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@xxxxxxxxxx>
> ---
> 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@xxxxxxxxxx 
> ---
>  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