Re: [PATCH v4 1/3] kexec: Move vmcoreinfo out of the kernel's .bss section

Re: [PATCH v4 1/3] kexec: Move vmcoreinfo out of the kernel's .bss section

[Dave Young]

Add ia64i list,  and s390 list although Michael has tested it

On 04/20/17 at 07:39pm, Xunlei Pang wrote:
> As Eric said,
> "what we need to do is move the variable vmcoreinfo_note out
> of the kernel's .bss section.  And modify the code to regenerate
> and keep this information in something like the control page.
> 
> Definitely something like this needs a page all to itself, and ideally
> far away from any other kernel data structures.  I clearly was not
> watching closely the data someone decided to keep this silly thing
> in the kernel's .bss section."
> 
> This patch allocates extra pages for these vmcoreinfo_XXX variables,
> one advantage is that it enhances some safety of vmcoreinfo, because
> vmcoreinfo now is kept far away from other kernel data structures.
> 
> Suggested-by: Eric Biederman <ebiederm@xmission.com>
> Cc: Michael Holzheu <holzheu@linux.vnet.ibm.com>
> Cc: Juergen Gross <jgross@suse.com>
> Signed-off-by: Xunlei Pang <xlpang@redhat.com>
> ---
> v3->v4:
> -Rebased on the latest linux-next
> -Handle S390 vmcoreinfo_note properly
> -Handle the newly-added xen/mmu_pv.c
> 
>  arch/ia64/kernel/machine_kexec.c |  5 -----
>  arch/s390/kernel/machine_kexec.c |  1 +
>  arch/s390/kernel/setup.c         |  6 ------
>  arch/x86/kernel/crash.c          |  2 +-
>  arch/x86/xen/mmu_pv.c            |  4 ++--
>  include/linux/crash_core.h       |  2 +-
>  kernel/crash_core.c              | 27 +++++++++++++++++++++++----
>  kernel/ksysfs.c                  |  2 +-
>  8 files changed, 29 insertions(+), 20 deletions(-)
> 
> diff --git a/arch/ia64/kernel/machine_kexec.c b/arch/ia64/kernel/machine_kexec.c
> index 599507b..c14815d 100644
> --- a/arch/ia64/kernel/machine_kexec.c
> +++ b/arch/ia64/kernel/machine_kexec.c
> @@ -163,8 +163,3 @@ void arch_crash_save_vmcoreinfo(void)
>  #endif
>  }
>  
> -phys_addr_t paddr_vmcoreinfo_note(void)
> -{
> -	return ia64_tpa((unsigned long)(char *)&vmcoreinfo_note);
> -}
> -
> diff --git a/arch/s390/kernel/machine_kexec.c b/arch/s390/kernel/machine_kexec.c
> index 49a6bd4..3d0b14a 100644
> --- a/arch/s390/kernel/machine_kexec.c
> +++ b/arch/s390/kernel/machine_kexec.c
> @@ -246,6 +246,7 @@ void arch_crash_save_vmcoreinfo(void)
>  	VMCOREINFO_SYMBOL(lowcore_ptr);
>  	VMCOREINFO_SYMBOL(high_memory);
>  	VMCOREINFO_LENGTH(lowcore_ptr, NR_CPUS);
> +	mem_assign_absolute(S390_lowcore.vmcore_info, paddr_vmcoreinfo_note());
>  }
>  
>  void machine_shutdown(void)
> diff --git a/arch/s390/kernel/setup.c b/arch/s390/kernel/setup.c
> index 3ae756c..3d1d808 100644
> --- a/arch/s390/kernel/setup.c
> +++ b/arch/s390/kernel/setup.c
> @@ -496,11 +496,6 @@ static void __init setup_memory_end(void)
>  	pr_notice("The maximum memory size is %luMB\n", memory_end >> 20);
>  }
>  
> -static void __init setup_vmcoreinfo(void)
> -{
> -	mem_assign_absolute(S390_lowcore.vmcore_info, paddr_vmcoreinfo_note());
> -}
> -
>  #ifdef CONFIG_CRASH_DUMP
>  
>  /*
> @@ -939,7 +934,6 @@ void __init setup_arch(char **cmdline_p)
>  #endif
>  
>  	setup_resources();
> -	setup_vmcoreinfo();
>  	setup_lowcore();
>  	smp_fill_possible_mask();
>  	cpu_detect_mhz_feature();
> diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
> index 22217ec..44404e2 100644
> --- a/arch/x86/kernel/crash.c
> +++ b/arch/x86/kernel/crash.c
> @@ -457,7 +457,7 @@ static int prepare_elf64_headers(struct crash_elf_data *ced,
>  	bufp += sizeof(Elf64_Phdr);
>  	phdr->p_type = PT_NOTE;
>  	phdr->p_offset = phdr->p_paddr = paddr_vmcoreinfo_note();
> -	phdr->p_filesz = phdr->p_memsz = sizeof(vmcoreinfo_note);
> +	phdr->p_filesz = phdr->p_memsz = VMCOREINFO_NOTE_SIZE;
>  	(ehdr->e_phnum)++;
>  
>  #ifdef CONFIG_X86_64
> diff --git a/arch/x86/xen/mmu_pv.c b/arch/x86/xen/mmu_pv.c
> index 9d9ae66..35543fa 100644
> --- a/arch/x86/xen/mmu_pv.c
> +++ b/arch/x86/xen/mmu_pv.c
> @@ -2723,8 +2723,8 @@ void xen_destroy_contiguous_region(phys_addr_t pstart, unsigned int order)
>  phys_addr_t paddr_vmcoreinfo_note(void)
>  {
>  	if (xen_pv_domain())
> -		return virt_to_machine(&vmcoreinfo_note).maddr;
> +		return virt_to_machine(vmcoreinfo_note).maddr;
>  	else
> -		return __pa_symbol(&vmcoreinfo_note);
> +		return __pa(vmcoreinfo_note);
>  }
>  #endif /* CONFIG_KEXEC_CORE */
> diff --git a/include/linux/crash_core.h b/include/linux/crash_core.h
> index eb71a70..ba283a2 100644
> --- a/include/linux/crash_core.h
> +++ b/include/linux/crash_core.h
> @@ -53,7 +53,7 @@
>  #define VMCOREINFO_PHYS_BASE(value) \
>  	vmcoreinfo_append_str("PHYS_BASE=%lx\n", (unsigned long)value)
>  
> -extern u32 vmcoreinfo_note[VMCOREINFO_NOTE_SIZE/4];
> +extern u32 *vmcoreinfo_note;
>  extern size_t vmcoreinfo_size;
>  extern size_t vmcoreinfo_max_size;
>  
> diff --git a/kernel/crash_core.c b/kernel/crash_core.c
> index fcbd568..0321f04 100644
> --- a/kernel/crash_core.c
> +++ b/kernel/crash_core.c
> @@ -14,10 +14,10 @@
>  #include <asm/sections.h>
>  
>  /* vmcoreinfo stuff */
> -static unsigned char vmcoreinfo_data[VMCOREINFO_BYTES];
> -u32 vmcoreinfo_note[VMCOREINFO_NOTE_SIZE/4];
> +static unsigned char *vmcoreinfo_data;
>  size_t vmcoreinfo_size;
> -size_t vmcoreinfo_max_size = sizeof(vmcoreinfo_data);
> +size_t vmcoreinfo_max_size = VMCOREINFO_BYTES;
> +u32 *vmcoreinfo_note;
>  
>  /*
>   * parsing the "crashkernel" commandline
> @@ -326,6 +326,9 @@ static void update_vmcoreinfo_note(void)
>  
>  void crash_save_vmcoreinfo(void)
>  {
> +	if (!vmcoreinfo_note)
> +		return;
> +
>  	vmcoreinfo_append_str("CRASHTIME=%ld\n", get_seconds());
>  	update_vmcoreinfo_note();
>  }
> @@ -356,11 +359,27 @@ void __weak arch_crash_save_vmcoreinfo(void)
>  
>  phys_addr_t __weak paddr_vmcoreinfo_note(void)
>  {
> -	return __pa_symbol((unsigned long)(char *)&vmcoreinfo_note);
> +	return __pa(vmcoreinfo_note);
>  }
>  
>  static int __init crash_save_vmcoreinfo_init(void)
>  {
> +	/* One page should be enough for VMCOREINFO_BYTES under all archs */

Can we add a comment in the VMCOREINFO_BYTES header file about the one
page assumption?

Or just define the VMCOREINFO_BYTES as PAGE_SIZE instead of 4096
 
> +	vmcoreinfo_data = (unsigned char *)get_zeroed_page(GFP_KERNEL);
> +	if (!vmcoreinfo_data) {
> +		pr_warn("Memory allocation for vmcoreinfo_data failed\n");
> +		return -ENOMEM;
> +	}
> +
> +	vmcoreinfo_note = alloc_pages_exact(VMCOREINFO_NOTE_SIZE,
> +						GFP_KERNEL | __GFP_ZERO);
> +	if (!vmcoreinfo_note) {
> +		free_page((unsigned long)vmcoreinfo_data);
> +		vmcoreinfo_data = NULL;
> +		pr_warn("Memory allocation for vmcoreinfo_note failed\n");
> +		return -ENOMEM;
> +	}
> +
>  	VMCOREINFO_OSRELEASE(init_uts_ns.name.release);
>  	VMCOREINFO_PAGESIZE(PAGE_SIZE);
>  
> diff --git a/kernel/ksysfs.c b/kernel/ksysfs.c
> index 23cd706..c40a4e5 100644
> --- a/kernel/ksysfs.c
> +++ b/kernel/ksysfs.c
> @@ -134,7 +134,7 @@ static ssize_t vmcoreinfo_show(struct kobject *kobj,
>  {
>  	phys_addr_t vmcore_base = paddr_vmcoreinfo_note();
>  	return sprintf(buf, "%pa %x\n", &vmcore_base,
> -		       (unsigned int)sizeof(vmcoreinfo_note));
> +			(unsigned int)VMCOREINFO_NOTE_SIZE);
>  }
>  KERNEL_ATTR_RO(vmcoreinfo);
>  
> -- 
> 1.8.3.1
> 
> 
> _______________________________________________
> kexec mailing list
> kexec@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/kexec

Thanks
Dave

Re: [PATCH v4 1/3] kexec: Move vmcoreinfo out of the kernel's .bss section

[Xunlei Pang]

On 04/26/2017 at 03:19 PM, Dave Young wrote:
> Add ia64i list,  and s390 list although Michael has tested it
>
> On 04/20/17 at 07:39pm, Xunlei Pang wrote:
>> As Eric said,
>> "what we need to do is move the variable vmcoreinfo_note out
>> of the kernel's .bss section.  And modify the code to regenerate
>> and keep this information in something like the control page.
>>
>> Definitely something like this needs a page all to itself, and ideally
>> far away from any other kernel data structures.  I clearly was not
>> watching closely the data someone decided to keep this silly thing
>> in the kernel's .bss section."
>>
>> This patch allocates extra pages for these vmcoreinfo_XXX variables,
>> one advantage is that it enhances some safety of vmcoreinfo, because
>> vmcoreinfo now is kept far away from other kernel data structures.
>>
>> Suggested-by: Eric Biederman <ebiederm@xmission.com>
>> Cc: Michael Holzheu <holzheu@linux.vnet.ibm.com>
>> Cc: Juergen Gross <jgross@suse.com>
>> Signed-off-by: Xunlei Pang <xlpang@redhat.com>
>> ---
>> v3->v4:
>> -Rebased on the latest linux-next
>> -Handle S390 vmcoreinfo_note properly
>> -Handle the newly-added xen/mmu_pv.c
>>
>>  arch/ia64/kernel/machine_kexec.c |  5 -----
>>  arch/s390/kernel/machine_kexec.c |  1 +
>>  arch/s390/kernel/setup.c         |  6 ------
>>  arch/x86/kernel/crash.c          |  2 +-
>>  arch/x86/xen/mmu_pv.c            |  4 ++--
>>  include/linux/crash_core.h       |  2 +-
>>  kernel/crash_core.c              | 27 +++++++++++++++++++++++----
>>  kernel/ksysfs.c                  |  2 +-
>>  8 files changed, 29 insertions(+), 20 deletions(-)
>>
>> diff --git a/arch/ia64/kernel/machine_kexec.c b/arch/ia64/kernel/machine_kexec.c
>> index 599507b..c14815d 100644
>> --- a/arch/ia64/kernel/machine_kexec.c
>> +++ b/arch/ia64/kernel/machine_kexec.c
>> @@ -163,8 +163,3 @@ void arch_crash_save_vmcoreinfo(void)
>>  #endif
>>  }
>>  
>> -phys_addr_t paddr_vmcoreinfo_note(void)
>> -{
>> -	return ia64_tpa((unsigned long)(char *)&vmcoreinfo_note);
>> -}
>> -
>> diff --git a/arch/s390/kernel/machine_kexec.c b/arch/s390/kernel/machine_kexec.c
>> index 49a6bd4..3d0b14a 100644
>> --- a/arch/s390/kernel/machine_kexec.c
>> +++ b/arch/s390/kernel/machine_kexec.c
>> @@ -246,6 +246,7 @@ void arch_crash_save_vmcoreinfo(void)
>>  	VMCOREINFO_SYMBOL(lowcore_ptr);
>>  	VMCOREINFO_SYMBOL(high_memory);
>>  	VMCOREINFO_LENGTH(lowcore_ptr, NR_CPUS);
>> +	mem_assign_absolute(S390_lowcore.vmcore_info, paddr_vmcoreinfo_note());
>>  }
>>  
>>  void machine_shutdown(void)
>> diff --git a/arch/s390/kernel/setup.c b/arch/s390/kernel/setup.c
>> index 3ae756c..3d1d808 100644
>> --- a/arch/s390/kernel/setup.c
>> +++ b/arch/s390/kernel/setup.c
>> @@ -496,11 +496,6 @@ static void __init setup_memory_end(void)
>>  	pr_notice("The maximum memory size is %luMB\n", memory_end >> 20);
>>  }
>>  
>> -static void __init setup_vmcoreinfo(void)
>> -{
>> -	mem_assign_absolute(S390_lowcore.vmcore_info, paddr_vmcoreinfo_note());
>> -}
>> -
>>  #ifdef CONFIG_CRASH_DUMP
>>  
>>  /*
>> @@ -939,7 +934,6 @@ void __init setup_arch(char **cmdline_p)
>>  #endif
>>  
>>  	setup_resources();
>> -	setup_vmcoreinfo();
>>  	setup_lowcore();
>>  	smp_fill_possible_mask();
>>  	cpu_detect_mhz_feature();
>> diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
>> index 22217ec..44404e2 100644
>> --- a/arch/x86/kernel/crash.c
>> +++ b/arch/x86/kernel/crash.c
>> @@ -457,7 +457,7 @@ static int prepare_elf64_headers(struct crash_elf_data *ced,
>>  	bufp += sizeof(Elf64_Phdr);
>>  	phdr->p_type = PT_NOTE;
>>  	phdr->p_offset = phdr->p_paddr = paddr_vmcoreinfo_note();
>> -	phdr->p_filesz = phdr->p_memsz = sizeof(vmcoreinfo_note);
>> +	phdr->p_filesz = phdr->p_memsz = VMCOREINFO_NOTE_SIZE;
>>  	(ehdr->e_phnum)++;
>>  
>>  #ifdef CONFIG_X86_64
>> diff --git a/arch/x86/xen/mmu_pv.c b/arch/x86/xen/mmu_pv.c
>> index 9d9ae66..35543fa 100644
>> --- a/arch/x86/xen/mmu_pv.c
>> +++ b/arch/x86/xen/mmu_pv.c
>> @@ -2723,8 +2723,8 @@ void xen_destroy_contiguous_region(phys_addr_t pstart, unsigned int order)
>>  phys_addr_t paddr_vmcoreinfo_note(void)
>>  {
>>  	if (xen_pv_domain())
>> -		return virt_to_machine(&vmcoreinfo_note).maddr;
>> +		return virt_to_machine(vmcoreinfo_note).maddr;
>>  	else
>> -		return __pa_symbol(&vmcoreinfo_note);
>> +		return __pa(vmcoreinfo_note);
>>  }
>>  #endif /* CONFIG_KEXEC_CORE */
>> diff --git a/include/linux/crash_core.h b/include/linux/crash_core.h
>> index eb71a70..ba283a2 100644
>> --- a/include/linux/crash_core.h
>> +++ b/include/linux/crash_core.h
>> @@ -53,7 +53,7 @@
>>  #define VMCOREINFO_PHYS_BASE(value) \
>>  	vmcoreinfo_append_str("PHYS_BASE=%lx\n", (unsigned long)value)
>>  
>> -extern u32 vmcoreinfo_note[VMCOREINFO_NOTE_SIZE/4];
>> +extern u32 *vmcoreinfo_note;
>>  extern size_t vmcoreinfo_size;
>>  extern size_t vmcoreinfo_max_size;
>>  
>> diff --git a/kernel/crash_core.c b/kernel/crash_core.c
>> index fcbd568..0321f04 100644
>> --- a/kernel/crash_core.c
>> +++ b/kernel/crash_core.c
>> @@ -14,10 +14,10 @@
>>  #include <asm/sections.h>
>>  
>>  /* vmcoreinfo stuff */
>> -static unsigned char vmcoreinfo_data[VMCOREINFO_BYTES];
>> -u32 vmcoreinfo_note[VMCOREINFO_NOTE_SIZE/4];
>> +static unsigned char *vmcoreinfo_data;
>>  size_t vmcoreinfo_size;
>> -size_t vmcoreinfo_max_size = sizeof(vmcoreinfo_data);
>> +size_t vmcoreinfo_max_size = VMCOREINFO_BYTES;
>> +u32 *vmcoreinfo_note;
>>  
>>  /*
>>   * parsing the "crashkernel" commandline
>> @@ -326,6 +326,9 @@ static void update_vmcoreinfo_note(void)
>>  
>>  void crash_save_vmcoreinfo(void)
>>  {
>> +	if (!vmcoreinfo_note)
>> +		return;
>> +
>>  	vmcoreinfo_append_str("CRASHTIME=%ld\n", get_seconds());
>>  	update_vmcoreinfo_note();
>>  }
>> @@ -356,11 +359,27 @@ void __weak arch_crash_save_vmcoreinfo(void)
>>  
>>  phys_addr_t __weak paddr_vmcoreinfo_note(void)
>>  {
>> -	return __pa_symbol((unsigned long)(char *)&vmcoreinfo_note);
>> +	return __pa(vmcoreinfo_note);
>>  }
>>  
>>  static int __init crash_save_vmcoreinfo_init(void)
>>  {
>> +	/* One page should be enough for VMCOREINFO_BYTES under all archs */
> Can we add a comment in the VMCOREINFO_BYTES header file about the one
> page assumption?
>
> Or just define the VMCOREINFO_BYTES as PAGE_SIZE instead of 4096

Yes, I considered this before, but VMCOREINFO_BYTES is also used by VMCOREINFO_NOTE_SIZE
definition which is exported to sysfs, also some platform has larger page size(64KB), so
I didn't touch this 4096 value.

I think I should use kmalloc() to allocate both of them, then move this comment to Patch3 
kimage_crash_copy_vmcoreinfo().

Regards,
Xunlei

>  
>> +	vmcoreinfo_data = (unsigned char *)get_zeroed_page(GFP_KERNEL);
>> +	if (!vmcoreinfo_data) {
>> +		pr_warn("Memory allocation for vmcoreinfo_data failed\n");
>> +		return -ENOMEM;
>> +	}
>> +
>> +	vmcoreinfo_note = alloc_pages_exact(VMCOREINFO_NOTE_SIZE,
>> +						GFP_KERNEL | __GFP_ZERO);
>> +	if (!vmcoreinfo_note) {
>> +		free_page((unsigned long)vmcoreinfo_data);
>> +		vmcoreinfo_data = NULL;
>> +		pr_warn("Memory allocation for vmcoreinfo_note failed\n");
>> +		return -ENOMEM;
>> +	}
>> +
>>  	VMCOREINFO_OSRELEASE(init_uts_ns.name.release);
>>  	VMCOREINFO_PAGESIZE(PAGE_SIZE);
>>  
>> diff --git a/kernel/ksysfs.c b/kernel/ksysfs.c
>> index 23cd706..c40a4e5 100644
>> --- a/kernel/ksysfs.c
>> +++ b/kernel/ksysfs.c
>> @@ -134,7 +134,7 @@ static ssize_t vmcoreinfo_show(struct kobject *kobj,
>>  {
>>  	phys_addr_t vmcore_base = paddr_vmcoreinfo_note();
>>  	return sprintf(buf, "%pa %x\n", &vmcore_base,
>> -		       (unsigned int)sizeof(vmcoreinfo_note));
>> +			(unsigned int)VMCOREINFO_NOTE_SIZE);
>>  }
>>  KERNEL_ATTR_RO(vmcoreinfo);
>>  
>> -- 
>> 1.8.3.1
>>
>>
>> _______________________________________________
>> kexec mailing list
>> kexec@lists.infradead.org
>> http://lists.infradead.org/mailman/listinfo/kexec
> Thanks
> Dave
>
> _______________________________________________
> kexec mailing list
> kexec@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/kexec

Re: [PATCH v4 1/3] kexec: Move vmcoreinfo out of the kernel's .bss section

[Xunlei Pang]

On 04/26/2017 at 05:51 PM, Xunlei Pang wrote:
> On 04/26/2017 at 03:19 PM, Dave Young wrote:
>> Add ia64i list,  and s390 list although Michael has tested it
>>
>> On 04/20/17 at 07:39pm, Xunlei Pang wrote:
>>> As Eric said,
>>> "what we need to do is move the variable vmcoreinfo_note out
>>> of the kernel's .bss section.  And modify the code to regenerate
>>> and keep this information in something like the control page.
>>>
>>> Definitely something like this needs a page all to itself, and ideally
>>> far away from any other kernel data structures.  I clearly was not
>>> watching closely the data someone decided to keep this silly thing
>>> in the kernel's .bss section."
>>>
>>> This patch allocates extra pages for these vmcoreinfo_XXX variables,
>>> one advantage is that it enhances some safety of vmcoreinfo, because
>>> vmcoreinfo now is kept far away from other kernel data structures.
>>>
>>> Suggested-by: Eric Biederman <ebiederm@xmission.com>
>>> Cc: Michael Holzheu <holzheu@linux.vnet.ibm.com>
>>> Cc: Juergen Gross <jgross@suse.com>
>>> Signed-off-by: Xunlei Pang <xlpang@redhat.com>
>>> ---
>>> v3->v4:
>>> -Rebased on the latest linux-next
>>> -Handle S390 vmcoreinfo_note properly
>>> -Handle the newly-added xen/mmu_pv.c
>>>
>>>  arch/ia64/kernel/machine_kexec.c |  5 -----
>>>  arch/s390/kernel/machine_kexec.c |  1 +
>>>  arch/s390/kernel/setup.c         |  6 ------
>>>  arch/x86/kernel/crash.c          |  2 +-
>>>  arch/x86/xen/mmu_pv.c            |  4 ++--
>>>  include/linux/crash_core.h       |  2 +-
>>>  kernel/crash_core.c              | 27 +++++++++++++++++++++++----
>>>  kernel/ksysfs.c                  |  2 +-
>>>  8 files changed, 29 insertions(+), 20 deletions(-)
>>>
>>> diff --git a/arch/ia64/kernel/machine_kexec.c b/arch/ia64/kernel/machine_kexec.c
>>> index 599507b..c14815d 100644
>>> --- a/arch/ia64/kernel/machine_kexec.c
>>> +++ b/arch/ia64/kernel/machine_kexec.c
>>> @@ -163,8 +163,3 @@ void arch_crash_save_vmcoreinfo(void)
>>>  #endif
>>>  }
>>>  
>>> -phys_addr_t paddr_vmcoreinfo_note(void)
>>> -{
>>> -	return ia64_tpa((unsigned long)(char *)&vmcoreinfo_note);
>>> -}
>>> -
>>> diff --git a/arch/s390/kernel/machine_kexec.c b/arch/s390/kernel/machine_kexec.c
>>> index 49a6bd4..3d0b14a 100644
>>> --- a/arch/s390/kernel/machine_kexec.c
>>> +++ b/arch/s390/kernel/machine_kexec.c
>>> @@ -246,6 +246,7 @@ void arch_crash_save_vmcoreinfo(void)
>>>  	VMCOREINFO_SYMBOL(lowcore_ptr);
>>>  	VMCOREINFO_SYMBOL(high_memory);
>>>  	VMCOREINFO_LENGTH(lowcore_ptr, NR_CPUS);
>>> +	mem_assign_absolute(S390_lowcore.vmcore_info, paddr_vmcoreinfo_note());
>>>  }
>>>  
>>>  void machine_shutdown(void)
>>> diff --git a/arch/s390/kernel/setup.c b/arch/s390/kernel/setup.c
>>> index 3ae756c..3d1d808 100644
>>> --- a/arch/s390/kernel/setup.c
>>> +++ b/arch/s390/kernel/setup.c
>>> @@ -496,11 +496,6 @@ static void __init setup_memory_end(void)
>>>  	pr_notice("The maximum memory size is %luMB\n", memory_end >> 20);
>>>  }
>>>  
>>> -static void __init setup_vmcoreinfo(void)
>>> -{
>>> -	mem_assign_absolute(S390_lowcore.vmcore_info, paddr_vmcoreinfo_note());
>>> -}
>>> -
>>>  #ifdef CONFIG_CRASH_DUMP
>>>  
>>>  /*
>>> @@ -939,7 +934,6 @@ void __init setup_arch(char **cmdline_p)
>>>  #endif
>>>  
>>>  	setup_resources();
>>> -	setup_vmcoreinfo();
>>>  	setup_lowcore();
>>>  	smp_fill_possible_mask();
>>>  	cpu_detect_mhz_feature();
>>> diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
>>> index 22217ec..44404e2 100644
>>> --- a/arch/x86/kernel/crash.c
>>> +++ b/arch/x86/kernel/crash.c
>>> @@ -457,7 +457,7 @@ static int prepare_elf64_headers(struct crash_elf_data *ced,
>>>  	bufp += sizeof(Elf64_Phdr);
>>>  	phdr->p_type = PT_NOTE;
>>>  	phdr->p_offset = phdr->p_paddr = paddr_vmcoreinfo_note();
>>> -	phdr->p_filesz = phdr->p_memsz = sizeof(vmcoreinfo_note);
>>> +	phdr->p_filesz = phdr->p_memsz = VMCOREINFO_NOTE_SIZE;
>>>  	(ehdr->e_phnum)++;
>>>  
>>>  #ifdef CONFIG_X86_64
>>> diff --git a/arch/x86/xen/mmu_pv.c b/arch/x86/xen/mmu_pv.c
>>> index 9d9ae66..35543fa 100644
>>> --- a/arch/x86/xen/mmu_pv.c
>>> +++ b/arch/x86/xen/mmu_pv.c
>>> @@ -2723,8 +2723,8 @@ void xen_destroy_contiguous_region(phys_addr_t pstart, unsigned int order)
>>>  phys_addr_t paddr_vmcoreinfo_note(void)
>>>  {
>>>  	if (xen_pv_domain())
>>> -		return virt_to_machine(&vmcoreinfo_note).maddr;
>>> +		return virt_to_machine(vmcoreinfo_note).maddr;
>>>  	else
>>> -		return __pa_symbol(&vmcoreinfo_note);
>>> +		return __pa(vmcoreinfo_note);
>>>  }
>>>  #endif /* CONFIG_KEXEC_CORE */
>>> diff --git a/include/linux/crash_core.h b/include/linux/crash_core.h
>>> index eb71a70..ba283a2 100644
>>> --- a/include/linux/crash_core.h
>>> +++ b/include/linux/crash_core.h
>>> @@ -53,7 +53,7 @@
>>>  #define VMCOREINFO_PHYS_BASE(value) \
>>>  	vmcoreinfo_append_str("PHYS_BASE=%lx\n", (unsigned long)value)
>>>  
>>> -extern u32 vmcoreinfo_note[VMCOREINFO_NOTE_SIZE/4];
>>> +extern u32 *vmcoreinfo_note;
>>>  extern size_t vmcoreinfo_size;
>>>  extern size_t vmcoreinfo_max_size;
>>>  
>>> diff --git a/kernel/crash_core.c b/kernel/crash_core.c
>>> index fcbd568..0321f04 100644
>>> --- a/kernel/crash_core.c
>>> +++ b/kernel/crash_core.c
>>> @@ -14,10 +14,10 @@
>>>  #include <asm/sections.h>
>>>  
>>>  /* vmcoreinfo stuff */
>>> -static unsigned char vmcoreinfo_data[VMCOREINFO_BYTES];
>>> -u32 vmcoreinfo_note[VMCOREINFO_NOTE_SIZE/4];
>>> +static unsigned char *vmcoreinfo_data;
>>>  size_t vmcoreinfo_size;
>>> -size_t vmcoreinfo_max_size = sizeof(vmcoreinfo_data);
>>> +size_t vmcoreinfo_max_size = VMCOREINFO_BYTES;
>>> +u32 *vmcoreinfo_note;
>>>  
>>>  /*
>>>   * parsing the "crashkernel" commandline
>>> @@ -326,6 +326,9 @@ static void update_vmcoreinfo_note(void)
>>>  
>>>  void crash_save_vmcoreinfo(void)
>>>  {
>>> +	if (!vmcoreinfo_note)
>>> +		return;
>>> +
>>>  	vmcoreinfo_append_str("CRASHTIME=%ld\n", get_seconds());
>>>  	update_vmcoreinfo_note();
>>>  }
>>> @@ -356,11 +359,27 @@ void __weak arch_crash_save_vmcoreinfo(void)
>>>  
>>>  phys_addr_t __weak paddr_vmcoreinfo_note(void)
>>>  {
>>> -	return __pa_symbol((unsigned long)(char *)&vmcoreinfo_note);
>>> +	return __pa(vmcoreinfo_note);
>>>  }
>>>  
>>>  static int __init crash_save_vmcoreinfo_init(void)
>>>  {
>>> +	/* One page should be enough for VMCOREINFO_BYTES under all archs */
>> Can we add a comment in the VMCOREINFO_BYTES header file about the one
>> page assumption?
>>
>> Or just define the VMCOREINFO_BYTES as PAGE_SIZE instead of 4096
> Yes, I considered this before, but VMCOREINFO_BYTES is also used by VMCOREINFO_NOTE_SIZE
> definition which is exported to sysfs, also some platform has larger page size(64KB), so
> I didn't touch this 4096 value.
>
> I think I should use kmalloc() to allocate both of them, then move this comment to Patch3 
> kimage_crash_copy_vmcoreinfo().

But on the other hand, using a separate page for them seems safer compared with
using frequently-used slab, what's your opinion?

Regards,
Xunlei

>
> Regards,
> Xunlei
>
>>  
>>> +	vmcoreinfo_data = (unsigned char *)get_zeroed_page(GFP_KERNEL);
>>> +	if (!vmcoreinfo_data) {
>>> +		pr_warn("Memory allocation for vmcoreinfo_data failed\n");
>>> +		return -ENOMEM;
>>> +	}
>>> +
>>> +	vmcoreinfo_note = alloc_pages_exact(VMCOREINFO_NOTE_SIZE,
>>> +						GFP_KERNEL | __GFP_ZERO);
>>> +	if (!vmcoreinfo_note) {
>>> +		free_page((unsigned long)vmcoreinfo_data);
>>> +		vmcoreinfo_data = NULL;
>>> +		pr_warn("Memory allocation for vmcoreinfo_note failed\n");
>>> +		return -ENOMEM;
>>> +	}
>>> +
>>>  	VMCOREINFO_OSRELEASE(init_uts_ns.name.release);
>>>  	VMCOREINFO_PAGESIZE(PAGE_SIZE);
>>>  
>>> diff --git a/kernel/ksysfs.c b/kernel/ksysfs.c
>>> index 23cd706..c40a4e5 100644
>>> --- a/kernel/ksysfs.c
>>> +++ b/kernel/ksysfs.c
>>> @@ -134,7 +134,7 @@ static ssize_t vmcoreinfo_show(struct kobject *kobj,
>>>  {
>>>  	phys_addr_t vmcore_base = paddr_vmcoreinfo_note();
>>>  	return sprintf(buf, "%pa %x\n", &vmcore_base,
>>> -		       (unsigned int)sizeof(vmcoreinfo_note));
>>> +			(unsigned int)VMCOREINFO_NOTE_SIZE);
>>>  }
>>>  KERNEL_ATTR_RO(vmcoreinfo);
>>>  
>>> -- 
>>> 1.8.3.1
>>>
>>>
>>> _______________________________________________
>>> kexec mailing list
>>> kexec@lists.infradead.org
>>> http://lists.infradead.org/mailman/listinfo/kexec
>> Thanks
>> Dave
>>
>> _______________________________________________
>> kexec mailing list
>> kexec@lists.infradead.org
>> http://lists.infradead.org/mailman/listinfo/kexec

Re: [PATCH v4 1/3] kexec: Move vmcoreinfo out of the kernel's .bss section

[Dave Young]

[snip]
> >>>  
> >>>  static int __init crash_save_vmcoreinfo_init(void)
> >>>  {
> >>> +	/* One page should be enough for VMCOREINFO_BYTES under all archs */
> >> Can we add a comment in the VMCOREINFO_BYTES header file about the one
> >> page assumption?
> >>
> >> Or just define the VMCOREINFO_BYTES as PAGE_SIZE instead of 4096
> > Yes, I considered this before, but VMCOREINFO_BYTES is also used by VMCOREINFO_NOTE_SIZE
> > definition which is exported to sysfs, also some platform has larger page size(64KB), so
> > I didn't touch this 4096 value.
> >
> > I think I should use kmalloc() to allocate both of them, then move this comment to Patch3 
> > kimage_crash_copy_vmcoreinfo().
> 
> But on the other hand, using a separate page for them seems safer compared with
> using frequently-used slab, what's your opinion?

I feel current page based way is better.

For 64k page the vmcore note size will increase it seems fine. Do you
have concern in mind?

Thanks

Re: [PATCH v4 1/3] kexec: Move vmcoreinfo out of the kernel's .bss section

[Xunlei Pang]

On 04/27/2017 at 11:06 AM, Dave Young wrote:
> [snip]
>>>>>  
>>>>>  static int __init crash_save_vmcoreinfo_init(void)
>>>>>  {
>>>>> +	/* One page should be enough for VMCOREINFO_BYTES under all archs */
>>>> Can we add a comment in the VMCOREINFO_BYTES header file about the one
>>>> page assumption?
>>>>
>>>> Or just define the VMCOREINFO_BYTES as PAGE_SIZE instead of 4096
>>> Yes, I considered this before, but VMCOREINFO_BYTES is also used by VMCOREINFO_NOTE_SIZE
>>> definition which is exported to sysfs, also some platform has larger page size(64KB), so
>>> I didn't touch this 4096 value.
>>>
>>> I think I should use kmalloc() to allocate both of them, then move this comment to Patch3 
>>> kimage_crash_copy_vmcoreinfo().
>> But on the other hand, using a separate page for them seems safer compared with
>> using frequently-used slab, what's your opinion?
> I feel current page based way is better.
>
> For 64k page the vmcore note size will increase it seems fine. Do you
> have concern in mind?

Since tools are supposed to acquire vmcoreinfo note size from sysfs, it should be safe to do so,
except that there is some waste in memory for larger PAGE_SIZE.

Regards,
Xunlei

Re: [PATCH v4 1/3] kexec: Move vmcoreinfo out of the kernel's .bss section

[Dave Young]

Hi Xunlei,

On 04/27/17 at 01:25pm, Xunlei Pang wrote:
> On 04/27/2017 at 11:06 AM, Dave Young wrote:
> > [snip]
> >>>>>  
> >>>>>  static int __init crash_save_vmcoreinfo_init(void)
> >>>>>  {
> >>>>> +	/* One page should be enough for VMCOREINFO_BYTES under all archs */
> >>>> Can we add a comment in the VMCOREINFO_BYTES header file about the one
> >>>> page assumption?
> >>>>
> >>>> Or just define the VMCOREINFO_BYTES as PAGE_SIZE instead of 4096
> >>> Yes, I considered this before, but VMCOREINFO_BYTES is also used by VMCOREINFO_NOTE_SIZE
> >>> definition which is exported to sysfs, also some platform has larger page size(64KB), so
> >>> I didn't touch this 4096 value.
> >>>
> >>> I think I should use kmalloc() to allocate both of them, then move this comment to Patch3 
> >>> kimage_crash_copy_vmcoreinfo().
> >> But on the other hand, using a separate page for them seems safer compared with
> >> using frequently-used slab, what's your opinion?
> > I feel current page based way is better.
> >
> > For 64k page the vmcore note size will increase it seems fine. Do you
> > have concern in mind?
> 
> Since tools are supposed to acquire vmcoreinfo note size from sysfs, it should be safe to do so,
> except that there is some waste in memory for larger PAGE_SIZE.

Either way is fine to me, I think it is up to your implementation, if
choose page alloc then modify the macro with PAGE_SIZE looks better.

Thanks
Dave

Re: [PATCH v4 1/3] kexec: Move vmcoreinfo out of the kernel's .bss section

[Xunlei Pang]

On 04/27/2017 at 01:44 PM, Dave Young wrote:
> Hi Xunlei,
>
> On 04/27/17 at 01:25pm, Xunlei Pang wrote:
>> On 04/27/2017 at 11:06 AM, Dave Young wrote:
>>> [snip]
>>>>>>>  
>>>>>>>  static int __init crash_save_vmcoreinfo_init(void)
>>>>>>>  {
>>>>>>> +	/* One page should be enough for VMCOREINFO_BYTES under all archs */
>>>>>> Can we add a comment in the VMCOREINFO_BYTES header file about the one
>>>>>> page assumption?
>>>>>>
>>>>>> Or just define the VMCOREINFO_BYTES as PAGE_SIZE instead of 4096
>>>>> Yes, I considered this before, but VMCOREINFO_BYTES is also used by VMCOREINFO_NOTE_SIZE
>>>>> definition which is exported to sysfs, also some platform has larger page size(64KB), so
>>>>> I didn't touch this 4096 value.
>>>>>
>>>>> I think I should use kmalloc() to allocate both of them, then move this comment to Patch3 
>>>>> kimage_crash_copy_vmcoreinfo().
>>>> But on the other hand, using a separate page for them seems safer compared with
>>>> using frequently-used slab, what's your opinion?
>>> I feel current page based way is better.
>>>
>>> For 64k page the vmcore note size will increase it seems fine. Do you
>>> have concern in mind?
>> Since tools are supposed to acquire vmcoreinfo note size from sysfs, it should be safe to do so,
>> except that there is some waste in memory for larger PAGE_SIZE.
> Either way is fine to me, I think it is up to your implementation, if
> choose page alloc then modify the macro with PAGE_SIZE looks better.

OK, I will use PAGE_SIZE then, thanks for your comments.

>
> Thanks
> Dave
>
> _______________________________________________
> kexec mailing list
> kexec@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/kexec