linux-user: Provide safe_syscall for s390x

Signed-off-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Riku Voipio <riku.voipio@linaro.org>
This commit is contained in:
Richard Henderson 2016-06-21 17:32:12 -07:00 committed by Riku Voipio
parent 31f875f211
commit c9bc3437a9
2 changed files with 113 additions and 0 deletions

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@ -12,4 +12,27 @@
#ifndef QEMU_HOSTDEP_H
#define QEMU_HOSTDEP_H
/* We have a safe-syscall.inc.S */
#define HAVE_SAFE_SYSCALL
#ifndef __ASSEMBLER__
/* These are defined by the safe-syscall.inc.S file */
extern char safe_syscall_start[];
extern char safe_syscall_end[];
/* Adjust the signal context to rewind out of safe-syscall if we're in it */
static inline void rewind_if_in_safe_syscall(void *puc)
{
struct ucontext *uc = puc;
unsigned long *pcreg = &uc->uc_mcontext.psw.addr;
if (*pcreg > (uintptr_t)safe_syscall_start
&& *pcreg < (uintptr_t)safe_syscall_end) {
*pcreg = (uintptr_t)safe_syscall_start;
}
}
#endif /* __ASSEMBLER__ */
#endif

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@ -0,0 +1,90 @@
/*
* safe-syscall.inc.S : 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 <rth@twiddle.net>
* 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
/* 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.
*/
safe_syscall_base:
.cfi_startproc
stmg %r6,%r15,48(%r15) /* save all call-saved registers */
.cfi_offset %r15,-40
.cfi_offset %r14,-48
.cfi_offset %r13,-56
.cfi_offset %r12,-64
.cfi_offset %r11,-72
.cfi_offset %r10,-80
.cfi_offset %r9,-88
.cfi_offset %r8,-96
.cfi_offset %r7,-104
.cfi_offset %r6,-112
lgr %r1,%r15
lg %r0,8(%r15) /* load eos */
aghi %r15,-160
.cfi_adjust_cfa_offset 160
stg %r1,0(%r15) /* store back chain */
stg %r0,8(%r15) /* store eos */
/* The syscall calling convention isn't the same as the
* C one:
* we enter with r2 == *signal_pending
* r3 == syscall number
* r4, r5, r6, (stack) == syscall arguments
* and return the result in r2
* and the syscall instruction needs
* r1 == syscall number
* r2 ... r7 == syscall arguments
* and returns the result in r2
* Shuffle everything around appropriately.
*/
lgr %r8,%r2 /* signal_pending pointer */
lgr %r1,%r3 /* syscall number */
lgr %r2,%r4 /* syscall args */
lgr %r3,%r5
lgr %r4,%r6
lmg %r5,%r7,320(%r15)
/* 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.
*/
safe_syscall_start:
/* if signal_pending is non-zero, don't do the call */
lt %r0,0(%r8)
jne 2f
svc 0
safe_syscall_end:
1: lg %r15,0(%r15) /* load back chain */
.cfi_remember_state
.cfi_adjust_cfa_offset -160
lmg %r6,%r15,48(%r15) /* load saved registers */
br %r14
.cfi_restore_state
2: lghi %r2, -TARGET_ERESTARTSYS
j 1b
.cfi_endproc
.size safe_syscall_base, .-safe_syscall_base