[PATCH v4 21/39] unwind_user/sframe: Add prctl() interface for registering .sframe sections

[Josh Poimboeuf]

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.

Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
---
 include/uapi/linux/prctl.h | 5 ++++-
 kernel/sys.c               | 9 +++++++++
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/include/uapi/linux/prctl.h b/include/uapi/linux/prctl.h
index 5c6080680cb2..4a52e3f9ccc9 100644
--- a/include/uapi/linux/prctl.h
+++ b/include/uapi/linux/prctl.h
@@ -351,6 +351,9 @@ 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
+
+#define PR_ADD_SFRAME			77
+#define PR_REMOVE_SFRAME		78
 
 #endif /* _LINUX_PRCTL_H */
diff --git a/kernel/sys.c b/kernel/sys.c
index c4c701c6f0b4..414dfd6ee9fa 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -64,6 +64,7 @@
 #include <linux/rcupdate.h>
 #include <linux/uidgid.h>
 #include <linux/cred.h>
+#include <linux/sframe.h>
 
 #include <linux/nospec.h>
 
@@ -2809,6 +2810,14 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3,
 			return -EINVAL;
 		error = arch_lock_shadow_stack_status(me, arg2);
 		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:
 		error = -EINVAL;
 		break;
-- 
2.48.1