Offset that has been chosen for kaslr during kernel decompression can be
easily computed as a difference between _text and __START_KERNEL. We are
already making use of this in dump_kernel_offset() notifier and in
arch_crash_save_vmcoreinfo().
Introduce kaslr_offset() that makes this computation instead of
hard-coding it, so that other kernel code (such as live patching) can make
use of it. Also convert existing users to make use of it.
Signed-off-by: Jiri Kosina <jkosina@xxxxxxx>
---
It'd be great to potentially have Ack from x86 guys for this patch so that
I could take it through livepatching.git with the depending 2/2 patch.
Thanks.
v1 -> v2: convert arch_crash_save_vmcoreinfo(), as spotted by Josh
Poimboeuf.
arch/x86/include/asm/setup.h | 6 ++++++
arch/x86/kernel/machine_kexec_64.c | 3 ++-
arch/x86/kernel/setup.c | 2 +-
3 files changed, 9 insertions(+), 2 deletions(-)
diff --git a/arch/x86/include/asm/setup.h b/arch/x86/include/asm/setup.h
index f69e06b..785ac2f 100644
--- a/arch/x86/include/asm/setup.h
+++ b/arch/x86/include/asm/setup.h
@@ -65,12 +65,18 @@ static inline void x86_ce4100_early_setup(void) { }
* This is set up by the setup-routine at boot-time
*/
extern struct boot_params boot_params;
+extern char _text[];
static inline bool kaslr_enabled(void)
{
return !!(boot_params.hdr.loadflags & KASLR_FLAG);
}
+static inline unsigned long kaslr_offset(void)
+{
+ return (unsigned long)&_text - __START_KERNEL;
+}
+
/*
* Do NOT EVER look at the BIOS memory size location.
* It does not work on many machines.
diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c
index 415480d..e102963 100644
--- a/arch/x86/kernel/machine_kexec_64.c
+++ b/arch/x86/kernel/machine_kexec_64.c
@@ -25,6 +25,7 @@
#include <asm/io_apic.h>
#include <asm/debugreg.h>
#include <asm/kexec-bzimage64.h>
+#include <asm/setup.h>
#ifdef CONFIG_KEXEC_FILE
static struct kexec_file_ops *kexec_file_loaders[] = {
@@ -334,7 +335,7 @@ void arch_crash_save_vmcoreinfo(void)
VMCOREINFO_LENGTH(node_data, MAX_NUMNODES);
#endif
vmcoreinfo_append_str("KERNELOFFSET=%lx\n",
- (unsigned long)&_text - __START_KERNEL);
+ kaslr_offset());
}
/* arch-dependent functionality related to kexec file-based syscall */
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index d74ac33..5056d3c 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -834,7 +834,7 @@ dump_kernel_offset(struct notifier_block *self, unsigned long v, void *p)
{
if (kaslr_enabled()) {
pr_emerg("Kernel Offset: 0x%lx from 0x%lx (relocation range: 0x%lx-0x%lx)\n",
- (unsigned long)&_text - __START_KERNEL,
+ kaslr_offset(),
__START_KERNEL,
__START_KERNEL_map,
MODULES_VADDR-1);
--
Jiri Kosina
SUSE Labs
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