From: Peter Maydell <peter.maydell@linaro.org>
To: qemu-devel@nongnu.org
Cc: patches@linaro.org, Riku Voipio <riku.voipio@iki.fi>
Subject: [Qemu-devel] [PATCH 3/6] linux-user: SIGSEGV on signal entry need not be fatal
Date: Thu, 28 Jul 2016 16:44:47 +0100 [thread overview]
Message-ID: <1469720690-32060-4-git-send-email-peter.maydell@linaro.org> (raw)
In-Reply-To: <1469720690-32060-1-git-send-email-peter.maydell@linaro.org>
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.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
linux-user/signal.c | 87 ++++++++++++++++++++++++++++++-----------------------
1 file changed, 49 insertions(+), 38 deletions(-)
diff --git a/linux-user/signal.c b/linux-user/signal.c
index aa052e2..d87c551 100644
--- a/linux-user/signal.c
+++ b/linux-user/signal.c
@@ -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)
--
1.9.1
next prev parent reply other threads:[~2016-07-28 15:44 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-07-28 15:44 [Qemu-devel] [PATCH 0/6] linux-user: Handle SEGV on signal entry/exit correctly Peter Maydell
2016-07-28 15:44 ` [Qemu-devel] [PATCH 1/6] linux-user: Recheck for pending synchronous signals too Peter Maydell
2016-07-28 15:44 ` [Qemu-devel] [PATCH 2/6] linux-user: Pass si_type information to queue_signal() explicitly Peter Maydell
2016-07-28 15:44 ` Peter Maydell [this message]
2016-07-28 15:44 ` [Qemu-devel] [PATCH 4/6] linux-user: ARM: Give SIGSEGV if signal frame setup fails Peter Maydell
2016-07-28 15:44 ` [Qemu-devel] [PATCH 5/6] linux-user: SIGSEGV from sigreturn need not be fatal Peter Maydell
2016-07-28 15:44 ` [Qemu-devel] [PATCH 6/6] linux-user: Implement force_sigsegv() via force_sig() Peter Maydell
2016-08-06 2:24 ` [Qemu-devel] [PATCH 0/6] linux-user: Handle SEGV on signal entry/exit correctly Richard Henderson
2016-09-21 18:53 ` Riku Voipio
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