309 lines
10 KiB
Diff
309 lines
10 KiB
Diff
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From a64afc225240b2b27129ccfb0516d7c958b98040 Mon Sep 17 00:00:00 2001
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From: Florian Weimer <fweimer@redhat.com>
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Date: Wed, 21 Apr 2021 11:50:43 +0200
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Subject: [PATCH 364/576] nptl_db: Support different libpthread/ld.so load
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orders (bug 27744)
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libthread_db is loaded once GDB encounters libpthread, and at this
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point, ld.so may not have been processed by GDB yet. As a result,
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_rtld_global cannot be accessed by regular means from libthread_db.
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To make this work until GDB can be fixed, acess _rtld_global through
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a pointer stored in libpthread.
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The new test does not reproduce bug 27744 with
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--disable-hardcoded-path-in-tests, but is still a valid smoke test.
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With --enable-hardcoded-path-in-tests, it is necessary to avoid
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add-symbol-file because this can tickle a GDB bug.
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Fixes commit 1daccf403b1bd86370eb94edca794dc106d02039 ("nptl: Move
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stack list variables into _rtld_global").
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Tested-by: Emil Velikov <emil.velikov@collabora.com>
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---
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nptl/Makefile | 19 +++-
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nptl/pthread_create.c | 8 ++
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nptl/tst-pthread-gdb-attach-static.c | 1 +
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nptl/tst-pthread-gdb-attach.c | 143 +++++++++++++++++++++++++++
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nptl_db/structs.def | 3 +-
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nptl_db/td_init.c | 15 +--
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nptl_db/thread_dbP.h | 2 +
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7 files changed, 180 insertions(+), 11 deletions(-)
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create mode 100644 nptl/tst-pthread-gdb-attach-static.c
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create mode 100644 nptl/tst-pthread-gdb-attach.c
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diff --git a/nptl/Makefile b/nptl/Makefile
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index 8fe92d43fa..e665d37e52 100644
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--- a/nptl/Makefile
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+++ b/nptl/Makefile
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@@ -313,7 +313,8 @@ tests = tst-attr2 tst-attr3 tst-default-attr \
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tst-thread-affinity-sched \
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tst-pthread-defaultattr-free \
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tst-pthread-attr-sigmask \
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- tst-pthread-timedlock-lockloop
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+ tst-pthread-timedlock-lockloop \
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+ tst-pthread-gdb-attach tst-pthread-gdb-attach-static
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tests-container = tst-pthread-getattr
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@@ -359,6 +360,19 @@ CPPFLAGS-test-cond-printers.c := $(CFLAGS-printers-tests)
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CPPFLAGS-test-rwlockattr-printers.c := $(CFLAGS-printers-tests)
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CPPFLAGS-test-rwlock-printers.c := $(CFLAGS-printers-tests)
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+# Reuse the CFLAGS setting for the GDB attaching test. It needs
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+# debugging information.
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+CFLAGS-tst-pthread-gdb-attach.c := $(CFLAGS-printers-tests)
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+CPPFLAGS-tst-pthread-gdb-attach.c := $(CFLAGS-printers-tests)
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+ifeq ($(build-shared)$(build-hardcoded-path-in-tests),yesno)
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+CPPFLAGS-tst-pthread-gdb-attach.c += -DDO_ADD_SYMBOL_FILE=1
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+else
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+CPPFLAGS-tst-pthread-gdb-attach.c += -DDO_ADD_SYMBOL_FILE=0
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+endif
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+CFLAGS-tst-pthread-gdb-attach-static.c := $(CFLAGS-printers-tests)
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+CPPFLAGS-tst-pthread-gdb-attach-static.c := \
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+ $(CFLAGS-printers-tests) -DDO_ADD_SYMBOL_FILE=0
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+
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ifeq ($(build-shared),yes)
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tests-printers-libs := $(shared-thread-library)
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else
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@@ -430,7 +444,8 @@ link-libc-static := $(common-objpfx)libc.a $(static-gnulib) \
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tests-static += tst-stackguard1-static \
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tst-cancel24-static \
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tst-mutex8-static tst-mutexpi8-static tst-sem11-static \
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- tst-sem12-static tst-cond11-static
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+ tst-sem12-static tst-cond11-static \
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+ tst-pthread-gdb-attach-static
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tests += tst-cancel24-static
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diff --git a/nptl/pthread_create.c b/nptl/pthread_create.c
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index 6c645aff48..f13d8e44a4 100644
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--- a/nptl/pthread_create.c
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+++ b/nptl/pthread_create.c
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@@ -51,6 +51,14 @@ static td_thr_events_t __nptl_threads_events __attribute_used__;
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/* Pointer to descriptor with the last event. */
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static struct pthread *__nptl_last_event __attribute_used__;
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+#ifdef SHARED
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+/* This variable is used to access _rtld_global from libthread_db. If
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+ GDB loads libpthread before ld.so, it is not possible to resolve
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+ _rtld_global directly during libpthread initialization. */
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+static struct rtld_global *__nptl_rtld_global __attribute_used__
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+ = &_rtld_global;
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+#endif
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+
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/* Number of threads running. */
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unsigned int __nptl_nthreads = 1;
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diff --git a/nptl/tst-pthread-gdb-attach-static.c b/nptl/tst-pthread-gdb-attach-static.c
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new file mode 100644
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index 0000000000..e159632cac
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--- /dev/null
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+++ b/nptl/tst-pthread-gdb-attach-static.c
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@@ -0,0 +1 @@
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+#include "tst-pthread-gdb-attach.c"
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diff --git a/nptl/tst-pthread-gdb-attach.c b/nptl/tst-pthread-gdb-attach.c
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new file mode 100644
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index 0000000000..0603ad844d
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--- /dev/null
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+++ b/nptl/tst-pthread-gdb-attach.c
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@@ -0,0 +1,143 @@
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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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+
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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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+
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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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+
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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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+
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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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+
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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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+
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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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+
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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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+
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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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+
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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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+
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+ TEST_COMPARE (altered_by_debugger, 2);
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+ return NULL;
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+}
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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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+
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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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+
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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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+
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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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+
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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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+
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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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+
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+#include <support/test-driver.c>
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diff --git a/nptl_db/structs.def b/nptl_db/structs.def
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index 999a9fc35a..8a613dd2f5 100644
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--- a/nptl_db/structs.def
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+++ b/nptl_db/structs.def
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@@ -100,8 +100,7 @@ DB_STRUCT_FIELD (pthread, dtvp)
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#endif
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#if !(IS_IN (libpthread) && !defined SHARED)
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-DB_STRUCT (rtld_global)
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-DB_RTLD_VARIABLE (_rtld_global)
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+DB_VARIABLE (__nptl_rtld_global)
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#endif
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DB_RTLD_GLOBAL_FIELD (dl_tls_dtv_slotinfo_list)
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DB_RTLD_GLOBAL_FIELD (dl_stack_user)
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diff --git a/nptl_db/td_init.c b/nptl_db/td_init.c
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index 1d15681228..06b5adc5c2 100644
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--- a/nptl_db/td_init.c
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+++ b/nptl_db/td_init.c
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@@ -33,13 +33,14 @@ td_init (void)
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bool
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__td_ta_rtld_global (td_thragent_t *ta)
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{
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- if (ta->ta_addr__rtld_global == 0
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- && td_mod_lookup (ta->ph, LD_SO, SYM__rtld_global,
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- &ta->ta_addr__rtld_global) != PS_OK)
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+ if (ta->ta_addr__rtld_global == 0)
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{
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- ta->ta_addr__rtld_global = (void*)-1;
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- return false;
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+ psaddr_t rtldglobalp;
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+ if (DB_GET_VALUE (rtldglobalp, ta, __nptl_rtld_global, 0) == TD_OK)
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+ ta->ta_addr__rtld_global = rtldglobalp;
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+ else
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+ ta->ta_addr__rtld_global = (void *) -1;
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}
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- else
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- return ta->ta_addr__rtld_global != (void*)-1;
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+
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+ return ta->ta_addr__rtld_global != (void *)-1;
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}
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diff --git a/nptl_db/thread_dbP.h b/nptl_db/thread_dbP.h
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index 580a70c471..712fa3aeb6 100644
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--- a/nptl_db/thread_dbP.h
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+++ b/nptl_db/thread_dbP.h
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@@ -108,6 +108,8 @@ struct td_thragent
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# undef DB_SYMBOL
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# undef DB_VARIABLE
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+ psaddr_t ta_addr__rtld_global;
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+
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/* The method of locating a thread's th_unique value. */
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enum
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{
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--
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2.31.1
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