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linux-user: SIGSEGV on signal entry need not be fatal

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A failed write to memory trying to set up the signal frame
should trigger a SIGSEGV, but this need not be fatal: the
guest has a chance to catch it. Implement this via a force_sigsegv()
function with the same behaviour as the kernel function of that
name: make sure that we don't try to re-take a failed SIGSEGV,
and force a synchronous signal.

Reviewed-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Riku Voipio <riku.voipio@linaro.org>
This commit is contained in:
Peter Maydell 2016-07-28 16:44:47 +01:00 committed by Riku Voipio
parent 9d2803f720
commit 0939166997
1 changed files with 49 additions and 38 deletions
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87
linux-user/signal.c
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@ -512,6 +512,33 @@ void signal_init(void)
}
}
#if !((defined(TARGET_ARM) && !defined(TARGET_AARCH64)) || \
defined(TARGET_X86_64) || defined(TARGET_UNICORE32))
/* Force a SIGSEGV if we couldn't write to memory trying to set
* up the signal frame. oldsig is the signal we were trying to handle
* at the point of failure.
*/
static void force_sigsegv(int oldsig)
{
CPUState *cpu = thread_cpu;
CPUArchState *env = cpu->env_ptr;
target_siginfo_t info;
if (oldsig == SIGSEGV) {
/* Make sure we don't try to deliver the signal again; this will
* end up with handle_pending_signal() calling force_sig().
*/
sigact_table[oldsig - 1]._sa_handler = TARGET_SIG_DFL;
}
info.si_signo = TARGET_SIGSEGV;
info.si_errno = 0;
info.si_code = TARGET_SI_KERNEL;
info._sifields._kill._pid = 0;
info._sifields._kill._uid = 0;
queue_signal(env, info.si_signo, QEMU_SI_KILL, &info);
}
#endif
/* abort execution with signal */
static void QEMU_NORETURN force_sig(int target_sig)
@ -1011,10 +1038,7 @@ static void setup_frame(int sig, struct target_sigaction *ka,
return;
give_sigsegv:
if (sig == TARGET_SIGSEGV) {
ka->_sa_handler = TARGET_SIG_DFL;
}
force_sig(TARGET_SIGSEGV /* , current */);
force_sigsegv(sig);
}
/* compare linux/arch/i386/kernel/signal.c:setup_rt_frame() */
@ -1084,10 +1108,7 @@ static void setup_rt_frame(int sig, struct target_sigaction *ka,
return;
give_sigsegv:
if (sig == TARGET_SIGSEGV) {
ka->_sa_handler = TARGET_SIG_DFL;
}
force_sig(TARGET_SIGSEGV /* , current */);
force_sigsegv(sig);
}
static int
@ -1416,7 +1437,7 @@ static void target_setup_frame(int usig, struct target_sigaction *ka,
give_sigsegv:
unlock_user_struct(frame, frame_addr, 1);
force_sig(TARGET_SIGSEGV);
force_sigsegv(usig);
}
static void setup_rt_frame(int sig, struct target_sigaction *ka,
@ -2441,7 +2462,7 @@ sigill_and_return:
#endif
sigsegv:
unlock_user(sf, sf_addr, sizeof(struct target_signal_frame));
force_sig(TARGET_SIGSEGV);
force_sigsegv(sig);
}
static void setup_rt_frame(int sig, struct target_sigaction *ka,
@ -3033,7 +3054,7 @@ static void setup_frame(int sig, struct target_sigaction * ka,
return;
give_sigsegv:
force_sig(TARGET_SIGSEGV/*, current*/);
force_sigsegv(sig);
}
long do_sigreturn(CPUMIPSState *regs)
@ -3142,7 +3163,7 @@ static void setup_rt_frame(int sig, struct target_sigaction *ka,
give_sigsegv:
unlock_user_struct(frame, frame_addr, 1);
force_sig(TARGET_SIGSEGV/*, current*/);
force_sigsegv(sig);
}
long do_rt_sigreturn(CPUMIPSState *env)
@ -3345,7 +3366,7 @@ static void setup_frame(int sig, struct target_sigaction *ka,
give_sigsegv:
unlock_user_struct(frame, frame_addr, 1);
force_sig(TARGET_SIGSEGV);
force_sigsegv(sig);
}
static void setup_rt_frame(int sig, struct target_sigaction *ka,
@ -3405,7 +3426,7 @@ static void setup_rt_frame(int sig, struct target_sigaction *ka,
give_sigsegv:
unlock_user_struct(frame, frame_addr, 1);
force_sig(TARGET_SIGSEGV);
force_sigsegv(sig);
}
long do_sigreturn(CPUSH4State *regs)
@ -3652,7 +3673,7 @@ static void setup_frame(int sig, struct target_sigaction *ka,
unlock_user_struct(frame, frame_addr, 1);
return;
badframe:
force_sig(TARGET_SIGSEGV);
force_sigsegv(sig);
}
static void setup_rt_frame(int sig, struct target_sigaction *ka,
@ -3822,7 +3843,7 @@ static void setup_frame(int sig, struct target_sigaction *ka,
unlock_user_struct(frame, frame_addr, 1);
return;
badframe:
force_sig(TARGET_SIGSEGV);
force_sigsegv(sig);
}
static void setup_rt_frame(int sig, struct target_sigaction *ka,
@ -4061,10 +4082,7 @@ static void setup_rt_frame(int sig, struct target_sigaction *ka,
give_sigsegv:
unlock_user_struct(frame, frame_addr, 1);
if (sig == TARGET_SIGSEGV) {
ka->_sa_handler = TARGET_SIG_DFL;
}
force_sig(TARGET_SIGSEGV);
force_sigsegv(sig);
}
long do_sigreturn(CPUOpenRISCState *env)
@ -4245,7 +4263,7 @@ static void setup_frame(int sig, struct target_sigaction *ka,
return;
give_sigsegv:
force_sig(TARGET_SIGSEGV);
force_sigsegv(sig);
}
static void setup_rt_frame(int sig, struct target_sigaction *ka,
@ -4300,7 +4318,7 @@ static void setup_rt_frame(int sig, struct target_sigaction *ka,
return;
give_sigsegv:
force_sig(TARGET_SIGSEGV);
force_sigsegv(sig);
}
static int
@ -4811,7 +4829,7 @@ static void setup_frame(int sig, struct target_sigaction *ka,
sigsegv:
unlock_user_struct(frame, frame_addr, 1);
force_sig(TARGET_SIGSEGV);
force_sigsegv(sig);
}
static void setup_rt_frame(int sig, struct target_sigaction *ka,
@ -4906,7 +4924,7 @@ static void setup_rt_frame(int sig, struct target_sigaction *ka,
sigsegv:
unlock_user_struct(rt_sf, rt_sf_addr, 1);
force_sig(TARGET_SIGSEGV);
force_sigsegv(sig);
}
@ -5155,7 +5173,7 @@ static void setup_frame(int sig, struct target_sigaction *ka,
return;
give_sigsegv:
force_sig(TARGET_SIGSEGV);
force_sigsegv(sig);
}
static inline int target_rt_setup_ucontext(struct target_ucontext *uc,
@ -5294,7 +5312,7 @@ static void setup_rt_frame(int sig, struct target_sigaction *ka,
give_sigsegv:
unlock_user_struct(frame, frame_addr, 1);
force_sig(TARGET_SIGSEGV);
force_sigsegv(sig);
}
long do_sigreturn(CPUM68KState *env)
@ -5501,10 +5519,8 @@ static void setup_frame(int sig, struct target_sigaction *ka,
if (err) {
give_sigsegv:
if (sig == TARGET_SIGSEGV) {
ka->_sa_handler = TARGET_SIG_DFL;
}
force_sig(TARGET_SIGSEGV);
force_sigsegv(sig);
return;
}
env->ir[IR_RA] = r26;
@ -5558,10 +5574,8 @@ static void setup_rt_frame(int sig, struct target_sigaction *ka,
if (err) {
give_sigsegv:
if (sig == TARGET_SIGSEGV) {
ka->_sa_handler = TARGET_SIG_DFL;
}
force_sig(TARGET_SIGSEGV);
force_sigsegv(sig);
return;
}
env->ir[IR_RA] = r26;
@ -5758,10 +5772,7 @@ static void setup_rt_frame(int sig, struct target_sigaction *ka,
return;
give_sigsegv:
if (sig == TARGET_SIGSEGV) {
ka->_sa_handler = TARGET_SIG_DFL;
}
force_sig(TARGET_SIGSEGV /* , current */);
force_sigsegv(sig);
}
long do_rt_sigreturn(CPUTLGState *env)