| /* |
| * 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 |
| 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. |
| */ |
| lda [%g0] ASI_M_MMUREGS, %l5 ! read mmu-ctrl reg |
| or %l5, 0x2, %l5 ! turn on no-fault bit |
| 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' */ |
| |
| lda [%g0] ASI_M_MMUREGS, %twin_tmp1 ! load mmu-ctrl again |
| andn %twin_tmp1, 0x2, %twin_tmp1 ! clear no-fault bit |
| sta %twin_tmp1, [%g0] ASI_M_MMUREGS ! store it |
| |
| mov AC_M_SFAR, %twin_tmp2 |
| lda [%twin_tmp2] ASI_M_MMUREGS, %g0 ! read fault address |
| |
| mov AC_M_SFSR, %twin_tmp2 |
| 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 |
