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95 lines
3.2 KiB
ArmAsm
95 lines
3.2 KiB
ArmAsm
/*
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* safe-syscall.inc.S : host-specific assembly fragment
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* to handle signals occurring at the same time as system calls.
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* This is intended to be included by common-user/safe-syscall.S
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*
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* Written by Richard Henderson <rth@twiddle.net>
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* Copyright (C) 2016 Red Hat, Inc.
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*
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* This work is licensed under the terms of the GNU GPL, version 2 or later.
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* See the COPYING file in the top-level directory.
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*/
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.global safe_syscall_base
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.global safe_syscall_start
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.global safe_syscall_end
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.type safe_syscall_base, @function
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.text
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/* This is the entry point for making a system call. The calling
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* convention here is that of a C varargs function with the
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* first argument an 'int *' to the signal_pending flag, the
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* second one the system call number (as a 'long'), and all further
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* arguments being syscall arguments (also 'long').
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*/
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#if _CALL_ELF == 2
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safe_syscall_base:
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.cfi_startproc
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.localentry safe_syscall_base,0
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#else
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.section ".opd","aw"
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.align 3
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safe_syscall_base:
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.quad .L.safe_syscall_base,.TOC.@tocbase,0
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.previous
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.L.safe_syscall_base:
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.cfi_startproc
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#endif
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/* We enter with r3 == &signal_pending
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* r4 == syscall number
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* r5 ... r10 == syscall arguments
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* and return the result in r3
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* and the syscall instruction needs
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* r0 == syscall number
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* r3 ... r8 == syscall arguments
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* and returns the result in r3
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* Shuffle everything around appropriately.
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*/
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std 14, 16(1) /* Preserve r14 in SP+16 */
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.cfi_offset 14, 16
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mr 14, 3 /* signal_pending */
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mr 0, 4 /* syscall number */
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mr 3, 5 /* syscall arguments */
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mr 4, 6
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mr 5, 7
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mr 6, 8
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mr 7, 9
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mr 8, 10
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/* This next sequence of code works in conjunction with the
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* rewind_if_safe_syscall_function(). If a signal is taken
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* and the interrupted PC is anywhere between 'safe_syscall_start'
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* and 'safe_syscall_end' then we rewind it to 'safe_syscall_start'.
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* The code sequence must therefore be able to cope with this, and
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* the syscall instruction must be the final one in the sequence.
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*/
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safe_syscall_start:
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/* if signal_pending is non-zero, don't do the call */
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lwz 12, 0(14)
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cmpwi 0, 12, 0
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bne- 2f
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sc
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safe_syscall_end:
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/* code path when we did execute the syscall */
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ld 14, 16(1) /* restore r14 */
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bso- 1f
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blr
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/* code path when we didn't execute the syscall */
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2: ld 14, 16(1) /* restore r14 */
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addi 3, 0, QEMU_ERESTARTSYS
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/* code path setting errno */
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1: b safe_syscall_set_errno_tail
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nop /* per abi, for the linker to modify */
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.cfi_endproc
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#if _CALL_ELF == 2
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.size safe_syscall_base, .-safe_syscall_base
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#else
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.size safe_syscall_base, .-.L.safe_syscall_base
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.size .L.safe_syscall_base, .-.L.safe_syscall_base
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#endif
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