blob: bc1f5a97928065d42095cf0f95cdfe275b70b1c6 [file] [log] [blame]
* : host-specific assembly fragment
* to handle signals occurring at the same time as system calls.
* This is intended to be included by linux-user/safe-syscall.S
* Written by Richard Henderson <>
* Copyright (C) 2016 Red Hat, Inc.
* This work is licensed under the terms of the GNU GPL, version 2 or later.
* See the COPYING file in the top-level directory.
.global safe_syscall_base
.global safe_syscall_start
.global safe_syscall_end
.type safe_syscall_base, #function
.type safe_syscall_start, #function
.type safe_syscall_end, #function
/* This is the entry point for making a system call. The calling
* convention here is that of a C varargs function with the
* first argument an 'int *' to the signal_pending flag, the
* second one the system call number (as a 'long'), and all further
* arguments being syscall arguments (also 'long').
* We return a long which is the syscall's return value, which
* may be negative-errno on failure. Conversion to the
* -1-and-errno-set convention is done by the calling wrapper.
/* The syscall calling convention isn't the same as the
* C one:
* we enter with x0 == *signal_pending
* x1 == syscall number
* x2 ... x7, (stack) == syscall arguments
* and return the result in x0
* and the syscall instruction needs
* x8 == syscall number
* x0 ... x6 == syscall arguments
* and returns the result in x0
* Shuffle everything around appropriately.
mov x9, x0 /* signal_pending pointer */
mov x8, x1 /* syscall number */
mov x0, x2 /* syscall arguments */
mov x1, x3
mov x2, x4
mov x3, x5
mov x4, x6
mov x5, x7
ldr x6, [sp]
/* This next sequence of code works in conjunction with the
* rewind_if_safe_syscall_function(). If a signal is taken
* and the interrupted PC is anywhere between 'safe_syscall_start'
* and 'safe_syscall_end' then we rewind it to 'safe_syscall_start'.
* The code sequence must therefore be able to cope with this, and
* the syscall instruction must be the final one in the sequence.
/* if signal_pending is non-zero, don't do the call */
ldr w10, [x9]
cbnz w10, 0f
svc 0x0
/* code path for having successfully executed the syscall */
/* code path when we didn't execute the syscall */
.size safe_syscall_base, .-safe_syscall_base