/* $Id: entry.S,v 1.37 2004/06/11 13:02:46 doyu Exp $ * * linux/arch/sh/entry.S * * Copyright (C) 1999, 2000, 2002 Niibe Yutaka * Copyright (C) 2003 Paul Mundt * * 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. * */ ! NOTE: ! GNU as (as of 2.9.1) changes bf/s into bt/s and bra, when the address ! to be jumped is too far, but it causes illegal slot exception. /* * entry.S contains the system-call and fault low-level handling routines. * This also contains the timer-interrupt handler, as well as all interrupts * and faults that can result in a task-switch. * * NOTE: This code handles signal-recognition, which happens every time * after a timer-interrupt and after each system call. * * NOTE: This code uses a convention that instructions in the delay slot * of a transfer-control instruction are indented by an extra space, thus: * * jmp @k0 ! control-transfer instruction * ldc k1, ssr ! delay slot * * Stack layout in 'ret_from_syscall': * ptrace needs to have all regs on the stack. * if the order here is changed, it needs to be * updated in ptrace.c and ptrace.h * * r0 * ... * r15 = stack pointer * spc * pr * ssr * gbr * mach * macl * syscall # * */ #if defined(CONFIG_PREEMPT) # define preempt_stop() cli #else # define preempt_stop() # define resume_kernel __restore_all #endif #if defined(CONFIG_SH_STANDARD_BIOS) || defined(CONFIG_SH_KGDB) ! Handle kernel debug if either kgdb (SW) or gdb-stub (FW) is present. ! If both are configured, handle the debug traps (breakpoints) in SW, ! but still allow BIOS traps to FW. .align 2 debug_kernel: #if defined(CONFIG_SH_STANDARD_BIOS) && defined(CONFIG_SH_KGDB) /* Force BIOS call to FW (debug_trap put TRA in r8) */ mov r8,r0 shlr2 r0 cmp/eq #0x3f,r0 bt debug_kernel_fw #endif /* CONFIG_SH_STANDARD_BIOS && CONFIG_SH_KGDB */ debug_enter: #if defined(CONFIG_SH_KGDB) /* Jump to kgdb, pass stacked regs as arg */ debug_kernel_sw: mov.l 3f, r0 jmp @r0 mov r15, r4 .align 2 3: .long kgdb_handle_exception #endif /* CONFIG_SH_KGDB */ #endif /* CONFIG_SH_STANDARD_BIOS || CONFIG_SH_KGDB */ .align 2 debug_trap: #if defined(CONFIG_SH_STANDARD_BIOS) || defined(CONFIG_SH_KGDB) mov #OFF_SR, r0 mov.l @(r0,r15), r0 ! get status register shll r0 shll r0 ! kernel space? bt/s debug_kernel #endif mov.l @r15, r0 ! Restore R0 value mov.l 1f, r8 jmp @r8 nop .align 2 ENTRY(exception_error) ! sti mov.l 2f, r0 jmp @r0 nop ! .align 2 1: .long break_point_trap_software 2: .long do_exception_error .align 2 ret_from_exception: preempt_stop() ENTRY(ret_from_irq) ! mov #OFF_SR, r0 mov.l @(r0,r15), r0 ! get status register shll r0 shll r0 ! kernel space? get_current_thread_info r8, r0 bt resume_kernel ! Yes, it's from kernel, go back soon #ifdef CONFIG_PREEMPT bra resume_userspace nop ENTRY(resume_kernel) mov.l @(TI_PRE_COUNT,r8), r0 ! current_thread_info->preempt_count tst r0, r0 bf noresched need_resched: mov.l @(TI_FLAGS,r8), r0 ! current_thread_info->flags tst #_TIF_NEED_RESCHED, r0 ! need_resched set? bt noresched mov #OFF_SR, r0 mov.l @(r0,r15), r0 ! get status register and #0xf0, r0 ! interrupts off (exception path)? cmp/eq #0xf0, r0 bt noresched mov.l 1f, r0 mov.l r0, @(TI_PRE_COUNT,r8) sti mov.l 2f, r0 jsr @r0 nop mov #0, r0 mov.l r0, @(TI_PRE_COUNT,r8) cli bra need_resched nop noresched: bra __restore_all nop .align 2 1: .long PREEMPT_ACTIVE 2: .long schedule #endif ENTRY(resume_userspace) ! r8: current_thread_info cli mov.l @(TI_FLAGS,r8), r0 ! current_thread_info->flags tst #_TIF_WORK_MASK, r0 bt/s __restore_all tst #_TIF_NEED_RESCHED, r0 .align 2 work_pending: ! r0: current_thread_info->flags ! r8: current_thread_info ! t: result of "tst #_TIF_NEED_RESCHED, r0" bf/s work_resched tst #(_TIF_SIGPENDING | _TIF_RESTORE_SIGMASK), r0 work_notifysig: bt/s __restore_all mov r15, r4 mov r12, r5 ! set arg1(save_r0) mov r0, r6 mov.l 2f, r1 mov.l 3f, r0 jmp @r1 lds r0, pr work_resched: #ifndef CONFIG_PREEMPT ! gUSA handling mov.l @(OFF_SP,r15), r0 ! get user space stack pointer mov r0, r1 shll r0 bf/s 1f shll r0 bf/s 1f mov #OFF_PC, r0 ! SP >= 0xc0000000 : gUSA mark mov.l @(r0,r15), r2 ! get user space PC (program counter) mov.l @(OFF_R0,r15), r3 ! end point cmp/hs r3, r2 ! r2 >= r3? bt 1f add r3, r1 ! rewind point #2 mov.l r1, @(r0,r15) ! reset PC to rewind point #2 ! 1: #endif mov.l 1f, r1 jsr @r1 ! schedule nop cli ! mov.l @(TI_FLAGS,r8), r0 ! current_thread_info->flags tst #_TIF_WORK_MASK, r0 bt __restore_all bra work_pending tst #_TIF_NEED_RESCHED, r0 .align 2 1: .long schedule 2: .long do_notify_resume 3: .long restore_all .align 2 syscall_exit_work: ! r0: current_thread_info->flags ! r8: current_thread_info tst #_TIF_SYSCALL_TRACE, r0 bt/s work_pending tst #_TIF_NEED_RESCHED, r0 sti ! XXX setup arguments... mov.l 4f, r0 ! do_syscall_trace jsr @r0 nop bra resume_userspace nop .align 2 syscall_trace_entry: ! Yes it is traced. ! XXX setup arguments... mov.l 4f, r11 ! Call do_syscall_trace which notifies jsr @r11 ! superior (will chomp R[0-7]) nop ! Reload R0-R4 from kernel stack, where the ! parent may have modified them using ! ptrace(POKEUSR). (Note that R0-R2 are ! used by the system call handler directly ! from the kernel stack anyway, so don't need ! to be reloaded here.) This allows the parent ! to rewrite system calls and args on the fly. mov.l @(OFF_R4,r15), r4 ! arg0 mov.l @(OFF_R5,r15), r5 mov.l @(OFF_R6,r15), r6 mov.l @(OFF_R7,r15), r7 ! arg3 mov.l @(OFF_R3,r15), r3 ! syscall_nr ! Arrange for do_syscall_trace to be called ! again as the system call returns. mov.l 2f, r10 ! Number of syscalls cmp/hs r10, r3 bf syscall_call mov #-ENOSYS, r0 bra syscall_exit mov.l r0, @(OFF_R0,r15) ! Return value __restore_all: mov.l 1f,r0 jmp @r0 nop .align 2 1: .long restore_all /* * Syscall interface: * * Syscall #: R3 * Arguments #0 to #3: R4--R7 * Arguments #4 to #6: R0, R1, R2 * TRA: (number of arguments + 0x10) x 4 * * This code also handles delegating other traps to the BIOS/gdb stub * according to: * * Trap number * (TRA>>2) Purpose * -------- ------- * 0x0-0xf old syscall ABI * 0x10-0x1f new syscall ABI * 0x20-0xff delegated through debug_trap to BIOS/gdb stub. * * Note: When we're first called, the TRA value must be shifted * right 2 bits in order to get the value that was used as the "trapa" * argument. */ .align 2 .globl ret_from_fork ret_from_fork: mov.l 1f, r8 jsr @r8 mov r0, r4 bra syscall_exit nop .align 2 1: .long schedule_tail ! ENTRY(system_call) #if !defined(CONFIG_CPU_SH2) mov.l 1f, r9 mov.l @r9, r8 ! Read from TRA (Trap Address) Register #endif ! ! Is the trap argument >= 0x20? (TRA will be >= 0x80) mov #0x7f, r9 cmp/hi r9, r8 bt/s 0f mov #OFF_TRA, r9 add r15, r9 ! mov.l r8, @r9 ! set TRA value to tra sti ! Call the system call handler through the table. ! First check for bad syscall number mov r3, r9 mov.l 2f, r8 ! Number of syscalls cmp/hs r8, r9 get_current_thread_info r8, r10 bf good_system_call syscall_badsys: ! Bad syscall number mov #-ENOSYS, r0 bra resume_userspace mov.l r0, @(OFF_R0,r15) ! Return value ! 0: bra debug_trap nop ! good_system_call: ! Good syscall number mov.l @(TI_FLAGS,r8), r8 mov #_TIF_SYSCALL_TRACE, r10 tst r10, r8 bf syscall_trace_entry ! syscall_call: shll2 r9 ! x4 mov.l 3f, r8 ! Load the address of sys_call_table add r8, r9 mov.l @r9, r8 jsr @r8 ! jump to specific syscall handler nop mov.l @(OFF_R0,r15), r12 ! save r0 mov.l r0, @(OFF_R0,r15) ! save the return value ! syscall_exit: cli ! get_current_thread_info r8, r0 mov.l @(TI_FLAGS,r8), r0 ! current_thread_info->flags tst #_TIF_ALLWORK_MASK, r0 bf syscall_exit_work bra __restore_all nop .align 2 #if !defined(CONFIG_CPU_SH2) 1: .long TRA #endif 2: .long NR_syscalls 3: .long sys_call_table 4: .long do_syscall_trace