This is a note to let you know that I've just added the patch titled crash_core, vmcoreinfo: append 'SECTION_SIZE_BITS' to vmcoreinfo to the 5.12-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: crash_core-vmcoreinfo-append-section_size_bits-to-vmcoreinfo.patch and it can be found in the queue-5.12 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 4f5aecdff25f59fb5ea456d5152a913906ecf287 Mon Sep 17 00:00:00 2001 From: Pingfan Liu <kernelfans@xxxxxxxxx> Date: Tue, 15 Jun 2021 18:23:36 -0700 Subject: crash_core, vmcoreinfo: append 'SECTION_SIZE_BITS' to vmcoreinfo From: Pingfan Liu <kernelfans@xxxxxxxxx> commit 4f5aecdff25f59fb5ea456d5152a913906ecf287 upstream. 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/20210608103359.84907-1-kernelfans@xxxxxxxxx Link: http://lists.infradead.org/pipermail/kexec/2021-June/022676.html Signed-off-by: Pingfan Liu <kernelfans@xxxxxxxxx> Acked-by: Baoquan He <bhe@xxxxxxxxxx> Cc: Bhupesh Sharma <bhupesh.sharma@xxxxxxxxxx> Cc: Kazuhito Hagio <k-hagio@xxxxxxxxxxxxx> Cc: Dave Young <dyoung@xxxxxxxxxx> Cc: Boris Petkov <bp@xxxxxxxxx> Cc: Ingo Molnar <mingo@xxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: James Morse <james.morse@xxxxxxx> Cc: Mark Rutland <mark.rutland@xxxxxxx> Cc: Will Deacon <will@xxxxxxxxxx> Cc: Catalin Marinas <catalin.marinas@xxxxxxx> Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx> Cc: Paul Mackerras <paulus@xxxxxxxxx> Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx> Cc: Dave Anderson <anderson@xxxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- kernel/crash_core.c | 1 + 1 file changed, 1 insertion(+) --- a/kernel/crash_core.c +++ b/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); Patches currently in stable-queue which might be from kernelfans@xxxxxxxxx are queue-5.12/crash_core-vmcoreinfo-append-section_size_bits-to-vmcoreinfo.patch