c6f7f9c80c
On Linux, threads are treated much like separate processes by the kernel. In particular, it's possible to ptrace just a single thread. If gdb tries to attach to a multi-threaded inferior, where a non-main thread is already being traced (e.g., by strace), then gdb will get into an infinite loop attempting to attach. This patch fixes this problem by having the attach fail if ptrace fails to attach to any thread of the inferior.
106 lines
2.4 KiB
C
106 lines
2.4 KiB
C
/* This testcase is part of GDB, the GNU debugger.
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Copyright 2023 Free Software Foundation, Inc.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>. */
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#define _GNU_SOURCE
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#include <assert.h>
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#include <stdio.h>
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#include <unistd.h>
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#include <sys/ptrace.h>
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#include <pthread.h>
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#include <stdlib.h>
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#include <errno.h>
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int fds[2];
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_Atomic pid_t bg_tid = 0;
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pthread_barrier_t barrier;
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#define FIVE_MINUTES (5 * 60)
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/* One thread of the child process. This is traced by the parent
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process. */
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void *
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block (void *ignore)
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{
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bg_tid = gettid ();
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pthread_barrier_wait (&barrier);
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sleep (FIVE_MINUTES);
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return 0;
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}
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/* The parent process blocks in this function. */
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void
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parent_stop (pid_t child_thread_pid)
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{
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sleep (FIVE_MINUTES);
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}
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int
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main ()
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{
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int result;
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pthread_barrier_init (&barrier, NULL, 2);
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result = pipe (fds);
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assert (result != -1);
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pid_t child = fork ();
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if (child != 0)
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{
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/* Parent. */
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close (fds[1]);
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pid_t the_tid;
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result = read (fds[0], &the_tid, sizeof (the_tid));
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assert (result == sizeof (the_tid));
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/* Trace a single, non-main thread of the child. This should
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prevent gdb from attaching to the child at all. The bug here
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was that gdb would get into an infinite loop repeatedly
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trying to attach to this thread. */
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result = ptrace (PTRACE_SEIZE, the_tid, (void *) 0, (void *) 0);
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if (result == -1)
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perror ("ptrace");
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parent_stop (child);
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}
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else
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{
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/* Child. */
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close (fds[0]);
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pthread_t thr;
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result = pthread_create (&thr, 0, block, 0);
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assert (result == 0);
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/* Wait until the TID has been assigned. */
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pthread_barrier_wait (&barrier);
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assert (bg_tid != 0);
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result = write (fds[1], &bg_tid, sizeof (bg_tid));
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assert (result == sizeof (bg_tid));
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sleep (FIVE_MINUTES);
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}
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exit (0);
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}
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