From b7e289ed028ee73fda4c044e07d3ec6f783a0ef4 Mon Sep 17 00:00:00 2001
From: Elliott Hughes <enh@google.com>
Date: Fri, 25 Apr 2014 16:02:00 -0700
Subject: [PATCH] Pass si_code through to debuggerd.
Because we re-raise various signals, we corrupt the si_code that debuggerd
sees when it ptraces our siginfo. One possible solution (shown here) is to
pass the original si_code value in the message we send to debuggerd.
Change-Id: I76f9aa2c0442e5cab611d132532409e700383907
---
linker/debugger.cpp | 78 ++++++++++++++++++++++++---------------------
1 file changed, 42 insertions(+), 36 deletions(-)
diff --git a/linker/debugger.cpp b/linker/debugger.cpp
index a44380cb9..272c16a23 100644
--- a/linker/debugger.cpp
+++ b/linker/debugger.cpp
@@ -64,6 +64,9 @@ struct debugger_msg_t {
// version 2 added:
uintptr_t abort_msg_address;
+
+ // version 3 added:
+ int32_t original_si_code;
};
// see man(2) prctl, specifically the section about PR_GET_NAME
@@ -199,11 +202,44 @@ static bool have_siginfo(int signum) {
return result;
}
+static void send_debuggerd_packet(siginfo_t* info) {
+ int s = socket_abstract_client(DEBUGGER_SOCKET_NAME, SOCK_STREAM);
+ if (s == -1) {
+ __libc_format_log(ANDROID_LOG_FATAL, "libc", "Unable to open connection to debuggerd: %s",
+ strerror(errno));
+ return;
+ }
+
+ // debuggerd knows our pid from the credentials on the
+ // local socket but we need to tell it the tid of the crashing thread.
+ // debuggerd will be paranoid and verify that we sent a tid
+ // that's actually in our process.
+ debugger_msg_t msg;
+ msg.action = DEBUGGER_ACTION_CRASH;
+ msg.tid = gettid();
+ msg.abort_msg_address = reinterpret_cast<uintptr_t>(gAbortMessage);
+ msg.original_si_code = (info != NULL) ? info->si_code : 0;
+ int ret = TEMP_FAILURE_RETRY(write(s, &msg, sizeof(msg)));
+ if (ret == sizeof(msg)) {
+ char debuggerd_ack;
+ ret = TEMP_FAILURE_RETRY(read(s, &debuggerd_ack, 1));
+ int saved_errno = errno;
+ notify_gdb_of_libraries();
+ errno = saved_errno;
+ } else {
+ // read or write failed -- broken connection?
+ __libc_format_log(ANDROID_LOG_FATAL, "libc", "Failed while talking to debuggerd: %s",
+ strerror(errno));
+ }
+
+ close(s);
+}
+
/*
* Catches fatal signals so we can ask debuggerd to ptrace us before
* we crash.
*/
-void debuggerd_signal_handler(int signal_number, siginfo_t* info, void*) {
+static void debuggerd_signal_handler(int signal_number, siginfo_t* info, void*) {
// It's possible somebody cleared the SA_SIGINFO flag, which would mean
// our "info" arg holds an undefined value.
if (!have_siginfo(signal_number)) {
@@ -212,38 +248,7 @@ void debuggerd_signal_handler(int signal_number, siginfo_t* info, void*) {
log_signal_summary(signal_number, info);
- int s = socket_abstract_client(DEBUGGER_SOCKET_NAME, SOCK_STREAM);
- if (s != -1) {
- // debuggerd knows our pid from the credentials on the
- // local socket but we need to tell it the tid of the crashing thread.
- // debuggerd will be paranoid and verify that we sent a tid
- // that's actually in our process.
- debugger_msg_t msg;
- msg.action = DEBUGGER_ACTION_CRASH;
- msg.tid = gettid();
- msg.abort_msg_address = reinterpret_cast<uintptr_t>(gAbortMessage);
- int ret = TEMP_FAILURE_RETRY(write(s, &msg, sizeof(msg)));
- if (ret == sizeof(msg)) {
- // If the write failed, there is no point trying to read a response.
- char debuggerd_ack;
- ret = TEMP_FAILURE_RETRY(read(s, &debuggerd_ack, 1));
- int saved_errno = errno;
- notify_gdb_of_libraries();
- errno = saved_errno;
- }
-
- if (ret < 0) {
- // read or write failed -- broken connection?
- __libc_format_log(ANDROID_LOG_FATAL, "libc", "Failed while talking to debuggerd: %s",
- strerror(errno));
- }
-
- close(s);
- } else {
- // socket failed; maybe process ran out of fds?
- __libc_format_log(ANDROID_LOG_FATAL, "libc", "Unable to open connection to debuggerd: %s",
- strerror(errno));
- }
+ send_debuggerd_packet(info);
// Remove our net so we fault for real when we return.
signal(signal_number, SIG_DFL);
@@ -251,8 +256,9 @@ void debuggerd_signal_handler(int signal_number, siginfo_t* info, void*) {
// These signals are not re-thrown when we resume. This means that
// crashing due to (say) SIGPIPE doesn't work the way you'd expect it
// to. We work around this by throwing them manually. We don't want
- // to do this for *all* signals because it'll screw up the address for
- // faults like SIGSEGV.
+ // to do this for *all* signals because it'll screw up the si_addr for
+ // faults like SIGSEGV. It does screw up the si_code, which is why we
+ // passed that to debuggerd above.
switch (signal_number) {
case SIGABRT:
case SIGFPE:
@@ -267,7 +273,7 @@ void debuggerd_signal_handler(int signal_number, siginfo_t* info, void*) {
}
}
-void debuggerd_init() {
+__LIBC_HIDDEN__ void debuggerd_init() {
struct sigaction action;
memset(&action, 0, sizeof(action));
sigemptyset(&action.sa_mask);