Fix signal chain to allow for signal() call to be used
Bug: 17320614
Change-Id: Ia917307fb1b593644f524518e11e295b3c64be01
diff --git a/sigchainlib/sigchain.cc b/sigchainlib/sigchain.cc
index c655226..50bfe70 100644
--- a/sigchainlib/sigchain.cc
+++ b/sigchainlib/sigchain.cc
@@ -34,7 +34,7 @@
class SignalAction {
public:
- SignalAction() : claimed_(false) {
+ SignalAction() : claimed_(false), uses_old_style_(false) {
}
// Claim the signal and keep the action specified.
@@ -60,13 +60,22 @@
}
// Change the recorded action to that specified.
- void SetAction(const struct sigaction& action) {
+ // If oldstyle is true then this action is from an older style signal()
+ // call as opposed to sigaction(). In this case the sa_handler is
+ // used when invoking the user's handler.
+ void SetAction(const struct sigaction& action, bool oldstyle) {
action_ = action;
+ uses_old_style_ = oldstyle;
+ }
+
+ bool OldStyle() const {
+ return uses_old_style_;
}
private:
struct sigaction action_; // Action to be performed.
bool claimed_; // Whether signal is claimed or not.
+ bool uses_old_style_; // Action is created using signal(). Use sa_handler.
};
// User's signal handlers
@@ -115,7 +124,7 @@
}
const struct sigaction& action = user_sigactions[sig].GetAction();
- if ((action.sa_flags & SA_SIGINFO) == 0) {
+ if (user_sigactions[sig].OldStyle()) {
if (action.sa_handler != NULL) {
action.sa_handler(sig);
} else {
@@ -145,7 +154,7 @@
*old_action = user_sigactions[signal].GetAction();
}
if (new_action != NULL) {
- user_sigactions[signal].SetAction(*new_action);
+ user_sigactions[signal].SetAction(*new_action, false);
}
return 0;
}
@@ -168,6 +177,45 @@
return linked_sigaction(signal, new_action, old_action);
}
+sighandler_t signal(int signal, sighandler_t handler) {
+ struct sigaction sa;
+ sigemptyset(&sa.sa_mask);
+ sa.sa_handler = handler;
+ sa.sa_flags = SA_RESTART;
+ sighandler_t oldhandler;
+
+ // If this signal has been claimed as a signal chain, record the user's
+ // action but don't pass it on to the kernel.
+ // Note that we check that the signal number is in range here. An out of range signal
+ // number should behave exactly as the libc sigaction.
+ if (signal > 0 && signal < _NSIG && user_sigactions[signal].IsClaimed()) {
+ oldhandler = reinterpret_cast<sighandler_t>(user_sigactions[signal].GetAction().sa_handler);
+ user_sigactions[signal].SetAction(sa, true);
+ return oldhandler;
+ }
+
+ // Will only get here if the signal chain has not been claimed. We want
+ // to pass the sigaction on to the kernel via the real sigaction in libc.
+
+ void* linked_sigaction_sym = dlsym(RTLD_NEXT, "sigaction");
+ if (linked_sigaction_sym == nullptr) {
+ linked_sigaction_sym = dlsym(RTLD_DEFAULT, "sigaction");
+ if (linked_sigaction_sym == nullptr ||
+ linked_sigaction_sym == reinterpret_cast<void*>(sigaction)) {
+ log("Unable to find next sigaction in signal chain");
+ abort();
+ }
+ }
+
+ typedef int (*SigAction)(int, const struct sigaction*, struct sigaction*);
+ SigAction linked_sigaction = reinterpret_cast<SigAction>(linked_sigaction_sym);
+ if (linked_sigaction(signal, &sa, &sa) == -1) {
+ return SIG_ERR;
+ }
+
+ return reinterpret_cast<sighandler_t>(sa.sa_handler);
+}
+
int sigprocmask(int how, const sigset_t* bionic_new_set, sigset_t* bionic_old_set) {
const sigset_t* new_set_ptr = bionic_new_set;
sigset_t tmpset;