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Diffstat (limited to 'arch/xtensa/kernel/entry.S')
| -rw-r--r-- | arch/xtensa/kernel/entry.S | 1938 |
1 files changed, 1938 insertions, 0 deletions
diff --git a/arch/xtensa/kernel/entry.S b/arch/xtensa/kernel/entry.S new file mode 100644 index 000000000..82bbfa5a0 --- /dev/null +++ b/arch/xtensa/kernel/entry.S @@ -0,0 +1,1938 @@ +/* + * 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 - 2008 by Tensilica Inc. + * + * Chris Zankel <chris@zankel.net> + * + */ + +#include <linux/linkage.h> +#include <asm/asm-offsets.h> +#include <asm/processor.h> +#include <asm/coprocessor.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 <asm/tlbflush.h> +#include <variant/tie-asm.h> + +/* Unimplemented features. */ + +#undef KERNEL_STACK_OVERFLOW_CHECK + +/* 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: a3 + * depc: a2, original value saved on stack (PT_DEPC) + * excsave1: dispatch table + * + * 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 address. Don't use call0..call12 + */ + +ENTRY(user_exception) + + /* Save a1, a2, a3, and set SP. */ + + 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 + xsr a2, icountlevel + s32i a3, a1, PT_SAR + s32i a2, a1, PT_ICOUNTLEVEL + +#if XCHAL_HAVE_THREADPTR + rur a2, threadptr + s32i a2, a1, PT_THREADPTR +#endif + + /* 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 register frames starting from the top field 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: /* Now, jump to the common exception handler. */ + + j common_exception + +ENDPROC(user_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: a3 + * depc: a2, original value saved on stack (PT_DEPC) + * excsave_1: dispatch table + * + * 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 address. Don't use call0..call12 + */ + +ENTRY(kernel_exception) + + /* Save a1, a2, a3, and set SP. */ + + 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 + xsr a2, icountlevel + s32i a3, a1, PT_SAR + s32i a2, a1, PT_ICOUNTLEVEL + + /* 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 some registers, disable loops and clear the syscall flag. */ + + rsr a2, debugcause + rsr a3, epc1 + s32i a2, a1, PT_DEBUGCAUSE + s32i a3, a1, PT_PC + + movi a2, -1 + rsr a3, excvaddr + s32i a2, a1, PT_SYSCALL + 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, excsave1 + 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 they were previously enabled and + * we're not handling an IRQ + */ + + rsr a3, ps + addi a0, a0, -EXCCAUSE_LEVEL1_INTERRUPT + movi a2, LOCKLEVEL + extui a3, a3, PS_INTLEVEL_SHIFT, PS_INTLEVEL_WIDTH + # a3 = PS.INTLEVEL + moveqz a3, a2, a0 # a3 = LOCKLEVEL iff interrupt + movi a2, 1 << PS_WOE_BIT + 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 + + /* Save SCOMPARE1 */ + +#if XCHAL_HAVE_S32C1I + rsr a2, scompare1 + s32i a2, a1, PT_SCOMPARE1 +#endif + + /* Save optional registers. */ + + save_xtregs_opt a1 a2 a4 a5 a6 a7 PT_XTREGS_OPT + +#ifdef CONFIG_TRACE_IRQFLAGS + l32i a4, a1, PT_DEPC + /* Double exception means we came here with an exception + * while PS.EXCM was set, i.e. interrupts disabled. + */ + bgeui a4, VALID_DOUBLE_EXCEPTION_ADDRESS, 1f + l32i a4, a1, PT_EXCCAUSE + bnei a4, EXCCAUSE_LEVEL1_INTERRUPT, 1f + /* We came here with an interrupt means interrupts were enabled + * and we've just disabled them. + */ + movi a4, trace_hardirqs_off + callx4 a4 +1: +#endif + + /* Go to second-level dispatcher. Set up parameters to pass to the + * exception handler and call the exception handler. + */ + + rsr a4, excsave1 + 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 */ + .global common_exception_return +common_exception_return: + +1: + rsil a2, LOCKLEVEL + + /* Jump if we are returning from kernel exceptions. */ + + l32i a3, a1, PT_PS + GET_THREAD_INFO(a2, a1) + l32i a4, a2, TI_FLAGS + _bbci.l a3, PS_UM_BIT, 6f + + /* 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. + * Note that we don't disable interrupts here. + */ + + _bbsi.l a4, TIF_NEED_RESCHED, 3f + _bbsi.l a4, TIF_NOTIFY_RESUME, 2f + _bbci.l a4, TIF_SIGPENDING, 5f + +2: l32i a4, a1, PT_DEPC + bgeui a4, VALID_DOUBLE_EXCEPTION_ADDRESS, 4f + + /* Call do_signal() */ + + rsil a2, 0 + movi a4, do_notify_resume # int do_notify_resume(struct pt_regs*) + mov a6, a1 + callx4 a4 + j 1b + +3: /* Reschedule */ + + rsil a2, 0 + movi a4, schedule # void schedule (void) + callx4 a4 + j 1b + +#ifdef CONFIG_PREEMPT +6: + _bbci.l a4, TIF_NEED_RESCHED, 4f + + /* Check current_thread_info->preempt_count */ + + l32i a4, a2, TI_PRE_COUNT + bnez a4, 4f + movi a4, preempt_schedule_irq + callx4 a4 + j 1b +#endif + +5: +#ifdef CONFIG_DEBUG_TLB_SANITY + l32i a4, a1, PT_DEPC + bgeui a4, VALID_DOUBLE_EXCEPTION_ADDRESS, 4f + movi a4, check_tlb_sanity + callx4 a4 +#endif +6: +4: +#ifdef CONFIG_TRACE_IRQFLAGS + l32i a4, a1, PT_DEPC + /* Double exception means we came here with an exception + * while PS.EXCM was set, i.e. interrupts disabled. + */ + bgeui a4, VALID_DOUBLE_EXCEPTION_ADDRESS, 1f + l32i a4, a1, PT_EXCCAUSE + bnei a4, EXCCAUSE_LEVEL1_INTERRUPT, 1f + /* We came here with an interrupt means interrupts were enabled + * and we'll reenable them on return. + */ + movi a4, trace_hardirqs_on + callx4 a4 +1: +#endif + /* Restore optional registers. */ + + load_xtregs_opt a1 a2 a4 a5 a6 a7 PT_XTREGS_OPT + + /* Restore SCOMPARE1 */ + +#if XCHAL_HAVE_S32C1I + l32i a2, a1, PT_SCOMPARE1 + wsr a2, scompare1 +#endif + wsr a3, ps /* disable interrupts */ + + _bbci.l a3, PS_UM_BIT, kernel_exception_exit + +user_exception_exit: + + /* Restore the state of the task and return from the exception. */ + + /* 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). + */ + +#if XCHAL_HAVE_THREADPTR + l32i a3, a1, PT_THREADPTR + wur a3, threadptr +#endif + +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: + + /* 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: + + /* Restore address registers. */ + + _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, epc1 + 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 + + /* We control single stepping through the ICOUNTLEVEL register. */ + + l32i a2, a1, PT_ICOUNTLEVEL + movi a3, -2 + wsr a2, icountlevel + wsr a3, icount + + /* 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 + +ENDPROC(kernel_exception) + +/* + * 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, SREG_EPS + XCHAL_DEBUGLEVEL + bbsi.l a0, PS_EXCM_BIT, 1f # exception mode + + /* Set EPC1 and EXCCAUSE */ + + wsr a2, depc # save a2 temporarily + rsr a2, SREG_EPC + XCHAL_DEBUGLEVEL + wsr a2, epc1 + + 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_BIT + or a2, a0, a2 + movi a0, debug_exception # restore a3, debug jump vector + wsr a2, ps + xsr a0, SREG_EXCSAVE + XCHAL_DEBUGLEVEL + + /* Switch to kernel/user stack, restore jump vector, and save a0 */ + + bbsi.l a2, PS_UM_BIT, 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, excsave1 + 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!! + +ENDPROC(debug_exception) + +/* + * 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, (1 << PS_WOE_BIT) | LOCKLEVEL + 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 + +ENDPROC(unrecoverable_exception) + +/* -------------------------- 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. + * + * This algorithm was taken from the Ross Morley's RTOS Porting Layer: + * + * /home/ross/rtos/porting/XtensaRTOS-PortingLayer-20090507/xtensa_vectors.S + * + * It leverages the existing window spill/fill routines and their support for + * double exceptions. The 'movsp' instruction will only cause an exception if + * the next window needs to be loaded. In fact this ALLOCA exception may be + * replaced at some point by changing the hardware to do a underflow exception + * of the proper size instead. + * + * This algorithm simply backs out the register changes started by the user + * excpetion handler, makes it appear that we have started a window underflow + * by rotating the window back and then setting the old window base (OWB) in + * the 'ps' register with the rolled back window base. The 'movsp' instruction + * will be re-executed and this time since the next window frames is in the + * active AR registers it won't cause an exception. + * + * If the WindowUnderflow code gets a TLB miss the page will get mapped + * the the partial windeowUnderflow will be handeled in the double exception + * handler. + * + * Entry condition: + * + * a0: trashed, original value saved on stack (PT_AREG0) + * a1: a1 + * a2: new stack pointer, original in DEPC + * a3: a3 + * depc: a2, original value saved on stack (PT_DEPC) + * excsave_1: dispatch table + * + * PT_DEPC >= VALID_DOUBLE_EXCEPTION_ADDRESS: double exception, DEPC + * < VALID_DOUBLE_EXCEPTION_ADDRESS: regular exception + */ + +ENTRY(fast_alloca) + rsr a0, windowbase + rotw -1 + rsr a2, ps + extui a3, a2, PS_OWB_SHIFT, PS_OWB_WIDTH + xor a3, a3, a4 + l32i a4, a6, PT_AREG0 + l32i a1, a6, PT_DEPC + rsr a6, depc + wsr a1, depc + slli a3, a3, PS_OWB_SHIFT + xor a2, a2, a3 + wsr a2, ps + rsync + + _bbci.l a4, 31, 4f + rotw -1 + _bbci.l a8, 30, 8f + rotw -1 + j _WindowUnderflow12 +8: j _WindowUnderflow8 +4: j _WindowUnderflow4 +ENDPROC(fast_alloca) + +/* + * 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: a3 + * depc: a2, original value saved on stack (PT_DEPC) + * excsave_1: dispatch table + */ + +ENTRY(fast_syscall_kernel) + + /* Skip syscall. */ + + rsr a0, epc1 + addi a0, a0, 3 + wsr a0, epc1 + + 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 + _beqi a0, __NR_xtensa, fast_syscall_xtensa + + j kernel_exception + +ENDPROC(fast_syscall_kernel) + +ENTRY(fast_syscall_user) + + /* Skip syscall. */ + + rsr a0, epc1 + addi a0, a0, 3 + wsr a0, epc1 + + 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 + _beqi a0, __NR_xtensa, fast_syscall_xtensa + + j user_exception + +ENDPROC(fast_syscall_user) + +ENTRY(fast_syscall_unrecoverable) + + /* Restore all states. */ + + l32i a0, a2, PT_AREG0 # restore a0 + xsr a2, depc # restore a2, depc + + wsr a0, excsave1 + movi a0, unrecoverable_exception + callx0 a0 + +ENDPROC(fast_syscall_unrecoverable) + +/* + * sysxtensa syscall handler + * + * int sysxtensa (SYS_XTENSA_ATOMIC_SET, ptr, val, unused); + * int sysxtensa (SYS_XTENSA_ATOMIC_ADD, ptr, val, unused); + * int sysxtensa (SYS_XTENSA_ATOMIC_EXG_ADD, ptr, val, unused); + * int sysxtensa (SYS_XTENSA_ATOMIC_CMP_SWP, ptr, oldval, newval); + * a2 a6 a3 a4 a5 + * + * Entry condition: + * + * a0: a2 (syscall-nr), original value saved on stack (PT_AREG0) + * a1: a1 + * a2: new stack pointer, original in a0 and DEPC + * a3: a3 + * a4..a15: unchanged + * depc: a2, original value saved on stack (PT_DEPC) + * excsave_1: dispatch table + * + * 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 preceding TRY + * statements and continues from there + * + * Usage TRY l32i a0, a1, 0 + * <other code> + * done: rfe + * CATCH <set return code> + * j done + */ + +#ifdef CONFIG_FAST_SYSCALL_XTENSA + +#define TRY \ + .section __ex_table, "a"; \ + .word 66f, 67f; \ + .text; \ +66: + +#define CATCH \ +67: + +ENTRY(fast_syscall_xtensa) + + s32i a7, a2, PT_AREG7 # we need an additional register + movi a7, 4 # sizeof(unsigned int) + access_ok a3, a7, a0, a2, .Leac # a0: scratch reg, a2: sp + + _bgeui a6, SYS_XTENSA_COUNT, .Lill + _bnei a6, SYS_XTENSA_ATOMIC_CMP_SWP, .Lnswp + + /* Fall through for ATOMIC_CMP_SWP. */ + +.Lswp: /* Atomic compare and swap */ + +TRY l32i a0, a3, 0 # read old value + bne a0, a4, 1f # same as old value? jump +TRY s32i a5, a3, 0 # different, modify value + l32i a7, a2, PT_AREG7 # restore a7 + l32i a0, a2, PT_AREG0 # restore a0 + movi a2, 1 # and return 1 + rfe + +1: l32i a7, a2, PT_AREG7 # restore a7 + l32i a0, a2, PT_AREG0 # restore a0 + movi a2, 0 # return 0 (note that we cannot set + rfe + +.Lnswp: /* Atomic set, add, and exg_add. */ + +TRY l32i a7, a3, 0 # orig + addi a6, a6, -SYS_XTENSA_ATOMIC_SET + add a0, a4, a7 # + arg + moveqz a0, a4, a6 # set + addi a6, a6, SYS_XTENSA_ATOMIC_SET +TRY s32i a0, a3, 0 # write new value + + mov a0, a2 + mov a2, a7 + l32i a7, a0, PT_AREG7 # restore a7 + l32i a0, a0, PT_AREG0 # restore a0 + rfe + +CATCH +.Leac: l32i a7, a2, PT_AREG7 # restore a7 + l32i a0, a2, PT_AREG0 # restore a0 + movi a2, -EFAULT + rfe + +.Lill: l32i a7, a2, PT_AREG7 # restore a7 + l32i a0, a2, PT_AREG0 # restore a0 + movi a2, -EINVAL + rfe + +ENDPROC(fast_syscall_xtensa) + +#else /* CONFIG_FAST_SYSCALL_XTENSA */ + +ENTRY(fast_syscall_xtensa) + + l32i a0, a2, PT_AREG0 # restore a0 + movi a2, -ENOSYS + rfe + +ENDPROC(fast_syscall_xtensa) + +#endif /* CONFIG_FAST_SYSCALL_XTENSA */ + + +/* 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: a3 + * depc: a2, original value saved on stack (PT_DEPC) + * excsave_1: dispatch table + * + * Note: We assume the stack pointer is EXC_TABLE_KSTK in the fixup handler. + */ + +#ifdef CONFIG_FAST_SYSCALL_SPILL_REGISTERS + +ENTRY(fast_syscall_spill_registers) + + /* Register a FIXUP handler (pass current wb as a parameter) */ + + xsr a3, excsave1 + movi a0, fast_syscall_spill_registers_fixup + s32i a0, a3, EXC_TABLE_FIXUP + rsr a0, windowbase + s32i a0, a3, EXC_TABLE_PARAM + xsr a3, excsave1 # restore a3 and excsave_1 + + /* Save a3, a4 and SAR on stack. */ + + rsr a0, sar + s32i a3, a2, PT_AREG3 + s32i a0, a2, PT_SAR + + /* The spill routine might clobber a4, a7, a8, a11, a12, and a15. */ + + s32i a4, a2, PT_AREG4 + s32i a7, a2, PT_AREG7 + s32i a8, a2, PT_AREG8 + s32i a11, a2, PT_AREG11 + s32i a12, a2, PT_AREG12 + s32i a15, a2, PT_AREG15 + + /* + * Rotate ws so that the current windowbase is at bit 0. + * Assume ws = xxxwww1yy (www1 current window frame). + * Rotate ws right so that a4 = yyxxxwww1. + */ + + rsr a0, windowbase + rsr a3, windowstart # a3 = xxxwww1yy + ssr a0 # holds WB + slli a0, a3, WSBITS + or a3, a3, a0 # a3 = xxxwww1yyxxxwww1yy + srl a3, a3 # a3 = 00xxxwww1yyxxxwww1 + + /* We are done if there are no more than the current register frame. */ + + extui a3, a3, 1, WSBITS-1 # a3 = 0yyxxxwww + movi a0, (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, a0 # 1yyxxxwww + + /* Skip empty frames - get 'oldest' WINDOWSTART-bit. */ + + wsr a3, windowstart # save shifted windowstart + neg a0, a3 + and a3, a0, a3 # first bit set from right: 000010000 + + ffs_ws a0, a3 # a0: shifts to skip empty frames + movi a3, WSBITS + sub a0, a3, a0 # WSBITS-a0:number of 0-bits from right + ssr a0 # save in SAR for later. + + rsr a3, windowbase + add a3, a3, a0 + 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. + */ + + +.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 + j .Lexit + +.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 a0, a5, -12 + s32e a8, a0, -48 + mov a8, a0 + + 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 a4, a13 + rotw -1 + + s32e a4, a8, -16 + s32e a5, a8, -12 + s32e a6, a8, -8 + s32e a7, a8, -4 + + rotw 3 + + _beqi a3, 1, .Lexit + j .Lloop + +.Lexit: + + /* Done. Do the final rotation and set WS */ + + rotw 1 + rsr a3, windowbase + ssl a3 + movi a3, 1 + sll a3, a3 + wsr a3, windowstart +.Lnospill: + + /* Advance PC, restore registers and SAR, and return from exception. */ + + l32i a3, a2, PT_SAR + l32i a0, a2, PT_AREG0 + wsr a3, sar + l32i a3, a2, PT_AREG3 + + /* Restore clobbered registers. */ + + l32i a4, a2, PT_AREG4 + l32i a7, a2, PT_AREG7 + l32i a8, a2, PT_AREG8 + l32i a11, a2, PT_AREG11 + l32i a12, a2, PT_AREG12 + l32i a15, a2, PT_AREG15 + + movi a2, 0 + rfe + +.Linvalid_mask: + + /* We get here because of an unrecoverable error in the window + * registers, so set up a dummy frame and kill the user 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 + + rsr a3, excsave1 + l32i a1, a3, EXC_TABLE_KSTK + + movi a4, (1 << PS_WOE_BIT) | LOCKLEVEL + wsr a4, ps + rsync + + movi a6, SIGSEGV + movi a4, do_exit + callx4 a4 + + /* shouldn't return, so panic */ + + wsr a0, excsave1 + movi a0, unrecoverable_exception + callx0 a0 # should not return +1: j 1b + + +ENDPROC(fast_syscall_spill_registers) + +/* 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. + * + * Note that we only need to restore the bits in windowstart that have not + * been spilled yet by the _spill_register routine. Luckily, a3 contains a + * rotated windowstart with only those bits set for frames that haven't been + * spilled yet. Because a3 is rotated such that bit 0 represents the register + * frame for the current windowbase - 1, we need to rotate a3 left by the + * value of the current windowbase + 1 and move it to windowstart. + * + * a0: value of depc, original value in depc + * a2: trashed, original value in EXC_TABLE_DOUBLE_SAVE + * a3: exctable, original value in excsave1 + */ + +ENTRY(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. + * + * Note: we use a3 to set the windowbase, so we take a special care + * of it, saving it in the original _spill_registers frame across + * the exception handler call. + */ + + xsr a3, excsave1 # get spill-mask + slli a3, a3, 1 # shift left by one + addi a3, a3, 1 # set the bit for the current window frame + + slli a2, a3, 32-WSBITS + src a2, a3, a2 # a2 = xxwww1yyxxxwww1yy...... + wsr a2, windowstart # set corrected windowstart + + srli a3, a3, 1 + rsr a2, excsave1 + l32i a2, a2, EXC_TABLE_DOUBLE_SAVE # restore a2 + xsr a2, excsave1 + s32i a3, a2, EXC_TABLE_DOUBLE_SAVE # save a3 + l32i a3, a2, EXC_TABLE_PARAM # original WB (in user task) + xsr a2, excsave1 + + /* Return to the original (user task) WINDOWBASE. + * We leave the following frame behind: + * a0, a1, a2 same + * a3: trashed (saved in EXC_TABLE_DOUBLE_SAVE) + * depc: depc (we have to return to that address) + * excsave_1: exctable + */ + + 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 + * depc: exception address + * excsave: exctable + * Note: This frame might be the same as above. + */ + + /* 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. */ + + rsr a3, excsave1 + rsr a0, exccause + addx4 a0, a0, a3 # find entry in table + l32i a0, a0, EXC_TABLE_FAST_USER # load handler + l32i a3, a3, EXC_TABLE_DOUBLE_SAVE + jx a0 + +ENDPROC(fast_syscall_spill_registers_fixup) + +ENTRY(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. */ + + rsr a2, excsave1 + s32i a3, a2, EXC_TABLE_DOUBLE_SAVE + movi a3, fast_syscall_spill_registers_fixup + s32i a3, a2, EXC_TABLE_FIXUP + rsr a3, windowbase + s32i a3, a2, EXC_TABLE_PARAM + l32i a2, a2, EXC_TABLE_KSTK + + /* Load WB at the time the exception occurred. */ + + rsr a3, sar # WB is still in SAR + neg a3, a3 + wsr a3, windowbase + rsync + + rsr a3, excsave1 + l32i a3, a3, EXC_TABLE_DOUBLE_SAVE + + rfde + +ENDPROC(fast_syscall_spill_registers_fixup_return) + +#else /* CONFIG_FAST_SYSCALL_SPILL_REGISTERS */ + +ENTRY(fast_syscall_spill_registers) + + l32i a0, a2, PT_AREG0 # restore a0 + movi a2, -ENOSYS + rfe + +ENDPROC(fast_syscall_spill_registers) + +#endif /* CONFIG_FAST_SYSCALL_SPILL_REGISTERS */ + +#ifdef CONFIG_MMU +/* + * 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 + +ENDPROC(fast_second_level_miss_double_kernel) + +/* 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: a3 + * depc: a2, original value saved on stack (PT_DEPC) + * excsave_1: dispatch table + * + * PT_DEPC >= VALID_DOUBLE_EXCEPTION_ADDRESS: double exception, DEPC + * < VALID_DOUBLE_EXCEPTION_ADDRESS: regular exception + */ + +ENTRY(fast_second_level_miss) + + /* Save a1 and a3. Note: we don't expect a double exception. */ + + s32i a1, a2, PT_AREG1 + s32i a3, a2, PT_AREG3 + + /* 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 a3, excvaddr # fault address + _PGD_OFFSET(a0, a3, a1) + l32i a0, a0, 0 # read pmdval + 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_DIRECTORY + */ + + movi a1, (-PAGE_OFFSET) & 0xffffffff + 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 + + /* + * We utilize all three wired-ways (7-9) to hold pmd translations. + * Memory regions are mapped to the DTLBs according to bits 28 and 29. + * This allows to map the three most common regions to three different + * DTLBs: + * 0,1 -> way 7 program (0040.0000) and virtual (c000.0000) + * 2 -> way 8 shared libaries (2000.0000) + * 3 -> way 0 stack (3000.0000) + */ + + extui a3, a3, 28, 2 # addr. bit 28 and 29 0,1,2,3 + rsr a1, ptevaddr + addx2 a3, a3, a3 # -> 0,3,6,9 + srli a1, a1, PAGE_SHIFT + extui a3, a3, 2, 2 # -> 0,0,1,2 + slli a1, a1, PAGE_SHIFT # ptevaddr & PAGE_MASK + addi a3, a3, DTLB_WAY_PGD + add a1, a1, a3 # ... + way_number + +3: wdtlb a0, a1 + dsync + + /* Exit critical section. */ + +4: rsr a3, excsave1 + 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 a3, a2, PT_AREG3 + l32i a2, a2, PT_DEPC + + 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 + +#if (DCACHE_WAY_SIZE > PAGE_SIZE) + +2: /* Special case for cache aliasing. + * We (should) only get here if a clear_user_page, copy_user_page + * or the aliased cache flush functions got preemptively interrupted + * by another task. Re-establish temporary mapping to the + * TLBTEMP_BASE areas. + */ + + /* We shouldn't be in a double exception */ + + l32i a0, a2, PT_DEPC + bgeui a0, VALID_DOUBLE_EXCEPTION_ADDRESS, 2f + + /* Make sure the exception originated in the special functions */ + + movi a0, __tlbtemp_mapping_start + rsr a3, epc1 + bltu a3, a0, 2f + movi a0, __tlbtemp_mapping_end + bgeu a3, a0, 2f + + /* Check if excvaddr was in one of the TLBTEMP_BASE areas. */ + + movi a3, TLBTEMP_BASE_1 + rsr a0, excvaddr + bltu a0, a3, 2f + + addi a1, a0, -TLBTEMP_SIZE + bgeu a1, a3, 2f + + /* Check if we have to restore an ITLB mapping. */ + + movi a1, __tlbtemp_mapping_itlb + rsr a3, epc1 + sub a3, a3, a1 + + /* Calculate VPN */ + + movi a1, PAGE_MASK + and a1, a1, a0 + + /* Jump for ITLB entry */ + + bgez a3, 1f + + /* We can use up to two TLBTEMP areas, one for src and one for dst. */ + + extui a3, a0, PAGE_SHIFT + DCACHE_ALIAS_ORDER, 1 + add a1, a3, a1 + + /* PPN is in a6 for the first TLBTEMP area and in a7 for the second. */ + + mov a0, a6 + movnez a0, a7, a3 + j 3b + + /* ITLB entry. We only use dst in a6. */ + +1: witlb a6, a1 + isync + j 4b + + +#endif // DCACHE_WAY_SIZE > PAGE_SIZE + + +2: /* Invalid PGD, default exception handling */ + + rsr a1, depc + s32i a1, a2, PT_AREG2 + mov a1, a2 + + rsr a2, ps + bbsi.l a2, PS_UM_BIT, 1f + j _kernel_exception +1: j _user_exception + +ENDPROC(fast_second_level_miss) + +/* + * 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: a3 + * depc: a2, original value saved on stack (PT_DEPC) + * excsave_1: dispatch table + * + * PT_DEPC >= VALID_DOUBLE_EXCEPTION_ADDRESS: double exception, DEPC + * < VALID_DOUBLE_EXCEPTION_ADDRESS: regular exception + */ + +ENTRY(fast_store_prohibited) + + /* Save a1 and a3. */ + + s32i a1, a2, PT_AREG1 + s32i a3, a2, PT_AREG3 + + GET_CURRENT(a1,a2) + l32i a0, a1, TASK_MM # tsk->mm + beqz a0, 9f + +8: rsr a1, excvaddr # fault address + _PGD_OFFSET(a0, a1, a3) + l32i a0, a0, 0 + beqz a0, 2f + + /* + * Note that we test _PAGE_WRITABLE_BIT only if PTE is present + * and is not PAGE_NONE. See pgtable.h for possible PTE layouts. + */ + + _PTE_OFFSET(a0, a1, a3) + l32i a3, a0, 0 # read pteval + movi a1, _PAGE_CA_INVALID + ball a3, a1, 2f + bbci.l a3, _PAGE_WRITABLE_BIT, 2f + + movi a1, _PAGE_ACCESSED | _PAGE_DIRTY | _PAGE_HW_WRITE + or a3, a3, a1 + rsr a1, excvaddr + s32i a3, 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 + wdtlb a3, a0 + + /* Exit critical section. */ + + movi a0, 0 + rsr a3, excsave1 + s32i a0, a3, EXC_TABLE_FIXUP + + /* Restore the working registers, and return. */ + + l32i a3, a2, PT_AREG3 + l32i a1, a2, PT_AREG1 + l32i a0, a2, PT_AREG0 + l32i a2, a2, PT_DEPC + + 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 a3, depc # still holds a2 + s32i a3, a2, PT_AREG2 + mov a1, a2 + + rsr a2, ps + bbsi.l a2, PS_UM_BIT, 1f + j _kernel_exception +1: j _user_exception + +ENDPROC(fast_store_prohibited) + +#endif /* CONFIG_MMU */ + +/* + * System Calls. + * + * void system_call (struct pt_regs* regs, int exccause) + * a2 a3 + */ + +ENTRY(system_call) + + entry a1, 32 + + /* regs->syscall = regs->areg[2] */ + + l32i a3, a2, PT_AREG2 + mov a6, a2 + movi a4, do_syscall_trace_enter + s32i a3, a2, PT_SYSCALL + callx4 a4 + + /* syscall = sys_call_table[syscall_nr] */ + + movi a4, sys_call_table; + movi a5, __NR_syscall_count + movi a6, -ENOSYS + bgeu a3, a5, 1f + + addx4 a4, a3, a4 + l32i a4, a4, 0 + movi a5, sys_ni_syscall; + beq a4, a5, 1f + + /* Load args: arg0 - arg5 are passed via regs. */ + + l32i a6, a2, PT_AREG6 + l32i a7, a2, PT_AREG3 + l32i a8, a2, PT_AREG4 + l32i a9, a2, PT_AREG5 + l32i a10, a2, PT_AREG8 + l32i a11, a2, PT_AREG9 + + /* Pass one additional argument to the syscall: pt_regs (on stack) */ + s32i a2, a1, 0 + + callx4 a4 + +1: /* regs->areg[2] = return_value */ + + s32i a6, a2, PT_AREG2 + movi a4, do_syscall_trace_leave + mov a6, a2 + callx4 a4 + retw + +ENDPROC(system_call) + +/* + * Spill live registers on the kernel stack macro. + * + * Entry condition: ps.woe is set, ps.excm is cleared + * Exit condition: windowstart has single bit set + * May clobber: a12, a13 + */ + .macro spill_registers_kernel + +#if XCHAL_NUM_AREGS > 16 + call12 1f + _j 2f + retw + .align 4 +1: + _entry a1, 48 + addi a12, a0, 3 +#if XCHAL_NUM_AREGS > 32 + .rept (XCHAL_NUM_AREGS - 32) / 12 + _entry a1, 48 + mov a12, a0 + .endr +#endif + _entry a1, 48 +#if XCHAL_NUM_AREGS % 12 == 0 + mov a8, a8 +#elif XCHAL_NUM_AREGS % 12 == 4 + mov a12, a12 +#elif XCHAL_NUM_AREGS % 12 == 8 + mov a4, a4 +#endif + retw +2: +#else + mov a12, a12 +#endif + .endm + +/* + * Task switch. + * + * struct task* _switch_to (struct task* prev, struct task* next) + * a2 a2 a3 + */ + +ENTRY(_switch_to) + + entry a1, 16 + + mov a11, a3 # and 'next' (a3) + + l32i a4, a2, TASK_THREAD_INFO + l32i a5, a3, TASK_THREAD_INFO + + save_xtregs_user a4 a6 a8 a9 a12 a13 THREAD_XTREGS_USER + +#if THREAD_RA > 1020 || THREAD_SP > 1020 + addi a10, a2, TASK_THREAD + s32i a0, a10, THREAD_RA - TASK_THREAD # save return address + s32i a1, a10, THREAD_SP - TASK_THREAD # save stack pointer +#else + s32i a0, a2, THREAD_RA # save return address + s32i a1, a2, THREAD_SP # save stack pointer +#endif + + /* Disable ints while we manipulate the stack pointer. */ + + rsil a14, LOCKLEVEL + rsr a3, excsave1 + rsync + s32i a3, a3, EXC_TABLE_FIXUP /* enter critical section */ + + /* Switch CPENABLE */ + +#if (XTENSA_HAVE_COPROCESSORS || XTENSA_HAVE_IO_PORTS) + l32i a3, a5, THREAD_CPENABLE + xsr a3, cpenable + s32i a3, a4, THREAD_CPENABLE +#endif + + /* Flush register file. */ + + spill_registers_kernel + + /* 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. + */ + + rsr a3, excsave1 # exc_table + movi a6, 0 + addi a7, a5, PT_REGS_OFFSET + s32i a6, a3, EXC_TABLE_FIXUP + s32i a7, a3, EXC_TABLE_KSTK + + /* restore context of the task 'next' */ + + l32i a0, a11, THREAD_RA # restore return address + l32i a1, a11, THREAD_SP # restore stack pointer + + load_xtregs_user a5 a6 a8 a9 a12 a13 THREAD_XTREGS_USER + + wsr a14, ps + rsync + + retw + +ENDPROC(_switch_to) + +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_leave + mov a6, a1 + callx4 a4 + + j common_exception_return + +ENDPROC(ret_from_fork) + +/* + * Kernel thread creation helper + * On entry, set up by copy_thread: a2 = thread_fn, a3 = thread_fn arg + * left from _switch_to: a6 = prev + */ +ENTRY(ret_from_kernel_thread) + + call4 schedule_tail + mov a6, a3 + callx4 a2 + j common_exception_return + +ENDPROC(ret_from_kernel_thread) |