Messages in this thread | | | Subject | Re: [RFC PATCH 10/10] powerpc/fsl_booke/kaslr: dump out kernel offset information on panic | From | Christophe Leroy <> | Date | Mon, 29 Jul 2019 13:43:05 +0200 |
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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 <yanaijie@huawei.com> > Cc: Diana Craciun <diana.craciun@nxp.com> > Cc: Michael Ellerman <mpe@ellerman.id.au> > Cc: Christophe Leroy <christophe.leroy@c-s.fr> > Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> > Cc: Paul Mackerras <paulus@samba.org> > Cc: Nicholas Piggin <npiggin@gmail.com> > Cc: Kees Cook <keescook@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 >
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