1 files changed, 95 insertions, 25 deletions

diff --git a/linux-user/signal.c b/linux-user/signal.c
index 24c91f37d9..e5fb9332e3 100644
--- a/linux-user/signal.c
+++ b/linux-user/signal.c
@@ -197,6 +197,55 @@ void target_to_host_old_sigset(sigset_t *sigset,
     target_to_host_sigset(sigset, &d);
 }
 
+/* Wrapper for sigprocmask function
+ * Emulates a sigprocmask in a safe way for the guest. Note that set and oldset
+ * are host signal set, not guest ones. This wraps the sigprocmask host calls
+ * that should be protected (calls originated from guest)
+ */
+int do_sigprocmask(int how, const sigset_t *set, sigset_t *oldset)
+{
+    int ret;
+    sigset_t val;
+    sigset_t *temp = NULL;
+    CPUState *cpu = thread_cpu;
+    TaskState *ts = (TaskState *)cpu->opaque;
+    bool segv_was_blocked = ts->sigsegv_blocked;
+
+    if (set) {
+        bool has_sigsegv = sigismember(set, SIGSEGV);
+        val = *set;
+        temp = &val;
+
+        sigdelset(temp, SIGSEGV);
+
+        switch (how) {
+        case SIG_BLOCK:
+            if (has_sigsegv) {
+                ts->sigsegv_blocked = true;
+            }
+            break;
+        case SIG_UNBLOCK:
+            if (has_sigsegv) {
+                ts->sigsegv_blocked = false;
+            }
+            break;
+        case SIG_SETMASK:
+            ts->sigsegv_blocked = has_sigsegv;
+            break;
+        default:
+            g_assert_not_reached();
+        }
+    }
+
+    ret = sigprocmask(how, temp, oldset);
+
+    if (oldset && segv_was_blocked) {
+        sigaddset(oldset, SIGSEGV);
+    }
+
+    return ret;
+}
+
 /* siginfo conversion */
 
 static inline void host_to_target_siginfo_noswap(target_siginfo_t *tinfo,
@@ -458,6 +507,19 @@ int queue_signal(CPUArchState *env, int sig, target_siginfo_t *info)
     k = &ts->sigtab[sig - 1];
     queue = gdb_queuesig ();
     handler = sigact_table[sig - 1]._sa_handler;
+
+    if (ts->sigsegv_blocked && sig == TARGET_SIGSEGV) {
+        /* Guest has blocked SIGSEGV but we got one anyway. Assume this
+         * is a forced SIGSEGV (ie one the kernel handles via force_sig_info
+         * because it got a real MMU fault). A blocked SIGSEGV in that
+         * situation is treated as if using the default handler. This is
+         * not correct if some other process has randomly sent us a SIGSEGV
+         * via kill(), but that is not easy to distinguish at this point,
+         * so we assume it doesn't happen.
+         */
+        handler = TARGET_SIG_DFL;
+    }
+
     if (!queue && handler == TARGET_SIG_DFL) {
         if (sig == TARGET_SIGTSTP || sig == TARGET_SIGTTIN || sig == TARGET_SIGTTOU) {
             kill(getpid(),SIGSTOP);
@@ -1056,7 +1118,7 @@ long do_sigreturn(CPUX86State *env)
     }
 
     target_to_host_sigset_internal(&set, &target_set);
-    sigprocmask(SIG_SETMASK, &set, NULL);
+    do_sigprocmask(SIG_SETMASK, &set, NULL);
 
     /* restore registers */
     if (restore_sigcontext(env, &frame->sc, &eax))
@@ -1081,7 +1143,7 @@ long do_rt_sigreturn(CPUX86State *env)
         if (!lock_user_struct(VERIFY_READ, frame, frame_addr, 1))
                 goto badframe;
         target_to_host_sigset(&set, &frame->uc.tuc_sigmask);
-        sigprocmask(SIG_SETMASK, &set, NULL);
+        do_sigprocmask(SIG_SETMASK, &set, NULL);
 
 	if (restore_sigcontext(env, &frame->uc.tuc_mcontext, &eax))
 		goto badframe;
@@ -1220,7 +1282,7 @@ static int target_restore_sigframe(CPUARMState *env,
     uint64_t pstate;
 
     target_to_host_sigset(&set, &sf->uc.tuc_sigmask);
-    sigprocmask(SIG_SETMASK, &set, NULL);
+    do_sigprocmask(SIG_SETMASK, &set, NULL);
 
     for (i = 0; i < 31; i++) {
         __get_user(env->xregs[i], &sf->uc.tuc_mcontext.regs[i]);
@@ -1340,7 +1402,7 @@ static void setup_frame(int sig, struct target_sigaction *ka,
 
 long do_rt_sigreturn(CPUARMState *env)
 {
-    struct target_rt_sigframe *frame;
+    struct target_rt_sigframe *frame = NULL;
     abi_ulong frame_addr = env->xregs[31];
 
     if (frame_addr & 15) {
@@ -1861,7 +1923,7 @@ static long do_sigreturn_v1(CPUARMState *env)
         }
 
         target_to_host_sigset_internal(&host_set, &set);
-        sigprocmask(SIG_SETMASK, &host_set, NULL);
+        do_sigprocmask(SIG_SETMASK, &host_set, NULL);
 
 	if (restore_sigcontext(env, &frame->sc))
 		goto badframe;
@@ -1942,7 +2004,7 @@ static int do_sigframe_return_v2(CPUARMState *env, target_ulong frame_addr,
     abi_ulong *regspace;
 
     target_to_host_sigset(&host_set, &uc->tuc_sigmask);
-    sigprocmask(SIG_SETMASK, &host_set, NULL);
+    do_sigprocmask(SIG_SETMASK, &host_set, NULL);
 
     if (restore_sigcontext(env, &uc->tuc_mcontext))
         return 1;
@@ -2033,7 +2095,7 @@ static long do_rt_sigreturn_v1(CPUARMState *env)
                 goto badframe;
 
         target_to_host_sigset(&host_set, &frame->uc.tuc_sigmask);
-        sigprocmask(SIG_SETMASK, &host_set, NULL);
+        do_sigprocmask(SIG_SETMASK, &host_set, NULL);
 
 	if (restore_sigcontext(env, &frame->uc.tuc_mcontext))
 		goto badframe;
@@ -2444,7 +2506,7 @@ long do_sigreturn(CPUSPARCState *env)
         }
 
         target_to_host_sigset_internal(&host_set, &set);
-        sigprocmask(SIG_SETMASK, &host_set, NULL);
+        do_sigprocmask(SIG_SETMASK, &host_set, NULL);
 
         if (err)
                 goto segv_and_exit;
@@ -2567,7 +2629,7 @@ void sparc64_set_context(CPUSPARCState *env)
                 goto do_sigsegv;
         }
         target_to_host_sigset_internal(&set, &target_set);
-        sigprocmask(SIG_SETMASK, &set, NULL);
+        do_sigprocmask(SIG_SETMASK, &set, NULL);
     }
     env->pc = pc;
     env->npc = npc;
@@ -2656,7 +2718,7 @@ void sparc64_get_context(CPUSPARCState *env)
 
     err = 0;
 
-    sigprocmask(0, NULL, &set);
+    do_sigprocmask(0, NULL, &set);
     host_to_target_sigset_internal(&target_set, &set);
     if (TARGET_NSIG_WORDS == 1) {
         err |= __put_user(target_set.sig[0],
@@ -2991,7 +3053,7 @@ long do_sigreturn(CPUMIPSState *regs)
     }
 
     target_to_host_sigset_internal(&blocked, &target_set);
-    sigprocmask(SIG_SETMASK, &blocked, NULL);
+    do_sigprocmask(SIG_SETMASK, &blocked, NULL);
 
     if (restore_sigcontext(regs, &frame->sf_sc))
    	goto badframe;
@@ -3095,7 +3157,7 @@ long do_rt_sigreturn(CPUMIPSState *env)
    	goto badframe;
 
     target_to_host_sigset(&blocked, &frame->rs_uc.tuc_sigmask);
-    sigprocmask(SIG_SETMASK, &blocked, NULL);
+    do_sigprocmask(SIG_SETMASK, &blocked, NULL);
 
     if (restore_sigcontext(env, &frame->rs_uc.tuc_mcontext))
         goto badframe;
@@ -3385,7 +3447,7 @@ long do_sigreturn(CPUSH4State *regs)
         goto badframe;
 
     target_to_host_sigset_internal(&blocked, &target_set);
-    sigprocmask(SIG_SETMASK, &blocked, NULL);
+    do_sigprocmask(SIG_SETMASK, &blocked, NULL);
 
     if (restore_sigcontext(regs, &frame->sc, &r0))
         goto badframe;
@@ -3414,7 +3476,7 @@ long do_rt_sigreturn(CPUSH4State *regs)
    	goto badframe;
 
     target_to_host_sigset(&blocked, &frame->uc.tuc_sigmask);
-    sigprocmask(SIG_SETMASK, &blocked, NULL);
+    do_sigprocmask(SIG_SETMASK, &blocked, NULL);
 
     if (restore_sigcontext(regs, &frame->uc.tuc_mcontext, &r0))
         goto badframe;
@@ -3644,7 +3706,7 @@ long do_sigreturn(CPUMBState *env)
             goto badframe;
     }
     target_to_host_sigset_internal(&set, &target_set);
-    sigprocmask(SIG_SETMASK, &set, NULL);
+    do_sigprocmask(SIG_SETMASK, &set, NULL);
 
     restore_sigcontext(&frame->uc.tuc_mcontext, env);
     /* We got here through a sigreturn syscall, our path back is via an
@@ -3819,7 +3881,7 @@ long do_sigreturn(CPUCRISState *env)
 			goto badframe;
 	}
 	target_to_host_sigset_internal(&set, &target_set);
-	sigprocmask(SIG_SETMASK, &set, NULL);
+        do_sigprocmask(SIG_SETMASK, &set, NULL);
 
 	restore_sigcontext(&frame->sc, env);
 	unlock_user_struct(frame, frame_addr, 0);
@@ -4350,7 +4412,7 @@ long do_sigreturn(CPUS390XState *env)
     }
 
     target_to_host_sigset_internal(&set, &target_set);
-    sigprocmask(SIG_SETMASK, &set, NULL); /* ~_BLOCKABLE? */
+    do_sigprocmask(SIG_SETMASK, &set, NULL); /* ~_BLOCKABLE? */
 
     if (restore_sigregs(env, &frame->sregs)) {
         goto badframe;
@@ -4378,7 +4440,7 @@ long do_rt_sigreturn(CPUS390XState *env)
     }
     target_to_host_sigset(&set, &frame->uc.tuc_sigmask);
 
-    sigprocmask(SIG_SETMASK, &set, NULL); /* ~_BLOCKABLE? */
+    do_sigprocmask(SIG_SETMASK, &set, NULL); /* ~_BLOCKABLE? */
 
     if (restore_sigregs(env, &frame->uc.tuc_mcontext)) {
         goto badframe;
@@ -4906,7 +4968,7 @@ long do_sigreturn(CPUPPCState *env)
        goto sigsegv;
 #endif
     target_to_host_sigset_internal(&blocked, &set);
-    sigprocmask(SIG_SETMASK, &blocked, NULL);
+    do_sigprocmask(SIG_SETMASK, &blocked, NULL);
 
     if (__get_user(sr_addr, &sc->regs))
         goto sigsegv;
@@ -4950,7 +5012,7 @@ static int do_setcontext(struct target_ucontext *ucp, CPUPPCState *env, int sig)
         return 1;
 
     target_to_host_sigset_internal(&blocked, &set);
-    sigprocmask(SIG_SETMASK, &blocked, NULL);
+    do_sigprocmask(SIG_SETMASK, &blocked, NULL);
     if (restore_user_regs(env, mcp, sig))
         goto sigsegv;
 
@@ -5324,7 +5386,7 @@ long do_sigreturn(CPUM68KState *env)
     }
 
     target_to_host_sigset_internal(&set, &target_set);
-    sigprocmask(SIG_SETMASK, &set, NULL);
+    do_sigprocmask(SIG_SETMASK, &set, NULL);
 
     /* restore registers */
 
@@ -5352,7 +5414,7 @@ long do_rt_sigreturn(CPUM68KState *env)
         goto badframe;
 
     target_to_host_sigset_internal(&set, &target_set);
-    sigprocmask(SIG_SETMASK, &set, NULL);
+    do_sigprocmask(SIG_SETMASK, &set, NULL);
 
     /* restore registers */
 
@@ -5599,7 +5661,7 @@ long do_sigreturn(CPUAlphaState *env)
     }
 
     target_to_host_sigset_internal(&set, &target_set);
-    sigprocmask(SIG_SETMASK, &set, NULL);
+    do_sigprocmask(SIG_SETMASK, &set, NULL);
 
     if (restore_sigcontext(env, sc)) {
         goto badframe;
@@ -5622,7 +5684,7 @@ long do_rt_sigreturn(CPUAlphaState *env)
         goto badframe;
     }
     target_to_host_sigset(&set, &frame->uc.tuc_sigmask);
-    sigprocmask(SIG_SETMASK, &set, NULL);
+    do_sigprocmask(SIG_SETMASK, &set, NULL);
 
     if (restore_sigcontext(env, &frame->uc.tuc_mcontext)) {
         goto badframe;
@@ -5716,6 +5778,14 @@ void process_pending_signals(CPUArchState *cpu_env)
         handler = sa->_sa_handler;
     }
 
+    if (ts->sigsegv_blocked && sig == TARGET_SIGSEGV) {
+        /* Guest has blocked SIGSEGV but we got one anyway. Assume this
+         * is a forced SIGSEGV (ie one the kernel handles via force_sig_info
+         * because it got a real MMU fault), and treat as if default handler.
+         */
+        handler = TARGET_SIG_DFL;
+    }
+
     if (handler == TARGET_SIG_DFL) {
         /* default handler : ignore some signal. The other are job control or fatal */
         if (sig == TARGET_SIGTSTP || sig == TARGET_SIGTTIN || sig == TARGET_SIGTTOU) {
@@ -5739,7 +5809,7 @@ void process_pending_signals(CPUArchState *cpu_env)
             sigaddset(&set, target_to_host_signal(sig));
 
         /* block signals in the handler using Linux */
-        sigprocmask(SIG_BLOCK, &set, &old_set);
+        do_sigprocmask(SIG_BLOCK, &set, &old_set);
         /* save the previous blocked signal state to restore it at the
            end of the signal execution (see do_sigreturn) */
         host_to_target_sigset_internal(&target_old_set, &old_set);