[PATCH] vmcoreinfo: export SECTION_HAS_MEM_MAP

[PATCH] vmcoreinfo: export SECTION_HAS_MEM_MAP

[David Hildenbrand (Arm)]

The crash tool currently hardcodes SECTION_HAS_MEM_MAP, and makedumpfile
needs similar information (although still relying on
SECTION_MARKED_PRESENT, it should switch to SECTION_HAS_MEM_MAP).

Let's just export the value instead, so tools that work on vmcoreinfo
will not have to guess.

Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
---
Result of the discussion in reply to "[PATCH v2 00/13] mm/sparse: remove
SECTION_MARKED_PRESENT and further cleanups" [1]

This patch can go in independently. It would be preferable if both
go into the same kernel release ;)

[1] https://lore.kernel.org/r/20260921-b4-sparsemem_cleanups-v2-0-54d81d65e125@kernel.org 
---
 kernel/vmcore_info.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/vmcore_info.c b/kernel/vmcore_info.c
index 5a417f8a922a..7833a36064a8 100644
--- a/kernel/vmcore_info.c
+++ b/kernel/vmcore_info.c
@@ -182,6 +182,7 @@ static int __init crash_save_vmcoreinfo_init(void)
 	VMCOREINFO_STRUCT_SIZE(mem_section);
 	VMCOREINFO_OFFSET(mem_section, section_mem_map);
 	VMCOREINFO_NUMBER(SECTION_SIZE_BITS);
+	VMCOREINFO_NUMBER(SECTION_HAS_MEM_MAP);
 	VMCOREINFO_NUMBER(MAX_PHYSMEM_BITS);
 #endif
 	VMCOREINFO_STRUCT_SIZE(page);

---

base-commit: 57e4ac91fc62d75d84b5a03827a19ceb4094ecd9

change-id: 20260928-section_has_mem_map-6205dc90a09f

--

Cheers,

David

Re: [PATCH] vmcoreinfo: export SECTION_HAS_MEM_MAP

[Baoquan He]

On 09/28/26 at 10:48am, David Hildenbrand (Arm) wrote:
> The crash tool currently hardcodes SECTION_HAS_MEM_MAP, and makedumpfile
> needs similar information (although still relying on
> SECTION_MARKED_PRESENT, it should switch to SECTION_HAS_MEM_MAP).
> 
> Let's just export the value instead, so tools that work on vmcoreinfo
> will not have to guess.
> 
> Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
> ---
> Result of the discussion in reply to "[PATCH v2 00/13] mm/sparse: remove
> SECTION_MARKED_PRESENT and further cleanups" [1]
> 
> This patch can go in independently. It would be preferable if both
> go into the same kernel release ;)
> 
> [1] https://lore.kernel.org/r/20260921-b4-sparsemem_cleanups-v2-0-54d81d65e125@kernel.org 
> ---
>  kernel/vmcore_info.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/kernel/vmcore_info.c b/kernel/vmcore_info.c
> index 5a417f8a922a..7833a36064a8 100644
> --- a/kernel/vmcore_info.c
> +++ b/kernel/vmcore_info.c
> @@ -182,6 +182,7 @@ static int __init crash_save_vmcoreinfo_init(void)
>  	VMCOREINFO_STRUCT_SIZE(mem_section);
>  	VMCOREINFO_OFFSET(mem_section, section_mem_map);
>  	VMCOREINFO_NUMBER(SECTION_SIZE_BITS);
> +	VMCOREINFO_NUMBER(SECTION_HAS_MEM_MAP);
>  	VMCOREINFO_NUMBER(MAX_PHYSMEM_BITS);
>  #endif
>  	VMCOREINFO_STRUCT_SIZE(page);

It would be good to add one section in
Documentation/admin-guide/kdump/vmcoreinfo.rst, e.g

SECTION_HAS_MEM_MAP
-------------------

Indicates a memory section has struct page array (mem_map). User-space
tools should read this value but not hardcode it since the bit position
could change between kernel versions.

The code change looks good to me.

> 
> ---
> 
> base-commit: 57e4ac91fc62d75d84b5a03827a19ceb4094ecd9
> 
> change-id: 20260928-section_has_mem_map-6205dc90a09f
> 
> --
> 
> Cheers,
> 
> David
> 

Re: [PATCH] vmcoreinfo: export SECTION_HAS_MEM_MAP

[David Hildenbrand (Arm)]

On 9/28/26 11:11, Baoquan He wrote:
> On 09/28/26 at 10:48am, David Hildenbrand (Arm) wrote:
>> The crash tool currently hardcodes SECTION_HAS_MEM_MAP, and makedumpfile
>> needs similar information (although still relying on
>> SECTION_MARKED_PRESENT, it should switch to SECTION_HAS_MEM_MAP).
>>
>> Let's just export the value instead, so tools that work on vmcoreinfo
>> will not have to guess.
>>
>> Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
>> ---
>> Result of the discussion in reply to "[PATCH v2 00/13] mm/sparse: remove
>> SECTION_MARKED_PRESENT and further cleanups" [1]
>>
>> This patch can go in independently. It would be preferable if both
>> go into the same kernel release ;)
>>
>> [1] https://lore.kernel.org/r/20260921-b4-sparsemem_cleanups-v2-0-54d81d65e125@kernel.org 
>> ---
>>  kernel/vmcore_info.c | 1 +
>>  1 file changed, 1 insertion(+)
>>
>> diff --git a/kernel/vmcore_info.c b/kernel/vmcore_info.c
>> index 5a417f8a922a..7833a36064a8 100644
>> --- a/kernel/vmcore_info.c
>> +++ b/kernel/vmcore_info.c
>> @@ -182,6 +182,7 @@ static int __init crash_save_vmcoreinfo_init(void)
>>  	VMCOREINFO_STRUCT_SIZE(mem_section);
>>  	VMCOREINFO_OFFSET(mem_section, section_mem_map);
>>  	VMCOREINFO_NUMBER(SECTION_SIZE_BITS);
>> +	VMCOREINFO_NUMBER(SECTION_HAS_MEM_MAP);
>>  	VMCOREINFO_NUMBER(MAX_PHYSMEM_BITS);
>>  #endif
>>  	VMCOREINFO_STRUCT_SIZE(page);
> 
> It would be good to add one section in
> Documentation/admin-guide/kdump/vmcoreinfo.rst, e.g
> 
> SECTION_HAS_MEM_MAP
> -------------------
> 
> Indicates a memory section has struct page array (mem_map). User-space
> tools should read this value but not hardcode it since the bit position
> could change between kernel versions.

I'm not particularly happy about having core-kernel defines documented in
kdump/vmcoreinfo.rst, though?

If it would be something vmcoreinfo special, sure. But not for basic defines.

"See the kernel source code" is really what anybody using this should be doing?

-- 
Cheers,

David

Re: [PATCH] vmcoreinfo: export SECTION_HAS_MEM_MAP

[Baoquan He]

On 09/28/26 at 11:14am, David Hildenbrand (Arm) wrote:
> On 9/28/26 11:11, Baoquan He wrote:
> > On 09/28/26 at 10:48am, David Hildenbrand (Arm) wrote:
> >> The crash tool currently hardcodes SECTION_HAS_MEM_MAP, and makedumpfile
> >> needs similar information (although still relying on
> >> SECTION_MARKED_PRESENT, it should switch to SECTION_HAS_MEM_MAP).
> >>
> >> Let's just export the value instead, so tools that work on vmcoreinfo
> >> will not have to guess.
> >>
> >> Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
> >> ---
> >> Result of the discussion in reply to "[PATCH v2 00/13] mm/sparse: remove
> >> SECTION_MARKED_PRESENT and further cleanups" [1]
> >>
> >> This patch can go in independently. It would be preferable if both
> >> go into the same kernel release ;)
> >>
> >> [1] https://lore.kernel.org/r/20260921-b4-sparsemem_cleanups-v2-0-54d81d65e125@kernel.org 
> >> ---
> >>  kernel/vmcore_info.c | 1 +
> >>  1 file changed, 1 insertion(+)
> >>
> >> diff --git a/kernel/vmcore_info.c b/kernel/vmcore_info.c
> >> index 5a417f8a922a..7833a36064a8 100644
> >> --- a/kernel/vmcore_info.c
> >> +++ b/kernel/vmcore_info.c
> >> @@ -182,6 +182,7 @@ static int __init crash_save_vmcoreinfo_init(void)
> >>  	VMCOREINFO_STRUCT_SIZE(mem_section);
> >>  	VMCOREINFO_OFFSET(mem_section, section_mem_map);
> >>  	VMCOREINFO_NUMBER(SECTION_SIZE_BITS);
> >> +	VMCOREINFO_NUMBER(SECTION_HAS_MEM_MAP);
> >>  	VMCOREINFO_NUMBER(MAX_PHYSMEM_BITS);
> >>  #endif
> >>  	VMCOREINFO_STRUCT_SIZE(page);
> > 
> > It would be good to add one section in
> > Documentation/admin-guide/kdump/vmcoreinfo.rst, e.g
> > 
> > SECTION_HAS_MEM_MAP
> > -------------------
> > 
> > Indicates a memory section has struct page array (mem_map). User-space
> > tools should read this value but not hardcode it since the bit position
> > could change between kernel versions.
> 
> I'm not particularly happy about having core-kernel defines documented in
> kdump/vmcoreinfo.rst, though?
> 
> If it would be something vmcoreinfo special, sure. But not for basic defines.
> 
> "See the kernel source code" is really what anybody using this should be doing?

I can't remember who suggested adding this document. The benefit is
users can read document to understand how it works, no need to look
at the code. I don't have strong preference on this.

So I am fine with both. Or we can add it if anyone really complains.

For the patch itself,

Acked-by: Baoquan He <baoquan.he@linux.dev>

Thanks
Baoquan

Re: [PATCH] vmcoreinfo: export SECTION_HAS_MEM_MAP

[Dave Young]

On 9/28/26 4:48 PM, David Hildenbrand (Arm) wrote:
> The crash tool currently hardcodes SECTION_HAS_MEM_MAP, and makedumpfile
> needs similar information (although still relying on
> SECTION_MARKED_PRESENT, it should switch to SECTION_HAS_MEM_MAP).
> 
> Let's just export the value instead, so tools that work on vmcoreinfo
> will not have to guess.
> 
> Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
> ---
> Result of the discussion in reply to "[PATCH v2 00/13] mm/sparse: remove
> SECTION_MARKED_PRESENT and further cleanups" [1]
> 
> This patch can go in independently. It would be preferable if both
> go into the same kernel release ;)
> 
> [1] https://lore.kernel.org/r/20260921-b4-sparsemem_cleanups-v2-0-54d81d65e125@kernel.org 
> ---
>  kernel/vmcore_info.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/kernel/vmcore_info.c b/kernel/vmcore_info.c
> index 5a417f8a922a..7833a36064a8 100644
> --- a/kernel/vmcore_info.c
> +++ b/kernel/vmcore_info.c
> @@ -182,6 +182,7 @@ static int __init crash_save_vmcoreinfo_init(void)
>  	VMCOREINFO_STRUCT_SIZE(mem_section);
>  	VMCOREINFO_OFFSET(mem_section, section_mem_map);
>  	VMCOREINFO_NUMBER(SECTION_SIZE_BITS);
> +	VMCOREINFO_NUMBER(SECTION_HAS_MEM_MAP);
>  	VMCOREINFO_NUMBER(MAX_PHYSMEM_BITS);
>  #endif
>  	VMCOREINFO_STRUCT_SIZE(page);

Current crash code looks below:
#define SECTION_MARKED_PRESENT          (1UL<<0)
#define SECTION_HAS_MEM_MAP             (1UL<<1)
#define SECTION_IS_ONLINE               (1UL<<2)
#define SECTION_IS_EARLY                (1UL<<3)
#define SECTION_TAINT_ZONE_DEVICE       (1UL<<4)
#define SECTION_MAP_LAST_BIT            (1UL<<5)
#define SECTION_MAP_MASK                (~(SECTION_MAP_LAST_BIT-1))


And it does not match the kernel for below chunk with ifdef
#ifdef CONFIG_ZONE_DEVICE
        SECTION_TAINT_ZONE_DEVICE_BIT,
#endif
#ifdef CONFIG_SPARSEMEM_VMEMMAP_PREINIT
        SECTION_IS_VMEMMAP_PREINIT_BIT,
#endif

The last bit could be wrong in crash.  So all numbers should be exported in vmcoreinfo.

Thoughts?


ThanksDave

Re: [PATCH] vmcoreinfo: export SECTION_HAS_MEM_MAP

[David Hildenbrand (Arm)]

On 9/28/26 12:23, Dave Young wrote:
> On 9/28/26 4:48 PM, David Hildenbrand (Arm) wrote:
>> The crash tool currently hardcodes SECTION_HAS_MEM_MAP, and makedumpfile
>> needs similar information (although still relying on
>> SECTION_MARKED_PRESENT, it should switch to SECTION_HAS_MEM_MAP).
>>
>> Let's just export the value instead, so tools that work on vmcoreinfo
>> will not have to guess.
>>
>> Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
>> ---
>> Result of the discussion in reply to "[PATCH v2 00/13] mm/sparse: remove
>> SECTION_MARKED_PRESENT and further cleanups" [1]
>>
>> This patch can go in independently. It would be preferable if both
>> go into the same kernel release ;)
>>
>> [1] https://lore.kernel.org/r/20260921-b4-sparsemem_cleanups-v2-0-54d81d65e125@kernel.org 
>> ---
>>  kernel/vmcore_info.c | 1 +
>>  1 file changed, 1 insertion(+)
>>
>> diff --git a/kernel/vmcore_info.c b/kernel/vmcore_info.c
>> index 5a417f8a922a..7833a36064a8 100644
>> --- a/kernel/vmcore_info.c
>> +++ b/kernel/vmcore_info.c
>> @@ -182,6 +182,7 @@ static int __init crash_save_vmcoreinfo_init(void)
>>  	VMCOREINFO_STRUCT_SIZE(mem_section);
>>  	VMCOREINFO_OFFSET(mem_section, section_mem_map);
>>  	VMCOREINFO_NUMBER(SECTION_SIZE_BITS);
>> +	VMCOREINFO_NUMBER(SECTION_HAS_MEM_MAP);
>>  	VMCOREINFO_NUMBER(MAX_PHYSMEM_BITS);
>>  #endif
>>  	VMCOREINFO_STRUCT_SIZE(page);
> 
> Current crash code looks below:
> #define SECTION_MARKED_PRESENT          (1UL<<0)
> #define SECTION_HAS_MEM_MAP             (1UL<<1)
> #define SECTION_IS_ONLINE               (1UL<<2)
> #define SECTION_IS_EARLY                (1UL<<3)
> #define SECTION_TAINT_ZONE_DEVICE       (1UL<<4)
> #define SECTION_MAP_LAST_BIT            (1UL<<5)
> #define SECTION_MAP_MASK                (~(SECTION_MAP_LAST_BIT-1))
> 
> 
> And it does not match the kernel for below chunk with ifdef
> #ifdef CONFIG_ZONE_DEVICE
>         SECTION_TAINT_ZONE_DEVICE_BIT,
> #endif
> #ifdef CONFIG_SPARSEMEM_VMEMMAP_PREINIT
>         SECTION_IS_VMEMMAP_PREINIT_BIT,
> #endif
> 
> The last bit could be wrong in crash.  So all numbers should be exported in vmcoreinfo.
> 
> Thoughts?

You know the crash code best, so likely ... it's time one of the crash people
takes over this patch?

-- 
Cheers,

David

Re: [PATCH] vmcoreinfo: export SECTION_HAS_MEM_MAP

[Bradley Morgan]

On 28 September 2026 09:48:21 BST, "David Hildenbrand (Arm)"
<david@kernel.org> wrote:
>The crash tool currently hardcodes SECTION_HAS_MEM_MAP, and makedumpfile
>needs similar information (although still relying on
>SECTION_MARKED_PRESENT, it should switch to SECTION_HAS_MEM_MAP).
>
>Let's just export the value instead, so tools that work on vmcoreinfo
>will not have to guess.

I guess that works

Reviewed-by: Bradley Morgan <brads@mainlining.org>


>
>Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
>---
>Result of the discussion in reply to "[PATCH v2 00/13] mm/sparse: remove
>SECTION_MARKED_PRESENT and further cleanups" [1]
>
>This patch can go in independently. It would be preferable if both
>go into the same kernel release ;)
>
>[1]
>https://lore.kernel.org/r/20260921-b4-sparsemem_cleanups-v2-0-54d81d65e125@kernel.org
>---
> kernel/vmcore_info.c | 1 +
> 1 file changed, 1 insertion(+)
>
>diff --git a/kernel/vmcore_info.c b/kernel/vmcore_info.c
>index 5a417f8a922a..7833a36064a8 100644
>--- a/kernel/vmcore_info.c
>+++ b/kernel/vmcore_info.c
>@@ -182,6 +182,7 @@ static int __init crash_save_vmcoreinfo_init(void)
> 	VMCOREINFO_STRUCT_SIZE(mem_section);
> 	VMCOREINFO_OFFSET(mem_section, section_mem_map);
> 	VMCOREINFO_NUMBER(SECTION_SIZE_BITS);
>+	VMCOREINFO_NUMBER(SECTION_HAS_MEM_MAP);
> 	VMCOREINFO_NUMBER(MAX_PHYSMEM_BITS);
> #endif
> 	VMCOREINFO_STRUCT_SIZE(page);
>
>---
>
>base-commit: 57e4ac91fc62d75d84b5a03827a19ceb4094ecd9
>
>change-id: 20260928-section_has_mem_map-6205dc90a09f
>
>--
>
>Cheers,
>
>David
>
>
>

--- Thanks!
"I'm not a very positive person" - Linus torvalds

Re: [PATCH] vmcoreinfo: export SECTION_HAS_MEM_MAP

[Dave Young]

On 9/28/26 7:42 PM, David Hildenbrand (Arm) wrote:
> On 9/28/26 12:23, Dave Young wrote:
>> On 9/28/26 4:48 PM, David Hildenbrand (Arm) wrote:
>>> The crash tool currently hardcodes SECTION_HAS_MEM_MAP, and makedumpfile
>>> needs similar information (although still relying on
>>> SECTION_MARKED_PRESENT, it should switch to SECTION_HAS_MEM_MAP).
>>>
>>> Let's just export the value instead, so tools that work on vmcoreinfo
>>> will not have to guess.
>>>
>>> Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
>>> ---
>>> Result of the discussion in reply to "[PATCH v2 00/13] mm/sparse: remove
>>> SECTION_MARKED_PRESENT and further cleanups" [1]
>>>
>>> This patch can go in independently. It would be preferable if both
>>> go into the same kernel release ;)
>>>
>>> [1] https://lore.kernel.org/r/20260921-b4-sparsemem_cleanups-v2-0-54d81d65e125@kernel.org 
>>> ---
>>>  kernel/vmcore_info.c | 1 +
>>>  1 file changed, 1 insertion(+)
>>>
>>> diff --git a/kernel/vmcore_info.c b/kernel/vmcore_info.c
>>> index 5a417f8a922a..7833a36064a8 100644
>>> --- a/kernel/vmcore_info.c
>>> +++ b/kernel/vmcore_info.c
>>> @@ -182,6 +182,7 @@ static int __init crash_save_vmcoreinfo_init(void)
>>>  	VMCOREINFO_STRUCT_SIZE(mem_section);
>>>  	VMCOREINFO_OFFSET(mem_section, section_mem_map);
>>>  	VMCOREINFO_NUMBER(SECTION_SIZE_BITS);
>>> +	VMCOREINFO_NUMBER(SECTION_HAS_MEM_MAP);
>>>  	VMCOREINFO_NUMBER(MAX_PHYSMEM_BITS);
>>>  #endif
>>>  	VMCOREINFO_STRUCT_SIZE(page);
>>
>> Current crash code looks below:
>> #define SECTION_MARKED_PRESENT          (1UL<<0)
>> #define SECTION_HAS_MEM_MAP             (1UL<<1)
>> #define SECTION_IS_ONLINE               (1UL<<2)
>> #define SECTION_IS_EARLY                (1UL<<3)
>> #define SECTION_TAINT_ZONE_DEVICE       (1UL<<4)
>> #define SECTION_MAP_LAST_BIT            (1UL<<5)
>> #define SECTION_MAP_MASK                (~(SECTION_MAP_LAST_BIT-1))
>>
>>
>> And it does not match the kernel for below chunk with ifdef
>> #ifdef CONFIG_ZONE_DEVICE
>>         SECTION_TAINT_ZONE_DEVICE_BIT,
>> #endif
>> #ifdef CONFIG_SPARSEMEM_VMEMMAP_PREINIT
>>         SECTION_IS_VMEMMAP_PREINIT_BIT,
>> #endif
>>
>> The last bit could be wrong in crash.  So all numbers should be exported in vmcoreinfo.
>>
>> Thoughts?
> 
> You know the crash code best, so likely ... it's time one of the crash people
> takes over this patch?

Rethinking about it I'm hesitating to add many more to vmcoreinfo although it is reasonable,  about the #ifdef things, there are other places other than mm, crash can not depend on the /proc/config.gz which is not reliable in the old kernel memory, maybe it will be helpful to export another elf note for old kernel's kconfig.  So I'd like to support to use your patch for the time being as the first bit is always needed and leave the remaining concerns a follow up item.

Thanks
Dave

Re: [PATCH] vmcoreinfo: export SECTION_HAS_MEM_MAP

[HAGIO KAZUHITO(萩尾 一仁)]

On 2026/09/29 9:25, Dave Young wrote:
> On 9/28/26 7:42 PM, David Hildenbrand (Arm) wrote:
>> On 9/28/26 12:23, Dave Young wrote:
>>> On 9/28/26 4:48 PM, David Hildenbrand (Arm) wrote:
>>>> The crash tool currently hardcodes SECTION_HAS_MEM_MAP, and makedumpfile
>>>> needs similar information (although still relying on
>>>> SECTION_MARKED_PRESENT, it should switch to SECTION_HAS_MEM_MAP).
>>>>
>>>> Let's just export the value instead, so tools that work on vmcoreinfo
>>>> will not have to guess.
>>>>
>>>> Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
>>>> ---
>>>> Result of the discussion in reply to "[PATCH v2 00/13] mm/sparse: remove
>>>> SECTION_MARKED_PRESENT and further cleanups" [1]
>>>>
>>>> This patch can go in independently. It would be preferable if both
>>>> go into the same kernel release ;)
>>>>
>>>> [1] https://lore.kernel.org/r/20260921-b4-sparsemem_cleanups-v2-0-54d81d65e125@kernel.org
>>>> ---
>>>>   kernel/vmcore_info.c | 1 +
>>>>   1 file changed, 1 insertion(+)
>>>>
>>>> diff --git a/kernel/vmcore_info.c b/kernel/vmcore_info.c
>>>> index 5a417f8a922a..7833a36064a8 100644
>>>> --- a/kernel/vmcore_info.c
>>>> +++ b/kernel/vmcore_info.c
>>>> @@ -182,6 +182,7 @@ static int __init crash_save_vmcoreinfo_init(void)
>>>>   	VMCOREINFO_STRUCT_SIZE(mem_section);
>>>>   	VMCOREINFO_OFFSET(mem_section, section_mem_map);
>>>>   	VMCOREINFO_NUMBER(SECTION_SIZE_BITS);
>>>> +	VMCOREINFO_NUMBER(SECTION_HAS_MEM_MAP);
>>>>   	VMCOREINFO_NUMBER(MAX_PHYSMEM_BITS);
>>>>   #endif
>>>>   	VMCOREINFO_STRUCT_SIZE(page);
>>>
>>> Current crash code looks below:
>>> #define SECTION_MARKED_PRESENT          (1UL<<0)
>>> #define SECTION_HAS_MEM_MAP             (1UL<<1)
>>> #define SECTION_IS_ONLINE               (1UL<<2)
>>> #define SECTION_IS_EARLY                (1UL<<3)
>>> #define SECTION_TAINT_ZONE_DEVICE       (1UL<<4)
>>> #define SECTION_MAP_LAST_BIT            (1UL<<5)
>>> #define SECTION_MAP_MASK                (~(SECTION_MAP_LAST_BIT-1))
>>>
>>>
>>> And it does not match the kernel for below chunk with ifdef
>>> #ifdef CONFIG_ZONE_DEVICE
>>>          SECTION_TAINT_ZONE_DEVICE_BIT,
>>> #endif
>>> #ifdef CONFIG_SPARSEMEM_VMEMMAP_PREINIT
>>>          SECTION_IS_VMEMMAP_PREINIT_BIT,
>>> #endif
>>>
>>> The last bit could be wrong in crash.  So all numbers should be exported in vmcoreinfo.
>>>
>>> Thoughts?
>>
>> You know the crash code best, so likely ... it's time one of the crash people
>> takes over this patch?
> 
> Rethinking about it I'm hesitating to add many more to vmcoreinfo although it is reasonable,  about the #ifdef things, there are other places other than mm, crash can not depend on the /proc/config.gz which is not reliable in the old kernel memory, maybe it will be helpful to export another elf note for old kernel's kconfig.  So I'd like to support to use your patch for the time being as the first bit is always needed and leave the remaining concerns a follow up item.

I agree, from makedumpfile's view point.

(to be exact, makedumpfile needs this but maybe crash can read enum values from vmlinux.)

Thanks,
Kazu

> 
> Thanks
> Dave

Re: [PATCH] vmcoreinfo: export SECTION_HAS_MEM_MAP

[Anshuman Khandual]

On Mon, Sep 28, 2026 at 10:48:21AM +0200, David Hildenbrand (Arm) wrote:
> The crash tool currently hardcodes SECTION_HAS_MEM_MAP, and makedumpfile
> needs similar information (although still relying on
> SECTION_MARKED_PRESENT, it should switch to SECTION_HAS_MEM_MAP).
> 
> Let's just export the value instead, so tools that work on vmcoreinfo
> will not have to guess.
> 
> Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>

Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>

> ---
> Result of the discussion in reply to "[PATCH v2 00/13] mm/sparse: remove
> SECTION_MARKED_PRESENT and further cleanups" [1]
> 
> This patch can go in independently. It would be preferable if both
> go into the same kernel release ;)
> 
> [1] https://lore.kernel.org/r/20260921-b4-sparsemem_cleanups-v2-0-54d81d65e125@kernel.org 
> ---
>  kernel/vmcore_info.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/kernel/vmcore_info.c b/kernel/vmcore_info.c
> index 5a417f8a922a..7833a36064a8 100644
> --- a/kernel/vmcore_info.c
> +++ b/kernel/vmcore_info.c
> @@ -182,6 +182,7 @@ static int __init crash_save_vmcoreinfo_init(void)
>  	VMCOREINFO_STRUCT_SIZE(mem_section);
>  	VMCOREINFO_OFFSET(mem_section, section_mem_map);
>  	VMCOREINFO_NUMBER(SECTION_SIZE_BITS);
> +	VMCOREINFO_NUMBER(SECTION_HAS_MEM_MAP);
>  	VMCOREINFO_NUMBER(MAX_PHYSMEM_BITS);
>  #endif
>  	VMCOREINFO_STRUCT_SIZE(page);
> 
> ---
> 
> base-commit: 57e4ac91fc62d75d84b5a03827a19ceb4094ecd9
> 
> change-id: 20260928-section_has_mem_map-6205dc90a09f
> 
> --
> 
> Cheers,
> 
> David
> 

Re: [PATCH] vmcoreinfo: export SECTION_HAS_MEM_MAP

[David Hildenbrand (Arm)]

On 9/29/26 04:02, HAGIO KAZUHITO(萩尾 一仁) wrote:
> 
> 
> On 2026/09/29 9:25, Dave Young wrote:
>> On 9/28/26 7:42 PM, David Hildenbrand (Arm) wrote:
>>>
>>> You know the crash code best, so likely ... it's time one of the crash people
>>> takes over this patch?
>>
>> Rethinking about it I'm hesitating to add many more to vmcoreinfo although it is reasonable,  about the #ifdef things, there are other places other than mm, crash can not depend on the /proc/config.gz which is not reliable in the old kernel memory, maybe it will be helpful to export another elf note for old kernel's kconfig.  So I'd like to support to use your patch for the time being as the first bit is always needed and leave the remaining concerns a follow up item.
> 
> I agree, from makedumpfile's view point.
> 
> (to be exact, makedumpfile needs this but maybe crash can read enum values from vmlinux.)

That's a good point, maybe that indeed works for crash.

-- 
Cheers,

David