The branch main has been updated by kib: URL: https://cgit.FreeBSD.org/src/commit/?id=4daf2d3e7db53a113108f9a02ceaf5051d416184
commit 4daf2d3e7db53a113108f9a02ceaf5051d416184 Author: Konstantin Belousov <[email protected]> AuthorDate: 2026-01-26 16:09:18 +0000 Commit: Konstantin Belousov <[email protected]> CommitDate: 2026-01-28 02:26:52 +0000 posix_spawn: use rfork_thread on all arches Do not allocate or switch to the custom stack on non-x86. Reviewed by: markj Sponsored by: The FreeBSD Foundation MFC after: 1 week Differential revision: https://reviews.freebsd.org/D54898 --- lib/libc/gen/posix_spawn.c | 39 ++++++++++++++++++--------------------- 1 file changed, 18 insertions(+), 21 deletions(-) diff --git a/lib/libc/gen/posix_spawn.c b/lib/libc/gen/posix_spawn.c index c64915078317..656c0f20f798 100644 --- a/lib/libc/gen/posix_spawn.c +++ b/lib/libc/gen/posix_spawn.c @@ -236,7 +236,6 @@ struct posix_spawn_args { #define PSPAWN_STACK_ALIGN(sz) \ (((sz) + PSPAWN_STACK_ALIGNBYTES) & ~PSPAWN_STACK_ALIGNBYTES) -#if defined(__i386__) || defined(__amd64__) /* * Below we'll assume that _RFORK_THREAD_STACK_SIZE is appropriately aligned for * the posix_spawn() case where we do not end up calling execvpe and won't ever @@ -245,7 +244,6 @@ struct posix_spawn_args { #define _RFORK_THREAD_STACK_SIZE 4096 _Static_assert((_RFORK_THREAD_STACK_SIZE % PSPAWN_STACK_ALIGNMENT) == 0, "Inappropriate stack size alignment"); -#endif static int _posix_spawn_thr(void *data) @@ -287,12 +285,14 @@ do_posix_spawn(pid_t *pid, const char *path, pid_t p; int pfd; bool do_pfd; -#ifdef _RFORK_THREAD_STACK_SIZE char *stack; - size_t cnt, stacksz; + size_t stacksz; +#if defined(__i386__) || defined(__amd64__) stacksz = _RFORK_THREAD_STACK_SIZE; if (use_env_path) { + size_t cnt; + /* * We need to make sure we have enough room on the stack for the * potential alloca() in execvPe if it gets kicked back an @@ -319,6 +319,9 @@ do_posix_spawn(pid_t *pid, const char *path, return (ENOMEM); stacksz = (((uintptr_t)stack + stacksz) & ~PSPAWN_STACK_ALIGNBYTES) - (uintptr_t)stack; +#else + stack = NULL; + stacksz = 0; #endif psa.path = path; psa.fa = fa; @@ -341,13 +344,16 @@ do_posix_spawn(pid_t *pid, const char *path, * a special property of the libthr rtld locks ensure that * rtld is operational in the child. In particular, libthr * rtld locks do not store owner' tid into the lock word. - */ -#ifdef _RFORK_THREAD_STACK_SIZE - /* - * x86 stores the return address on the stack, so rfork(2) cannot work - * as-is because the child would clobber the return address of the - * parent. Because of this, we must use rfork_thread instead while - * almost every other arch stores the return address in a register. + * + * x86 stores the return address on the stack, so rfork(2) + * cannot work as-is because the child would clobber the + * return address of the parent. Because of this, we must use + * rfork_thread instead. + * + * Every other architecture stores the return address in a + * register, the trivial rfork_thread() wrapper is provided + * for them. The only minor drawback is that the stack is + * temporarily allocated. */ if (do_pfd) { p = pdrfork_thread(&pfd, PD_CLOEXEC | (*sa)->sa_pdflags, @@ -357,16 +363,7 @@ do_posix_spawn(pid_t *pid, const char *path, &psa); } free(stack); -#else - if (do_pfd) { - p = pdrfork(&pfd, PD_CLOEXEC | (*sa)->sa_pdflags, RFSPAWN); - } else { - p = rfork(RFSPAWN); - } - if (p == 0) - /* _posix_spawn_thr does not return */ - _posix_spawn_thr(&psa); -#endif + /* * The above block should leave us in a state where we've either * succeeded and we're ready to process the results, or we need to
