[PATCH v13 18/18] unwind_user/sframe: Add prctl() interface for registering .sframe sections

Jens Remus
2026-01-27T15:37:03Z

From: Josh Poimboeuf <jpoimboe@kernel.org>

The kernel doesn't have direct visibility to the ELF contents of shared
libraries. Add some prctl() interfaces which allow glibc to tell the
kernel where to find .sframe sections.

[
This adds an interface for prctl() for testing loading of sframes for
libraries. But this interface should really be a system call. This patch
is for testing purposes only and should not be applied to mainline.
]

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Andrii Nakryiko <andrii@kernel.org>
Cc: Indu Bhagat <indu.bhagat@oracle.com>
Cc: "Jose E. Marchesi" <jemarch@gnu.org>
Cc: Beau Belgrave <beaub@linux.microsoft.com>
Cc: Jens Remus <jremus@linux.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Florian Weimer <fweimer@redhat.com>
Cc: Sam James <sam@gentoo.org>
Cc: Kees Cook <kees@kernel.org>
Cc: "Carlos O'Donell" <codonell@redhat.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Jens Remus <jremus@linux.ibm.com>
---
include/uapi/linux/prctl.h | 6 +++++-
kernel/sys.c | 9 +++++++++
2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/include/uapi/linux/prctl.h b/include/uapi/linux/prctl.h
index 51c4e8c82b1e..91d2c9eb3aa3 100644
--- a/include/uapi/linux/prctl.h
+++ b/include/uapi/linux/prctl.h
@@ -368,7 +368,7 @@ struct prctl_mm_map {
* configuration. All bits may be locked via this call, including
* undefined bits.
*/
-#define PR_LOCK_SHADOW_STACK_STATUS 76
+#define PR_LOCK_SHADOW_STACK_STATUS 76

/*
* Controls the mode of timer_create() for CRIU restore operations.
@@ -386,4 +386,8 @@ struct prctl_mm_map {
# define PR_FUTEX_HASH_SET_SLOTS 1
# define PR_FUTEX_HASH_GET_SLOTS 2

+/* SFRAME management */
+#define PR_ADD_SFRAME 79
+#define PR_REMOVE_SFRAME 80
+
#endif /* _LINUX_PRCTL_H */
diff --git a/kernel/sys.c b/kernel/sys.c
index 8b58eece4e58..ea088b643eb4 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -65,6 +65,7 @@
#include <linux/rcupdate.h>
#include <linux/uidgid.h>
#include <linux/cred.h>
+#include <linux/sframe.h>

#include <linux/nospec.h>

@@ -2868,6 +2869,14 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3,
case PR_FUTEX_HASH:
error = futex_hash_prctl(arg2, arg3, arg4);
break;
+ case PR_ADD_SFRAME:
+ error = sframe_add_section(arg2, arg3, arg4, arg5);
+ break;
+ case PR_REMOVE_SFRAME:
+ if (arg3 || arg4 || arg5)
+ return -EINVAL;
+ error = sframe_remove_section(arg2);
+ break;
default:
trace_task_prctl_unknown(option, arg2, arg3, arg4, arg5);
error = -EINVAL;
--
2.51.0