[PATCH] bfd: Add support to read note that describes xsave layout

[Jan Beulich]

On 11.09.2025 09:17, Vignesh Balasubramanian wrote:
> --- a/bfd/elf.c
> +++ b/bfd/elf.c
> @@ -114,6 +114,7 @@ SECTION
>  #define NOTE_PSEUDO_SECTION_X86_SEGBASES 	".reg-x86-segbases"
>  #define NOTE_PSEUDO_SECTION_XFP          	".reg-xfp"
>  #define NOTE_PSEUDO_SECTION_XSTATE       	".reg-xstate"
> +#define NOTE_PSEUDO_SECTION_XSAVE_LAYOUT	".reg.xsave.layout"

Why dots instead of dashes as separators here, and ...

> @@ -10492,6 +10493,14 @@ elfcore_grok_sspreg (bfd *abfd, Elf_Internal_Note *note)
>    return elfcore_make_note_pseudosection (abfd, NOTE_PSEUDO_SECTION_SSP, note);
>  }
>  
> +/* Linux dumps the XSAVE Layout description in a note named "LINUX"
> +   with a note type of NT_X86_XSAVE_LAYOUT. */
> +static bool
> +elfcore_grok_xsave_layout_desc (bfd *abfd, Elf_Internal_Note *note)
> +{
> +  return elfcore_make_note_pseudosection (abfd, ".reg-xsave-layout", note);

... why not using the #define here?

> @@ -12390,6 +12400,17 @@ elfcore_write_xstatereg (bfd *abfd, char *buf, int *bufsiz,
>  			     note_name, NT_X86_XSTATE, xfpregs, size);
>  }
>  
> +char *
> +elfcore_write_xsave_layout (bfd *abfd, char *buf, int *bufsiz,
> +			    const void *xsave_layout, int size)
> +{
> +  return elfcore_write_note (abfd, buf, bufsiz,
> +			     NOTE_NAME_LINUX,
> +			     NT_X86_XSAVE_LAYOUT,
> +			     xsave_layout,
> +			     size);
> +}
> +
>  static char *
>  elfcore_write_sspreg (bfd *abfd, char *buf, int *bufsiz,
>  		      const void *ssp, int size)
> @@ -13035,7 +13056,8 @@ elfcore_write_register_note (bfd *abfd,
>        { NOTE_PSEUDO_SECTION_TDESC,            elfcore_write_gdb_tdesc},
>        { NOTE_PSEUDO_SECTION_X86_SEGBASES,     elfcore_write_x86_segbases},
>        { NOTE_PSEUDO_SECTION_XFP,              elfcore_write_prxfpreg},
> -      { NOTE_PSEUDO_SECTION_XSTATE,           elfcore_write_xstatereg} /* NB/ No comma.  */
> +      { NOTE_PSEUDO_SECTION_XSTATE,           elfcore_write_xstatereg},
> +      { NOTE_PSEUDO_SECTION_XSAVE_LAYOUT,     elfcore_write_xsave_layout} /* NB/ No comma.  */
>      };

Considering the subject: There's more code here dealing with writing of
such a note ...

> --- a/binutils/readelf.c
> +++ b/binutils/readelf.c
> @@ -21375,6 +21375,8 @@ get_note_type (Filedata * filedata, unsigned e_type)
>  	return _("NT_386_IOPERM (x86 I/O permissions)");
>        case NT_X86_XSTATE:
>  	return _("NT_X86_XSTATE (x86 XSAVE extended state)");
> +      case NT_X86_XSAVE_LAYOUT:
> +	return _("NT_X86_XSAVE_LAYOUT (x86 XSAVE Layout description)");
>        case NT_X86_CET:
>  	return _("NT_X86_CET (x86 CET state)");
>        case NT_X86_SHSTK:

... than the "reading" of it (you only recognize it aiui, without actually
displaying its contents in a human-readable manner). IOW I'd suggest
s/read/handle/ along with adding "minimal" for the subject.

Jan