[PATCH v5 3/6] crash: add phdr for possible CPUs in elfcorehdr

[Sourabh Jain]

On 22/11/22 23:28, Eric DeVolder wrote:
>
>
> On 11/20/22 17:25, Sourabh Jain wrote:
>> On architectures like PowerPC the crash notes are available for all
>> possible CPUs. So let's populate the elfcorehdr for all possible
>> CPUs having crash notes to avoid updating elfcorehdr during in-kernel
>> crash update on CPU hotplug events.
>>
>> The similar technique was used in kexec-tool for kexec_load case.
>>
>> Signed-off-by: Sourabh Jain <sourabhjain at linux.ibm.com>
>> ---
>>   kernel/crash_core.c | 9 ++++++---
>>   1 file changed, 6 insertions(+), 3 deletions(-)
>>
>> diff --git a/kernel/crash_core.c b/kernel/crash_core.c
>> index bca1b198d9e55..f6cccdcadc9f3 100644
>> --- a/kernel/crash_core.c
>> +++ b/kernel/crash_core.c
>> @@ -364,16 +364,19 @@ int crash_prepare_elf64_headers(struct kimage 
>> *image, struct crash_mem *mem,
>>       ehdr->e_ehsize = sizeof(Elf64_Ehdr);
>>       ehdr->e_phentsize = sizeof(Elf64_Phdr);
>>   -    /* Prepare one phdr of type PT_NOTE for each present CPU */
>> -    for_each_present_cpu(cpu) {
>> +    /* Prepare one phdr of type PT_NOTE for possible CPU with crash 
>> note. */
>> +    for_each_possible_cpu(cpu) {
>>           if (IS_ENABLED(CONFIG_HOTPLUG_CPU)) {
>>               /* Skip the soon-to-be offlined cpu */
>>               if (image->hotplug_event && (cpu == image->offlinecpu))
>>                   continue;
>>           }
>>   -        phdr->p_type = PT_NOTE;
>>           notes_addr = per_cpu_ptr_to_phys(per_cpu_ptr(crash_notes, 
>> cpu));
>> +        if (!notes_addr)
>> +            continue;
>> +
>> +        phdr->p_type = PT_NOTE;
>>           phdr->p_offset = phdr->p_paddr = notes_addr;
>>           phdr->p_filesz = phdr->p_memsz = sizeof(note_buf_t);
>>           (ehdr->e_phnum)++;
>>
>
> I did a quick test of this for x86_64 and it works.
>
> Reviewed-by: Eric DeVolder <eric.devolder at oracle.com>


Thanks for testing it out.

- Sourabh Jain