diff options
Diffstat (limited to 'arch/xtensa/kernel/vectors.S')
| -rw-r--r-- | arch/xtensa/kernel/vectors.S | 250 |
1 files changed, 184 insertions, 66 deletions
diff --git a/arch/xtensa/kernel/vectors.S b/arch/xtensa/kernel/vectors.S index f9e175382aa9..cb8fd44caabc 100644 --- a/arch/xtensa/kernel/vectors.S +++ b/arch/xtensa/kernel/vectors.S @@ -78,6 +78,7 @@ ENTRY(_UserExceptionVector) s32i a0, a2, PT_DEPC # mark it as a regular exception addx4 a0, a0, a3 # find entry in table l32i a0, a0, EXC_TABLE_FAST_USER # load handler + xsr a3, excsave1 # restore a3 and dispatch table jx a0 ENDPROC(_UserExceptionVector) @@ -104,6 +105,7 @@ ENTRY(_KernelExceptionVector) s32i a0, a2, PT_DEPC # mark it as a regular exception addx4 a0, a0, a3 # find entry in table l32i a0, a0, EXC_TABLE_FAST_KERNEL # load handler address + xsr a3, excsave1 # restore a3 and dispatch table jx a0 ENDPROC(_KernelExceptionVector) @@ -168,7 +170,7 @@ ENDPROC(_KernelExceptionVector) * * a0: DEPC * a1: a1 - * a2: trashed, original value in EXC_TABLE_DOUBLE_A2 + * a2: trashed, original value in EXC_TABLE_DOUBLE_SAVE * a3: exctable * depc: a0 * excsave_1: a3 @@ -204,47 +206,46 @@ ENDPROC(_KernelExceptionVector) .section .DoubleExceptionVector.text, "ax" .begin literal_prefix .DoubleExceptionVector + .globl _DoubleExceptionVector_WindowUnderflow + .globl _DoubleExceptionVector_WindowOverflow ENTRY(_DoubleExceptionVector) - /* Deliberately destroy excsave (don't assume it's value was valid). */ - - wsr a3, excsave1 # save a3 + xsr a3, excsave1 + s32i a2, a3, EXC_TABLE_DOUBLE_SAVE /* Check for kernel double exception (usually fatal). */ - rsr a3, ps - _bbci.l a3, PS_UM_BIT, .Lksp + rsr a2, ps + _bbci.l a2, PS_UM_BIT, .Lksp /* Check if we are currently handling a window exception. */ /* Note: We don't need to indicate that we enter a critical section. */ xsr a0, depc # get DEPC, save a0 - movi a3, WINDOW_VECTORS_VADDR - _bltu a0, a3, .Lfixup - addi a3, a3, WINDOW_VECTORS_SIZE - _bgeu a0, a3, .Lfixup + movi a2, WINDOW_VECTORS_VADDR + _bltu a0, a2, .Lfixup + addi a2, a2, WINDOW_VECTORS_SIZE + _bgeu a0, a2, .Lfixup /* Window overflow/underflow exception. Get stack pointer. */ - mov a3, a2 - /* This explicit literal and the following references to it are made - * in order to fit DoubleExceptionVector.literals into the available - * 16-byte gap before DoubleExceptionVector.text in the absence of - * link time relaxation. See kernel/vmlinux.lds.S - */ - .literal .Lexc_table, exc_table - l32r a2, .Lexc_table - l32i a2, a2, EXC_TABLE_KSTK + l32i a2, a3, EXC_TABLE_KSTK /* Check for overflow/underflow exception, jump if overflow. */ - _bbci.l a0, 6, .Lovfl - - /* a0: depc, a1: a1, a2: kstk, a3: a2, depc: a0, excsave: a3 */ + _bbci.l a0, 6, _DoubleExceptionVector_WindowOverflow - /* Restart window underflow exception. + /* + * Restart window underflow exception. + * Currently: + * depc = orig a0, + * a0 = orig DEPC, + * a2 = new sp based on KSTK from exc_table + * a3 = excsave_1 + * excsave_1 = orig a3 + * * We return to the instruction in user space that caused the window * underflow exception. Therefore, we change window base to the value * before we entered the window underflow exception and prepare the @@ -252,10 +253,11 @@ ENTRY(_DoubleExceptionVector) * by changing depc (in a0). * Note: We can trash the current window frame (a0...a3) and depc! */ - +_DoubleExceptionVector_WindowUnderflow: + xsr a3, excsave1 wsr a2, depc # save stack pointer temporarily rsr a0, ps - extui a0, a0, PS_OWB_SHIFT, 4 + extui a0, a0, PS_OWB_SHIFT, PS_OWB_WIDTH wsr a0, windowbase rsync @@ -263,28 +265,57 @@ ENTRY(_DoubleExceptionVector) xsr a2, depc # save a2 and get stack pointer s32i a0, a2, PT_AREG0 - - wsr a3, excsave1 # save a3 - l32r a3, .Lexc_table - + xsr a3, excsave1 rsr a0, exccause s32i a0, a2, PT_DEPC # mark it as a regular exception addx4 a0, a0, a3 + xsr a3, excsave1 l32i a0, a0, EXC_TABLE_FAST_USER jx a0 -.Lfixup:/* Check for a fixup handler or if we were in a critical section. */ + /* + * We only allow the ITLB miss exception if we are in kernel space. + * All other exceptions are unexpected and thus unrecoverable! + */ + +#ifdef CONFIG_MMU + .extern fast_second_level_miss_double_kernel + +.Lksp: /* a0: a0, a1: a1, a2: a2, a3: trashed, depc: depc, excsave: a3 */ + + rsr a3, exccause + beqi a3, EXCCAUSE_ITLB_MISS, 1f + addi a3, a3, -EXCCAUSE_DTLB_MISS + bnez a3, .Lunrecoverable +1: movi a3, fast_second_level_miss_double_kernel + jx a3 +#else +.equ .Lksp, .Lunrecoverable +#endif + + /* Critical! We can't handle this situation. PANIC! */ - /* a0: depc, a1: a1, a2: a2, a3: trashed, depc: a0, excsave1: a3 */ + .extern unrecoverable_exception - l32r a3, .Lexc_table - s32i a2, a3, EXC_TABLE_DOUBLE_SAVE # temporary variable +.Lunrecoverable_fixup: + l32i a2, a3, EXC_TABLE_DOUBLE_SAVE + xsr a0, depc + +.Lunrecoverable: + rsr a3, excsave1 + wsr a0, excsave1 + movi a0, unrecoverable_exception + callx0 a0 + +.Lfixup:/* Check for a fixup handler or if we were in a critical section. */ + + /* a0: depc, a1: a1, a2: trash, a3: exctable, depc: a0, excsave1: a3 */ /* Enter critical section. */ l32i a2, a3, EXC_TABLE_FIXUP s32i a3, a3, EXC_TABLE_FIXUP - beq a2, a3, .Lunrecoverable_fixup # critical! + beq a2, a3, .Lunrecoverable_fixup # critical section beqz a2, .Ldflt # no handler was registered /* a0: depc, a1: a1, a2: trash, a3: exctable, depc: a0, excsave: a3 */ @@ -293,58 +324,145 @@ ENTRY(_DoubleExceptionVector) .Ldflt: /* Get stack pointer. */ - l32i a3, a3, EXC_TABLE_DOUBLE_SAVE - addi a2, a3, -PT_USER_SIZE - -.Lovfl: /* Jump to default handlers. */ + l32i a2, a3, EXC_TABLE_DOUBLE_SAVE + addi a2, a2, -PT_USER_SIZE - /* a0: depc, a1: a1, a2: kstk, a3: a2, depc: a0, excsave: a3 */ + /* a0: depc, a1: a1, a2: kstk, a3: exctable, depc: a0, excsave: a3 */ - xsr a3, depc s32i a0, a2, PT_DEPC - s32i a3, a2, PT_AREG0 + l32i a0, a3, EXC_TABLE_DOUBLE_SAVE + xsr a0, depc + s32i a0, a2, PT_AREG0 - /* a0: avail, a1: a1, a2: kstk, a3: avail, depc: a2, excsave: a3 */ + /* a0: avail, a1: a1, a2: kstk, a3: exctable, depc: a2, excsave: a3 */ - l32r a3, .Lexc_table rsr a0, exccause addx4 a0, a0, a3 + xsr a3, excsave1 l32i a0, a0, EXC_TABLE_FAST_USER jx a0 /* - * We only allow the ITLB miss exception if we are in kernel space. - * All other exceptions are unexpected and thus unrecoverable! + * Restart window OVERFLOW exception. + * Currently: + * depc = orig a0, + * a0 = orig DEPC, + * a2 = new sp based on KSTK from exc_table + * a3 = EXCSAVE_1 + * excsave_1 = orig a3 + * + * We return to the instruction in user space that caused the window + * overflow exception. Therefore, we change window base to the value + * before we entered the window overflow exception and prepare the + * registers to return as if we were coming from a regular exception + * by changing DEPC (in a0). + * + * NOTE: We CANNOT trash the current window frame (a0...a3), but we + * can clobber depc. + * + * The tricky part here is that overflow8 and overflow12 handlers + * save a0, then clobber a0. To restart the handler, we have to restore + * a0 if the double exception was past the point where a0 was clobbered. + * + * To keep things simple, we take advantage of the fact all overflow + * handlers save a0 in their very first instruction. If DEPC was past + * that instruction, we can safely restore a0 from where it was saved + * on the stack. + * + * a0: depc, a1: a1, a2: kstk, a3: exc_table, depc: a0, excsave1: a3 */ +_DoubleExceptionVector_WindowOverflow: + extui a2, a0, 0, 6 # get offset into 64-byte vector handler + beqz a2, 1f # if at start of vector, don't restore -#ifdef CONFIG_MMU - .extern fast_second_level_miss_double_kernel + addi a0, a0, -128 + bbsi a0, 8, 1f # don't restore except for overflow 8 and 12 + bbsi a0, 7, 2f -.Lksp: /* a0: a0, a1: a1, a2: a2, a3: trashed, depc: depc, excsave: a3 */ + /* + * Restore a0 as saved by _WindowOverflow8(). + * + * FIXME: we really need a fixup handler for this L32E, + * for the extremely unlikely case where the overflow handler's + * reference thru a0 gets a hardware TLB refill that bumps out + * the (distinct, aliasing) TLB entry that mapped its prior + * references thru a9, and where our reference now thru a9 + * gets a 2nd-level miss exception (not hardware TLB refill). + */ - rsr a3, exccause - beqi a3, EXCCAUSE_ITLB_MISS, 1f - addi a3, a3, -EXCCAUSE_DTLB_MISS - bnez a3, .Lunrecoverable -1: movi a3, fast_second_level_miss_double_kernel - jx a3 -#else -.equ .Lksp, .Lunrecoverable -#endif + l32e a2, a9, -16 + wsr a2, depc # replace the saved a0 + j 1f - /* Critical! We can't handle this situation. PANIC! */ +2: + /* + * Restore a0 as saved by _WindowOverflow12(). + * + * FIXME: we really need a fixup handler for this L32E, + * for the extremely unlikely case where the overflow handler's + * reference thru a0 gets a hardware TLB refill that bumps out + * the (distinct, aliasing) TLB entry that mapped its prior + * references thru a13, and where our reference now thru a13 + * gets a 2nd-level miss exception (not hardware TLB refill). + */ - .extern unrecoverable_exception + l32e a2, a13, -16 + wsr a2, depc # replace the saved a0 +1: + /* + * Restore WindowBase while leaving all address registers restored. + * We have to use ROTW for this, because WSR.WINDOWBASE requires + * an address register (which would prevent restore). + * + * Window Base goes from 0 ... 7 (Module 8) + * Window Start is 8 bits; Ex: (0b1010 1010):0x55 from series of call4s + */ + + rsr a0, ps + extui a0, a0, PS_OWB_SHIFT, PS_OWB_WIDTH + rsr a2, windowbase + sub a0, a2, a0 + extui a0, a0, 0, 3 -.Lunrecoverable_fixup: l32i a2, a3, EXC_TABLE_DOUBLE_SAVE - xsr a0, depc + xsr a3, excsave1 + beqi a0, 1, .L1pane + beqi a0, 3, .L3pane -.Lunrecoverable: - rsr a3, excsave1 - wsr a0, excsave1 - movi a0, unrecoverable_exception - callx0 a0 + rsr a0, depc + rotw -2 + + /* + * We are now in the user code's original window frame. + * Process the exception as a user exception as if it was + * taken by the user code. + * + * This is similar to the user exception vector, + * except that PT_DEPC isn't set to EXCCAUSE. + */ +1: + xsr a3, excsave1 + wsr a2, depc + l32i a2, a3, EXC_TABLE_KSTK + s32i a0, a2, PT_AREG0 + rsr a0, exccause + + s32i a0, a2, PT_DEPC + + addx4 a0, a0, a3 + l32i a0, a0, EXC_TABLE_FAST_USER + xsr a3, excsave1 + jx a0 + +.L1pane: + rsr a0, depc + rotw -1 + j 1b + +.L3pane: + rsr a0, depc + rotw -3 + j 1b .end literal_prefix |