crash_prepare_elf64_headers() writes into the elfcorehdr an ELF PT_NOTE for all possible CPUs. As such, subsequent changes to CPUs (ie. hot un/plug, online/offline) do not need to rewrite the elfcorehdr. The kimage->file_mode term covers kdump images loaded via the kexec_file_load() syscall. Since crash_prepare_elf64_headers() wrote the initial elfcorehdr, no update to the elfcorehdr is needed for CPU changes. The kimage->elfcorehdr_updated term covers kdump images loaded via the kexec_load() syscall. At least one memory or CPU change must occur to cause crash_prepare_elf64_headers() to rewrite the elfcorehdr. Afterwards, no update to the elfcorehdr is needed for CPU changes. This code is intentionally *NOT* hoisted into crash_handle_hotplug_event() as it would prevent the arch-specific handler from running for CPU changes. This would break PPC, for example, which needs to update other information besides the elfcorehdr, on CPU changes. Signed-off-by: Eric DeVolder <eric.devolder@xxxxxxxxxx> Reviewed-by: Sourabh Jain <sourabhjain@xxxxxxxxxxxxx> Acked-by: Hari Bathini <hbathini@xxxxxxxxxxxxx> Acked-by: Baoquan He <bhe@xxxxxxxxxx> --- arch/x86/kernel/crash.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c index caf22bcb61af..18d2a18d1073 100644 --- a/arch/x86/kernel/crash.c +++ b/arch/x86/kernel/crash.c @@ -467,6 +467,16 @@ void arch_crash_handle_hotplug_event(struct kimage *image) unsigned long mem, memsz; unsigned long elfsz = 0; + /* + * As crash_prepare_elf64_headers() has already described all + * possible CPUs, there is no need to update the elfcorehdr + * for additional CPU changes. + */ + if ((image->file_mode || image->elfcorehdr_updated) && + ((image->hp_action == KEXEC_CRASH_HP_ADD_CPU) || + (image->hp_action == KEXEC_CRASH_HP_REMOVE_CPU))) + return; + /* * Create the new elfcorehdr reflecting the changes to CPU and/or * memory resources. -- 2.31.1
