The branch main has been updated by kib: URL: https://cgit.FreeBSD.org/src/commit/?id=860c4d94ac46cee35a678cf3c9cdbd437dfed75e
commit 860c4d94ac46cee35a678cf3c9cdbd437dfed75e Author: Konstantin Belousov <[email protected]> AuthorDate: 2024-07-17 04:05:33 +0000 Commit: Konstantin Belousov <[email protected]> CommitDate: 2024-07-29 23:57:33 +0000 rtld: add LD_NO_DL_ITERATE_PHDR_AFTER_FORK env var which makes threaded fork ignore the phdr rtld lock, in particular allowing the dl_iterate_phdr() to block in callback. The cost is that the image started in this mode cannot use dl_iterate_phdr() after fork. PR: 280318 Sponsored by: The FreeBSD Foundation MFC after: 1 week --- libexec/rtld-elf/rtld.1 | 10 +++++++++- libexec/rtld-elf/rtld.c | 1 + libexec/rtld-elf/rtld.h | 1 + libexec/rtld-elf/rtld_lock.c | 7 +++++-- 4 files changed, 16 insertions(+), 3 deletions(-) diff --git a/libexec/rtld-elf/rtld.1 b/libexec/rtld-elf/rtld.1 index 992138b1ffc0..31e046a5cdc4 100644 --- a/libexec/rtld-elf/rtld.1 +++ b/libexec/rtld-elf/rtld.1 @@ -26,7 +26,7 @@ .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. .\" -.Dd April 28, 2024 +.Dd July 24, 2025 .Dt RTLD 1 .Os .Sh NAME @@ -329,6 +329,14 @@ The static TLS extra space is used when loading objects compiled for initial-exec TLS code model with .Xr dlopen 3 . The minimum value that can be specified is \'128\'. +.It Ev LD_NO_DL_ITERATE_PHDR_AFTER_FORK +Allow +.Xr dl_iterate_phdr 3 +to block in callback, without causing deadlock with the +.Xr fork 2 . +The drawback is that the image started in this mode cannot use +.Xr dl_iterate_phdr 3 +after fork. .El .Sh DIRECT EXECUTION MODE .Nm diff --git a/libexec/rtld-elf/rtld.c b/libexec/rtld-elf/rtld.c index f49c429d0061..1f0c59722ac6 100644 --- a/libexec/rtld-elf/rtld.c +++ b/libexec/rtld-elf/rtld.c @@ -375,6 +375,7 @@ static struct ld_env_var_desc ld_env_vars[] = { LD_ENV_DESC(TRACE_LOADED_OBJECTS_ALL, false), LD_ENV_DESC(SHOW_AUXV, false), LD_ENV_DESC(STATIC_TLS_EXTRA, false), + LD_ENV_DESC(NO_DL_ITERATE_PHDR_AFTER_FORK, false), }; const char * diff --git a/libexec/rtld-elf/rtld.h b/libexec/rtld-elf/rtld.h index fcd42f3841b3..656e980c6261 100644 --- a/libexec/rtld-elf/rtld.h +++ b/libexec/rtld-elf/rtld.h @@ -376,6 +376,7 @@ enum { LD_TRACE_LOADED_OBJECTS_ALL, LD_SHOW_AUXV, LD_STATIC_TLS_EXTRA, + LD_NO_DL_ITERATE_PHDR_AFTER_FORK, }; void _rtld_error(const char *, ...) __printflike(1, 2) __exported; diff --git a/libexec/rtld-elf/rtld_lock.c b/libexec/rtld-elf/rtld_lock.c index 0c790450dcec..323bb7494c32 100644 --- a/libexec/rtld-elf/rtld_lock.c +++ b/libexec/rtld-elf/rtld_lock.c @@ -463,6 +463,7 @@ _rtld_atfork_pre(int *locks) if (locks == NULL) return; + bzero(ls, sizeof(ls)); /* * Warning: this did not worked well with the rtld compat @@ -472,7 +473,8 @@ _rtld_atfork_pre(int *locks) * _rtld_atfork_pre() must provide the working implementation * of the locks anyway, and libthr locks are fine. */ - wlock_acquire(rtld_phdr_lock, &ls[0]); + if (ld_get_env_var(LD_NO_DL_ITERATE_PHDR_AFTER_FORK) == NULL) + wlock_acquire(rtld_phdr_lock, &ls[0]); wlock_acquire(rtld_bind_lock, &ls[1]); /* XXXKIB: I am really sorry for this. */ @@ -492,5 +494,6 @@ _rtld_atfork_post(int *locks) ls[0].lockstate = locks[2]; ls[1].lockstate = locks[0]; lock_release(rtld_bind_lock, &ls[1]); - lock_release(rtld_phdr_lock, &ls[0]); + if (ld_get_env_var(LD_NO_DL_ITERATE_PHDR_AFTER_FORK) == NULL) + lock_release(rtld_phdr_lock, &ls[0]); }
