[RFC,10/10] powerpc/fsl_booke/kaslr: dump out kernel offset information on panic
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Message ID 20190717080621.40424-11-yanaijie@huawei.com
State Superseded
Headers show
Series
  • implement KASLR for powerpc/fsl_booke/32
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Commit Message

Jason Yan July 17, 2019, 8:06 a.m. UTC
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(+)

Comments

Christophe Leroy July 29, 2019, 11:43 a.m. UTC | #1
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
>
Jason Yan July 29, 2019, 2:08 p.m. UTC | #2
On 2019/7/29 19:43, Christophe Leroy wrote:
> 
> 
> 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 ?
> 

I'm trying to keep the same fashion as x86/arm64 do. But I agree
with you that it's simpler to not print anything else if not randomized.

> 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
>>
> 
> .
>

Patch
diff mbox series

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");
+
+	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