linux-kernel - [PATCH v8 12/12] unwind_user/sframe: Add prctl() interface for registering .sframe sections

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Message-ID: <20250708021200.397301537@kernel.org>
Date: Mon, 07 Jul 2025 22:11:27 -0400
From: Steven Rostedt <rostedt@...nel.org>
To: linux-kernel@...r.kernel.org,
 linux-trace-kernel@...r.kernel.org,
 bpf@...r.kernel.org,
 x86@...nel.org
Cc: Masami Hiramatsu <mhiramat@...nel.org>,
 Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
 Josh Poimboeuf <jpoimboe@...nel.org>,
 Peter Zijlstra <peterz@...radead.org>,
 Ingo Molnar <mingo@...nel.org>,
 Jiri Olsa <jolsa@...nel.org>,
 Namhyung Kim <namhyung@...nel.org>,
 Thomas Gleixner <tglx@...utronix.de>,
 Andrii Nakryiko <andrii@...nel.org>,
 Indu Bhagat <indu.bhagat@...cle.com>,
 "Jose E. Marchesi" <jemarch@....org>,
 Beau Belgrave <beaub@...ux.microsoft.com>,
 Jens Remus <jremus@...ux.ibm.com>,
 Linus Torvalds <torvalds@...ux-foundation.org>,
 Andrew Morton <akpm@...ux-foundation.org>,
 Jens Axboe <axboe@...nel.dk>,
 Florian Weimer <fweimer@...hat.com>,
 Sam James <sam@...too.org>
Subject: [PATCH v8 12/12] unwind_user/sframe: Add prctl() interface for registering .sframe
 sections

From: Josh Poimboeuf <jpoimboe@...nel.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.
]

Signed-off-by: Josh Poimboeuf <jpoimboe@...nel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
---
 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 43dec6eed559..c575cf7151b1 100644
--- a/include/uapi/linux/prctl.h
+++ b/include/uapi/linux/prctl.h
@@ -351,7 +351,7 @@ 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.
@@ -371,4 +371,8 @@ struct prctl_mm_map {
 # define PR_FUTEX_HASH_GET_SLOTS	2
 # define PR_FUTEX_HASH_GET_IMMUTABLE	3

+/* 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 adc0de0aa364..cf788e66dc86 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>

@@ -2824,6 +2825,14 @@ 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;
-- 
2.47.2