Le 17/07/2019 à 10:06, Jason Yan a écrit :
When kaslr is enabled, the kernel offset is different for every boot.
This brings some difficult to debug the kernel. Dump out the kernel
offset when panic so that we can easily debug the kernel.
Signed-off-by: Jason Yan <yanai...@huawei.com>
Cc: Diana Craciun <diana.crac...@nxp.com>
Cc: Michael Ellerman <m...@ellerman.id.au>
Cc: Christophe Leroy <christophe.le...@c-s.fr>
Cc: Benjamin Herrenschmidt <b...@kernel.crashing.org>
Cc: Paul Mackerras <pau...@samba.org>
Cc: Nicholas Piggin <npig...@gmail.com>
Cc: Kees Cook <keesc...@chromium.org>
---
arch/powerpc/include/asm/page.h | 5 +++++
arch/powerpc/kernel/machine_kexec.c | 1 +
arch/powerpc/kernel/setup-common.c | 23 +++++++++++++++++++++++
3 files changed, 29 insertions(+)
diff --git a/arch/powerpc/include/asm/page.h b/arch/powerpc/include/asm/page.h
index 60a68d3a54b1..cd3ac530e58d 100644
--- a/arch/powerpc/include/asm/page.h
+++ b/arch/powerpc/include/asm/page.h
@@ -317,6 +317,11 @@ struct vm_area_struct;
extern unsigned long kimage_vaddr;
+static inline unsigned long kaslr_offset(void)
+{
+ return kimage_vaddr - KERNELBASE;
+}
+
#include <asm-generic/memory_model.h>
#endif /* __ASSEMBLY__ */
#include <asm/slice.h>
diff --git a/arch/powerpc/kernel/machine_kexec.c
b/arch/powerpc/kernel/machine_kexec.c
index c4ed328a7b96..078fe3d76feb 100644
--- a/arch/powerpc/kernel/machine_kexec.c
+++ b/arch/powerpc/kernel/machine_kexec.c
@@ -86,6 +86,7 @@ void arch_crash_save_vmcoreinfo(void)
VMCOREINFO_STRUCT_SIZE(mmu_psize_def);
VMCOREINFO_OFFSET(mmu_psize_def, shift);
#endif
+ vmcoreinfo_append_str("KERNELOFFSET=%lx\n", kaslr_offset());
}
/*
diff --git a/arch/powerpc/kernel/setup-common.c
b/arch/powerpc/kernel/setup-common.c
index 1f8db666468d..49e540c0adeb 100644
--- a/arch/powerpc/kernel/setup-common.c
+++ b/arch/powerpc/kernel/setup-common.c
@@ -715,12 +715,35 @@ static struct notifier_block ppc_panic_block = {
.priority = INT_MIN /* may not return; must be done last */
};
+/*
+ * Dump out kernel offset information on panic.
+ */
+static int dump_kernel_offset(struct notifier_block *self, unsigned long v,
+ void *p)
+{
+ const unsigned long offset = kaslr_offset();
+
+ if (IS_ENABLED(CONFIG_RANDOMIZE_BASE) && offset > 0)
+ pr_emerg("Kernel Offset: 0x%lx from 0x%lx\n",
+ offset, KERNELBASE);
+ else
+ pr_emerg("Kernel Offset: disabled\n");
Do we really need that else branch ?
Why not just make the below atomic_notifier_chain_register()
conditionnal to IS_ENABLED(CONFIG_RANDOMIZE_BASE) && offset > 0
and not print anything otherwise ?
Christophe
+
+ return 0;
+}
+
+static struct notifier_block kernel_offset_notifier = {
+ .notifier_call = dump_kernel_offset
+};
+
void __init setup_panic(void)
{
/* PPC64 always does a hard irq disable in its panic handler */
if (!IS_ENABLED(CONFIG_PPC64) && !ppc_md.panic)
return;
atomic_notifier_chain_register(&panic_notifier_list, &ppc_panic_block);
+ atomic_notifier_chain_register(&panic_notifier_list,
+ &kernel_offset_notifier);
}
#ifdef CONFIG_CHECK_CACHE_COHERENCY
