[RFC PATCH v2 24/24] unwind_user/eh_frame: Add prctl() interface for (un)registering .eh_frame_hdr sections

@@ -6,6 +6,8 @@
 #include <linux/srcu.h>
 #include <linux/unwind_user_types.h>
 
+struct eh_frame_setup;
+
 #ifdef CONFIG_HAVE_UNWIND_USER_EH_FRAME
 
 struct eh_frame_section {

@@ -40,6 +42,12 @@ extern int eh_frame_add_section(unsigned long eh_frame_hdr_start,
 				unsigned long text_start,
 				unsigned long text_end);
 extern int eh_frame_remove_section(unsigned long eh_frame_hdr_start);
+
+extern int eh_frame_register(struct eh_frame_setup __user *user_data,
+			     __kernel_size_t size);
+extern int eh_frame_unregister(struct eh_frame_setup __user *user_data,
+			       __kernel_size_t size);
+
 extern int eh_frame_find(unsigned long ip, struct unwind_user_frame *frame);
 
 static inline bool current_has_eh_frame(void)

@@ -78,6 +86,18 @@ static inline int eh_frame_find(unsigned long ip, struct unwind_user_frame *fram
 	return -ENOSYS;
 }
 
+static inline int eh_frame_register(struct eh_frame_setup __user *user_data,
+				    __kernel_size_t size)
+{
+	return -EINVAL;
+}
+
+static inline int eh_frame_unregister(struct eh_frame_setup __user *user_data,
+				      __kernel_size_t size)
+{
+	return -EINVAL;
+}
+
 static inline bool current_has_eh_frame(void) { return false; }
 
 #endif /* CONFIG_HAVE_UNWIND_USER_EH_FRAME */

@@ -0,0 +1,14 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+#ifndef _UAPI_LINUX_EH_FRAME_H
+#define _UAPI_LINUX_EH_FRAME_H
+
+#include <linux/types.h>
+
+struct eh_frame_setup {
+	__u64	eh_frame_hdr_start;
+	__u64	eh_frame_hdr_size;
+	__u64	text_start;
+	__u64	text_size;
+};
+
+#endif /* _UAPI_LINUX_EH_FRAME_H */

@@ -416,4 +416,8 @@ struct prctl_mm_map {
 # define PR_CFI_DISABLE		_BITUL(1)
 # define PR_CFI_LOCK		_BITUL(2)
 
+/* EH_FRAME management */
+#define PR_REGISTER_EH_FRAME		82
+#define PR_UNREGISTER_EH_FRAME		83
+
 #endif /* _LINUX_PRCTL_H */

@@ -65,6 +65,7 @@
 #include <linux/rcupdate.h>
 #include <linux/uidgid.h>
 #include <linux/cred.h>
+#include <linux/eh_frame.h>
 
 #include <linux/nospec.h>
 

@@ -2907,6 +2908,16 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3,
 		if (arg3 & PR_CFI_LOCK && !(arg3 & PR_CFI_DISABLE))
 			error = arch_prctl_lock_branch_landing_pad_state(me);
 		break;
+	case PR_REGISTER_EH_FRAME:
+		if (arg4 || arg5)
+			return -EINVAL;
+		error = eh_frame_register((void __user *)arg2, arg3);
+		break;
+	case PR_UNREGISTER_EH_FRAME:
+		if (arg4 || arg5)
+			return -EINVAL;
+		error = eh_frame_unregister((void __user *)arg2, arg3);
+		break;
 	default:
 		trace_task_prctl_unknown(option, arg2, arg3, arg4, arg5);
 		error = -EINVAL;

@@ -15,6 +15,7 @@
 #include <linux/types.h>
 #include <linux/unwind_user_types.h>
 #include <linux/unwind_user_eh_frame_types.h>
+#include <uapi/linux/eh_frame.h>
 
 #include "eh_frame.h"
 #include "eh_frame_debug.h"

@@ -1609,3 +1610,48 @@ void eh_frame_free_mm(struct mm_struct *mm)
 
 	mtree_destroy(&mm->eh_frame_mt);
 }
+
+int eh_frame_register(struct eh_frame_setup __user *user_data, __kernel_size_t size)
+{
+	struct eh_frame_setup data;
+	unsigned long eh_frame_hdr_end, text_end;
+
+	if (!user_data || !size)
+		return -EINVAL;
+
+	if (size != sizeof(data))
+		return -EINVAL;
+
+	if (copy_from_user(&data, user_data, sizeof(data)))
+		return -EFAULT;
+
+	if (check_add_overflow(data.eh_frame_hdr_start, data.eh_frame_hdr_size,
+			       &eh_frame_hdr_end))
+		return -EINVAL;
+
+	if (check_add_overflow(data.text_start, data.text_size, &text_end))
+		return -EINVAL;
+
+	return eh_frame_add_section(data.eh_frame_hdr_start, eh_frame_hdr_end,
+				    data.text_start, text_end);
+}
+
+int eh_frame_unregister(struct eh_frame_setup __user *user_data, __kernel_size_t size)
+{
+	struct eh_frame_setup data;
+
+	if (!user_data || !size)
+		return -EINVAL;
+
+	if (size != sizeof(data))
+		return -EINVAL;
+
+	if (copy_from_user(&data, user_data, sizeof(data)))
+		return -EFAULT;
+
+	/* Unregister only uses eh_frame_hdr_start */
+	if (data.eh_frame_hdr_size || data.text_start || data.text_size)
+		return -EINVAL;
+
+	return eh_frame_remove_section(data.eh_frame_hdr_start);
+}