powerpc/fsl_booke/kaslr: dump out kernel offset information on panic

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.

This code is derived from x86/arm64 which has similar functionality.

Signed-off-by: Jason Yan <yanaijie@huawei.com>
Reviewed-by: Christophe Leroy <christophe.leroy@c-s.fr>
Reviewed-by: Diana Craciun <diana.craciun@nxp.com>
Tested-by: Diana Craciun <diana.craciun@nxp.com>
Signed-off-by: Scott Wood <oss@buserror.net>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

diff --git a/arch/powerpc/include/asm/page.h b/arch/powerpc/include/asm/page.h
index 88fa53f89f5a5f290ae2a9353d81c0302762e5c4..f2f3ed5a89694fc916462db6d313e2a1a285fc8c 100644 (file)
--- a/arch/powerpc/include/asm/page.h
+++ b/arch/powerpc/include/asm/page.h
@@ -327,6 +327,11 @@ struct vm_area_struct;
 
 extern unsigned long kernstart_virt_addr;
 
+static inline unsigned long kaslr_offset(void)
+{
+       return kernstart_virt_addr - KERNELBASE;
+}
+
 #include <asm-generic/memory_model.h>
 #endif /* __ASSEMBLY__ */
 #include <asm/slice.h>

diff --git a/arch/powerpc/kernel/setup-common.c b/arch/powerpc/kernel/setup-common.c
index 25aaa390300091e310a81dfa28f9ccde7cc05a5f..488f1eecc0deb06838bbe0de9ccc2d807547717e 100644 (file)
--- a/arch/powerpc/kernel/setup-common.c
+++ b/arch/powerpc/kernel/setup-common.c
@@ -715,8 +715,28 @@ 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)
+{
+       pr_emerg("Kernel Offset: 0x%lx from 0x%lx\n",
+                kaslr_offset(), KERNELBASE);
+
+       return 0;
+}
+
+static struct notifier_block kernel_offset_notifier = {
+       .notifier_call = dump_kernel_offset
+};
+
 void __init setup_panic(void)
 {
+       if (IS_ENABLED(CONFIG_RANDOMIZE_BASE) && kaslr_offset() > 0)
+               atomic_notifier_chain_register(&panic_notifier_list,
+                                              &kernel_offset_notifier);
+
        /* PPC64 always does a hard irq disable in its panic handler */
        if (!IS_ENABLED(CONFIG_PPC64) && !ppc_md.panic)
                return;