[PATCH v7 4/8] crash: add phdr for possible CPUs in elfcorehdr

[Laurent Dufour]

On 15/01/2023 16:02:02, 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 is 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(-)

This patch is not applying on ppc/next (53ab112a9508).

As far as I could see, crash_prepare_elf64_headers() is defined in the file
kernel/kexec_file.c and that's not recent, see babac4a84a88 (kexec_file,
x86: move re-factored code to generic side, 2018-04-13)

Am I missing something?

> 
> diff --git a/kernel/crash_core.c b/kernel/crash_core.c
> index 910d377ea317e..19f987b3851e8 100644
> --- a/kernel/crash_core.c
> +++ b/kernel/crash_core.c
> @@ -364,8 +364,8 @@ 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) {
>  #ifdef CONFIG_CRASH_HOTPLUG
>  		if (IS_ENABLED(CONFIG_HOTPLUG_CPU)) {
>  			/* Skip the soon-to-be offlined cpu */
> @@ -373,8 +373,11 @@ int crash_prepare_elf64_headers(struct kimage *image, struct crash_mem *mem,
>  				continue;
>  		}
>  #endif
> -		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)++;