Merge "crash_dump: print the identity of tracers." am: e67c7b94c2 (fa310945) · Commits · e / os / android_system_core

debuggerd/crash_dump.cpp

+18 −0

Original line number	Diff line number	Diff line
		@@ -79,9 +79,27 @@ static bool pid_contains_tid(int pid_proc_fd, pid_t tid) {
		return fstatat(pid_proc_fd, task_path.c_str(), &st, 0) == 0;
		}

		static pid_t get_tracer(pid_t tracee) {
		// Check to see if the thread is being ptraced by another process.
		android::procinfo::ProcessInfo process_info;
		if (android::procinfo::GetProcessInfo(tracee, &process_info)) {
		return process_info.tracer;
		}
		return -1;
		}

		// Attach to a thread, and verify that it's still a member of the given process
		static bool ptrace_seize_thread(int pid_proc_fd, pid_t tid, std::string* error) {
		if (ptrace(PTRACE_SEIZE, tid, 0, 0) != 0) {
		if (errno == EPERM) {
		pid_t tracer = get_tracer(tid);
		if (tracer != -1) {
		*error = StringPrintf("failed to attach to thread %d, already traced by %d (%s)", tid,
		tracer, get_process_name(tracer).c_str());
		return false;
		}
		}

		*error = StringPrintf("failed to attach to thread %d: %s", tid, strerror(errno));
		return false;
		}

+36 −1

Original line number	Diff line number	Diff line
		@@ -16,10 +16,11 @@

		#include <err.h>
		#include <fcntl.h>
		#include <unistd.h>
		#include <sys/capability.h>
		#include <sys/prctl.h>
		#include <sys/ptrace.h>
		#include <sys/types.h>
		#include <unistd.h>

		#include <chrono>
		#include <regex>
		@@ -569,6 +570,40 @@ TEST_F(CrasherTest, fake_pid) {
		ASSERT_BACKTRACE_FRAME(result, "tgkill");
		}

		TEST_F(CrasherTest, competing_tracer) {
		int intercept_result;
		unique_fd output_fd;
		StartProcess([]() {
		while (true) {
		}
		});

		StartIntercept(&output_fd);
		FinishCrasher();

		ASSERT_EQ(0, ptrace(PTRACE_SEIZE, crasher_pid, 0, 0));
		ASSERT_EQ(0, kill(crasher_pid, SIGABRT));

		int status;
		ASSERT_EQ(crasher_pid, waitpid(crasher_pid, &status, 0));
		ASSERT_TRUE(WIFSTOPPED(status));
		ASSERT_EQ(SIGABRT, WSTOPSIG(status));

		ASSERT_EQ(0, ptrace(PTRACE_CONT, crasher_pid, 0, SIGABRT));
		FinishIntercept(&intercept_result);
		ASSERT_EQ(1, intercept_result) << "tombstoned reported failure";

		std::string result;
		ConsumeFd(std::move(output_fd), &result);
		std::string regex = R"(failed to attach to thread \d+, already traced by )";
		regex += std::to_string(gettid());
		regex += R"( \(.+debuggerd_test)";
		ASSERT_MATCH(result, regex.c_str());

		ASSERT_EQ(0, ptrace(PTRACE_DETACH, crasher_pid, 0, SIGABRT));
		AssertDeath(SIGABRT);
		}

		TEST(crash_dump, zombie) {
		pid_t forkpid = fork();