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Diffstat (limited to 'arch/xtensa/kernel/entry.S')
| -rw-r--r-- | arch/xtensa/kernel/entry.S | 1996 |
1 files changed, 1996 insertions, 0 deletions
diff --git a/arch/xtensa/kernel/entry.S b/arch/xtensa/kernel/entry.S new file mode 100644 index 00000000000000..c64a01f71de692 --- /dev/null +++ b/arch/xtensa/kernel/entry.S @@ -0,0 +1,1996 @@ +/* + * arch/xtensa/kernel/entry.S + * + * Low-level exception handling + * + * This file is subject to the terms and conditions of the GNU General Public + * License. See the file "COPYING" in the main directory of this archive + * for more details. + * + * Copyright (C) 2004-2005 by Tensilica Inc. + * + * Chris Zankel <chris@zankel.net> + * + */ + +#include <linux/linkage.h> +#include <asm/offsets.h> +#include <asm/processor.h> +#include <asm/thread_info.h> +#include <asm/uaccess.h> +#include <asm/unistd.h> +#include <asm/ptrace.h> +#include <asm/current.h> +#include <asm/pgtable.h> +#include <asm/page.h> +#include <asm/signal.h> +#include <xtensa/coreasm.h> + +/* Unimplemented features. */ + +#undef SIGNAL_HANDLING_IN_DOUBLE_EXCEPTION +#undef KERNEL_STACK_OVERFLOW_CHECK +#undef PREEMPTIBLE_KERNEL +#undef ALLOCA_EXCEPTION_IN_IRAM + +/* Not well tested. + * + * - fast_coprocessor + */ + +/* + * Macro to find first bit set in WINDOWBASE from the left + 1 + * + * 100....0 -> 1 + * 010....0 -> 2 + * 000....1 -> WSBITS + */ + + .macro ffs_ws bit mask + +#if XCHAL_HAVE_NSA + nsau \bit, \mask # 32-WSBITS ... 31 (32 iff 0) + addi \bit, \bit, WSBITS - 32 + 1 # uppest bit set -> return 1 +#else + movi \bit, WSBITS +#if WSBITS > 16 + _bltui \mask, 0x10000, 99f + addi \bit, \bit, -16 + extui \mask, \mask, 16, 16 +#endif +#if WSBITS > 8 +99: _bltui \mask, 0x100, 99f + addi \bit, \bit, -8 + srli \mask, \mask, 8 +#endif +99: _bltui \mask, 0x10, 99f + addi \bit, \bit, -4 + srli \mask, \mask, 4 +99: _bltui \mask, 0x4, 99f + addi \bit, \bit, -2 + srli \mask, \mask, 2 +99: _bltui \mask, 0x2, 99f + addi \bit, \bit, -1 +99: + +#endif + .endm + +/* ----------------- DEFAULT FIRST LEVEL EXCEPTION HANDLERS ----------------- */ + +/* + * First-level exception handler for user exceptions. + * Save some special registers, extra states and all registers in the AR + * register file that were in use in the user task, and jump to the common + * exception code. + * We save SAR (used to calculate WMASK), and WB and WS (we don't have to + * save them for kernel exceptions). + * + * Entry condition for user_exception: + * + * a0: trashed, original value saved on stack (PT_AREG0) + * a1: a1 + * a2: new stack pointer, original value in depc + * a3: dispatch table + * depc: a2, original value saved on stack (PT_DEPC) + * excsave1: a3 + * + * PT_DEPC >= VALID_DOUBLE_EXCEPTION_ADDRESS: double exception, DEPC + * < VALID_DOUBLE_EXCEPTION_ADDRESS: regular exception + * + * Entry condition for _user_exception: + * + * a0-a3 and depc have been saved to PT_AREG0...PT_AREG3 and PT_DEPC + * excsave has been restored, and + * stack pointer (a1) has been set. + * + * Note: _user_exception might be at an odd adress. Don't use call0..call12 + */ + +ENTRY(user_exception) + + /* Save a2, a3, and depc, restore excsave_1 and set SP. */ + + xsr a3, EXCSAVE_1 + rsr a0, DEPC + s32i a1, a2, PT_AREG1 + s32i a0, a2, PT_AREG2 + s32i a3, a2, PT_AREG3 + mov a1, a2 + + .globl _user_exception +_user_exception: + + /* Save SAR and turn off single stepping */ + + movi a2, 0 + rsr a3, SAR + wsr a2, ICOUNTLEVEL + s32i a3, a1, PT_SAR + + /* Rotate ws so that the current windowbase is at bit0. */ + /* Assume ws = xxwww1yyyy. Rotate ws right, so that a2 = yyyyxxwww1 */ + + rsr a2, WINDOWBASE + rsr a3, WINDOWSTART + ssr a2 + s32i a2, a1, PT_WINDOWBASE + s32i a3, a1, PT_WINDOWSTART + slli a2, a3, 32-WSBITS + src a2, a3, a2 + srli a2, a2, 32-WSBITS + s32i a2, a1, PT_WMASK # needed for restoring registers + + /* Save only live registers. */ + + _bbsi.l a2, 1, 1f + s32i a4, a1, PT_AREG4 + s32i a5, a1, PT_AREG5 + s32i a6, a1, PT_AREG6 + s32i a7, a1, PT_AREG7 + _bbsi.l a2, 2, 1f + s32i a8, a1, PT_AREG8 + s32i a9, a1, PT_AREG9 + s32i a10, a1, PT_AREG10 + s32i a11, a1, PT_AREG11 + _bbsi.l a2, 3, 1f + s32i a12, a1, PT_AREG12 + s32i a13, a1, PT_AREG13 + s32i a14, a1, PT_AREG14 + s32i a15, a1, PT_AREG15 + _bnei a2, 1, 1f # only one valid frame? + + /* Only one valid frame, skip saving regs. */ + + j 2f + + /* Save the remaining registers. + * We have to save all registers up to the first '1' from + * the right, except the current frame (bit 0). + * Assume a2 is: 001001000110001 + * All regiser frames starting from the top fiel to the marked '1' + * must be saved. + */ + +1: addi a3, a2, -1 # eliminate '1' in bit 0: yyyyxxww0 + neg a3, a3 # yyyyxxww0 -> YYYYXXWW1+1 + and a3, a3, a2 # max. only one bit is set + + /* Find number of frames to save */ + + ffs_ws a0, a3 # number of frames to the '1' from left + + /* Store information into WMASK: + * bits 0..3: xxx1 masked lower 4 bits of the rotated windowstart, + * bits 4...: number of valid 4-register frames + */ + + slli a3, a0, 4 # number of frames to save in bits 8..4 + extui a2, a2, 0, 4 # mask for the first 16 registers + or a2, a3, a2 + s32i a2, a1, PT_WMASK # needed when we restore the reg-file + + /* Save 4 registers at a time */ + +1: rotw -1 + s32i a0, a5, PT_AREG_END - 16 + s32i a1, a5, PT_AREG_END - 12 + s32i a2, a5, PT_AREG_END - 8 + s32i a3, a5, PT_AREG_END - 4 + addi a0, a4, -1 + addi a1, a5, -16 + _bnez a0, 1b + + /* WINDOWBASE still in SAR! */ + + rsr a2, SAR # original WINDOWBASE + movi a3, 1 + ssl a2 + sll a3, a3 + wsr a3, WINDOWSTART # set corresponding WINDOWSTART bit + wsr a2, WINDOWBASE # and WINDOWSTART + rsync + + /* We are back to the original stack pointer (a1) */ + +2: +#if XCHAL_EXTRA_SA_SIZE + + /* For user exceptions, save the extra state into the user's TCB. + * Note: We must assume that xchal_extra_store_funcbody destroys a2..a15 + */ + + GET_CURRENT(a2,a1) + addi a2, a2, THREAD_CP_SAVE + xchal_extra_store_funcbody +#endif + + /* Now, jump to the common exception handler. */ + + j common_exception + + +/* + * First-level exit handler for kernel exceptions + * Save special registers and the live window frame. + * Note: Even though we changes the stack pointer, we don't have to do a + * MOVSP here, as we do that when we return from the exception. + * (See comment in the kernel exception exit code) + * + * Entry condition for kernel_exception: + * + * a0: trashed, original value saved on stack (PT_AREG0) + * a1: a1 + * a2: new stack pointer, original in DEPC + * a3: dispatch table + * depc: a2, original value saved on stack (PT_DEPC) + * excsave_1: a3 + * + * PT_DEPC >= VALID_DOUBLE_EXCEPTION_ADDRESS: double exception, DEPC + * < VALID_DOUBLE_EXCEPTION_ADDRESS: regular exception + * + * Entry condition for _kernel_exception: + * + * a0-a3 and depc have been saved to PT_AREG0...PT_AREG3 and PT_DEPC + * excsave has been restored, and + * stack pointer (a1) has been set. + * + * Note: _kernel_exception might be at an odd adress. Don't use call0..call12 + */ + +ENTRY(kernel_exception) + + /* Save a0, a2, a3, DEPC and set SP. */ + + xsr a3, EXCSAVE_1 # restore a3, excsave_1 + rsr a0, DEPC # get a2 + s32i a1, a2, PT_AREG1 + s32i a0, a2, PT_AREG2 + s32i a3, a2, PT_AREG3 + mov a1, a2 + + .globl _kernel_exception +_kernel_exception: + + /* Save SAR and turn off single stepping */ + + movi a2, 0 + rsr a3, SAR + wsr a2, ICOUNTLEVEL + s32i a3, a1, PT_SAR + + /* Rotate ws so that the current windowbase is at bit0. */ + /* Assume ws = xxwww1yyyy. Rotate ws right, so that a2 = yyyyxxwww1 */ + + rsr a2, WINDOWBASE # don't need to save these, we only + rsr a3, WINDOWSTART # need shifted windowstart: windowmask + ssr a2 + slli a2, a3, 32-WSBITS + src a2, a3, a2 + srli a2, a2, 32-WSBITS + s32i a2, a1, PT_WMASK # needed for kernel_exception_exit + + /* Save only the live window-frame */ + + _bbsi.l a2, 1, 1f + s32i a4, a1, PT_AREG4 + s32i a5, a1, PT_AREG5 + s32i a6, a1, PT_AREG6 + s32i a7, a1, PT_AREG7 + _bbsi.l a2, 2, 1f + s32i a8, a1, PT_AREG8 + s32i a9, a1, PT_AREG9 + s32i a10, a1, PT_AREG10 + s32i a11, a1, PT_AREG11 + _bbsi.l a2, 3, 1f + s32i a12, a1, PT_AREG12 + s32i a13, a1, PT_AREG13 + s32i a14, a1, PT_AREG14 + s32i a15, a1, PT_AREG15 + +1: + +#ifdef KERNEL_STACK_OVERFLOW_CHECK + + /* Stack overflow check, for debugging */ + extui a2, a1, TASK_SIZE_BITS,XX + movi a3, SIZE?? + _bge a2, a3, out_of_stack_panic + +#endif + +/* + * This is the common exception handler. + * We get here from the user exception handler or simply by falling through + * from the kernel exception handler. + * Save the remaining special registers, switch to kernel mode, and jump + * to the second-level exception handler. + * + */ + +common_exception: + + /* Save EXCVADDR, DEBUGCAUSE, and PC, and clear LCOUNT */ + + rsr a2, DEBUGCAUSE + rsr a3, EPC_1 + s32i a2, a1, PT_DEBUGCAUSE + s32i a3, a1, PT_PC + + rsr a3, EXCVADDR + movi a2, 0 + s32i a3, a1, PT_EXCVADDR + xsr a2, LCOUNT + s32i a2, a1, PT_LCOUNT + + /* It is now save to restore the EXC_TABLE_FIXUP variable. */ + + rsr a0, EXCCAUSE + movi a3, 0 + rsr a2, EXCSAVE_1 + s32i a0, a1, PT_EXCCAUSE + s32i a3, a2, EXC_TABLE_FIXUP + + /* All unrecoverable states are saved on stack, now, and a1 is valid, + * so we can allow exceptions and interrupts (*) again. + * Set PS(EXCM = 0, UM = 0, RING = 0, OWB = 0, WOE = 1, INTLEVEL = X) + * + * (*) We only allow interrupts if PS.INTLEVEL was not set to 1 before + * (interrupts disabled) and if this exception is not an interrupt. + */ + + rsr a3, PS + addi a0, a0, -4 + movi a2, 1 + extui a3, a3, 0, 1 # a3 = PS.INTLEVEL[0] + moveqz a3, a2, a0 # a3 = 1 iff interrupt exception + movi a2, PS_WOE_MASK + or a3, a3, a2 + rsr a0, EXCCAUSE + xsr a3, PS + + s32i a3, a1, PT_PS # save ps + + /* Save LBEG, LEND */ + + rsr a2, LBEG + rsr a3, LEND + s32i a2, a1, PT_LBEG + s32i a3, a1, PT_LEND + + /* Go to second-level dispatcher. Set up parameters to pass to the + * exception handler and call the exception handler. + */ + + movi a4, exc_table + mov a6, a1 # pass stack frame + mov a7, a0 # pass EXCCAUSE + addx4 a4, a0, a4 + l32i a4, a4, EXC_TABLE_DEFAULT # load handler + + /* Call the second-level handler */ + + callx4 a4 + + /* Jump here for exception exit */ + +common_exception_return: + + /* Jump if we are returning from kernel exceptions. */ + +1: l32i a3, a1, PT_PS + _bbsi.l a3, PS_UM_SHIFT, 2f + j kernel_exception_exit + + /* Specific to a user exception exit: + * We need to check some flags for signal handling and rescheduling, + * and have to restore WB and WS, extra states, and all registers + * in the register file that were in use in the user task. + */ + +2: wsr a3, PS /* disable interrupts */ + + /* Check for signals (keep interrupts disabled while we read TI_FLAGS) + * Note: PS.INTLEVEL = 0, PS.EXCM = 1 + */ + + GET_THREAD_INFO(a2,a1) + l32i a4, a2, TI_FLAGS + + /* Enable interrupts again. + * Note: When we get here, we certainly have handled any interrupts. + * (Hint: There is only one user exception frame on stack) + */ + + movi a3, PS_WOE_MASK + + _bbsi.l a4, TIF_NEED_RESCHED, 3f + _bbci.l a4, TIF_SIGPENDING, 4f + +#ifndef SIGNAL_HANDLING_IN_DOUBLE_EXCEPTION + l32i a4, a1, PT_DEPC + bgeui a4, VALID_DOUBLE_EXCEPTION_ADDRESS, 4f +#endif + + /* Reenable interrupts and call do_signal() */ + + wsr a3, PS + movi a4, do_signal # int do_signal(struct pt_regs*, sigset_t*) + mov a6, a1 + movi a7, 0 + callx4 a4 + j 1b + +3: /* Reenable interrupts and reschedule */ + + wsr a3, PS + movi a4, schedule # void schedule (void) + callx4 a4 + j 1b + + /* Restore the state of the task and return from the exception. */ + + + /* If we are returning from a user exception, and the process + * to run next has PT_SINGLESTEP set, we want to setup + * ICOUNT and ICOUNTLEVEL to step one instruction. + * PT_SINGLESTEP is set by sys_ptrace (ptrace.c) + */ + +4: /* a2 holds GET_CURRENT(a2,a1) */ + + l32i a3, a2, TI_TASK + l32i a3, a3, TASK_PTRACE + bbci.l a3, PT_SINGLESTEP_BIT, 1f # jump if single-step flag is not set + + movi a3, -2 # PT_SINGLESTEP flag is set, + movi a4, 1 # icountlevel of 1 means it won't + wsr a3, ICOUNT # start counting until after rfe + wsr a4, ICOUNTLEVEL # so setup icount & icountlevel. + isync + +1: + +#if XCHAL_EXTRA_SA_SIZE + + /* For user exceptions, restore the extra state from the user's TCB. */ + + /* Note: a2 still contains GET_CURRENT(a2,a1) */ + addi a2, a2, THREAD_CP_SAVE + xchal_extra_load_funcbody + + /* We must assume that xchal_extra_store_funcbody destroys + * registers a2..a15. FIXME, this list can eventually be + * reduced once real register requirements of the macro are + * finalized. */ + +#endif /* XCHAL_EXTRA_SA_SIZE */ + + + /* Switch to the user thread WINDOWBASE. Save SP temporarily in DEPC */ + + l32i a2, a1, PT_WINDOWBASE + l32i a3, a1, PT_WINDOWSTART + wsr a1, DEPC # use DEPC as temp storage + wsr a3, WINDOWSTART # restore WINDOWSTART + ssr a2 # preserve user's WB in the SAR + wsr a2, WINDOWBASE # switch to user's saved WB + rsync + rsr a1, DEPC # restore stack pointer + l32i a2, a1, PT_WMASK # register frames saved (in bits 4...9) + rotw -1 # we restore a4..a7 + _bltui a6, 16, 1f # only have to restore current window? + + /* The working registers are a0 and a3. We are restoring to + * a4..a7. Be careful not to destroy what we have just restored. + * Note: wmask has the format YYYYM: + * Y: number of registers saved in groups of 4 + * M: 4 bit mask of first 16 registers + */ + + mov a2, a6 + mov a3, a5 + +2: rotw -1 # a0..a3 become a4..a7 + addi a3, a7, -4*4 # next iteration + addi a2, a6, -16 # decrementing Y in WMASK + l32i a4, a3, PT_AREG_END + 0 + l32i a5, a3, PT_AREG_END + 4 + l32i a6, a3, PT_AREG_END + 8 + l32i a7, a3, PT_AREG_END + 12 + _bgeui a2, 16, 2b + + /* Clear unrestored registers (don't leak anything to user-land */ + +1: rsr a0, WINDOWBASE + rsr a3, SAR + sub a3, a0, a3 + beqz a3, 2f + extui a3, a3, 0, WBBITS + +1: rotw -1 + addi a3, a7, -1 + movi a4, 0 + movi a5, 0 + movi a6, 0 + movi a7, 0 + bgei a3, 1, 1b + + /* We are back were we were when we started. + * Note: a2 still contains WMASK (if we've returned to the original + * frame where we had loaded a2), or at least the lower 4 bits + * (if we have restored WSBITS-1 frames). + */ + +2: j common_exception_exit + + /* This is the kernel exception exit. + * We avoided to do a MOVSP when we entered the exception, but we + * have to do it here. + */ + +kernel_exception_exit: + + /* Disable interrupts (a3 holds PT_PS) */ + + wsr a3, PS + +#ifdef PREEMPTIBLE_KERNEL + +#ifdef CONFIG_PREEMPT + + /* + * Note: We've just returned from a call4, so we have + * at least 4 addt'l regs. + */ + + /* Check current_thread_info->preempt_count */ + + GET_THREAD_INFO(a2) + l32i a3, a2, TI_PREEMPT + bnez a3, 1f + + l32i a2, a2, TI_FLAGS + +1: + +#endif + +#endif + + /* Check if we have to do a movsp. + * + * We only have to do a movsp if the previous window-frame has + * been spilled to the *temporary* exception stack instead of the + * task's stack. This is the case if the corresponding bit in + * WINDOWSTART for the previous window-frame was set before + * (not spilled) but is zero now (spilled). + * If this bit is zero, all other bits except the one for the + * current window frame are also zero. So, we can use a simple test: + * 'and' WINDOWSTART and WINDOWSTART-1: + * + * (XXXXXX1[0]* - 1) AND XXXXXX1[0]* = XXXXXX0[0]* + * + * The result is zero only if one bit was set. + * + * (Note: We might have gone through several task switches before + * we come back to the current task, so WINDOWBASE might be + * different from the time the exception occurred.) + */ + + /* Test WINDOWSTART before and after the exception. + * We actually have WMASK, so we only have to test if it is 1 or not. + */ + + l32i a2, a1, PT_WMASK + _beqi a2, 1, common_exception_exit # Spilled before exception,jump + + /* Test WINDOWSTART now. If spilled, do the movsp */ + + rsr a3, WINDOWSTART + addi a0, a3, -1 + and a3, a3, a0 + _bnez a3, common_exception_exit + + /* Do a movsp (we returned from a call4, so we have at least a0..a7) */ + + addi a0, a1, -16 + l32i a3, a0, 0 + l32i a4, a0, 4 + s32i a3, a1, PT_SIZE+0 + s32i a4, a1, PT_SIZE+4 + l32i a3, a0, 8 + l32i a4, a0, 12 + s32i a3, a1, PT_SIZE+8 + s32i a4, a1, PT_SIZE+12 + + /* Common exception exit. + * We restore the special register and the current window frame, and + * return from the exception. + * + * Note: We expect a2 to hold PT_WMASK + */ + +common_exception_exit: + + _bbsi.l a2, 1, 1f + l32i a4, a1, PT_AREG4 + l32i a5, a1, PT_AREG5 + l32i a6, a1, PT_AREG6 + l32i a7, a1, PT_AREG7 + _bbsi.l a2, 2, 1f + l32i a8, a1, PT_AREG8 + l32i a9, a1, PT_AREG9 + l32i a10, a1, PT_AREG10 + l32i a11, a1, PT_AREG11 + _bbsi.l a2, 3, 1f + l32i a12, a1, PT_AREG12 + l32i a13, a1, PT_AREG13 + l32i a14, a1, PT_AREG14 + l32i a15, a1, PT_AREG15 + + /* Restore PC, SAR */ + +1: l32i a2, a1, PT_PC + l32i a3, a1, PT_SAR + wsr a2, EPC_1 + wsr a3, SAR + + /* Restore LBEG, LEND, LCOUNT */ + + l32i a2, a1, PT_LBEG + l32i a3, a1, PT_LEND + wsr a2, LBEG + l32i a2, a1, PT_LCOUNT + wsr a3, LEND + wsr a2, LCOUNT + + /* Check if it was double exception. */ + + l32i a0, a1, PT_DEPC + l32i a3, a1, PT_AREG3 + l32i a2, a1, PT_AREG2 + _bgeui a0, VALID_DOUBLE_EXCEPTION_ADDRESS, 1f + + /* Restore a0...a3 and return */ + + l32i a0, a1, PT_AREG0 + l32i a1, a1, PT_AREG1 + rfe + +1: wsr a0, DEPC + l32i a0, a1, PT_AREG0 + l32i a1, a1, PT_AREG1 + rfde + +/* + * Debug exception handler. + * + * Currently, we don't support KGDB, so only user application can be debugged. + * + * When we get here, a0 is trashed and saved to excsave[debuglevel] + */ + +ENTRY(debug_exception) + + rsr a0, EPS + XCHAL_DEBUGLEVEL + bbsi.l a0, PS_EXCM_SHIFT, 1f # exception mode + + /* Set EPC_1 and EXCCAUSE */ + + wsr a2, DEPC # save a2 temporarily + rsr a2, EPC + XCHAL_DEBUGLEVEL + wsr a2, EPC_1 + + movi a2, EXCCAUSE_MAPPED_DEBUG + wsr a2, EXCCAUSE + + /* Restore PS to the value before the debug exc but with PS.EXCM set.*/ + + movi a2, 1 << PS_EXCM_SHIFT + or a2, a0, a2 + movi a0, debug_exception # restore a3, debug jump vector + wsr a2, PS + xsr a0, EXCSAVE + XCHAL_DEBUGLEVEL + + /* Switch to kernel/user stack, restore jump vector, and save a0 */ + + bbsi.l a2, PS_UM_SHIFT, 2f # jump if user mode + + addi a2, a1, -16-PT_SIZE # assume kernel stack + s32i a0, a2, PT_AREG0 + movi a0, 0 + s32i a1, a2, PT_AREG1 + s32i a0, a2, PT_DEPC # mark it as a regular exception + xsr a0, DEPC + s32i a3, a2, PT_AREG3 + s32i a0, a2, PT_AREG2 + mov a1, a2 + j _kernel_exception + +2: rsr a2, EXCSAVE_1 + l32i a2, a2, EXC_TABLE_KSTK # load kernel stack pointer + s32i a0, a2, PT_AREG0 + movi a0, 0 + s32i a1, a2, PT_AREG1 + s32i a0, a2, PT_DEPC + xsr a0, DEPC + s32i a3, a2, PT_AREG3 + s32i a0, a2, PT_AREG2 + mov a1, a2 + j _user_exception + + /* Debug exception while in exception mode. */ +1: j 1b // FIXME!! + + +/* + * We get here in case of an unrecoverable exception. + * The only thing we can do is to be nice and print a panic message. + * We only produce a single stack frame for panic, so ??? + * + * + * Entry conditions: + * + * - a0 contains the caller address; original value saved in excsave1. + * - the original a0 contains a valid return address (backtrace) or 0. + * - a2 contains a valid stackpointer + * + * Notes: + * + * - If the stack pointer could be invalid, the caller has to setup a + * dummy stack pointer (e.g. the stack of the init_task) + * + * - If the return address could be invalid, the caller has to set it + * to 0, so the backtrace would stop. + * + */ + .align 4 +unrecoverable_text: + .ascii "Unrecoverable error in exception handler\0" + +ENTRY(unrecoverable_exception) + + movi a0, 1 + movi a1, 0 + + wsr a0, WINDOWSTART + wsr a1, WINDOWBASE + rsync + + movi a1, PS_WOE_MASK | 1 + wsr a1, PS + rsync + + movi a1, init_task + movi a0, 0 + addi a1, a1, PT_REGS_OFFSET + + movi a4, panic + movi a6, unrecoverable_text + + callx4 a4 + +1: j 1b + + +/* -------------------------- FAST EXCEPTION HANDLERS ----------------------- */ + +/* + * Fast-handler for alloca exceptions + * + * The ALLOCA handler is entered when user code executes the MOVSP + * instruction and the caller's frame is not in the register file. + * In this case, the caller frame's a0..a3 are on the stack just + * below sp (a1), and this handler moves them. + * + * For "MOVSP <ar>,<as>" without destination register a1, this routine + * simply moves the value from <as> to <ar> without moving the save area. + * + * Entry condition: + * + * a0: trashed, original value saved on stack (PT_AREG0) + * a1: a1 + * a2: new stack pointer, original in DEPC + * a3: dispatch table + * depc: a2, original value saved on stack (PT_DEPC) + * excsave_1: a3 + * + * PT_DEPC >= VALID_DOUBLE_EXCEPTION_ADDRESS: double exception, DEPC + * < VALID_DOUBLE_EXCEPTION_ADDRESS: regular exception + */ + +#if XCHAL_HAVE_BE +#define _EXTUI_MOVSP_SRC(ar) extui ar, ar, 4, 4 +#define _EXTUI_MOVSP_DST(ar) extui ar, ar, 0, 4 +#else +#define _EXTUI_MOVSP_SRC(ar) extui ar, ar, 0, 4 +#define _EXTUI_MOVSP_DST(ar) extui ar, ar, 4, 4 +#endif + +ENTRY(fast_alloca) + + /* We shouldn't be in a double exception. */ + + l32i a0, a2, PT_DEPC + _bgeui a0, VALID_DOUBLE_EXCEPTION_ADDRESS, .Lunhandled_double + + rsr a0, DEPC # get a2 + s32i a4, a2, PT_AREG4 # save a4 and + s32i a0, a2, PT_AREG2 # a2 to stack + + /* Exit critical section. */ + + movi a0, 0 + s32i a0, a3, EXC_TABLE_FIXUP + + /* Restore a3, excsave_1 */ + + xsr a3, EXCSAVE_1 # make sure excsave_1 is valid for dbl. + rsr a4, EPC_1 # get exception address + s32i a3, a2, PT_AREG3 # save a3 to stack + +#ifdef ALLOCA_EXCEPTION_IN_IRAM +#error iram not supported +#else + /* Note: l8ui not allowed in IRAM/IROM!! */ + l8ui a0, a4, 1 # read as(src) from MOVSP instruction +#endif + movi a3, .Lmovsp_src + _EXTUI_MOVSP_SRC(a0) # extract source register number + addx8 a3, a0, a3 + jx a3 + +.Lunhandled_double: + wsr a0, EXCSAVE_1 + movi a0, unrecoverable_exception + callx0 a0 + + .align 8 +.Lmovsp_src: + l32i a3, a2, PT_AREG0; _j 1f; .align 8 + mov a3, a1; _j 1f; .align 8 + l32i a3, a2, PT_AREG2; _j 1f; .align 8 + l32i a3, a2, PT_AREG3; _j 1f; .align 8 + l32i a3, a2, PT_AREG4; _j 1f; .align 8 + mov a3, a5; _j 1f; .align 8 + mov a3, a6; _j 1f; .align 8 + mov a3, a7; _j 1f; .align 8 + mov a3, a8; _j 1f; .align 8 + mov a3, a9; _j 1f; .align 8 + mov a3, a10; _j 1f; .align 8 + mov a3, a11; _j 1f; .align 8 + mov a3, a12; _j 1f; .align 8 + mov a3, a13; _j 1f; .align 8 + mov a3, a14; _j 1f; .align 8 + mov a3, a15; _j 1f; .align 8 + +1: + +#ifdef ALLOCA_EXCEPTION_IN_IRAM +#error iram not supported +#else + l8ui a0, a4, 0 # read ar(dst) from MOVSP instruction +#endif + addi a4, a4, 3 # step over movsp + _EXTUI_MOVSP_DST(a0) # extract destination register + wsr a4, EPC_1 # save new epc_1 + + _bnei a0, 1, 1f # no 'movsp a1, ax': jump + + /* Move the save area. This implies the use of the L32E + * and S32E instructions, because this move must be done with + * the user's PS.RING privilege levels, not with ring 0 + * (kernel's) privileges currently active with PS.EXCM + * set. Note that we have stil registered a fixup routine with the + * double exception vector in case a double exception occurs. + */ + + /* a0,a4:avail a1:old user stack a2:exc. stack a3:new user stack. */ + + l32e a0, a1, -16 + l32e a4, a1, -12 + s32e a0, a3, -16 + s32e a4, a3, -12 + l32e a0, a1, -8 + l32e a4, a1, -4 + s32e a0, a3, -8 + s32e a4, a3, -4 + + /* Restore stack-pointer and all the other saved registers. */ + + mov a1, a3 + + l32i a4, a2, PT_AREG4 + l32i a3, a2, PT_AREG3 + l32i a0, a2, PT_AREG0 + l32i a2, a2, PT_AREG2 + rfe + + /* MOVSP <at>,<as> was invoked with <at> != a1. + * Because the stack pointer is not being modified, + * we should be able to just modify the pointer + * without moving any save area. + * The processor only traps these occurrences if the + * caller window isn't live, so unfortunately we can't + * use this as an alternate trap mechanism. + * So we just do the move. This requires that we + * resolve the destination register, not just the source, + * so there's some extra work. + * (PERHAPS NOT REALLY NEEDED, BUT CLEANER...) + */ + + /* a0 dst-reg, a1 user-stack, a2 stack, a3 value of src reg. */ + +1: movi a4, .Lmovsp_dst + addx8 a4, a0, a4 + jx a4 + + .align 8 +.Lmovsp_dst: + s32i a3, a2, PT_AREG0; _j 1f; .align 8 + mov a1, a3; _j 1f; .align 8 + s32i a3, a2, PT_AREG2; _j 1f; .align 8 + s32i a3, a2, PT_AREG3; _j 1f; .align 8 + s32i a3, a2, PT_AREG4; _j 1f; .align 8 + mov a5, a3; _j 1f; .align 8 + mov a6, a3; _j 1f; .align 8 + mov a7, a3; _j 1f; .align 8 + mov a8, a3; _j 1f; .align 8 + mov a9, a3; _j 1f; .align 8 + mov a10, a3; _j 1f; .align 8 + mov a11, a3; _j 1f; .align 8 + mov a12, a3; _j 1f; .align 8 + mov a13, a3; _j 1f; .align 8 + mov a14, a3; _j 1f; .align 8 + mov a15, a3; _j 1f; .align 8 + +1: l32i a4, a2, PT_AREG4 + l32i a3, a2, PT_AREG3 + l32i a0, a2, PT_AREG0 + l32i a2, a2, PT_AREG2 + rfe + + +/* + * fast system calls. + * + * WARNING: The kernel doesn't save the entire user context before + * handling a fast system call. These functions are small and short, + * usually offering some functionality not available to user tasks. + * + * BE CAREFUL TO PRESERVE THE USER'S CONTEXT. + * + * Entry condition: + * + * a0: trashed, original value saved on stack (PT_AREG0) + * a1: a1 + * a2: new stack pointer, original in DEPC + * a3: dispatch table + * depc: a2, original value saved on stack (PT_DEPC) + * excsave_1: a3 + */ + +ENTRY(fast_syscall_kernel) + + /* Skip syscall. */ + + rsr a0, EPC_1 + addi a0, a0, 3 + wsr a0, EPC_1 + + l32i a0, a2, PT_DEPC + bgeui a0, VALID_DOUBLE_EXCEPTION_ADDRESS, fast_syscall_unrecoverable + + rsr a0, DEPC # get syscall-nr + _beqz a0, fast_syscall_spill_registers + + addi a0, a0, -__NR_sysxtensa + _beqz a0, fast_syscall_sysxtensa + + j kernel_exception + + +ENTRY(fast_syscall_user) + + /* Skip syscall. */ + + rsr a0, EPC_1 + addi a0, a0, 3 + wsr a0, EPC_1 + + l32i a0, a2, PT_DEPC + bgeui a0, VALID_DOUBLE_EXCEPTION_ADDRESS, fast_syscall_unrecoverable + + rsr a0, DEPC # get syscall-nr + _beqz a0, fast_syscall_spill_registers + + addi a0, a0, -__NR_sysxtensa + _beqz a0, fast_syscall_sysxtensa + + j user_exception + +ENTRY(fast_syscall_unrecoverable) + + /* Restore all states. */ + + l32i a0, a2, PT_AREG0 # restore a0 + xsr a2, DEPC # restore a2, depc + rsr a3, EXCSAVE_1 + + wsr a0, EXCSAVE_1 + movi a0, unrecoverable_exception + callx0 a0 + + + +/* + * sysxtensa syscall handler + * + * int sysxtensa (XTENSA_ATOMIC_SET, ptr, val, unused); + * int sysxtensa (XTENSA_ATOMIC_ADD, ptr, val, unused); + * int sysxtensa (XTENSA_ATOMIC_EXG_ADD, ptr, val, unused); + * int sysxtensa (XTENSA_ATOMIC_CMP_SWP, ptr, oldval, newval); + * a2 a6 a3 a4 a5 + * + * Entry condition: + * + * a0: trashed, original value saved on stack (PT_AREG0) + * a1: a1 + * a2: new stack pointer, original in DEPC + * a3: dispatch table + * depc: a2, original value saved on stack (PT_DEPC) + * excsave_1: a3 + * + * PT_DEPC >= VALID_DOUBLE_EXCEPTION_ADDRESS: double exception, DEPC + * < VALID_DOUBLE_EXCEPTION_ADDRESS: regular exception + * + * Note: we don't have to save a2; a2 holds the return value + * + * We use the two macros TRY and CATCH: + * + * TRY adds an entry to the __ex_table fixup table for the immediately + * following instruction. + * + * CATCH catches any exception that occurred at one of the preceeding TRY + * statements and continues from there + * + * Usage TRY l32i a0, a1, 0 + * <other code> + * done: rfe + * CATCH <set return code> + * j done + */ + +#define TRY \ + .section __ex_table, "a"; \ + .word 66f, 67f; \ + .text; \ +66: + +#define CATCH \ +67: + +ENTRY(fast_syscall_sysxtensa) + + _beqz a6, 1f + _blti a6, SYSXTENSA_COUNT, 2f + +1: j user_exception + +2: xsr a3, EXCSAVE_1 # restore a3, excsave1 + s32i a7, a2, PT_AREG7 + + movi a7, 4 # sizeof(unsigned int) + verify_area a3, a7, a0, a2, .Leac + + _beqi a6, SYSXTENSA_ATOMIC_SET, .Lset + _beqi a6, SYSXTENSA_ATOMIC_EXG_ADD, .Lexg + _beqi a6, SYSXTENSA_ATOMIC_ADD, .Ladd + + /* Fall through for SYSXTENSA_ATOMIC_CMP_SWP */ + +.Lswp: /* Atomic compare and swap */ + +TRY l32i a7, a3, 0 # read old value + bne a7, a4, 1f # same as old value? jump + s32i a5, a3, 0 # different, modify value + movi a7, 1 # and return 1 + j .Lret + +1: movi a7, 0 # same values: return 0 + j .Lret + +.Ladd: /* Atomic add */ +.Lexg: /* Atomic (exchange) add */ + +TRY l32i a7, a3, 0 + add a4, a4, a7 + s32i a4, a3, 0 + j .Lret + +.Lset: /* Atomic set */ + +TRY l32i a7, a3, 0 # read old value as return value + s32i a4, a3, 0 # write new value + +.Lret: mov a0, a2 + mov a2, a7 + l32i a7, a0, PT_AREG7 + l32i a3, a0, PT_AREG3 + l32i a0, a0, PT_AREG0 + rfe + +CATCH +.Leac: movi a7, -EFAULT + j .Lret + + + +/* fast_syscall_spill_registers. + * + * Entry condition: + * + * a0: trashed, original value saved on stack (PT_AREG0) + * a1: a1 + * a2: new stack pointer, original in DEPC + * a3: dispatch table + * depc: a2, original value saved on stack (PT_DEPC) + * excsave_1: a3 + * + * Note: We assume the stack pointer is EXC_TABLE_KSTK in the fixup handler. + * Note: We don't need to save a2 in depc (return value) + */ + +ENTRY(fast_syscall_spill_registers) + + /* Register a FIXUP handler (pass current wb as a parameter) */ + + movi a0, fast_syscall_spill_registers_fixup + s32i a0, a3, EXC_TABLE_FIXUP + rsr a0, WINDOWBASE + s32i a0, a3, EXC_TABLE_PARAM + + /* Save a3 and SAR on stack. */ + + rsr a0, SAR + xsr a3, EXCSAVE_1 # restore a3 and excsave_1 + s32i a0, a2, PT_AREG4 # store SAR to PT_AREG4 + s32i a3, a2, PT_AREG3 + + /* The spill routine might clobber a7, a11, and a15. */ + + s32i a7, a2, PT_AREG5 + s32i a11, a2, PT_AREG6 + s32i a15, a2, PT_AREG7 + + call0 _spill_registers # destroys a3, DEPC, and SAR + + /* Advance PC, restore registers and SAR, and return from exception. */ + + l32i a3, a2, PT_AREG4 + l32i a0, a2, PT_AREG0 + wsr a3, SAR + l32i a3, a2, PT_AREG3 + + /* Restore clobbered registers. */ + + l32i a7, a2, PT_AREG5 + l32i a11, a2, PT_AREG6 + l32i a15, a2, PT_AREG7 + + movi a2, 0 + rfe + +/* Fixup handler. + * + * We get here if the spill routine causes an exception, e.g. tlb miss. + * We basically restore WINDOWBASE and WINDOWSTART to the condition when + * we entered the spill routine and jump to the user exception handler. + * + * a0: value of depc, original value in depc + * a2: trashed, original value in EXC_TABLE_DOUBLE_SAVE + * a3: exctable, original value in excsave1 + */ + +fast_syscall_spill_registers_fixup: + + rsr a2, WINDOWBASE # get current windowbase (a2 is saved) + xsr a0, DEPC # restore depc and a0 + ssl a2 # set shift (32 - WB) + + /* We need to make sure the current registers (a0-a3) are preserved. + * To do this, we simply set the bit for the current window frame + * in WS, so that the exception handlers save them to the task stack. + */ + + rsr a3, EXCSAVE_1 # get spill-mask + slli a2, a3, 1 # shift left by one + + slli a3, a2, 32-WSBITS + src a2, a2, a3 # a1 = xxwww1yyxxxwww1yy...... + wsr a2, WINDOWSTART # set corrected windowstart + + movi a3, exc_table + l32i a2, a3, EXC_TABLE_DOUBLE_SAVE # restore a2 + l32i a3, a3, EXC_TABLE_PARAM # original WB (in user task) + + /* Return to the original (user task) WINDOWBASE. + * We leave the following frame behind: + * a0, a1, a2 same + * a3: trashed (saved in excsave_1) + * depc: depc (we have to return to that address) + * excsave_1: a3 + */ + + wsr a3, WINDOWBASE + rsync + + /* We are now in the original frame when we entered _spill_registers: + * a0: return address + * a1: used, stack pointer + * a2: kernel stack pointer + * a3: available, saved in EXCSAVE_1 + * depc: exception address + * excsave: a3 + * Note: This frame might be the same as above. + */ + +#ifdef SIGNAL_HANDLING_IN_DOUBLE_EXCEPTION + /* Restore registers we precautiously saved. + * We have the value of the 'right' a3 + */ + + l32i a7, a2, PT_AREG5 + l32i a11, a2, PT_AREG6 + l32i a15, a2, PT_AREG7 +#endif + + /* Setup stack pointer. */ + + addi a2, a2, -PT_USER_SIZE + s32i a0, a2, PT_AREG0 + + /* Make sure we return to this fixup handler. */ + + movi a3, fast_syscall_spill_registers_fixup_return + s32i a3, a2, PT_DEPC # setup depc + + /* Jump to the exception handler. */ + + movi a3, exc_table + rsr a0, EXCCAUSE + addx4 a0, a0, a3 # find entry in table + l32i a0, a0, EXC_TABLE_FAST_USER # load handler + jx a0 + +fast_syscall_spill_registers_fixup_return: + + /* When we return here, all registers have been restored (a2: DEPC) */ + + wsr a2, DEPC # exception address + + /* Restore fixup handler. */ + + xsr a3, EXCSAVE_1 + movi a2, fast_syscall_spill_registers_fixup + s32i a2, a3, EXC_TABLE_FIXUP + rsr a2, WINDOWBASE + s32i a2, a3, EXC_TABLE_PARAM + l32i a2, a3, EXC_TABLE_KSTK + +#ifdef SIGNAL_HANDLING_IN_DOUBLE_EXCEPTION + /* Save registers again that might be clobbered. */ + + s32i a7, a2, PT_AREG5 + s32i a11, a2, PT_AREG6 + s32i a15, a2, PT_AREG7 +#endif + + /* Load WB at the time the exception occurred. */ + + rsr a3, SAR # WB is still in SAR + neg a3, a3 + wsr a3, WINDOWBASE + rsync + + /* Restore a3 and return. */ + + movi a3, exc_table + xsr a3, EXCSAVE_1 + + rfde + + +/* + * spill all registers. + * + * This is not a real function. The following conditions must be met: + * + * - must be called with call0. + * - uses DEPC, a3 and SAR. + * - the last 'valid' register of each frame are clobbered. + * - the caller must have registered a fixup handler + * (or be inside a critical section) + * - PS_EXCM must be set (PS_WOE cleared?) + */ + +ENTRY(_spill_registers) + + /* + * Rotate ws so that the current windowbase is at bit 0. + * Assume ws = xxxwww1yy (www1 current window frame). + * Rotate ws right so that a2 = yyxxxwww1. + */ + + wsr a2, DEPC # preserve a2 + rsr a2, WINDOWBASE + rsr a3, WINDOWSTART + ssr a2 # holds WB + slli a2, a3, WSBITS + or a3, a3, a2 # a2 = xxxwww1yyxxxwww1yy + srl a3, a3 + + /* We are done if there are no more than the current register frame. */ + + extui a3, a3, 1, WSBITS-2 # a3 = 0yyxxxwww + movi a2, (1 << (WSBITS-1)) + _beqz a3, .Lnospill # only one active frame? jump + + /* We want 1 at the top, so that we return to the current windowbase */ + + or a3, a3, a2 # 1yyxxxwww + + /* Skip empty frames - get 'oldest' WINDOWSTART-bit. */ + + wsr a3, WINDOWSTART # save shifted windowstart + neg a2, a3 + and a3, a2, a3 # first bit set from right: 000010000 + + ffs_ws a2, a3 # a2: shifts to skip empty frames + movi a3, WSBITS + sub a2, a3, a2 # WSBITS-a2:number of 0-bits from right + ssr a2 # save in SAR for later. + + rsr a3, WINDOWBASE + add a3, a3, a2 + rsr a2, DEPC # restore a2 + wsr a3, WINDOWBASE + rsync + + rsr a3, WINDOWSTART + srl a3, a3 # shift windowstart + + /* WB is now just one frame below the oldest frame in the register + window. WS is shifted so the oldest frame is in bit 0, thus, WB + and WS differ by one 4-register frame. */ + + /* Save frames. Depending what call was used (call4, call8, call12), + * we have to save 4,8. or 12 registers. + */ + + _bbsi.l a3, 1, .Lc4 + _bbsi.l a3, 2, .Lc8 + + /* Special case: we have a call12-frame starting at a4. */ + + _bbci.l a3, 3, .Lc12 # bit 3 shouldn't be zero! (Jump to Lc12 first) + + s32e a4, a1, -16 # a1 is valid with an empty spill area + l32e a4, a5, -12 + s32e a8, a4, -48 + mov a8, a4 + l32e a4, a1, -16 + j .Lc12c + +.Lloop: _bbsi.l a3, 1, .Lc4 + _bbci.l a3, 2, .Lc12 + +.Lc8: s32e a4, a13, -16 + l32e a4, a5, -12 + s32e a8, a4, -32 + s32e a5, a13, -12 + s32e a6, a13, -8 + s32e a7, a13, -4 + s32e a9, a4, -28 + s32e a10, a4, -24 + s32e a11, a4, -20 + + srli a11, a3, 2 # shift windowbase by 2 + rotw 2 + _bnei a3, 1, .Lloop + +.Lexit: /* Done. Do the final rotation, set WS, and return. */ + + rotw 1 + rsr a3, WINDOWBASE + ssl a3 + movi a3, 1 + sll a3, a3 + wsr a3, WINDOWSTART + +.Lnospill: + jx a0 + +.Lc4: s32e a4, a9, -16 + s32e a5, a9, -12 + s32e a6, a9, -8 + s32e a7, a9, -4 + + srli a7, a3, 1 + rotw 1 + _bnei a3, 1, .Lloop + j .Lexit + +.Lc12: _bbci.l a3, 3, .Linvalid_mask # bit 2 shouldn't be zero! + + /* 12-register frame (call12) */ + + l32e a2, a5, -12 + s32e a8, a2, -48 + mov a8, a2 + +.Lc12c: s32e a9, a8, -44 + s32e a10, a8, -40 + s32e a11, a8, -36 + s32e a12, a8, -32 + s32e a13, a8, -28 + s32e a14, a8, -24 + s32e a15, a8, -20 + srli a15, a3, 3 + + /* The stack pointer for a4..a7 is out of reach, so we rotate the + * window, grab the stackpointer, and rotate back. + * Alternatively, we could also use the following approach, but that + * makes the fixup routine much more complicated: + * rotw 1 + * s32e a0, a13, -16 + * ... + * rotw 2 + */ + + rotw 1 + mov a5, a13 + rotw -1 + + s32e a4, a9, -16 + s32e a5, a9, -12 + s32e a6, a9, -8 + s32e a7, a9, -4 + + rotw 3 + + _beqi a3, 1, .Lexit + j .Lloop + +.Linvalid_mask: + + /* We get here because of an unrecoverable error in the window + * registers. If we are in user space, we kill the application, + * however, this condition is unrecoverable in kernel space. + */ + + rsr a0, PS + _bbci.l a0, PS_UM_SHIFT, 1f + + /* User space: Setup a dummy frame and kill application. + * Note: We assume EXC_TABLE_KSTK contains a valid stack pointer. + */ + + movi a0, 1 + movi a1, 0 + + wsr a0, WINDOWSTART + wsr a1, WINDOWBASE + rsync + + movi a0, 0 + + movi a3, exc_table + l32i a1, a3, EXC_TABLE_KSTK + wsr a3, EXCSAVE_1 + + movi a4, PS_WOE_MASK | 1 + wsr a4, PS + rsync + + movi a6, SIGSEGV + movi a4, do_exit + callx4 a4 + +1: /* Kernel space: PANIC! */ + + wsr a0, EXCSAVE_1 + movi a0, unrecoverable_exception + callx0 a0 # should not return +1: j 1b + +/* + * We should never get here. Bail out! + */ + +ENTRY(fast_second_level_miss_double_kernel) + +1: movi a0, unrecoverable_exception + callx0 a0 # should not return +1: j 1b + +/* First-level entry handler for user, kernel, and double 2nd-level + * TLB miss exceptions. Note that for now, user and kernel miss + * exceptions share the same entry point and are handled identically. + * + * An old, less-efficient C version of this function used to exist. + * We include it below, interleaved as comments, for reference. + * + * Entry condition: + * + * a0: trashed, original value saved on stack (PT_AREG0) + * a1: a1 + * a2: new stack pointer, original in DEPC + * a3: dispatch table + * depc: a2, original value saved on stack (PT_DEPC) + * excsave_1: a3 + * + * PT_DEPC >= VALID_DOUBLE_EXCEPTION_ADDRESS: double exception, DEPC + * < VALID_DOUBLE_EXCEPTION_ADDRESS: regular exception + */ + +ENTRY(fast_second_level_miss) + + /* Save a1. Note: we don't expect a double exception. */ + + s32i a1, a2, PT_AREG1 + + /* We need to map the page of PTEs for the user task. Find + * the pointer to that page. Also, it's possible for tsk->mm + * to be NULL while tsk->active_mm is nonzero if we faulted on + * a vmalloc address. In that rare case, we must use + * active_mm instead to avoid a fault in this handler. See + * + * http://mail.nl.linux.org/linux-mm/2002-08/msg00258.html + * (or search Internet on "mm vs. active_mm") + * + * if (!mm) + * mm = tsk->active_mm; + * pgd = pgd_offset (mm, regs->excvaddr); + * pmd = pmd_offset (pgd, regs->excvaddr); + * pmdval = *pmd; + */ + + GET_CURRENT(a1,a2) + l32i a0, a1, TASK_MM # tsk->mm + beqz a0, 9f + +8: rsr a1, EXCVADDR # fault address + _PGD_OFFSET(a0, a1, a1) + l32i a0, a0, 0 # read pmdval + //beqi a0, _PAGE_USER, 2f + beqz a0, 2f + + /* Read ptevaddr and convert to top of page-table page. + * + * vpnval = read_ptevaddr_register() & PAGE_MASK; + * vpnval += DTLB_WAY_PGTABLE; + * pteval = mk_pte (virt_to_page(pmd_val(pmdval)), PAGE_KERNEL); + * write_dtlb_entry (pteval, vpnval); + * + * The messy computation for 'pteval' above really simplifies + * into the following: + * + * pteval = ((pmdval - PAGE_OFFSET) & PAGE_MASK) | PAGE_KERNEL + */ + + movi a1, -PAGE_OFFSET + add a0, a0, a1 # pmdval - PAGE_OFFSET + extui a1, a0, 0, PAGE_SHIFT # ... & PAGE_MASK + xor a0, a0, a1 + + + movi a1, PAGE_DIRECTORY + or a0, a0, a1 # ... | PAGE_DIRECTORY + + rsr a1, PTEVADDR + srli a1, a1, PAGE_SHIFT + slli a1, a1, PAGE_SHIFT # ptevaddr & PAGE_MASK + addi a1, a1, DTLB_WAY_PGTABLE # ... + way_number + + wdtlb a0, a1 + dsync + + /* Exit critical section. */ + + movi a0, 0 + s32i a0, a3, EXC_TABLE_FIXUP + + /* Restore the working registers, and return. */ + + l32i a0, a2, PT_AREG0 + l32i a1, a2, PT_AREG1 + l32i a2, a2, PT_DEPC + xsr a3, EXCSAVE_1 + + bgeui a2, VALID_DOUBLE_EXCEPTION_ADDRESS, 1f + + /* Restore excsave1 and return. */ + + rsr a2, DEPC + rfe + + /* Return from double exception. */ + +1: xsr a2, DEPC + esync + rfde + +9: l32i a0, a1, TASK_ACTIVE_MM # unlikely case mm == 0 + j 8b + +2: /* Invalid PGD, default exception handling */ + + rsr a1, DEPC + xsr a3, EXCSAVE_1 + s32i a1, a2, PT_AREG2 + s32i a3, a2, PT_AREG3 + mov a1, a2 + + rsr a2, PS + bbsi.l a2, PS_UM_SHIFT, 1f + j _kernel_exception +1: j _user_exception + + +/* + * StoreProhibitedException + * + * Update the pte and invalidate the itlb mapping for this pte. + * + * Entry condition: + * + * a0: trashed, original value saved on stack (PT_AREG0) + * a1: a1 + * a2: new stack pointer, original in DEPC + * a3: dispatch table + * depc: a2, original value saved on stack (PT_DEPC) + * excsave_1: a3 + * + * PT_DEPC >= VALID_DOUBLE_EXCEPTION_ADDRESS: double exception, DEPC + * < VALID_DOUBLE_EXCEPTION_ADDRESS: regular exception + */ + +ENTRY(fast_store_prohibited) + + /* Save a1 and a4. */ + + s32i a1, a2, PT_AREG1 + s32i a4, a2, PT_AREG4 + + GET_CURRENT(a1,a2) + l32i a0, a1, TASK_MM # tsk->mm + beqz a0, 9f + +8: rsr a1, EXCVADDR # fault address + _PGD_OFFSET(a0, a1, a4) + l32i a0, a0, 0 + //beqi a0, _PAGE_USER, 2f # FIXME use _PAGE_INVALID + beqz a0, 2f + + _PTE_OFFSET(a0, a1, a4) + l32i a4, a0, 0 # read pteval + movi a1, _PAGE_VALID | _PAGE_RW + bnall a4, a1, 2f + + movi a1, _PAGE_ACCESSED | _PAGE_DIRTY | _PAGE_WRENABLE + or a4, a4, a1 + rsr a1, EXCVADDR + s32i a4, a0, 0 + + /* We need to flush the cache if we have page coloring. */ +#if (DCACHE_WAY_SIZE > PAGE_SIZE) && XCHAL_DCACHE_IS_WRITEBACK + dhwb a0, 0 +#endif + pdtlb a0, a1 + beqz a0, 1f + idtlb a0 // FIXME do we need this? + wdtlb a4, a0 +1: + + /* Exit critical section. */ + + movi a0, 0 + s32i a0, a3, EXC_TABLE_FIXUP + + /* Restore the working registers, and return. */ + + l32i a4, a2, PT_AREG4 + l32i a1, a2, PT_AREG1 + l32i a0, a2, PT_AREG0 + l32i a2, a2, PT_DEPC + + /* Restore excsave1 and a3. */ + + xsr a3, EXCSAVE_1 + bgeui a2, VALID_DOUBLE_EXCEPTION_ADDRESS, 1f + + rsr a2, DEPC + rfe + + /* Double exception. Restore FIXUP handler and return. */ + +1: xsr a2, DEPC + esync + rfde + +9: l32i a0, a1, TASK_ACTIVE_MM # unlikely case mm == 0 + j 8b + +2: /* If there was a problem, handle fault in C */ + + rsr a4, DEPC # still holds a2 + xsr a3, EXCSAVE_1 + s32i a4, a2, PT_AREG2 + s32i a3, a2, PT_AREG3 + l32i a4, a2, PT_AREG4 + mov a1, a2 + + rsr a2, PS + bbsi.l a2, PS_UM_SHIFT, 1f + j _kernel_exception +1: j _user_exception + + +#if XCHAL_EXTRA_SA_SIZE + +#warning fast_coprocessor untested + +/* + * Entry condition: + * + * a0: trashed, original value saved on stack (PT_AREG0) + * a1: a1 + * a2: new stack pointer, original in DEPC + * a3: dispatch table + * depc: a2, original value saved on stack (PT_DEPC) + * excsave_1: a3 + * + * PT_DEPC >= VALID_DOUBLE_EXCEPTION_ADDRESS: double exception, DEPC + * < VALID_DOUBLE_EXCEPTION_ADDRESS: regular exception + */ + +ENTRY(fast_coprocessor_double) + wsr a0, EXCSAVE_1 + movi a0, unrecoverable_exception + callx0 a0 + +ENTRY(fast_coprocessor) + + /* Fatal if we are in a double exception. */ + + l32i a0, a2, PT_DEPC + _bgeui a0, VALID_DOUBLE_EXCEPTION_ADDRESS, fast_coprocessor_double + + /* Save some registers a1, a3, a4, SAR */ + + xsr a3, EXCSAVE_1 + s32i a3, a2, PT_AREG3 + rsr a3, SAR + s32i a4, a2, PT_AREG4 + s32i a1, a2, PT_AREG1 + s32i a5, a1, PT_AREG5 + s32i a3, a2, PT_SAR + mov a1, a2 + + /* Currently, the HAL macros only guarantee saving a0 and a1. + * These can and will be refined in the future, but for now, + * just save the remaining registers of a2...a15. + */ + s32i a6, a1, PT_AREG6 + s32i a7, a1, PT_AREG7 + s32i a8, a1, PT_AREG8 + s32i a9, a1, PT_AREG9 + s32i a10, a1, PT_AREG10 + s32i a11, a1, PT_AREG11 + s32i a12, a1, PT_AREG12 + s32i a13, a1, PT_AREG13 + s32i a14, a1, PT_AREG14 + s32i a15, a1, PT_AREG15 + + /* Find coprocessor number. Subtract first CP EXCCAUSE from EXCCAUSE */ + + rsr a0, EXCCAUSE + addi a3, a0, -XCHAL_EXCCAUSE_COPROCESSOR0_DISABLED + + /* Set corresponding CPENABLE bit */ + + movi a4, 1 + ssl a3 # SAR: 32 - coprocessor_number + rsr a5, CPENABLE + sll a4, a4 + or a4, a5, a4 + wsr a4, CPENABLE + rsync + movi a5, coprocessor_info # list of owner and offset into cp_save + addx8 a0, a4, a5 # entry for CP + + bne a4, a5, .Lload # bit wasn't set before, cp not in use + + /* Now compare the current task with the owner of the coprocessor. + * If they are the same, there is no reason to save or restore any + * coprocessor state. Having already enabled the coprocessor, + * branch ahead to return. + */ + GET_CURRENT(a5,a1) + l32i a4, a0, COPROCESSOR_INFO_OWNER # a4: current owner for this CP + beq a4, a5, .Ldone + + /* Find location to dump current coprocessor state: + * task_struct->task_cp_save_offset + coprocessor_offset[coprocessor] + * + * Note: a0 pointer to the entry in the coprocessor owner table, + * a3 coprocessor number, + * a4 current owner of coprocessor. + */ + l32i a5, a0, COPROCESSOR_INFO_OFFSET + addi a2, a4, THREAD_CP_SAVE + add a2, a2, a5 + + /* Store current coprocessor states. (a5 still has CP number) */ + + xchal_cpi_store_funcbody + + /* The macro might have destroyed a3 (coprocessor number), but + * SAR still has 32 - coprocessor_number! + */ + movi a3, 32 + rsr a4, SAR + sub a3, a3, a4 + +.Lload: /* A new task now owns the corpocessors. Save its TCB pointer into + * the coprocessor owner table. + * + * Note: a0 pointer to the entry in the coprocessor owner table, + * a3 coprocessor number. + */ + GET_CURRENT(a4,a1) + s32i a4, a0, 0 + + /* Find location from where to restore the current coprocessor state.*/ + + l32i a5, a0, COPROCESSOR_INFO_OFFSET + addi a2, a4, THREAD_CP_SAVE + add a2, a2, a4 + + xchal_cpi_load_funcbody + + /* We must assume that the xchal_cpi_store_funcbody macro destroyed + * registers a2..a15. + */ + +.Ldone: l32i a15, a1, PT_AREG15 + l32i a14, a1, PT_AREG14 + l32i a13, a1, PT_AREG13 + l32i a12, a1, PT_AREG12 + l32i a11, a1, PT_AREG11 + l32i a10, a1, PT_AREG10 + l32i a9, a1, PT_AREG9 + l32i a8, a1, PT_AREG8 + l32i a7, a1, PT_AREG7 + l32i a6, a1, PT_AREG6 + l32i a5, a1, PT_AREG5 + l32i a4, a1, PT_AREG4 + l32i a3, a1, PT_AREG3 + l32i a2, a1, PT_AREG2 + l32i a0, a1, PT_AREG0 + l32i a1, a1, PT_AREG1 + + rfe + +#endif /* XCHAL_EXTRA_SA_SIZE */ + +/* + * Task switch. + * + * struct task* _switch_to (struct task* prev, struct task* next) + * a2 a2 a3 + */ + +ENTRY(_switch_to) + + entry a1, 16 + + mov a4, a3 # preserve a3 + + s32i a0, a2, THREAD_RA # save return address + s32i a1, a2, THREAD_SP # save stack pointer + + /* Disable ints while we manipulate the stack pointer; spill regs. */ + + movi a5, PS_EXCM_MASK | LOCKLEVEL + xsr a5, PS + rsr a3, EXCSAVE_1 + rsync + s32i a3, a3, EXC_TABLE_FIXUP /* enter critical section */ + + call0 _spill_registers + + /* Set kernel stack (and leave critical section) + * Note: It's save to set it here. The stack will not be overwritten + * because the kernel stack will only be loaded again after + * we return from kernel space. + */ + + l32i a0, a4, TASK_THREAD_INFO + rsr a3, EXCSAVE_1 # exc_table + movi a1, 0 + addi a0, a0, PT_REGS_OFFSET + s32i a1, a3, EXC_TABLE_FIXUP + s32i a0, a3, EXC_TABLE_KSTK + + /* restore context of the task that 'next' addresses */ + + l32i a0, a4, THREAD_RA /* restore return address */ + l32i a1, a4, THREAD_SP /* restore stack pointer */ + + wsr a5, PS + rsync + + retw + + +ENTRY(ret_from_fork) + + /* void schedule_tail (struct task_struct *prev) + * Note: prev is still in a6 (return value from fake call4 frame) + */ + movi a4, schedule_tail + callx4 a4 + + movi a4, do_syscall_trace + callx4 a4 + + j common_exception_return + + + +/* + * Table of syscalls + */ + +.data +.align 4 +.global sys_call_table +sys_call_table: + +#define SYSCALL(call, narg) .word call +#include "syscalls.h" + +/* + * Number of arguments of each syscall + */ + +.global sys_narg_table +sys_narg_table: + +#undef SYSCALL +#define SYSCALL(call, narg) .byte narg +#include "syscalls.h" + |