tequilaOS/platform_system_core
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crash_dump: switch to PTRACE_SEIZE.

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ptrace(PTRACE_ATTACH) does not immediately put the traced process in a
stopped state. If we manage to call PTRACE_CONT on it before it
finishes, we'll fail. Switch to using PTRACE_SEIZE and PTRACE_INTERRUPT
to guarantee that the target stops immediately.

This also has the advantage of never putting the process in group-stop
state, which means if we exit prematurely (e.g. if we crash during
stack unwinding), the target process will be resumed without any
intervention needed.

Bug: http://b/34472671
Test: while true; do debuggerd -b `pidof audioserver`; done
Change-Id: I7549f67489646cf300b8c9aa8c735e5e897806ef
This commit is contained in:
Josh Gao 2017-01-22 16:42:32 -08:00
parent 575941115e
commit 122479f4a0
1 changed files with 13 additions and 7 deletions
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20
debuggerd/crash_dump.cpp
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@ -57,8 +57,8 @@ static bool pid_contains_tid(pid_t pid, pid_t tid) {
}
// Attach to a thread, and verify that it's still a member of the given process
static bool ptrace_attach_thread(pid_t pid, pid_t tid, std::string* error) {
if (ptrace(PTRACE_ATTACH, tid, 0, 0) != 0) {
static bool ptrace_seize_thread(pid_t pid, pid_t tid, std::string* error) {
if (ptrace(PTRACE_SEIZE, tid, 0, 0) != 0) {
*error = StringPrintf("failed to attach to thread %d: %s", tid, strerror(errno));
return false;
}
@ -71,6 +71,12 @@ static bool ptrace_attach_thread(pid_t pid, pid_t tid, std::string* error) {
*error = StringPrintf("thread %d is not in process %d", tid, pid);
return false;
}
// Put the task into ptrace-stop state.
if (ptrace(PTRACE_INTERRUPT, tid, 0, 0) != 0) {
PLOG(FATAL) << "failed to interrupt thread " << tid;
}
return true;
}
@ -254,7 +260,7 @@ int main(int argc, char** argv) {
check_process(target_proc_fd, target);
std::string attach_error;
if (!ptrace_attach_thread(target, main_tid, &attach_error)) {
if (!ptrace_seize_thread(target, main_tid, &attach_error)) {
LOG(FATAL) << attach_error;
}
@ -279,9 +285,9 @@ int main(int argc, char** argv) {
LOG(INFO) << "performing dump of process " << target << " (target tid = " << main_tid << ")";
// At this point, the thread that made the request has been PTRACE_ATTACHed
// and has the signal that triggered things queued. Send PTRACE_CONT, and
// then wait for the signal.
// At this point, the thread that made the request has been attached and is
// in ptrace-stopped state. After resumption, the triggering signal that has
// been queued will be delivered.
if (ptrace(PTRACE_CONT, main_tid, 0, 0) != 0) {
PLOG(ERROR) << "PTRACE_CONT(" << main_tid << ") failed";
exit(1);
@ -320,7 +326,7 @@ int main(int argc, char** argv) {
siblings.erase(main_tid);
for (pid_t sibling_tid : siblings) {
if (!ptrace_attach_thread(target, sibling_tid, &attach_error)) {
if (!ptrace_seize_thread(target, sibling_tid, &attach_error)) {
LOG(WARNING) << attach_error;
} else {
attached_siblings.insert(sibling_tid);