[PATCH 6/6] x86: kaslr: report kernel offset on panic

Kees Cook
2013-04-25T21:55:21Z

When the system panics, include the kernel offset in the report to assist
in debugging.

Signed-off-by: Kees Cook <keescook@chromium.org>
---
arch/x86/kernel/setup.c | 24 ++++++++++++++++++++++++
1 file changed, 24 insertions(+)

diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index fae9134..95a33b1 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -830,6 +830,18 @@ static void __init trim_low_memory_range(void)
}

/*
+ * Dump out kernel offset information on panic.
+ */
+static int
+dump_kernel_offset(struct notifier_block *self, unsigned long v, void *p)
+{
+ pr_emerg("Kernel Offset: 0x%lx\n",
+ (unsigned long)&_text - __START_KERNEL);
+
+ return 0;
+}
+
+/*
* Determine if we were loaded by an EFI loader. If so, then we have also been
* passed the efi memmap, systab, etc., so we should use these data structures
* for initialization. Note, the efi init code path is determined by the
@@ -1249,3 +1261,15 @@ void __init i386_reserve_resources(void)
}

#endif /* CONFIG_X86_32 */
+
+static struct notifier_block kernel_offset_notifier = {
+ .notifier_call = dump_kernel_offset
+};
+
+static int __init register_kernel_offset_dumper(void)
+{
+ atomic_notifier_chain_register(&panic_notifier_list,
+ &kernel_offset_notifier);
+ return 0;
+}
+__initcall(register_kernel_offset_dumper);
--
1.7.9.5