[PATCH v10 11/11] [DO NOT APPLY]unwind_user/sframe: Add prctl() interface for registering .sframe sections

[Steven Rostedt]

From: Josh Poimboeuf <jpoim...@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.
]

Signed-off-by: Josh Poimboeuf <jpoim...@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rost...@goodmis.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 ed3aed264aeb..b807baa8a53b 100644
--- a/include/uapi/linux/prctl.h
+++ b/include/uapi/linux/prctl.h
@@ -358,7 +358,7 @@ 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.
@@ -376,4 +376,8 @@ 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 1e28b40053ce..e6ce79a3a7aa 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>
 
@@ -2805,6 +2806,14 @@ 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;
-- 
2.50.1