015de6884f
Linux supports multiple "PID namespaces". Processes in different PID namespaces have different views of the system process list. Sometimes, a single process can appear in more than one PID namespace, but with a different PID in each. When GDB and its target are in different PID namespaces, various features can break due to the mismatch between what the target believes its PID to be and what GDB believes its PID to be. The most visible broken functionality is thread enumeration silently failing. This patch explicitly warns users against trying to debug across PID namespaces. The patch introduced no new failures in my test suite run on an x86_64 installation of Ubuntu 14.10. It doesn't include a test: writing an automated test that exercises this code would be very involved because CLONE_NEWNS requires CAP_SYS_ADMIN; the easier way to reproduce the problem is to start a new lxc container. gdb/ 2014-11-11 Daniel Colascione <dancol@dancol.org> Warn about cross-PID-namespace debugging. * nat/linux-procfs.h (linux_proc_pid_get_ns): New prototype. * nat/linux-procfs.c (linux_proc_pid_get_ns): New function. * linux-thread-db.c (check_pid_namespace_match): New function. (thread_db_inferior_created): Call it.
134 lines
3.2 KiB
C
134 lines
3.2 KiB
C
/* Linux-specific PROCFS manipulation routines.
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Copyright (C) 2009-2014 Free Software Foundation, Inc.
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This file is part of GDB.
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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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#include "common-defs.h"
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#include "linux-procfs.h"
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#include "filestuff.h"
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/* Return the TGID of LWPID from /proc/pid/status. Returns -1 if not
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found. */
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static int
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linux_proc_get_int (pid_t lwpid, const char *field)
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{
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size_t field_len = strlen (field);
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FILE *status_file;
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char buf[100];
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int retval = -1;
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snprintf (buf, sizeof (buf), "/proc/%d/status", (int) lwpid);
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status_file = gdb_fopen_cloexec (buf, "r");
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if (status_file == NULL)
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{
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warning (_("unable to open /proc file '%s'"), buf);
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return -1;
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}
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while (fgets (buf, sizeof (buf), status_file))
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if (strncmp (buf, field, field_len) == 0 && buf[field_len] == ':')
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{
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retval = strtol (&buf[field_len + 1], NULL, 10);
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break;
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}
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fclose (status_file);
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return retval;
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}
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/* Return the TGID of LWPID from /proc/pid/status. Returns -1 if not
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found. */
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int
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linux_proc_get_tgid (pid_t lwpid)
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{
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return linux_proc_get_int (lwpid, "Tgid");
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}
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/* See linux-procfs.h. */
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pid_t
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linux_proc_get_tracerpid (pid_t lwpid)
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{
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return linux_proc_get_int (lwpid, "TracerPid");
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}
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/* Return non-zero if 'State' of /proc/PID/status contains STATE. */
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static int
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linux_proc_pid_has_state (pid_t pid, const char *state)
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{
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char buffer[100];
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FILE *procfile;
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int retval;
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int have_state;
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xsnprintf (buffer, sizeof (buffer), "/proc/%d/status", (int) pid);
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procfile = gdb_fopen_cloexec (buffer, "r");
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if (procfile == NULL)
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{
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warning (_("unable to open /proc file '%s'"), buffer);
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return 0;
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}
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have_state = 0;
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while (fgets (buffer, sizeof (buffer), procfile) != NULL)
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if (strncmp (buffer, "State:", 6) == 0)
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{
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have_state = 1;
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break;
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}
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retval = (have_state && strstr (buffer, state) != NULL);
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fclose (procfile);
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return retval;
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}
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/* Detect `T (stopped)' in `/proc/PID/status'.
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Other states including `T (tracing stop)' are reported as false. */
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int
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linux_proc_pid_is_stopped (pid_t pid)
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{
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return linux_proc_pid_has_state (pid, "T (stopped)");
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}
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/* See linux-procfs.h declaration. */
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int
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linux_proc_pid_is_zombie (pid_t pid)
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{
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return linux_proc_pid_has_state (pid, "Z (zombie)");
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}
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/* See linux-procfs.h declaration. */
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char *
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linux_proc_pid_get_ns (pid_t pid, const char *ns)
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{
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char buf[100];
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char nsval[64];
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int ret;
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xsnprintf (buf, sizeof (buf), "/proc/%d/ns/%s", (int) pid, ns);
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ret = readlink (buf, nsval, sizeof (nsval));
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if (0 < ret && ret < sizeof (nsval))
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{
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nsval[ret] = '\0';
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return xstrdup (nsval);
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}
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return NULL;
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}
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