ffe98631b3
Signed-off-by: Richard Henderson <richard.henderson@linaro.org> Reviewed-by: Daniel Henrique Barboza <danielhb413@gmail.com> Message-Id: <20220729172141.1789105-2-richard.henderson@linaro.org>
108 lines
3.4 KiB
ArmAsm
108 lines
3.4 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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* Copyright (C) 2022 Linaro, Ltd.
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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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/*
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* Standardize on the _CALL_FOO symbols used by GCC:
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* Apple XCode does not define _CALL_DARWIN.
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* Clang defines _CALL_ELF (64-bit) but not _CALL_SYSV (32-bit).
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*/
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#if !defined(_CALL_SYSV) && \
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!defined(_CALL_DARWIN) && \
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!defined(_CALL_AIX) && \
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!defined(_CALL_ELF)
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# if defined(__APPLE__)
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# define _CALL_DARWIN
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# elif defined(__ELF__) && TCG_TARGET_REG_BITS == 32
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# define _CALL_SYSV
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# else
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# error "Unknown ABI"
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# endif
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#endif
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#ifndef _CALL_SYSV
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# error "Unsupported ABI"
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#endif
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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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/*
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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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safe_syscall_base:
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.cfi_startproc
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stwu 1, -8(1)
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.cfi_def_cfa_offset 8
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stw 30, 4(1)
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.cfi_offset 30, -4
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/*
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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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mr 30, 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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/*
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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(30)
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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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lwz 30, 4(1) /* restore r30 */
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addi 1, 1, 8 /* restore stack */
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.cfi_restore 30
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.cfi_def_cfa_offset 0
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bnslr+ /* return on success */
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b safe_syscall_set_errno_tail
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/* code path when we didn't execute the syscall */
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2: lwz 30, 4(1)
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addi 1, 1, 8
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addi 3, 0, QEMU_ERESTARTSYS
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b safe_syscall_set_errno_tail
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.cfi_endproc
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.size safe_syscall_base, .-safe_syscall_base
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