Re: [PATCH v5 1/6] elf: Define note name macros

[Dave Martin <Dave.Martin@arm.com>]

Hi,

On Wed, Jan 15, 2025 at 02:47:58PM +0900, Akihiko Odaki wrote:
> elf.h had a comment saying:
> > Notes used in ET_CORE. Architectures export some of the arch register
> > sets using the corresponding note types via the PTRACE_GETREGSET and
> > PTRACE_SETREGSET requests.
> > The note name for these types is "LINUX", except NT_PRFPREG that is
> > named "CORE".
> 
> However, NT_PRSTATUS is also named "CORE". It is also unclear what
> "these types" refers to.
> 
> To fix these problems, define a name for each note type. The added
> definitions are macros so the kernel and userspace can directly refer to
> them to remove their duplicate definitions of note names.
> 
> Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
> Acked-by: Baoquan He <bhe@redhat.com>
> ---
>  include/uapi/linux/elf.h | 89 +++++++++++++++++++++++++++++++++++++++++++++---
>  1 file changed, 84 insertions(+), 5 deletions(-)
> 
> diff --git a/include/uapi/linux/elf.h b/include/uapi/linux/elf.h
> index b44069d29cec..592507aa9b3a 100644
> --- a/include/uapi/linux/elf.h
> +++ b/include/uapi/linux/elf.h
> @@ -368,101 +368,180 @@ typedef struct elf64_shdr {
>  #define ELF_OSABI ELFOSABI_NONE
>  #endif
>  
> +/* Note definitions: NN_ defines names. NT_ defines types. */
> +
> +#define NN_GNU_PROPERTY_TYPE_0	"GNU"
> +#define NT_GNU_PROPERTY_TYPE_0	5
> +

I guess this also works as a neutral way of saying that
NT_GNU_PROPERTY_TYPE_0 isn't _specifically_ for coredumps.

I would worry that moving this block is going to generate unwanted
context noise with other patches that may be in flight and add new
NT_ definitions.

But (a) changing the comments will cause that anyway, and
(b) if there are any new NT_ definitions in flight, we want people to
notice the conflict and add the accompanying NN_ definition.

So, perhaps context noise is not such a bad thing in this instance.

[...]

> +#define NN_LOONGARCH_HW_WATCH	"LINUX"
>  #define NT_LOONGARCH_HW_WATCH	0xa06   /* LoongArch hardware watchpoint registers */
>  
> -/* Note types with note name "GNU" */
> -#define NT_GNU_PROPERTY_TYPE_0	5
> -
>  /* Note header in a PT_NOTE section */
>  typedef struct elf32_note {
>    Elf32_Word	n_namesz;	/* Name size */

Reviewed-by: Dave Martin <Dave.Martin@arm.com>

Cheers
---Dave