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linux-user/i386: Implement setup_sigtramp

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Create and record the two signal trampolines.
Use them when the guest does not use SA_RESTORER.
Note that x86_64 does not use this code.

Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20210929130553.121567-11-richard.henderson@linaro.org>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>
This commit is contained in:
Richard Henderson 2021-09-29 09:05:37 -04:00 committed by Laurent Vivier
parent a22fccd8b7
commit 8ee8a10480
3 changed files with 43 additions and 18 deletions
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56
linux-user/i386/signal.c
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@ -310,6 +310,22 @@ get_sigframe(struct target_sigaction *ka, CPUX86State *env, size_t frame_size)
} }
#ifndef TARGET_X86_64 #ifndef TARGET_X86_64
static void install_sigtramp(void *tramp)
{
/* This is popl %eax ; movl $syscall,%eax ; int $0x80 */
__put_user(0xb858, (uint16_t *)(tramp + 0));
__put_user(TARGET_NR_sigreturn, (int32_t *)(tramp + 2));
__put_user(0x80cd, (uint16_t *)(tramp + 6));
}
static void install_rt_sigtramp(void *tramp)
{
/* This is movl $syscall,%eax ; int $0x80 */
__put_user(0xb8, (uint8_t *)(tramp + 0));
__put_user(TARGET_NR_rt_sigreturn, (int32_t *)(tramp + 1));
__put_user(0x80cd, (uint16_t *)(tramp + 5));
}
/* compare linux/arch/i386/kernel/signal.c:setup_frame() */ /* compare linux/arch/i386/kernel/signal.c:setup_frame() */
void setup_frame(int sig, struct target_sigaction *ka, void setup_frame(int sig, struct target_sigaction *ka,
target_sigset_t *set, CPUX86State *env) target_sigset_t *set, CPUX86State *env)
@ -338,16 +354,9 @@ void setup_frame(int sig, struct target_sigaction *ka,
if (ka->sa_flags & TARGET_SA_RESTORER) { if (ka->sa_flags & TARGET_SA_RESTORER) {
__put_user(ka->sa_restorer, &frame->pretcode); __put_user(ka->sa_restorer, &frame->pretcode);
} else { } else {
uint16_t val16; /* This is no longer used, but is retained for ABI compatibility. */
abi_ulong retcode_addr; install_sigtramp(frame->retcode);
retcode_addr = frame_addr + offsetof(struct sigframe, retcode); __put_user(default_sigreturn, &frame->pretcode);
__put_user(retcode_addr, &frame->pretcode);
/* This is popl %eax ; movl $,%eax ; int $0x80 */
val16 = 0xb858;
__put_user(val16, (uint16_t *)(frame->retcode+0));
__put_user(TARGET_NR_sigreturn, (int *)(frame->retcode+2));
val16 = 0x80cd;
__put_user(val16, (uint16_t *)(frame->retcode+6));
} }
/* Set up registers for signal handler */ /* Set up registers for signal handler */
@ -416,14 +425,9 @@ void setup_rt_frame(int sig, struct target_sigaction *ka,
if (ka->sa_flags & TARGET_SA_RESTORER) { if (ka->sa_flags & TARGET_SA_RESTORER) {
__put_user(ka->sa_restorer, &frame->pretcode); __put_user(ka->sa_restorer, &frame->pretcode);
} else { } else {
uint16_t val16; /* This is no longer used, but is retained for ABI compatibility. */
addr = frame_addr + offsetof(struct rt_sigframe, retcode); install_rt_sigtramp(frame->retcode);
__put_user(addr, &frame->pretcode); __put_user(default_rt_sigreturn, &frame->pretcode);
/* This is movl $,%eax ; int $0x80 */
__put_user(0xb8, (char *)(frame->retcode+0));
__put_user(TARGET_NR_rt_sigreturn, (int *)(frame->retcode+1));
val16 = 0x80cd;
__put_user(val16, (uint16_t *)(frame->retcode+5));
} }
#else #else
/* XXX: Would be slightly better to return -EFAULT here if test fails /* XXX: Would be slightly better to return -EFAULT here if test fails
@ -592,3 +596,19 @@ badframe:
force_sig(TARGET_SIGSEGV); force_sig(TARGET_SIGSEGV);
return -TARGET_QEMU_ESIGRETURN; return -TARGET_QEMU_ESIGRETURN;
} }
#ifndef TARGET_X86_64
void setup_sigtramp(abi_ulong sigtramp_page)
{
uint16_t *tramp = lock_user(VERIFY_WRITE, sigtramp_page, 2 * 8, 0);
assert(tramp != NULL);
default_sigreturn = sigtramp_page;
install_sigtramp(tramp);
default_rt_sigreturn = sigtramp_page + 8;
install_rt_sigtramp(tramp + 8);
unlock_user(tramp, sigtramp_page, 2 * 8);
}
#endif

2
linux-user/i386/target_signal.h
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@ -22,4 +22,6 @@ typedef struct target_sigaltstack {
#include "../generic/signal.h" #include "../generic/signal.h"
#define TARGET_ARCH_HAS_SETUP_FRAME #define TARGET_ARCH_HAS_SETUP_FRAME
#define TARGET_ARCH_HAS_SIGTRAMP_PAGE 1
#endif /* I386_TARGET_SIGNAL_H */ #endif /* I386_TARGET_SIGNAL_H */

3
linux-user/x86_64/target_signal.h
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@ -21,4 +21,7 @@ typedef struct target_sigaltstack {
#include "../generic/signal.h" #include "../generic/signal.h"
/* For x86_64, use of SA_RESTORER is mandatory. */
#define TARGET_ARCH_HAS_SIGTRAMP_PAGE 0
#endif /* X86_64_TARGET_SIGNAL_H */ #endif /* X86_64_TARGET_SIGNAL_H */