Date: Sun, 10 Jan 2021 06:26:31 GMT From: Konstantin Belousov <kib@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org Subject: git: 81b3a0a34145 - main - libc: implement rtld_get_stack_prot() for real Message-ID: <202101100626.10A6QV2J045256@gitrepo.freebsd.org>
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The branch main has been updated by kib: URL: https://cgit.FreeBSD.org/src/commit/?id=81b3a0a34145ee6c855f50c8035728f76d63c3f0 commit 81b3a0a34145ee6c855f50c8035728f76d63c3f0 Author: Konstantin Belousov <kib@FreeBSD.org> AuthorDate: 2021-01-10 03:05:42 +0000 Commit: Konstantin Belousov <kib@FreeBSD.org> CommitDate: 2021-01-10 06:25:43 +0000 libc: implement rtld_get_stack_prot() for real which makes stack prot correct for non-main threads created by binaries with statically linked libthr. Cache result, but do not engage into the full double-checked locking, since calculation of the return value is idempotent. PR: 252549 Reported and reviewed by: emaste MFC after: 1 week Sponsored by: The FreeBSD Foundation Differential Revision: https://reviews.freebsd.org/D28075 --- lib/libc/gen/dlfcn.c | 26 +++++++++++++++++++++++++- 1 file changed, 25 insertions(+), 1 deletion(-) diff --git a/lib/libc/gen/dlfcn.c b/lib/libc/gen/dlfcn.c index f7f162753b4b..395a6d9402e8 100644 --- a/lib/libc/gen/dlfcn.c +++ b/lib/libc/gen/dlfcn.c @@ -34,7 +34,9 @@ __FBSDID("$FreeBSD$"); /* * Linkage to services provided by the dynamic linker. */ +#include <sys/types.h> #include <sys/mman.h> +#include <machine/atomic.h> #include <dlfcn.h> #include <link.h> #include <stddef.h> @@ -256,8 +258,30 @@ _rtld_addr_phdr(const void *addr __unused, int _rtld_get_stack_prot(void) { +#ifndef IN_LIBDL + unsigned i; + int r; + static int ret; + + r = atomic_load_int(&ret); + if (r != 0) + return (r); - return (PROT_EXEC | PROT_READ | PROT_WRITE); + _once(&dl_phdr_info_once, dl_init_phdr_info); + r = PROT_EXEC | PROT_READ | PROT_WRITE; + for (i = 0; i < phdr_info.dlpi_phnum; i++) { + if (phdr_info.dlpi_phdr[i].p_type != PT_GNU_STACK) + continue; + r = PROT_READ | PROT_WRITE; + if ((phdr_info.dlpi_phdr[i].p_flags & PF_X) != 0) + r |= PROT_EXEC; + break; + } + atomic_store_int(&ret, r); + return (r); +#else + return (0); +#endif } #pragma weak _rtld_is_dlopened
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