Also note that we are in + * an invalid window which will be loaded, and this means + * that until we actually load the window up we are free + * to use any of the local registers contained within. + * + * On success these routine branch to fwin_user_stack_is_ok + * if the area at %sp is user readable and the window still + * needs to be loaded, else fwin_user_finish_up if the + * routine has done the loading itself. On failure (bogus + * user stack) the routine shall branch to the label called + * fwin_user_stack_is_bolixed. + * + * Contrary to the arch-specific window overflow stack + * check routines in wof.S, these routines are free to use + * any of the local registers they want to as this window + * does not belong to anyone at this point, however the + * outs and ins are still verboten as they are part of + * 'someone elses' window possibly. + */ + + .globl srmmu_fwin_stackchk +srmmu_fwin_stackchk: + /* LOCATION: Window 'W' */ + + /* Caller did 'andcc %sp, 0x7, %g0' */ + bne fwin_user_stack_is_bolixed + sethi %hi(PAGE_OFFSET), %l5 + + /* Check if the users stack is in kernel vma, then our + * trial and error technique below would succeed for + * the 'wrong' reason. + */ + mov AC_M_SFSR, %l4 + cmp %l5, %sp + bleu fwin_user_stack_is_bolixed +LEON_PI( lda [%l4] ASI_LEON_MMUREGS, %g0) ! clear fault status +SUN_PI_( lda [%l4] ASI_M_MMUREGS, %g0) ! clear fault status + + /* The technique is, turn off faults on this processor, + * just let the load rip, then check the sfsr to see if + * a fault did occur. Then we turn on fault traps again + * and branch conditionally based upon what happened. + */ +LEON_PI(lda [%g0] ASI_LEON_MMUREGS, %l5) ! read mmu-ctrl reg +SUN_PI_(lda [%g0] ASI_M_MMUREGS, %l5) ! read mmu-ctrl reg + or %l5, 0x2, %l5 ! turn on no-fault bit +LEON_PI(sta %l5, [%g0] ASI_LEON_MMUREGS) ! store it +SUN_PI_(sta %l5, [%g0] ASI_M_MMUREGS) ! store it + + /* Cross fingers and go for it. */ + LOAD_WINDOW(sp) + + /* A penny 'saved'... */ + save %g0, %g0, %g0 + save %g0, %g0, %g0 + /* Is a BADTRAP earned... */ + + /* LOCATION: Window 'T' */ + +LEON_PI(lda [%g0] ASI_LEON_MMUREGS, %twin_tmp1) ! load mmu-ctrl again +SUN_PI_(lda [%g0] ASI_M_MMUREGS, %twin_tmp1) ! load mmu-ctrl again + andn %twin_tmp1, 0x2, %twin_tmp1 ! clear no-fault bit +LEON_PI(sta %twin_tmp1, [%g0] ASI_LEON_MMUREGS) ! store it +SUN_PI_(sta %twin_tmp1, [%g0] ASI_M_MMUREGS) ! store it + + mov AC_M_SFAR, %twin_tmp2 +LEON_PI(lda [%twin_tmp2] ASI_LEON_MMUREGS, %g0) ! read fault address +SUN_PI_(lda [%twin_tmp2] ASI_M_MMUREGS, %g0) ! read fault address + + mov AC_M_SFSR, %twin_tmp2 +LEON_PI(lda [%twin_tmp2] ASI_LEON_MMUREGS, %twin_tmp2) ! read fault status +SUN_PI_(lda [%twin_tmp2] ASI_M_MMUREGS, %twin_tmp2) ! read fault status + andcc %twin_tmp2, 0x2, %g0 ! did fault occur? + + bne 1f ! yep, cleanup + nop + + wr %t_psr, 0x0, %psr + nop + b fwin_user_finish_up + 0x4 + nop + + /* Did I ever tell you about my window lobotomy? + * anyways... fwin_user_stack_is_bolixed expects + * to be in window 'W' so make it happy or else + * we watchdog badly. + */ +1: + restore %g0, %g0, %g0 + b fwin_user_stack_is_bolixed ! oh well + restore %g0, %g0, %g0 |