5d9f3ea081
r11 is a volatile register on PPC as per calling conventions. The safe_syscall code uses it to check if the signal_pending is set during the safe_syscall. When a syscall is interrupted on return from signal handling, the r11 might be corrupted before we retry the syscall leading to a crash. The registers r0-r13 are not to be used here as they have volatile/designated/reserved usages. Change the code to use r14 which is non-volatile. Use SP+16 which is a slot for LR, for save/restore of previous value of r14. SP+16 can be used, as LR is preserved across the syscall. Steps to reproduce: On PPC host, issue `qemu-x86_64 /usr/bin/cc -E -` Attempt Ctrl-C, the issue is reproduced. Reference: https://refspecs.linuxfoundation.org/ELF/ppc64/PPC-elf64abi-1.9.html#REG https://openpowerfoundation.org/wp-content/uploads/2016/03/ABI64BitOpenPOWERv1.1_16July2015_pub4.pdf Signed-off-by: Shivaprasad G Bhat <sbhat@linux.vnet.ibm.com> Tested-by: Richard Henderson <richard.henderson@linaro.org> Tested-by: Laurent Vivier <laurent@vivier.eu> Reviewed-by: Richard Henderson <richard.henderson@linaro.org> Reviewed-by: Laurent Vivier <laurent@vivier.eu> Message-Id: <153301568965.30312.10498134581068746871.stgit@dhcp-9-109-246-16> Signed-off-by: Laurent Vivier <laurent@vivier.eu>
97 lines
2.9 KiB
ArmAsm
97 lines
2.9 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 linux-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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* We return a long which is the syscall's return value, which
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* may be negative-errno on failure. Conversion to the
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* -1-and-errno-set convention is done by the calling wrapper.
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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- 0f
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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 to its original value */
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bnslr+
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/* syscall failed; return negative errno */
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neg 3, 3
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blr
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/* code path when we didn't execute the syscall */
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0: addi 3, 0, -TARGET_ERESTARTSYS
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ld 14, 16(1) /* restore r14 to its orginal value */
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blr
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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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