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3623d13821
Historically SH-2 Linux (and originally uClinux) used a syscall calling convention incompatible with the established SH-3/4 Linux ABI. This choice was made because the trap range used by the existing ABI, 0x10-0x17, overlaps with the hardware exception/interrupt trap range reserved by SH-2, and in particular, with the SH-2A divide-by-zero and division-overflow exceptions. Despite the documented syscall convention using the low bits of the trap number to signal the number of arguments the kernel should expect, no version of the kernel has ever used this information, nor is it useful; all of the registers need to be saved anyway. Therefore, it is possible to pick a new trap number, 0x1f, that is both supported by all existing SH-3/4 kernels and unassigned as a hardware trap in the SH-2 range. This makes it possible to produce SH-2 application binaries that are forwards-compatible with running on SH-3/4 kernels and to treat SH as a unified platform with varying ISA support levels rather than multiple gratuitously-incompatible platforms. This patch adjusts the range checking SH-2 and SH-2A kernels make for the syscall trap to accept the range 0x1f-0x2f rather than just 0x20-0x2f. As a result, trap 0x1f now acts as a syscall for all SH models. Signed-off-by: Rich Felker <dalias@libc.org>
403 lines
8.7 KiB
ArmAsm
403 lines
8.7 KiB
ArmAsm
/*
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* Copyright (C) 1999, 2000, 2002 Niibe Yutaka
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* Copyright (C) 2003 - 2008 Paul Mundt
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*
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* This file is subject to the terms and conditions of the GNU General Public
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* License. See the file "COPYING" in the main directory of this archive
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* for more details.
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*
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*/
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! NOTE:
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! GNU as (as of 2.9.1) changes bf/s into bt/s and bra, when the address
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! to be jumped is too far, but it causes illegal slot exception.
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/*
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* entry.S contains the system-call and fault low-level handling routines.
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* This also contains the timer-interrupt handler, as well as all interrupts
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* and faults that can result in a task-switch.
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*
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* NOTE: This code handles signal-recognition, which happens every time
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* after a timer-interrupt and after each system call.
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*
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* NOTE: This code uses a convention that instructions in the delay slot
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* of a transfer-control instruction are indented by an extra space, thus:
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*
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* jmp @k0 ! control-transfer instruction
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* ldc k1, ssr ! delay slot
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*
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* Stack layout in 'ret_from_syscall':
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* ptrace needs to have all regs on the stack.
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* if the order here is changed, it needs to be
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* updated in ptrace.c and ptrace.h
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*
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* r0
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* ...
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* r15 = stack pointer
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* spc
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* pr
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* ssr
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* gbr
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* mach
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* macl
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* syscall #
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*
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*/
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#include <asm/dwarf.h>
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#if defined(CONFIG_PREEMPT)
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# define preempt_stop() cli ; TRACE_IRQS_OFF
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#else
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# define preempt_stop()
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# define resume_kernel __restore_all
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#endif
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.align 2
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ENTRY(exception_error)
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!
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TRACE_IRQS_ON
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sti
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mov.l 1f, r0
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jmp @r0
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nop
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.align 2
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1: .long do_exception_error
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.align 2
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ret_from_exception:
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CFI_STARTPROC simple
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CFI_DEF_CFA r14, 0
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CFI_REL_OFFSET 17, 64
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CFI_REL_OFFSET 15, 60
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CFI_REL_OFFSET 14, 56
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CFI_REL_OFFSET 13, 52
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CFI_REL_OFFSET 12, 48
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CFI_REL_OFFSET 11, 44
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CFI_REL_OFFSET 10, 40
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CFI_REL_OFFSET 9, 36
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CFI_REL_OFFSET 8, 32
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preempt_stop()
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ENTRY(ret_from_irq)
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!
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mov #OFF_SR, r0
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mov.l @(r0,r15), r0 ! get status register
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shll r0
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shll r0 ! kernel space?
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get_current_thread_info r8, r0
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bt resume_kernel ! Yes, it's from kernel, go back soon
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#ifdef CONFIG_PREEMPT
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bra resume_userspace
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nop
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ENTRY(resume_kernel)
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cli
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TRACE_IRQS_OFF
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mov.l @(TI_PRE_COUNT,r8), r0 ! current_thread_info->preempt_count
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tst r0, r0
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bf noresched
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need_resched:
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mov.l @(TI_FLAGS,r8), r0 ! current_thread_info->flags
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tst #_TIF_NEED_RESCHED, r0 ! need_resched set?
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bt noresched
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mov #OFF_SR, r0
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mov.l @(r0,r15), r0 ! get status register
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shlr r0
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and #(0xf0>>1), r0 ! interrupts off (exception path)?
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cmp/eq #(0xf0>>1), r0
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bt noresched
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mov.l 1f, r0
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jsr @r0 ! call preempt_schedule_irq
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nop
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bra need_resched
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nop
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noresched:
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bra __restore_all
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nop
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.align 2
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1: .long preempt_schedule_irq
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#endif
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ENTRY(resume_userspace)
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! r8: current_thread_info
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cli
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TRACE_IRQS_OFF
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mov.l @(TI_FLAGS,r8), r0 ! current_thread_info->flags
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tst #(_TIF_WORK_MASK & 0xff), r0
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bt/s __restore_all
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tst #_TIF_NEED_RESCHED, r0
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.align 2
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work_pending:
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! r0: current_thread_info->flags
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! r8: current_thread_info
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! t: result of "tst #_TIF_NEED_RESCHED, r0"
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bf/s work_resched
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tst #(_TIF_SIGPENDING | _TIF_NOTIFY_RESUME), r0
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work_notifysig:
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bt/s __restore_all
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mov r15, r4
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mov r12, r5 ! set arg1(save_r0)
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mov r0, r6
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sti
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mov.l 2f, r1
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mov.l 3f, r0
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jmp @r1
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lds r0, pr
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work_resched:
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mov.l 1f, r1
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jsr @r1 ! schedule
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nop
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cli
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TRACE_IRQS_OFF
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!
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mov.l @(TI_FLAGS,r8), r0 ! current_thread_info->flags
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tst #(_TIF_WORK_MASK & 0xff), r0
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bt __restore_all
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bra work_pending
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tst #_TIF_NEED_RESCHED, r0
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.align 2
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1: .long schedule
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2: .long do_notify_resume
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3: .long resume_userspace
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.align 2
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syscall_exit_work:
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! r0: current_thread_info->flags
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! r8: current_thread_info
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tst #(_TIF_WORK_SYSCALL_MASK & 0xff), r0
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bt/s work_pending
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tst #_TIF_NEED_RESCHED, r0
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TRACE_IRQS_ON
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sti
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mov r15, r4
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mov.l 8f, r0 ! do_syscall_trace_leave
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jsr @r0
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nop
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bra resume_userspace
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nop
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.align 2
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syscall_trace_entry:
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! Yes it is traced.
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mov r15, r4
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mov.l 7f, r11 ! Call do_syscall_trace_enter which notifies
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jsr @r11 ! superior (will chomp R[0-7])
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nop
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mov.l r0, @(OFF_R0,r15) ! Save return value
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! Reload R0-R4 from kernel stack, where the
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! parent may have modified them using
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! ptrace(POKEUSR). (Note that R0-R2 are
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! reloaded from the kernel stack by syscall_call
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! below, so don't need to be reloaded here.)
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! This allows the parent to rewrite system calls
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! and args on the fly.
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mov.l @(OFF_R4,r15), r4 ! arg0
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mov.l @(OFF_R5,r15), r5
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mov.l @(OFF_R6,r15), r6
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mov.l @(OFF_R7,r15), r7 ! arg3
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mov.l @(OFF_R3,r15), r3 ! syscall_nr
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!
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mov.l 2f, r10 ! Number of syscalls
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cmp/hs r10, r3
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bf syscall_call
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mov #-ENOSYS, r0
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bra syscall_exit
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mov.l r0, @(OFF_R0,r15) ! Return value
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__restore_all:
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mov #OFF_SR, r0
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mov.l @(r0,r15), r0 ! get status register
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shlr2 r0
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and #0x3c, r0
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cmp/eq #0x3c, r0
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bt 1f
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TRACE_IRQS_ON
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bra 2f
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nop
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1:
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TRACE_IRQS_OFF
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2:
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mov.l 3f, r0
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jmp @r0
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nop
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.align 2
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3: .long restore_all
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.align 2
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syscall_badsys: ! Bad syscall number
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get_current_thread_info r8, r0
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mov #-ENOSYS, r0
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bra resume_userspace
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mov.l r0, @(OFF_R0,r15) ! Return value
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/*
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* The main debug trap handler.
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*
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* r8=TRA (not the trap number!)
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*
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* Note: This assumes that the trapa value is left in its original
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* form (without the shlr2 shift) so the calculation for the jump
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* call table offset remains a simple in place mask.
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*/
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debug_trap:
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mov r8, r0
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and #(0xf << 2), r0
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mov.l 1f, r8
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add r0, r8
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mov.l @r8, r8
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jsr @r8
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nop
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bra __restore_all
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nop
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CFI_ENDPROC
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.align 2
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1: .long debug_trap_table
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/*
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* Syscall interface:
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*
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* Syscall #: R3
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* Arguments #0 to #3: R4--R7
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* Arguments #4 to #6: R0, R1, R2
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* TRA: See following table.
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*
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* (TRA>>2) Purpose
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* -------- -------
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* 0x00-0x0f original SH-3/4 syscall ABI (not in general use).
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* 0x10-0x1f general SH-3/4 syscall ABI.
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* 0x1f unified SH-2/3/4 syscall ABI (preferred).
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* 0x20-0x2f original SH-2 syscall ABI.
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* 0x30-0x3f debug traps used by the kernel.
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* 0x40-0xff Not supported by all parts, so left unhandled.
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*
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* For making system calls, any trap number in the range for the
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* given cpu model may be used, but the unified trap number 0x1f is
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* preferred for compatibility with all models.
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*
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* The low bits of the trap number were once documented as matching
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* the number of arguments, but they were never actually used as such
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* by the kernel. SH-2 originally used its own separate trap range
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* because several hardware exceptions fell in the range used for the
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* SH-3/4 syscall ABI.
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*
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* This code also handles delegating other traps to the BIOS/gdb stub.
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*
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* Note: When we're first called, the TRA value must be shifted
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* right 2 bits in order to get the value that was used as the "trapa"
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* argument.
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*/
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.align 2
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.globl ret_from_fork
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ret_from_fork:
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mov.l 1f, r8
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jsr @r8
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mov r0, r4
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bra syscall_exit
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nop
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.align 2
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.globl ret_from_kernel_thread
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ret_from_kernel_thread:
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mov.l 1f, r8
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jsr @r8
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mov r0, r4
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mov.l @(OFF_R5,r15), r5 ! fn
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jsr @r5
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mov.l @(OFF_R4,r15), r4 ! arg
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bra syscall_exit
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nop
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.align 2
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1: .long schedule_tail
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/*
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* The poorly named main trapa decode and dispatch routine, for
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* system calls and debug traps through their respective jump tables.
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*/
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ENTRY(system_call)
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setup_frame_reg
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#if !defined(CONFIG_CPU_SH2)
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mov.l 1f, r9
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mov.l @r9, r8 ! Read from TRA (Trap Address) Register
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#endif
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mov #OFF_TRA, r10
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add r15, r10
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mov.l r8, @r10 ! set TRA value to tra
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/*
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* Check the trap type
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*/
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mov #((0x20 << 2) - 1), r9
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cmp/hi r9, r8
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bt/s debug_trap ! it's a debug trap..
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nop
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TRACE_IRQS_ON
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sti
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!
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get_current_thread_info r8, r10
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mov.l @(TI_FLAGS,r8), r8
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mov #(_TIF_WORK_SYSCALL_MASK & 0xff), r10
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mov #(_TIF_WORK_SYSCALL_MASK >> 8), r9
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tst r10, r8
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shll8 r9
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bf syscall_trace_entry
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tst r9, r8
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bf syscall_trace_entry
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!
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mov.l 2f, r8 ! Number of syscalls
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cmp/hs r8, r3
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bt syscall_badsys
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!
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syscall_call:
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shll2 r3 ! x4
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mov.l 3f, r8 ! Load the address of sys_call_table
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add r8, r3
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mov.l @r3, r8
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mov.l @(OFF_R2,r15), r2
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mov.l @(OFF_R1,r15), r1
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mov.l @(OFF_R0,r15), r0
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mov.l r2, @-r15
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mov.l r1, @-r15
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mov.l r0, @-r15
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jsr @r8 ! jump to specific syscall handler
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nop
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add #12, r15
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mov.l @(OFF_R0,r15), r12 ! save r0
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mov.l r0, @(OFF_R0,r15) ! save the return value
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!
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syscall_exit:
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cli
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TRACE_IRQS_OFF
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!
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get_current_thread_info r8, r0
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mov.l @(TI_FLAGS,r8), r0 ! current_thread_info->flags
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tst #(_TIF_ALLWORK_MASK & 0xff), r0
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mov #(_TIF_ALLWORK_MASK >> 8), r1
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bf syscall_exit_work
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shlr8 r0
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tst r0, r1
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bf syscall_exit_work
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bra __restore_all
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nop
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.align 2
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#if !defined(CONFIG_CPU_SH2)
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1: .long TRA
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#endif
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2: .long NR_syscalls
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3: .long sys_call_table
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7: .long do_syscall_trace_enter
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8: .long do_syscall_trace_leave
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