The branch main has been updated by kib:
URL:
https://cgit.FreeBSD.org/src/commit/?id=81b3a0a34145ee6c855f50c8035728f76d63c3f0
commit 81b3a0a34145ee6c855f50c8035728f76d63c3f0
Author: Konstantin Belousov <k...@freebsd.org>
AuthorDate: 2021-01-10 03:05:42 +0000
Commit: Konstantin Belousov <k...@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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