[binutils-gdb] bfd: Add minimal support to handle note that describes xsave layout

[Jan Beulich]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=e2b607517e5aa5cc0d3447d5078a0a53410a3989

commit e2b607517e5aa5cc0d3447d5078a0a53410a3989
Author: Vignesh Balasubramanian <vigbalas@amd.com>
Date:   Fri Dec 12 14:59:49 2025 +0100

    bfd: Add minimal support to handle note that describes xsave layout
    
    This note section is already supported by Linux kernel.
    https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/arch/x86/kernel/fpu/xstate.c?id=ba386777a30b38dabcc7fb8a89ec2869a09915f7
    
    Co-Authored-By: Jini Susan George <jinisusan.george@amd.com>

Diff:
---
 bfd/elf-bfd.h        |  2 ++
 bfd/elf.c            | 23 ++++++++++++++++++++++-
 binutils/readelf.c   |  2 ++
 include/elf/common.h |  2 ++
 4 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/bfd/elf-bfd.h b/bfd/elf-bfd.h
index 01bf6236a75..2b6dd8dadac 100644
--- a/bfd/elf-bfd.h
+++ b/bfd/elf-bfd.h
@@ -2973,6 +2973,8 @@ extern char *elfcore_write_prxfpreg
   (bfd *, char *, int *, const void *, int);
 extern char *elfcore_write_xstatereg
   (bfd *, char *, int *, const void *, int);
+extern char *elfcore_write_xsave_layout
+  (bfd *, char *, int *, const void *, int);
 extern char *elfcore_write_x86_segbases
   (bfd *, char *, int *, const void *, int);
 extern char *elfcore_write_i386_tls
diff --git a/bfd/elf.c b/bfd/elf.c
index 33c2d269a9c..9fbf1534220 100644
--- a/bfd/elf.c
+++ b/bfd/elf.c
@@ -115,6 +115,7 @@ 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"
 
 static int elf_sort_sections (const void *, const void *);
 static bool assign_file_positions_except_relocs (bfd *, struct bfd_link_info *);
@@ -10482,6 +10483,16 @@ 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,
+					  NOTE_PSEUDO_SECTION_XSAVE_LAYOUT,
+					  note);
+}
+
 static bool
 elfcore_grok_ppc_vmx (bfd *abfd, Elf_Internal_Note *note)
 {
@@ -11211,6 +11222,7 @@ elfcore_grok_note (bfd *abfd, Elf_Internal_Note *note)
 	case NT_S390_VXRS_LOW:	return elfcore_grok_s390_vxrs_low (abfd, note);
 	case NT_X86_SHSTK:	return elfcore_grok_sspreg (abfd, note);
 	case NT_X86_XSTATE:	return elfcore_grok_xstatereg (abfd, note);
+	case NT_X86_XSAVE_LAYOUT: return elfcore_grok_xsave_layout_desc (abfd, note);
 	default: break;
 	}
     }
@@ -12390,6 +12402,14 @@ 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)
@@ -13052,7 +13072,8 @@ 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.  */
     };
 
   int i;
diff --git a/binutils/readelf.c b/binutils/readelf.c
index 9e89a54174e..374bf2d586c 100644
--- a/binutils/readelf.c
+++ b/binutils/readelf.c
@@ -21411,6 +21411,8 @@ 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:
diff --git a/include/elf/common.h b/include/elf/common.h
index e280e17f3b7..fe5cf8ad642 100644
--- a/include/elf/common.h
+++ b/include/elf/common.h
@@ -697,6 +697,8 @@
 #define NT_X86_SHSTK	0x204		/* x86 SHSTK state.  */
 					/* This replaces NT_X86_CET (0x203).  */
 					/*   note name must be "LINUX".  */
+#define NT_X86_XSAVE_LAYOUT	0x205	/* XSAVE layout description */
+					/*   note name must be "LINUX".  */
 #define NT_S390_HIGH_GPRS 0x300		/* S/390 upper halves of GPRs  */
 					/*   note name must be "LINUX".  */
 #define NT_S390_TIMER	0x301		/* S390 timer */