x86: Add a GNU_PROPERTY_X86_ISA_1_USED note if needed

When -z separate-code, which is enabled by default for Linux/x86, is
used to create executable, ld won't place any data in the code-only
PT_LOAD segment.  If there are no data sections placed before the
code-only PT_LOAD segment, the program headers won't be mapped into
any PT_LOAD segment.  When the executable tries to access it (based
on the program header address passed in AT_PHDR), it will lead to
segfault.  This patch inserts a GNU_PROPERTY_X86_ISA_1_USED note if
there may be no data sections before the text section so that the
first PT_LOAD segment won't be code-only and will contain the program
header.

Testcases are adjusted to either pass "-z noseparate-code" to ld or
discard the .note.gnu.property section.  A Linux/x86 run-time test is
added.

bfd/

	PR ld/23428
	* elfxx-x86.c (_bfd_x86_elf_link_setup_gnu_properties): If the
	separate code program header is needed, make sure that the first
	read-only PT_LOAD segment has no code by adding a
	GNU_PROPERTY_X86_ISA_1_USED note.

ld/

	PR ld/23428
	* testsuite/ld-elf/linux-x86.S: New file.
	* testsuite/ld-elf/linux-x86.exp: Likewise.
	* testsuite/ld-elf/pr23428.c: Likewise.
	* testsuite/ld-elf/sec64k.exp: Pass "-z noseparate-code" to ld
	for Linux/x86 targets.
	* testsuite/ld-i386/abs-iamcu.d: Likewise.
	* testsuite/ld-i386/abs.d: Likewise.
	* testsuite/ld-i386/pr12718.d: Likewise.
	* testsuite/ld-i386/pr12921.d: Likewise.
	* testsuite/ld-x86-64/abs-k1om.d: Likewise.
	* testsuite/ld-x86-64/abs-l1om.d: Likewise.
	* testsuite/ld-x86-64/abs.d: Likewise.
	* testsuite/ld-x86-64/pr12718.d: Likewise.
	* testsuite/ld-x86-64/pr12921.d: Likewise.
	* testsuite/ld-linkonce/zeroeh.ld: Discard .note.gnu.property
	section.
	* testsuite/ld-scripts/print-memory-usage.t: Likewise.
	* testsuite/ld-scripts/size-2.t: Likewise.
	* testsuite/lib/ld-lib.exp (run_ld_link_exec_tests): Use ld
	to create executable if language is "asm".

1 files changed, 45 insertions, 15 deletions

diff --git a/bfd/elfxx-x86.c b/bfd/elfxx-x86.c
index a2497aa..2e4ff88 100644
--- a/bfd/elfxx-x86.c
+++ b/bfd/elfxx-x86.c
@@ -2524,6 +2524,7 @@ _bfd_x86_elf_link_setup_gnu_properties
   const struct elf_backend_data *bed;
   unsigned int class_align = ABI_64_P (info->output_bfd) ? 3 : 2;
   unsigned int got_align;
+  bfd_boolean has_text = FALSE;
 
   features = 0;
   if (info->ibt)
@@ -2538,24 +2539,59 @@ _bfd_x86_elf_link_setup_gnu_properties
     if (bfd_get_flavour (pbfd) == bfd_target_elf_flavour
 	&& bfd_count_sections (pbfd) != 0)
       {
+	if (!has_text)
+	  {
+	    /* Check if there is no non-empty text section.  */
+	    sec = bfd_get_section_by_name (pbfd, ".text");
+	    if (sec != NULL && sec->size != 0)
+	      has_text = TRUE;
+	  }
+
 	ebfd = pbfd;
 
 	if (elf_properties (pbfd) != NULL)
 	  break;
       }
 
-  if (ebfd != NULL && features)
+  bed = get_elf_backend_data (info->output_bfd);
+
+  htab = elf_x86_hash_table (info, bed->target_id);
+  if (htab == NULL)
+    return pbfd;
+
+  if (ebfd != NULL)
     {
-      /* If features is set, add GNU_PROPERTY_X86_FEATURE_1_IBT and
-	 GNU_PROPERTY_X86_FEATURE_1_SHSTK.  */
-      prop = _bfd_elf_get_property (ebfd,
-				    GNU_PROPERTY_X86_FEATURE_1_AND,
-				    4);
-      prop->u.number |= features;
-      prop->pr_kind = property_number;
+      prop = NULL;
+      if (features)
+	{
+	  /* If features is set, add GNU_PROPERTY_X86_FEATURE_1_IBT and
+	     GNU_PROPERTY_X86_FEATURE_1_SHSTK.  */
+	  prop = _bfd_elf_get_property (ebfd,
+					GNU_PROPERTY_X86_FEATURE_1_AND,
+					4);
+	  prop->u.number |= features;
+	  prop->pr_kind = property_number;
+	}
+      else if (has_text
+	       && elf_properties (ebfd) == NULL
+	       && elf_tdata (info->output_bfd)->o->build_id.sec == NULL
+	       && !htab->elf.dynamic_sections_created
+	       && !info->traditional_format
+	       && (info->output_bfd->flags & D_PAGED) != 0
+	       && info->separate_code)
+	{
+	  /* If the separate code program header is needed, make sure
+	     that the first read-only PT_LOAD segment has no code by
+	     adding a GNU_PROPERTY_X86_ISA_1_USED note.  */
+	  prop = _bfd_elf_get_property (ebfd,
+					GNU_PROPERTY_X86_ISA_1_USED,
+					4);
+	  prop->u.number = GNU_PROPERTY_X86_ISA_1_486;
+	  prop->pr_kind = property_number;
+	}
 
       /* Create the GNU property note section if needed.  */
-      if (pbfd == NULL)
+      if (prop != NULL && pbfd == NULL)
 	{
 	  sec = bfd_make_section_with_flags (ebfd,
 					     NOTE_GNU_PROPERTY_SECTION_NAME,
@@ -2581,12 +2617,6 @@ error_alignment:
 
   pbfd = _bfd_elf_link_setup_gnu_properties (info);
 
-  bed = get_elf_backend_data (info->output_bfd);
-
-  htab = elf_x86_hash_table (info, bed->target_id);
-  if (htab == NULL)
-    return pbfd;
-
   htab->r_info = init_table->r_info;
   htab->r_sym = init_table->r_sym;