Reland: Introduce sys_sigprocmask and sys_sigaction. (patchset #4 id:80001 of https://codereview.ch…

sandbox/linux/seccomp-bpf/trap.cc

Index: sandbox/linux/seccomp-bpf/trap.cc
diff --git a/sandbox/linux/seccomp-bpf/trap.cc b/sandbox/linux/seccomp-bpf/trap.cc
index 145e62469cacca37c07aa40916c1d27795082c11..b61ae7434c765af962de8077214f8b55d7345997 100644
--- a/sandbox/linux/seccomp-bpf/trap.cc
+++ b/sandbox/linux/seccomp-bpf/trap.cc
@@ -12,17 +12,15 @@
 #include <algorithm>
 #include <limits>
 
+#include "base/compiler_specific.h"
 #include "base/logging.h"
 #include "build/build_config.h"
 #include "sandbox/linux/bpf_dsl/seccomp_macros.h"
 #include "sandbox/linux/seccomp-bpf/die.h"
 #include "sandbox/linux/seccomp-bpf/syscall.h"
+#include "sandbox/linux/services/syscall_wrappers.h"
 #include "sandbox/linux/system_headers/linux_seccomp.h"
-
-// Android's signal.h doesn't define ucontext etc.
-#if defined(OS_ANDROID)
-#include "sandbox/linux/system_headers/android_ucontext.h"
-#endif
+#include "sandbox/linux/system_headers/linux_signal.h"
 
 namespace {
 
@@ -53,13 +51,13 @@ const char kSandboxDebuggingEnv[] = "CHROME_SANDBOX_DEBUGGING";
 // possibly even worse.
 bool GetIsInSigHandler(const ucontext_t* ctx) {
   // Note: on Android, sigismember does not take a pointer to const.
-  return sigismember(const_cast<sigset_t*>(&ctx->uc_sigmask), SIGBUS);
+  return sigismember(const_cast<sigset_t*>(&ctx->uc_sigmask), LINUX_SIGBUS);
 }
 
 void SetIsInSigHandler() {
   sigset_t mask;
-  if (sigemptyset(&mask) || sigaddset(&mask, SIGBUS) ||
-      sigprocmask(SIG_BLOCK, &mask, NULL)) {
+  if (sigemptyset(&mask) || sigaddset(&mask, LINUX_SIGBUS) ||
+      sandbox::sys_sigprocmask(LINUX_SIG_BLOCK, &mask, NULL)) {
     SANDBOX_DIE("Failed to block SIGBUS");
   }
 }
@@ -82,10 +80,13 @@ Trap::Trap()
       has_unsafe_traps_(false) {
   // Set new SIGSYS handler
   struct sigaction sa = {};
-  sa.sa_sigaction = SigSysAction;
-  sa.sa_flags = SA_SIGINFO | SA_NODEFER;
-  struct sigaction old_sa;
-  if (sigaction(SIGSYS, &sa, &old_sa) < 0) {
+  // In some toolchain, sa_sigaction is not declared in struct sigaction.
+  // So, here cast the pointer to the sa_handler's type. This works because
+  // |sa_handler| and |sa_sigaction| shares the same memory.
+  sa.sa_handler = reinterpret_cast<void (*)(int)>(SigSysAction);
+  sa.sa_flags = LINUX_SA_SIGINFO | LINUX_SA_NODEFER;
+  struct sigaction old_sa = {};
+  if (sys_sigaction(LINUX_SIGSYS, &sa, &old_sa) < 0) {
     SANDBOX_DIE("Failed to configure SIGSYS handler");
   }
 
@@ -99,8 +100,8 @@ Trap::Trap()
 
   // Unmask SIGSYS
   sigset_t mask;
-  if (sigemptyset(&mask) || sigaddset(&mask, SIGSYS) ||
-      sigprocmask(SIG_UNBLOCK, &mask, NULL)) {
+  if (sigemptyset(&mask) || sigaddset(&mask, LINUX_SIGSYS) ||
+      sys_sigprocmask(LINUX_SIG_UNBLOCK, &mask, NULL)) {
     SANDBOX_DIE("Failed to configure SIGSYS handler");
   }
 }
@@ -120,7 +121,14 @@ bpf_dsl::TrapRegistry* Trap::Registry() {
   return global_trap_;
 }
 
-void Trap::SigSysAction(int nr, siginfo_t* info, void* void_context) {
+void Trap::SigSysAction(int nr, LinuxSigInfo* info, void* void_context) {
+  if (info) {

[hidehiko, 2015/04/23 15:59:56]

Note: I temporarily reverted this part, because we starts to use sigaction() in
libc if MSAN is enabled. This will be back when we start to compile this with
PNaCl toolchain actually. Please see my comment/plan in syscall_wrappers.cc.

+    MSAN_UNPOISON(info, sizeof(*info));
+  }
+  if (void_context) {
+    MSAN_UNPOISON(void_context, sizeof(ucontext_t));
+  }
+
   if (!global_trap_) {
     RAW_SANDBOX_DIE(
         "This can't happen. Found no global singleton instance "
@@ -129,7 +137,7 @@ void Trap::SigSysAction(int nr, siginfo_t* info, void* void_context) {
   global_trap_->SigSys(nr, info, void_context);
 }
 
-void Trap::SigSys(int nr, siginfo_t* info, void* void_context) {
+void Trap::SigSys(int nr, LinuxSigInfo* info, void* void_context) {
   // Signal handlers should always preserve "errno". Otherwise, we could
   // trigger really subtle bugs.
   const int old_errno = errno;
@@ -137,7 +145,7 @@ void Trap::SigSys(int nr, siginfo_t* info, void* void_context) {
   // Various sanity checks to make sure we actually received a signal
   // triggered by a BPF filter. If something else triggered SIGSYS
   // (e.g. kill()), there is really nothing we can do with this signal.
-  if (nr != SIGSYS || info->si_code != SYS_SECCOMP || !void_context ||
+  if (nr != LINUX_SIGSYS || info->si_code != SYS_SECCOMP || !void_context ||
       info->si_errno <= 0 ||
       static_cast<size_t>(info->si_errno) > trap_array_size_) {
     // ATI drivers seem to send SIGSYS, so this cannot be FATAL.