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Message-ID: <9113cc5b-0e89-f423-712a-79220af82b92@huawei.com>
Date: Thu, 8 Aug 2019 16:39:26 +0800
From: Jason Yan <yanaijie@...wei.com>
To: Michael Ellerman <mpe@...erman.id.au>, <linuxppc-dev@...ts.ozlabs.org>,
<diana.craciun@....com>, <christophe.leroy@....fr>,
<benh@...nel.crashing.org>, <paulus@...ba.org>, <npiggin@...il.com>,
<keescook@...omium.org>, <kernel-hardening@...ts.openwall.com>
CC: <linux-kernel@...r.kernel.org>, <wangkefeng.wang@...wei.com>,
<yebin10@...wei.com>, <thunder.leizhen@...wei.com>,
<jingxiangfeng@...wei.com>, <fanchengyang@...wei.com>,
<zhaohongjiang@...wei.com>
Subject: Re: [PATCH v5 10/10] powerpc/fsl_booke/kaslr: dump out kernel offset
information on panic
On 2019/8/7 21:03, Michael Ellerman wrote:
> Jason Yan <yanaijie@...wei.com> writes:
>> 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.
>
> Some of this is taken from the arm64 version right? Please say so when
> you copy other people's code.
>
No problem. Architectures like x86 or arm64 or s390 both have this
similar code. I guess x86 is the first one.
>> 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());
>> }
>
> There's no mention of that in the commit log.
>
> Please split it into a separate patch and describe what you're doing and
> why.
OK
>
>> diff --git a/arch/powerpc/kernel/setup-common.c b/arch/powerpc/kernel/setup-common.c
>> index 1f8db666468d..064075f02837 100644
>> --- a/arch/powerpc/kernel/setup-common.c
>> +++ b/arch/powerpc/kernel/setup-common.c
>> @@ -715,12 +715,31 @@ 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)
>> {
>> /* 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);
>
>> + if (IS_ENABLED(CONFIG_RANDOMIZE_BASE) && kaslr_offset() > 0)
>> + atomic_notifier_chain_register(&panic_notifier_list,
>> + &kernel_offset_notifier);
>
> Don't you want to do that before the return above?
>
Eagle eye. This should not affected by the conditions above.
>> }
>
> cheers
>
> .
>
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