--- /dev/null
+/* $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 */
+#ifdef CONFIG_SH_STANDARD_BIOS
+ bra debug_kernel_fw
+ nop
+#endif
+#endif /* CONFIG_SH_STANDARD_BIOS || CONFIG_SH_KGDB */
+
+ .align 2
+debug_trap:
+#if defined(CONFIG_SH_STANDARD_BIOS) || defined(CONFIG_SH_KGDB)
+ mov r8, r0
+ shlr2 r0
+ cmp/eq #0x3f, r0 ! sh_bios() trap
+ bf 1f
+#ifdef CONFIG_SH_KGDB
+ cmp/eq #0xff, r0 ! XXX: KGDB trap, fix for SH-2.
+ bf 1f
+#endif
+ mov #OFF_SR, r0
+ mov.l @(r0,r15), r0 ! get status register
+ shll r0
+ shll r0 ! kernel space?
+ bt/s debug_kernel
+1:
+#endif
+ mov.l @r15, r0 ! Restore R0 value
+ mov.l 1f, r8
+ jmp @r8
+ nop
+
+ .align 2
+ENTRY(exception_error)
+ !
+#ifdef CONFIG_TRACE_IRQFLAGS
+ mov.l 3f, r0
+ jsr @r0
+ nop
+#endif
+ sti
+ mov.l 2f, r0
+ jmp @r0
+ nop
+
+!
+ .align 2
+1: .long break_point_trap_software
+2: .long do_exception_error
+#ifdef CONFIG_TRACE_IRQFLAGS
+3: .long trace_hardirqs_on
+#endif
+
+ .align 2
+ret_from_exception:
+ preempt_stop()
+#ifdef CONFIG_TRACE_IRQFLAGS
+ mov.l 4f, r0
+ jsr @r0
+ nop
+#endif
+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)
+
+#ifdef CONFIG_TRACE_IRQFLAGS
+ mov.l 3f, r0
+ jsr @r0
+ nop
+#endif
+ sti
+ mov.l 2f, r0
+ jsr @r0
+ nop
+ mov #0, r0
+ mov.l r0, @(TI_PRE_COUNT,r8)
+ cli
+#ifdef CONFIG_TRACE_IRQFLAGS
+ mov.l 4f, r0
+ jsr @r0
+ nop
+#endif
+
+ bra need_resched
+ nop
+
+noresched:
+ bra __restore_all
+ nop
+
+ .align 2
+1: .long PREEMPT_ACTIVE
+2: .long schedule
+#ifdef CONFIG_TRACE_IRQFLAGS
+3: .long trace_hardirqs_on
+4: .long trace_hardirqs_off
+#endif
+#endif
+
+ENTRY(resume_userspace)
+ ! r8: current_thread_info
+ cli
+#ifdef CONFIG_TRACE_IRQFLAGS
+ mov.l 5f, r0
+ jsr @r0
+ nop
+#endif
+ 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
+#ifdef CONFIG_TRACE_IRQFLAGS
+ mov.l 5f, r0
+ jsr @r0
+ nop
+#endif
+ !
+ 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
+#ifdef CONFIG_TRACE_IRQFLAGS
+4: .long trace_hardirqs_on
+5: .long trace_hardirqs_off
+#endif
+
+ .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
+#ifdef CONFIG_TRACE_IRQFLAGS
+ mov.l 5f, r0
+ jsr @r0
+ nop
+#endif
+ 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
+ !
+ 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
+
+ .align 2
+not_syscall_tra:
+ bra debug_trap
+ nop
+
+ .align 2
+syscall_badsys: ! Bad syscall number
+ mov #-ENOSYS, r0
+ bra resume_userspace
+ mov.l r0, @(OFF_R0,r15) ! Return value
+
+
+/*
+ * 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 not_syscall_tra
+ mov #OFF_TRA, r9
+ add r15, r9
+ mov.l r8, @r9 ! set TRA value to tra
+#ifdef CONFIG_TRACE_IRQFLAGS
+ mov.l 5f, r10
+ jsr @r10
+ nop
+#endif
+ sti
+
+ !
+ get_current_thread_info r8, r10
+ mov.l @(TI_FLAGS,r8), r8
+ mov #_TIF_SYSCALL_TRACE, r10
+ tst r10, r8
+ bf syscall_trace_entry
+ !
+ mov.l 2f, r8 ! Number of syscalls
+ cmp/hs r8, r3
+ bt syscall_badsys
+ !
+syscall_call:
+ shll2 r3 ! x4
+ mov.l 3f, r8 ! Load the address of sys_call_table
+ add r8, r3
+ mov.l @r3, 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
+#ifdef CONFIG_TRACE_IRQFLAGS
+ mov.l 6f, r0
+ jsr @r0
+ nop
+#endif
+ !
+ 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
+#ifdef CONFIG_TRACE_IRQFLAGS
+5: .long trace_hardirqs_on
+6: .long trace_hardirqs_off
+#endif
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