[08/18] crash_core, vmcoreinfo: append 'SECTION_SIZE_BITS' to vmcoreinfo

Commit Message

Andrew Morton June 16, 2021, 1:23 a.m. UTC

From: Pingfan Liu <[e-mail]>
Subject: crash_core, vmcoreinfo: append 'SECTION_SIZE_BITS' to vmcoreinfo

As mentioned in kernel commit 1d50e5d0c505 ("crash_core, vmcoreinfo:
Append 'MAX_PHYSMEM_BITS' to vmcoreinfo"), SECTION_SIZE_BITS in the
formula:

    #define SECTIONS_SHIFT    (MAX_PHYSMEM_BITS - SECTION_SIZE_BITS)

Besides SECTIONS_SHIFT, SECTION_SIZE_BITS is also used to calculate
PAGES_PER_SECTION in makedumpfile just like kernel.

Unfortunately, this arch-dependent macro SECTION_SIZE_BITS changes, e.g. 
recently in kernel commit f0b13ee23241 ("arm64/sparsemem: reduce
SECTION_SIZE_BITS").  But user space wants a stable interface to get this
info.  Such info is impossible to be deduced from a crashdump vmcore. 
Hence append SECTION_SIZE_BITS to vmcoreinfo.

Link: https://lkml.kernel.org/r/[e-mail]
Link: http://lists.infradead.org/pipermail/kexec/2021-June/022676.html
Signed-off-by: Pingfan Liu <[e-mail]>
Acked-by: Baoquan He <[e-mail]>
Cc: Bhupesh Sharma <[e-mail]>
Cc: Kazuhito Hagio <[e-mail]>
Cc: Dave Young <[e-mail]>
Cc: Boris Petkov <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Cc: Thomas Gleixner <[e-mail]>
Cc: James Morse <[e-mail]>
Cc: Mark Rutland <[e-mail]>
Cc: Will Deacon <[e-mail]>
Cc: Catalin Marinas <[e-mail]>
Cc: Michael Ellerman <[e-mail]>
Cc: Paul Mackerras <[e-mail]>
Cc: Benjamin Herrenschmidt <[e-mail]>
Cc: Dave Anderson <[e-mail]>
Cc: <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 kernel/crash_core.c |    1 +
 1 file changed, 1 insertion(+)

Patch

--- a/kernel/crash_core.c~crash_core-vmcoreinfo-append-section_size_bits-to-vmcoreinfo
+++ a/kernel/crash_core.c
@@ -464,6 +464,7 @@  static int __init crash_save_vmcoreinfo_
 	VMCOREINFO_LENGTH(mem_section, NR_SECTION_ROOTS);
 	VMCOREINFO_STRUCT_SIZE(mem_section);
 	VMCOREINFO_OFFSET(mem_section, section_mem_map);
+	VMCOREINFO_NUMBER(SECTION_SIZE_BITS);
 	VMCOREINFO_NUMBER(MAX_PHYSMEM_BITS);
 #endif
 	VMCOREINFO_STRUCT_SIZE(page);