[Qemu-devel] [PATCHv3 1/2] signal: added a wrapper for sigprocmask function

[Alex Barcelo <abarcelo@ac.upc.edu>]

Create a wrapper for signal mask changes initiated by the guest;
(this includes syscalls and also the sigreturns from signal.c)
this will give us a place to put code which prevents the guest
from changing the handling of signals used by QEMU itself
internally.

The wrapper is called from all the guest-initiated sigprocmask, but
is not called from internal qemu sigprocmask calls.

Signed-off-by: Alex Barcelo <abarcelo@ac.upc.edu>
---
 linux-user/qemu.h    |    1 +
 linux-user/signal.c  |   10 ++++++++++
 linux-user/syscall.c |   14 +++++++-------
 3 files changed, 18 insertions(+), 7 deletions(-)

diff --git a/linux-user/qemu.h b/linux-user/qemu.h
index 5e53dca..1d59458 100644
--- a/linux-user/qemu.h
+++ b/linux-user/qemu.h
@@ -240,6 +240,7 @@ int host_to_target_signal(int sig);
 long do_sigreturn(CPUArchState *env);
 long do_rt_sigreturn(CPUArchState *env);
 abi_long do_sigaltstack(abi_ulong uss_addr, abi_ulong uoss_addr, abi_ulong sp);
+int do_sigprocmask(int how, const sigset_t *set, sigset_t *oldset);
 
 #ifdef TARGET_I386
 /* vm86.c */
diff --git a/linux-user/signal.c b/linux-user/signal.c
index 95e2ffa..172de9a 100644
--- a/linux-user/signal.c
+++ b/linux-user/signal.c
@@ -5482,6 +5482,16 @@ long do_rt_sigreturn(CPUArchState *env)
 
 #endif
 
+/* 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)
+{
+    return sigprocmask(how, set, oldset);
+}
+
 void process_pending_signals(CPUArchState *cpu_env)
 {
     int sig;
diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index e4291ed..9b57671 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -5925,7 +5925,7 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1,
         {
             sigset_t cur_set;
             abi_ulong target_set;
-            sigprocmask(0, NULL, &cur_set);
+            do_sigprocmask(0, NULL, &cur_set);
             host_to_target_old_sigset(&target_set, &cur_set);
             ret = target_set;
         }
@@ -5936,10 +5936,10 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1,
         {
             sigset_t set, oset, cur_set;
             abi_ulong target_set = arg1;
-            sigprocmask(0, NULL, &cur_set);
+            do_sigprocmask(0, NULL, &cur_set);
             target_to_host_old_sigset(&set, &target_set);
             sigorset(&set, &set, &cur_set);
-            sigprocmask(SIG_SETMASK, &set, &oset);
+            do_sigprocmask(SIG_SETMASK, &set, &oset);
             host_to_target_old_sigset(&target_set, &oset);
             ret = target_set;
         }
@@ -5970,7 +5970,7 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1,
             mask = arg2;
             target_to_host_old_sigset(&set, &mask);
 
-            ret = get_errno(sigprocmask(how, &set, &oldset));
+            ret = get_errno(do_sigprocmask(how, &set, &oldset));
             if (!is_error(ret)) {
                 host_to_target_old_sigset(&mask, &oldset);
                 ret = mask;
@@ -6004,7 +6004,7 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1,
                 how = 0;
                 set_ptr = NULL;
             }
-            ret = get_errno(sigprocmask(how, set_ptr, &oldset));
+            ret = get_errno(do_sigprocmask(how, set_ptr, &oldset));
             if (!is_error(ret) && arg3) {
                 if (!(p = lock_user(VERIFY_WRITE, arg3, sizeof(target_sigset_t), 0)))
                     goto efault;
@@ -6044,7 +6044,7 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1,
                 how = 0;
                 set_ptr = NULL;
             }
-            ret = get_errno(sigprocmask(how, set_ptr, &oldset));
+            ret = get_errno(do_sigprocmask(how, set_ptr, &oldset));
             if (!is_error(ret) && arg3) {
                 if (!(p = lock_user(VERIFY_WRITE, arg3, sizeof(target_sigset_t), 0)))
                     goto efault;
@@ -7932,7 +7932,7 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1,
             }
             mask = arg2;
             target_to_host_old_sigset(&set, &mask);
-            sigprocmask(how, &set, &oldset);
+            do_sigprocmask(how, &set, &oldset);
             host_to_target_old_sigset(&mask, &oldset);
             ret = mask;
         }
-- 
1.7.5.4