From da1a679cde9b12d6e331f43d2d92a234f2d1f9b0 Mon Sep 17 00:00:00 2001
From: Roland McGrath <roland@redhat.com>
Date: Thu, 19 Jul 2007 01:48:39 -0700
Subject: [PATCH] Add /sys/kernel/notes

This patch adds the /sys/kernel/notes magic file.  Reading this delivers the
contents of the kernel's .notes section.  This lets userland easily glean any
detailed information about the running kernel's build that was stored there at
compile time.

Signed-off-by: Roland McGrath <roland@redhat.com>
Cc: Andi Kleen <ak@suse.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
 kernel/ksysfs.c | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/kernel/ksysfs.c b/kernel/ksysfs.c
index 559deca5ed15..2565e1b6dd7b 100644
--- a/kernel/ksysfs.c
+++ b/kernel/ksysfs.c
@@ -62,6 +62,28 @@ static ssize_t kexec_crash_loaded_show(struct kset *kset, char *page)
 KERNEL_ATTR_RO(kexec_crash_loaded);
 #endif /* CONFIG_KEXEC */
 
+/*
+ * Make /sys/kernel/notes give the raw contents of our kernel .notes section.
+ */
+extern const char __start_notes __attribute__((weak));
+extern const char __stop_notes __attribute__((weak));
+#define	notes_size (&__stop_notes - &__start_notes)
+
+static ssize_t notes_read(struct kobject *kobj, struct bin_attribute *bin_attr,
+			  char *buf, loff_t off, size_t count)
+{
+	memcpy(buf, &__start_notes + off, count);
+	return count;
+}
+
+static struct bin_attribute notes_attr = {
+	.attr = {
+		.name = "notes",
+		.mode = S_IRUGO,
+	},
+	.read = &notes_read,
+};
+
 decl_subsys(kernel, NULL, NULL);
 EXPORT_SYMBOL_GPL(kernel_subsys);
 
@@ -88,6 +110,12 @@ static int __init ksysfs_init(void)
 		error = sysfs_create_group(&kernel_subsys.kobj,
 					   &kernel_attr_group);
 
+	if (!error && notes_size > 0) {
+		notes_attr.size = notes_size;
+		error = sysfs_create_bin_file(&kernel_subsys.kobj,
+					      &notes_attr);
+	}
+
 	return error;
 }