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libthread_db is loaded once GDB encounters libpthread, and at this
point, ld.so may not have been processed by GDB yet. As a result,
_rtld_global cannot be accessed by regular means from libthread_db.
To make this work until GDB can be fixed, acess _rtld_global through
a pointer stored in libpthread.
The new test does not reproduce bug 27744 with
--disable-hardcoded-path-in-tests, but is still a valid smoke test.
With --enable-hardcoded-path-in-tests, it is necessary to avoid
add-symbol-file because this can tickle a GDB bug.
Fixes commit 1daccf403b ("nptl: Move
stack list variables into _rtld_global").
Tested-by: Emil Velikov <emil.velikov@collabora.com>
codonell/c-utf8
Florian Weimer
5 years ago
7 changed files with 180 additions and 11 deletions
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#include "tst-pthread-gdb-attach.c" |
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/* Smoke testing GDB process attach with thread-local variable access.
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Copyright (C) 2021 Free Software Foundation, Inc. |
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This file is part of the GNU C Library. |
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The GNU C Library is free software; you can redistribute it and/or |
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modify it under the terms of the GNU Lesser General Public |
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License as published by the Free Software Foundation; either |
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version 2.1 of the License, or (at your option) any later version. |
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The GNU C Library 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 GNU |
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Lesser General Public License for more details. |
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You should have received a copy of the GNU Lesser General Public |
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License along with the GNU C Library; if not, see |
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<https://www.gnu.org/licenses/>. */
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/* This test runs GDB against a forked copy of itself, to check
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whether libthread_db can be loaded, and that access to thread-local |
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variables works. */ |
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#include <errno.h> |
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#include <stdlib.h> |
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#include <support/check.h> |
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#include <support/support.h> |
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#include <support/temp_file.h> |
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#include <support/test-driver.h> |
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#include <support/xstdio.h> |
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#include <support/xthread.h> |
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#include <support/xunistd.h> |
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#include <unistd.h> |
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/* Starts out as zero, changed to 1 or 2 by the debugger, depending on
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the thread. */ |
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__thread volatile int altered_by_debugger; |
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/* Writes the GDB script to run the test to PATH. */ |
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static void |
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write_gdbscript (const char *path, int tested_pid) |
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{ |
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FILE *fp = xfopen (path, "w"); |
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fprintf (fp, |
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"set trace-commands on\n" |
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"set debug libthread-db 1\n" |
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#if DO_ADD_SYMBOL_FILE |
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/* Do not do this unconditionally to work around a GDB
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assertion failure: ../../gdb/symtab.c:6404: |
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internal-error: CORE_ADDR get_msymbol_address(objfile*, |
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const minimal_symbol*): Assertion `(objf->flags & |
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OBJF_MAINLINE) == 0' failed. */ |
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"add-symbol-file %1$s/nptl/tst-pthread-gdb-attach\n" |
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#endif |
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"set auto-load safe-path %1$s/nptl_db\n" |
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"set libthread-db-search-path %1$s/nptl_db\n" |
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"attach %2$d\n", |
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support_objdir_root, tested_pid); |
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fputs ("break debugger_inspection_point\n" |
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"continue\n" |
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"thread 1\n" |
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"print altered_by_debugger\n" |
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"print altered_by_debugger = 1\n" |
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"thread 2\n" |
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"print altered_by_debugger\n" |
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"print altered_by_debugger = 2\n" |
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"continue\n", |
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fp); |
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xfclose (fp); |
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} |
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/* The test sets a breakpoint on this function and alters the
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altered_by_debugger thread-local variable. */ |
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void __attribute__ ((weak)) |
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debugger_inspection_point (void) |
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{ |
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} |
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/* Thread function for the test thread in the subprocess. */ |
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static void * |
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subprocess_thread (void *closure) |
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{ |
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/* Wait until altered_by_debugger changes the value away from 0. */ |
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while (altered_by_debugger == 0) |
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{ |
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usleep (100 * 1000); |
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debugger_inspection_point (); |
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} |
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TEST_COMPARE (altered_by_debugger, 2); |
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return NULL; |
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} |
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/* This function implements the subprocess under test. It creates a
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second thread, waiting for its value to change to 2, and checks |
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that the main thread also changed its value to 1. */ |
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static void |
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in_subprocess (void) |
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{ |
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pthread_t thr = xpthread_create (NULL, subprocess_thread, NULL); |
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TEST_VERIFY (xpthread_join (thr) == NULL); |
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TEST_COMPARE (altered_by_debugger, 1); |
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_exit (0); |
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} |
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static int |
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do_test (void) |
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{ |
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pid_t tested_pid = xfork (); |
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if (tested_pid == 0) |
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in_subprocess (); |
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char *tested_pid_string = xasprintf ("%d", tested_pid); |
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char *gdbscript; |
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xclose (create_temp_file ("tst-pthread-gdb-attach-", &gdbscript)); |
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write_gdbscript (gdbscript, tested_pid); |
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pid_t gdb_pid = xfork (); |
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if (gdb_pid == 0) |
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{ |
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clearenv (); |
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xdup2 (STDOUT_FILENO, STDERR_FILENO); |
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execlp ("gdb", "gdb", "-nx", "-batch", "-x", gdbscript, NULL); |
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if (errno == ENOENT) |
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_exit (EXIT_UNSUPPORTED); |
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else |
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_exit (1); |
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} |
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int status; |
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TEST_COMPARE (xwaitpid (gdb_pid, &status, 0), gdb_pid); |
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if (WIFEXITED (status) && WEXITSTATUS (status) == EXIT_UNSUPPORTED) |
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/* gdb is not installed. */ |
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return EXIT_UNSUPPORTED; |
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TEST_COMPARE (status, 0); |
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TEST_COMPARE (xwaitpid (tested_pid, &status, 0), tested_pid); |
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TEST_COMPARE (status, 0); |
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free (tested_pid_string); |
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free (gdbscript); |
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return 0; |
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} |
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#include <support/test-driver.c> |
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