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crash_dump: avoid misleading error messages.

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I'm guessing that the original

  F crash_dump64: crash_dump.cpp:460] failed to attach to thread 1671, already traced by 0 ()

was probably a race, where there _was_ a tracer but they disappeared?
Whatever, it doesn't seem helpful to show "already traced by nobody",
and we also don't want to clobber errno in the fallthrough case
(previously just where get_tracer() failed, but now also where
get_tracer() returns "nobody").

Bug: http://b/188668580
Test: treehugger
Change-Id: I3fa3b4f7e32531d48dfbb0ef946ff351ed5d9171
This commit is contained in:
Elliott Hughes 2021-06-21 12:36:47 -07:00
parent 1c998ded12
commit a029d98ad0
1 changed files with 7 additions and 4 deletions
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11
debuggerd/crash_dump.cpp
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@ -32,6 +32,7 @@
#include <set>
#include <vector>
#include <android-base/errno_restorer.h>
#include <android-base/file.h>
#include <android-base/logging.h>
#include <android-base/macros.h>
@ -67,8 +68,9 @@
#include "protocol.h"
#include "util.h"
using android::base::unique_fd;
using android::base::ErrnoRestorer;
using android::base::StringPrintf;
using android::base::unique_fd;
static bool pid_contains_tid(int pid_proc_fd, pid_t tid) {
struct stat st;
@ -89,10 +91,11 @@ static pid_t get_tracer(pid_t tracee) {
static bool ptrace_seize_thread(int pid_proc_fd, pid_t tid, std::string* error, int flags = 0) {
if (ptrace(PTRACE_SEIZE, tid, 0, flags) != 0) {
if (errno == EPERM) {
pid_t tracer = get_tracer(tid);
if (tracer != -1) {
ErrnoRestorer errno_restorer; // In case get_tracer() fails and we fall through.
pid_t tracer_pid = get_tracer(tid);
if (tracer_pid > 0) {
*error = StringPrintf("failed to attach to thread %d, already traced by %d (%s)", tid,
tracer, get_process_name(tracer).c_str());
tracer_pid, get_process_name(tracer_pid).c_str());
return false;
}
}