/* * 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) 2004-2007 by Tensilica Inc. * * Chris Zankel * */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include /* Unimplemented features. */ #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 address. Don't use call0..call12 */ ENTRY(user_exception) /* Save a2, a3, and depc, restore excsave_1 and set SP. */ xsr a3, excsave1 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 /* 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 /* * 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 address. Don't use call0..call12 */ ENTRY(kernel_exception) /* Save a0, a2, a3, DEPC and set SP. */ xsr a3, excsave1 # 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 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 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, 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 optional registers. */ save_xtregs_opt a1 a2 a4 a5 a6 a7 PT_XTREGS_OPT /* 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 _bbci.l a3, PS_UM_BIT, 4f /* 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. */ GET_THREAD_INFO(a2,a1) l32i a4, a2, TI_FLAGS _bbsi.l a4, TIF_NEED_RESCHED, 3f _bbsi.l a4, TIF_NOTIFY_RESUME, 2f _bbci.l a4, TIF_SIGPENDING, 4f 2: l32i a4, a1, PT_DEPC bgeui a4, VALID_DOUBLE_EXCEPTION_ADDRESS, 4f /* Call do_signal() */ movi a4, do_notify_resume # int do_notify_resume(struct pt_regs*) mov a6, a1 callx4 a4 j 1b 3: /* Reschedule */ movi a4, schedule # void schedule (void) callx4 a4 j 1b 4: /* Restore optional registers. */ load_xtregs_opt a1 a2 a4 a5 a6 a7 PT_XTREGS_OPT 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). */ 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: #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: /* 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 /* * 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!! /* * 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) | 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 ," without destination register a1, this routine * simply moves the value from to 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, excsave1 # make sure excsave_1 is valid for dbl. rsr a4, epc1 # 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, excsave1 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, epc1 # 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 , was invoked with != 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, 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 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 ENTRY(fast_syscall_unrecoverable) /* Restore all states. */ l32i a0, a2, PT_AREG0 # restore a0 xsr a2, depc # restore a2, depc rsr a3, excsave1 wsr a0, excsave1 movi a0, unrecoverable_exception callx0 a0 /* * 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: dispatch table, original in excsave_1 * a4..a15: unchanged * 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 preceding TRY * statements and continues from there * * Usage TRY l32i a0, a1, 0 * * done: rfe * CATCH * j done */ #define TRY \ .section __ex_table, "a"; \ .word 66f, 67f; \ .text; \ 66: #define CATCH \ 67: ENTRY(fast_syscall_xtensa) xsr a3, excsave1 # restore a3, excsave1 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 addi a6, a6, -1 # assuming SYS_XTENSA_ATOMIC_SET = 1 _bgeui a6, SYS_XTENSA_COUNT - 1, .Lill _bnei a6, SYS_XTENSA_ATOMIC_CMP_SWP - 1, .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 addi a6, a6, 1 # restore a6 (really necessary?) 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 addi a6, a6, 1 # restore a6 (really necessary?) rfe .Lnswp: /* Atomic set, add, and exg_add. */ TRY l32i a7, a3, 0 # orig add a0, a4, a7 # + arg moveqz a0, a4, a6 # 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 addi a6, a6, 1 # restore a6 (really necessary?) 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_AREG0 # restore a7 l32i a0, a2, PT_AREG0 # restore a0 movi a2, -EINVAL rfe /* 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. */ 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, excsave1 # restore a3 and excsave_1 s32i a3, a2, PT_AREG3 s32i a4, a2, PT_AREG4 s32i a0, a2, PT_AREG5 # store SAR to PT_AREG5 /* The spill routine might clobber a7, a11, and a15. */ s32i a7, a2, PT_AREG7 s32i a11, a2, PT_AREG11 s32i a15, a2, PT_AREG15 call0 _spill_registers # destroys a3, a4, and SAR /* Advance PC, restore registers and SAR, and return from exception. */ l32i a3, a2, PT_AREG5 l32i a4, a2, PT_AREG4 l32i a0, a2, PT_AREG0 wsr a3, sar l32i a3, a2, PT_AREG3 /* Restore clobbered registers. */ l32i a7, a2, PT_AREG7 l32i a11, a2, PT_AREG11 l32i a15, a2, PT_AREG15 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, excsave1 # 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. */ /* 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, excsave1 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 /* 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, excsave1 rfde /* * spill all registers. * * This is not a real function. The following conditions must be met: * * - must be called with call0. * - uses a3, a4 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 a4 = yyxxxwww1. */ rsr a4, windowbase rsr a3, windowstart # a3 = xxxwww1yy ssr a4 # holds WB slli a4, a3, WSBITS or a3, a3, a4 # 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 a4, (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, a4 # 1yyxxxwww /* Skip empty frames - get 'oldest' WINDOWSTART-bit. */ wsr a3, windowstart # save shifted windowstart neg a4, a3 and a3, a4, a3 # first bit set from right: 000010000 ffs_ws a4, a3 # a4: shifts to skip empty frames movi a3, WSBITS sub a4, a3, a4 # WSBITS-a4:number of 0-bits from right ssr a4 # save in SAR for later. rsr a3, windowbase add a3, a3, a4 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 .Lnospill: ret .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 ret .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_BIT, 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, excsave1 movi a4, (1 << PS_WOE_BIT) | 1 wsr a4, ps rsync movi a6, SIGSEGV movi a4, do_exit callx4 a4 1: /* Kernel space: PANIC! */ wsr a0, excsave1 movi a0, unrecoverable_exception callx0 a0 # should not return 1: j 1b #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 /* 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 /* We deliberately destroy a3 that holds the exception table. */ 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: movi a3, exc_table # restore a3 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, excsave1 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, -(2 << (DCACHE_ALIAS_ORDER + PAGE_SHIFT)) 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 */ movi a3, exc_table rsr a1, depc xsr a3, excsave1 s32i a1, a2, PT_AREG2 s32i a3, a2, PT_AREG3 mov a1, a2 rsr a2, ps bbsi.l a2, PS_UM_BIT, 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 beqz a0, 2f /* Note that we assume _PAGE_WRITABLE_BIT is only set if pte is valid.*/ _PTE_OFFSET(a0, a1, a4) l32i a4, a0, 0 # read pteval bbci.l a4, _PAGE_WRITABLE_BIT, 2f movi a1, _PAGE_ACCESSED | _PAGE_DIRTY | _PAGE_HW_WRITE 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 wdtlb a4, a0 /* 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, excsave1 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, excsave1 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_BIT, 1f j _kernel_exception 1: j _user_exception #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 /* * Create a kernel thread * * int kernel_thread(int (*fn)(void *), void *arg, unsigned long flags) * a2 a2 a3 a4 */ ENTRY(kernel_thread) entry a1, 16 mov a5, a2 # preserve fn over syscall mov a7, a3 # preserve args over syscall movi a3, _CLONE_VM | _CLONE_UNTRACED movi a2, __NR_clone or a6, a4, a3 # arg0: flags mov a3, a1 # arg1: sp syscall beq a3, a1, 1f # branch if parent mov a6, a7 # args callx4 a5 # fn(args) movi a2, __NR_exit syscall # return value of fn(args) still in a6 1: retw /* * Do a system call from kernel instead of calling sys_execve, so we end up * with proper pt_regs. * * int kernel_execve(const char *fname, char *const argv[], charg *const envp[]) * a2 a2 a3 a4 */ ENTRY(kernel_execve) entry a1, 16 mov a6, a2 # arg0 is in a6 movi a2, __NR_execve syscall retw /* * Task switch. * * struct task* _switch_to (struct task* prev, struct task* next) * a2 a2 a3 */ ENTRY(_switch_to) entry a1, 16 mov a12, a2 # preserve 'prev' (a2) mov a13, a3 # and 'next' (a3) l32i a4, a2, TASK_THREAD_INFO l32i a5, a3, TASK_THREAD_INFO save_xtregs_user a4 a6 a8 a9 a10 a11 THREAD_XTREGS_USER s32i a0, a12, THREAD_RA # save return address s32i a1, a12, THREAD_SP # save stack pointer /* Disable ints while we manipulate the stack pointer. */ movi a14, (1 << PS_EXCM_BIT) | LOCKLEVEL xsr a14, ps 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. */ call0 _spill_registers # destroys a3, a4, and SAR /* 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 that 'next' addresses */ l32i a0, a13, THREAD_RA # restore return address l32i a1, a13, THREAD_SP # restore stack pointer load_xtregs_user a5 a6 a8 a9 a10 a11 THREAD_XTREGS_USER wsr a14, ps mov a2, a12 # return 'prev' 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_leave mov a6, a1 callx4 a4 j common_exception_return