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([2804:1b3:a7c0:c5fb:1cf6:d480:34ef:aedf]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-70422c977dasm6023811b3a.62.2024.06.11.08.32.35 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 11 Jun 2024 08:32:37 -0700 (PDT) From: Adhemerval Zanella To: libc-alpha@sourceware.org Cc: Stephen Roettger , jeffxu@chromium.org, Carlos O'Donell , Florian Weimer Subject: [RFC 4/5] elf: Enable RTLD_NODELETE on __libc_unwind_link_get Date: Tue, 11 Jun 2024 12:27:07 -0300 Message-ID: <20240611153220.165430-5-adhemerval.zanella@linaro.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240611153220.165430-1-adhemerval.zanella@linaro.org> References: <20240611153220.165430-1-adhemerval.zanella@linaro.org> MIME-Version: 1.0 X-Spam-Status: No, score=-12.4 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, RCVD_IN_DNSWL_NONE, SPF_HELO_NONE, SPF_PASS, TXREP, T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.30 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: libc-alpha-bounces+patch=linaro.org@sourceware.org The libgcc_s.so can also be sealed. The library is loaded once and not unloaded during process execution (only for memory debug with __libc_unwind_link_freeres). Checked on x86_64-linux-gnu and aarch64-linux-gnu. --- include/dlfcn.h | 2 ++ manual/tunables.texi | 4 ++++ misc/unwind-link.c | 5 +++-- sysdeps/unix/sysv/linux/tst-dl_mseal.c | 13 +++++++++++++ 4 files changed, 22 insertions(+), 2 deletions(-) diff --git a/include/dlfcn.h b/include/dlfcn.h index f49ee1b0c9..06e2ecbdd2 100644 --- a/include/dlfcn.h +++ b/include/dlfcn.h @@ -50,6 +50,8 @@ extern char **__libc_argv attribute_hidden; better error handling semantics for the library. */ #define __libc_dlopen(name) \ __libc_dlopen_mode (name, RTLD_NOW | __RTLD_DLOPEN) +#define __libc_dlopen_nodelete(name) \ + __libc_dlopen_mode (name, RTLD_NODELETE | RTLD_NOW | __RTLD_DLOPEN) extern void *__libc_dlopen_mode (const char *__name, int __mode) attribute_hidden; extern void *__libc_dlsym (void *__map, const char *__name) diff --git a/manual/tunables.texi b/manual/tunables.texi index 26fba6641d..be36d52cf9 100644 --- a/manual/tunables.texi +++ b/manual/tunables.texi @@ -381,6 +381,10 @@ Any preload libraries. @item Any library loaded with @code{dlopen} with @code{RTLD_NODELETE} flag. + +@item +Any runtime library used for process unwind (such as required by @code{backtrace} +or @code{pthread_exit}). @end itemize The tunable accepts three diferent values: @samp{0} where sealing is disabled, diff --git a/misc/unwind-link.c b/misc/unwind-link.c index 213a0162a4..7267ecbec3 100644 --- a/misc/unwind-link.c +++ b/misc/unwind-link.c @@ -48,7 +48,7 @@ __libc_unwind_link_get (void) /* Initialize a copy of the data, so that we do not need about unlocking in case the dynamic loader somehow triggers unwinding. */ - void *local_libgcc_handle = __libc_dlopen (LIBGCC_S_SO); + void *local_libgcc_handle = __libc_dlopen_nodelete (LIBGCC_S_SO); if (local_libgcc_handle == NULL) { __libc_lock_unlock (lock); @@ -100,7 +100,8 @@ __libc_unwind_link_get (void) __libc_lock_lock (lock); if (atomic_load_relaxed (&global_libgcc_handle) != NULL) - /* This thread lost the race. Clean up. */ + /* This thread lost the race. Drop the l_direct_opencount and issue + the debug log. */ __libc_dlclose (local_libgcc_handle); else { diff --git a/sysdeps/unix/sysv/linux/tst-dl_mseal.c b/sysdeps/unix/sysv/linux/tst-dl_mseal.c index 72a33d04c7..da1a3ebe5a 100644 --- a/sysdeps/unix/sysv/linux/tst-dl_mseal.c +++ b/sysdeps/unix/sysv/linux/tst-dl_mseal.c @@ -19,6 +19,7 @@ #include #include #include +#include #include #include #include @@ -31,6 +32,7 @@ #include #include #include +#include #define LIB_PRELOAD "lib-tst-dl_mseal-preload.so" @@ -70,6 +72,7 @@ static const char *expected_sealed_libs[] = LIB_NEEDED_2, LIB_DLOPEN_NODELETE, LIB_DLOPEN_NODELETE_DEP, + LIBGCC_S_SO, #endif "[vdso]", }; @@ -100,6 +103,13 @@ is_in_string_list (const char *s, const char *const list[], size_t len) return -1; } +static void * +tf (void *closure) +{ + pthread_exit (NULL); + return NULL; +} + static int handle_restart (void) { @@ -108,6 +118,9 @@ handle_restart (void) xdlopen (LIB_DLOPEN_DEFAULT, RTLD_NOW); #endif + /* pthread_exit will load LIBGCC_S_SO. */ + xpthread_join (xpthread_create (NULL, tf, NULL)); + FILE *fp = xfopen ("/proc/self/maps", "r"); char *line = NULL; size_t linesiz = 0;