ld: generate SFrame stack trace info for .plt.got

PR/32298 sframe: no SFrame stack trace info generated for .plt.got

Add support to generate SFrame stack trace info for .plt.got section.
Enhance the current definition of struct elf_x86_sframe_plt to include
initialized SFrame FDE/FREs applicable for .plt.got section.  There are
two variants of .plt.got entries: 16 byte and 8 byte.

8 byte:
    ff 25 00 00 00 00     jmpq  *name@GOTPCREL(%rip)
    66 90                 xchg  %ax,%ax

16 byte:
    f3 0f 1e fa           endbr64
    ff 25 66 2f 00 00     jmpq  *name@GOTPCREL(%rip)
    66 0f 1f 44 00 00     nopw   0x0(%rax,%rax,1)

For the testcase, define some application symbols such that their PLT
entry is placed in .plt.got and ensure SFrame information is generated
with and without -z ibtplt.

ChangeLog:
	PR/32298
	* bfd/elf64-x86-64.c (elf_x86_64_link_setup_gnu_properties):
	PLT GOT entry size is different for IBT vs non IBT PLTs.
	* bfd/elfxx-x86.c (enum dynobj_sframe_plt_type): New enum for
	SFRAME_PLT_GOT.
	(_bfd_x86_elf_create_sframe_plt): Handle SFRAME_PLT_GOT.
	(_bfd_x86_elf_write_sframe_plt): Likewise.
	(_bfd_x86_elf_late_size_sections): Likewise.
	(_bfd_x86_elf_finish_dynamic_sections): Likewise.
	* bfd/elfxx-x86.h (struct elf_x86_sframe_plt): Add new members
	to keep information about PLT GOT entries.
	(struct elf_x86_link_hash_table): Add support for creating
	SFrame section for .plt.got.
	* ld/testsuite/ld-x86-64/x86-64.exp: Add new tests.
	* ld/testsuite/ld-x86-64/sframe-pltgot-1.d: New test.
	* ld/testsuite/ld-x86-64/sframe-pltgot-1.s: New test.
	* ld/testsuite/ld-x86-64/sframe-pltgot-2.d: New test.

bfd/elf64-x86-64.c

@@ -906,6 +906,14 @@ static const sframe_frame_row_entry elf_x86_64_sframe_pltn_fre2 =
   SFRAME_V1_FRE_INFO (SFRAME_BASE_REG_SP, 1, SFRAME_FRE_OFFSET_1B) /* FRE info.  */
 };
 
+/* .sframe FRE covering the .plt section entry for IBT.  */
+static const sframe_frame_row_entry elf_x86_64_sframe_ibt_pltn_fre2 =
+{
+  9, /* SFrame FRE start address.  */
+  {16, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, /* 12 bytes.  */
+  SFRAME_V1_FRE_INFO (SFRAME_BASE_REG_SP, 1, SFRAME_FRE_OFFSET_1B) /* FRE info.  */
+};
+
 /* .sframe FRE covering the second .plt section entry.  */
 static const sframe_frame_row_entry elf_x86_64_sframe_sec_pltn_fre1 =
 {
@@ -914,7 +922,7 @@ static const sframe_frame_row_entry elf_x86_64_sframe_sec_pltn_fre1 =
   SFRAME_V1_FRE_INFO (SFRAME_BASE_REG_SP, 1, SFRAME_FRE_OFFSET_1B) /* FRE info.  */
 };
 
-/* SFrame helper object for non-lazy PLT.  Also used for IBT enabled PLT.  */
+/* SFrame helper object for non-lazy PLT.  */
 static const struct elf_x86_sframe_plt elf_x86_64_sframe_non_lazy_plt =
 {
   LAZY_PLT_ENTRY_SIZE,
@@ -927,10 +935,34 @@ static const struct elf_x86_sframe_plt elf_x86_64_sframe_non_lazy_plt =
   { &elf_x86_64_sframe_sec_pltn_fre1, &elf_x86_64_sframe_null_fre },
   0,
   0, /* There is no second PLT necessary.  */
-  { &elf_x86_64_sframe_null_fre }
+  { &elf_x86_64_sframe_null_fre },
+  NON_LAZY_PLT_ENTRY_SIZE,
+  1, /* Number of FREs for PLT GOT.  */
+  /* Array of SFrame FREs for PLT GOT.  */
+  { &elf_x86_64_sframe_null_fre },
 };
 
-/* SFrame helper object for lazy PLT.  Also used for IBT enabled PLT.  */
+/* SFrame helper object for non-lazy IBT enabled PLT.  */
+static const struct elf_x86_sframe_plt elf_x86_64_sframe_non_lazy_ibt_plt =
+{
+  LAZY_PLT_ENTRY_SIZE,
+  2, /* Number of FREs for PLT0.  */
+  /* Array of SFrame FREs for plt0.  */
+  { &elf_x86_64_sframe_plt0_fre1, &elf_x86_64_sframe_plt0_fre2 },
+  LAZY_PLT_ENTRY_SIZE,
+  1, /* Number of FREs for PLTn.  */
+  /* Array of SFrame FREs for plt.  */
+  { &elf_x86_64_sframe_sec_pltn_fre1, &elf_x86_64_sframe_null_fre },
+  0,
+  0, /* There is no second PLT necessary.  */
+  { &elf_x86_64_sframe_null_fre },
+  LAZY_PLT_ENTRY_SIZE,
+  1, /* Number of FREs for PLT GOT.  */
+  /* Array of SFrame FREs for PLT GOT.  */
+  { &elf_x86_64_sframe_null_fre },
+};
+
+/* SFrame helper object for lazy PLT. */
 static const struct elf_x86_sframe_plt elf_x86_64_sframe_plt =
 {
   LAZY_PLT_ENTRY_SIZE,
@@ -942,10 +974,34 @@ static const struct elf_x86_sframe_plt elf_x86_64_sframe_plt =
   /* Array of SFrame FREs for plt.  */
   { &elf_x86_64_sframe_pltn_fre1, &elf_x86_64_sframe_pltn_fre2 },
   NON_LAZY_PLT_ENTRY_SIZE,
-  1, /* Number of FREs for PLTn for second PLT.  */
-  /* FREs for second plt (stack trace info for .plt.got is
-     identical).  Used when IBT or non-lazy PLT is in effect.  */
-  { &elf_x86_64_sframe_sec_pltn_fre1 }
+  1, /* Number of FREs for second PLT.  */
+  /* Array of SFrame FREs for second PLT.  */
+  { &elf_x86_64_sframe_sec_pltn_fre1 },
+  NON_LAZY_PLT_ENTRY_SIZE,
+  1, /* Number of FREs for PLT GOT.  */
+  /* Array of SFrame FREs for PLT GOT.  */
+  { &elf_x86_64_sframe_null_fre },
+};
+
+/* SFrame helper object for lazy PLT with IBT. */
+static const struct elf_x86_sframe_plt elf_x86_64_sframe_ibt_plt =
+{
+  LAZY_PLT_ENTRY_SIZE,
+  2, /* Number of FREs for PLT0.  */
+  /* Array of SFrame FREs for plt0.  */
+  { &elf_x86_64_sframe_plt0_fre1, &elf_x86_64_sframe_plt0_fre2 },
+  LAZY_PLT_ENTRY_SIZE,
+  2, /* Number of FREs for PLTn.  */
+  /* Array of SFrame FREs for plt.  */
+  { &elf_x86_64_sframe_pltn_fre1, &elf_x86_64_sframe_ibt_pltn_fre2 },
+  LAZY_PLT_ENTRY_SIZE,
+  1, /* Number of FREs for second PLT.  */
+  /* Array of SFrame FREs for second plt.  */
+  { &elf_x86_64_sframe_sec_pltn_fre1 },
+  LAZY_PLT_ENTRY_SIZE,
+  1, /* Number of FREs for PLT GOT.  */
+  /* Array of SFrame FREs for PLT GOT.  */
+  { &elf_x86_64_sframe_null_fre },
 };
 
 /* These are the standard parameters.  */
@@ -5678,8 +5734,8 @@ elf_x86_64_link_setup_gnu_properties (struct bfd_link_info *info)
     {
       init_table.sframe_lazy_plt = &elf_x86_64_sframe_plt;
       init_table.sframe_non_lazy_plt = &elf_x86_64_sframe_non_lazy_plt;
-      init_table.sframe_lazy_ibt_plt = &elf_x86_64_sframe_plt;
-      init_table.sframe_non_lazy_ibt_plt = &elf_x86_64_sframe_non_lazy_plt;
+      init_table.sframe_lazy_ibt_plt = &elf_x86_64_sframe_ibt_plt;
+      init_table.sframe_non_lazy_ibt_plt = &elf_x86_64_sframe_non_lazy_ibt_plt;
     }
   else
     {

bfd/elfxx-x86.c

@@ -1817,7 +1817,8 @@ elf_x86_relative_reloc_compare (const void *pa, const void *pb)
 enum dynobj_sframe_plt_type
 {
   SFRAME_PLT = 1,
-  SFRAME_PLT_SEC = 2
+  SFRAME_PLT_SEC = 2,
+  SFRAME_PLT_GOT = 3,
 };
 
 /* Create SFrame stack trace info for the plt entries in the .plt section
@@ -1831,7 +1832,6 @@ _bfd_x86_elf_create_sframe_plt (bfd *output_bfd,
   struct elf_x86_link_hash_table *htab;
   const struct elf_backend_data *bed;
 
-  bool plt0_generated_p;
   unsigned int plt0_entry_size;
   unsigned char func_info;
   uint32_t fre_type;
@@ -1845,14 +1845,11 @@ _bfd_x86_elf_create_sframe_plt (bfd *output_bfd,
   unsigned plt_entry_size = 0;
   unsigned int num_pltn_fres = 0;
   unsigned int num_pltn_entries = 0;
+  const sframe_frame_row_entry * const *pltn_fres;
 
   bed = get_elf_backend_data (output_bfd);
   htab = elf_x86_hash_table (info, bed->target_id);
   /* Whether SFrame stack trace info for plt0 is to be generated.  */
-  plt0_generated_p = htab->plt.has_plt0;
-  plt0_entry_size
-    = (plt0_generated_p) ? htab->sframe_plt->plt0_entry_size : 0;
-
   switch (plt_sec_type)
     {
     case SFRAME_PLT:
@@ -1860,7 +1857,10 @@ _bfd_x86_elf_create_sframe_plt (bfd *output_bfd,
 	  ectx = &htab->plt_cfe_ctx;
 	  dpltsec = htab->elf.splt;
 
-	  plt_entry_size = htab->plt.plt_entry_size;
+	  plt0_entry_size
+	    = htab->plt.has_plt0 ? htab->sframe_plt->plt0_entry_size : 0;
+	  plt_entry_size = htab->sframe_plt->pltn_entry_size;
+	  pltn_fres = htab->sframe_plt->pltn_fres;
 	  num_pltn_fres = htab->sframe_plt->pltn_num_fres;
 	  num_pltn_entries
 	    = (dpltsec->size - plt0_entry_size) / plt_entry_size;
@@ -1870,14 +1870,32 @@ _bfd_x86_elf_create_sframe_plt (bfd *output_bfd,
     case SFRAME_PLT_SEC:
 	{
 	  ectx = &htab->plt_second_cfe_ctx;
-	  /* FIXME - this or htab->plt_second_sframe ?  */
-	  dpltsec = htab->plt_second_eh_frame;
+	  dpltsec = htab->plt_second;
+
+	  plt0_entry_size = 0;
 
 	  plt_entry_size = htab->sframe_plt->sec_pltn_entry_size;
+	  pltn_fres = htab->sframe_plt->sec_pltn_fres;
 	  num_pltn_fres = htab->sframe_plt->sec_pltn_num_fres;
 	  num_pltn_entries = dpltsec->size / plt_entry_size;
+
 	  break;
 	}
+      case SFRAME_PLT_GOT:
+	{
+	  ectx = &htab->plt_got_cfe_ctx;
+	  dpltsec = htab->plt_got;
+
+	  plt0_entry_size = 0;
+
+	  plt_entry_size = htab->sframe_plt->plt_got_entry_size;
+	  pltn_fres = htab->sframe_plt->plt_got_fres;
+	  num_pltn_fres = htab->sframe_plt->plt_got_num_fres;
+	  num_pltn_entries = dpltsec->size / plt_entry_size;
+
+	  break;
+	}
+
     default:
       /* No other value is possible.  */
       return false;
@@ -1897,7 +1915,7 @@ _bfd_x86_elf_create_sframe_plt (bfd *output_bfd,
 
   /* Add SFrame FDE and the associated FREs for plt0 if plt0 has been
      generated.  */
-  if (plt0_generated_p)
+  if (plt0_entry_size)
     {
       /* Add SFrame FDE for plt0, the function start address is updated later
 	 at _bfd_elf_merge_section_sframe time.  */
@@ -1934,16 +1952,17 @@ _bfd_x86_elf_create_sframe_plt (bfd *output_bfd,
 				      plt0_entry_size, /* func start addr.  */
 				      dpltsec->size - plt0_entry_size,
 				      func_info,
-				      16,
+				      plt_entry_size,
 				      0 /* Num FREs.  */);
 
       sframe_frame_row_entry pltn_fre;
-      /* Now add the FREs for pltn.  Simply adding the two FREs suffices due
+      /* Now add the FREs for pltn.  Simply adding the FREs suffices due
 	 to the usage of SFRAME_FDE_TYPE_PCMASK above.  */
       for (unsigned int j = 0; j < num_pltn_fres; j++)
 	{
-	  pltn_fre = *(htab->sframe_plt->pltn_fres[j]);
-	  sframe_encoder_add_fre (*ectx, 1, &pltn_fre);
+	  unsigned int func_idx = plt0_entry_size ? 1 : 0;
+	  pltn_fre = *(pltn_fres[j]);
+	  sframe_encoder_add_fre (*ectx, func_idx, &pltn_fre);
 	}
     }
 
@@ -1981,6 +2000,10 @@ _bfd_x86_elf_write_sframe_plt (bfd *output_bfd,
       ectx = htab->plt_second_cfe_ctx;
       sec = htab->plt_second_sframe;
       break;
+    case SFRAME_PLT_GOT:
+      ectx = htab->plt_got_cfe_ctx;
+      sec = htab->plt_got_sframe;
+      break;
     default:
       /* No other value is possible.  */
       return false;
@@ -2508,7 +2531,18 @@ _bfd_x86_elf_late_size_sections (bfd *output_bfd,
 	  htab->plt_sframe->size = sizeof (sframe_header) + 1;
 	}
 
-      /* FIXME - generate for .plt.got ?  */
+      if (htab->plt_got_sframe != NULL
+	  && htab->plt_got != NULL
+	  && htab->plt_got->size != 0
+	  && !bfd_is_abs_section (htab->plt_got->output_section))
+	{
+	  _bfd_x86_elf_create_sframe_plt (output_bfd, info, SFRAME_PLT_GOT);
+	  /* FIXME - Dirty Hack.  Set the size to something non-zero for now,
+	     so that the section does not get stripped out below.  The precise
+	     size of this section is known only when the contents are
+	     serialized in _bfd_x86_elf_write_sframe_plt.  */
+	  htab->plt_got_sframe->size = sizeof (sframe_header) + 1;
+	}
 
       if (htab->plt_second_sframe != NULL
 	  && htab->plt_second != NULL
@@ -2575,6 +2609,7 @@ _bfd_x86_elf_late_size_sections (bfd *output_bfd,
 	       || s == htab->plt_second_eh_frame
 	       || s == htab->plt_sframe
 	       || s == htab->plt_second_sframe
+	       || s == htab->plt_got_sframe
 	       || s == htab->elf.sdynbss
 	       || s == htab->elf.sdynrelro)
 	{
@@ -2619,7 +2654,8 @@ _bfd_x86_elf_late_size_sections (bfd *output_bfd,
 
       /* Skip allocating contents for .sframe section as it is written
 	 out differently.  See below.  */
-      if ((s == htab->plt_sframe) || (s == htab->plt_second_sframe))
+      if ((s == htab->plt_sframe) || (s == htab->plt_second_sframe)
+	  || (s == htab->plt_got_sframe))
 	continue;
 
       /* NB: Initially, the iplt section has minimal alignment to
@@ -2680,10 +2716,16 @@ _bfd_x86_elf_late_size_sections (bfd *output_bfd,
 	_bfd_x86_elf_write_sframe_plt (output_bfd, info, SFRAME_PLT);
 
       if (htab->plt_second_sframe != NULL
-	  && htab->elf.splt != NULL
-	  && htab->elf.splt->size != 0
+	  && htab->plt_second != NULL
+	  && htab->plt_second->size != 0
 	  && htab->plt_second_sframe->contents == NULL)
 	_bfd_x86_elf_write_sframe_plt (output_bfd, info, SFRAME_PLT_SEC);
+
+      if (htab->plt_got_sframe != NULL
+	  && htab->plt_got != NULL
+	  && htab->plt_got->size != 0
+	  && htab->plt_got_sframe->contents == NULL)
+	_bfd_x86_elf_write_sframe_plt (output_bfd, info, SFRAME_PLT_GOT);
     }
 
   if (resolved_plt != NULL
@@ -2994,6 +3036,34 @@ _bfd_x86_elf_finish_dynamic_sections (bfd *output_bfd,
 	    return NULL;
 	}
     }
+
+  if (htab->plt_got_sframe != NULL
+      && htab->plt_got_sframe->contents != NULL)
+    {
+      if (htab->plt_got != NULL
+	  && htab->plt_got->size != 0
+	  && (htab->plt_got->flags & SEC_EXCLUDE) == 0
+	  && htab->plt_got->output_section != NULL
+	  && htab->plt_got_sframe->output_section != NULL)
+	{
+	  bfd_vma plt_start = htab->plt_got->output_section->vma;
+	  bfd_vma sframe_start
+	    = (htab->plt_got_sframe->output_section->vma
+	       + htab->plt_got_sframe->output_offset
+	       + PLT_SFRAME_FDE_START_OFFSET);
+	  bfd_put_signed_32 (dynobj, plt_start - sframe_start,
+			     htab->plt_got_sframe->contents
+			     + PLT_SFRAME_FDE_START_OFFSET);
+	}
+      if (htab->plt_got_sframe->sec_info_type == SEC_INFO_TYPE_SFRAME)
+	{
+	  if (! _bfd_elf_merge_section_sframe (output_bfd, info,
+					       htab->plt_got_sframe,
+					       htab->plt_got_sframe->contents))
+	    return NULL;
+	}
+    }
+
   if (htab->elf.sgot && htab->elf.sgot->size > 0)
     elf_section_data (htab->elf.sgot->output_section)->this_hdr.sh_entsize
       = htab->got_entry_size;
@@ -4761,7 +4831,18 @@ _bfd_x86_elf_link_setup_gnu_properties
 
 	      htab->plt_second_sframe = sec;
 	    }
-	  /* FIXME - add later for plt_got. */
+
+	  /* .plt.got.  */
+	  if (htab->plt_got != NULL)
+	    {
+	      sec = bfd_make_section_anyway_with_flags (dynobj,
+							".sframe",
+							flags);
+	      if (sec == NULL)
+		info->callbacks->einfo (_("%F%P: failed to create PLT GOT .sframe section\n"));
+
+	      htab->plt_got_sframe = sec;
+	    }
 	}
     }
 

bfd/elfxx-x86.h

@@ -401,6 +401,10 @@ struct elf_x86_sframe_plt
   unsigned int sec_pltn_entry_size;
   unsigned int sec_pltn_num_fres;
   const sframe_frame_row_entry *sec_pltn_fres[SFRAME_PLTN_MAX_NUM_FRES];
+
+  unsigned int plt_got_entry_size;
+  unsigned int plt_got_num_fres;
+  const sframe_frame_row_entry *plt_got_fres[SFRAME_PLTN_MAX_NUM_FRES];
 };
 
 struct elf_x86_lazy_plt_layout
@@ -606,6 +610,8 @@ struct elf_x86_link_hash_table
   asection *plt_sframe;
   sframe_encoder_ctx *plt_second_cfe_ctx;
   asection *plt_second_sframe;
+  sframe_encoder_ctx *plt_got_cfe_ctx;
+  asection *plt_got_sframe;
 
   /* Parameters describing PLT generation, lazy or non-lazy.  */
   struct elf_x86_plt_layout plt;

ld/testsuite/ld-x86-64/sframe-ibt-plt-1.d

@@ -0,0 +1,33 @@
+#as: --gsframe
+#source: ibt-plt-3.s
+#objdump: --sframe=.sframe
+#ld: -shared -z ibtplt --no-rosegment
+#name: SFrame for IBT PLT .plt.sec
+
+.*: +file format .*
+
+Contents of the SFrame section .sframe:
+  Header :
+
+    Version: SFRAME_VERSION_2
+    Flags: SFRAME_F_FDE_SORTED
+    CFA fixed RA offset: \-8
+#...
+
+  Function Index :
+
+    func idx \[0\]: pc = 0x1000, size = 16 bytes
+    STARTPC +CFA +FP +RA +
+    0+1000 +sp\+16 +u +f +
+    0+1006 +sp\+24 +u +f +
+
+    func idx \[1\]: pc = 0x1010, size = 32 bytes
+    STARTPC\[m\] +CFA +FP +RA +
+    0+0000 +sp\+8 +u +f +
+    0+0009 +sp\+16 +u +f +
+
+    func idx \[2\]: pc = 0x1030, size = 32 bytes
+    STARTPC\[m\] +CFA +FP +RA +
+    0+0000 +sp\+8 +u +f +
+
+#...

ld/testsuite/ld-x86-64/sframe-pltgot-1.d

@@ -0,0 +1,28 @@
+#as: --gsframe
+#source: sframe-pltgot-1.s
+#objdump: --sframe=.sframe
+#ld: -shared -z ibtplt --no-rosegment
+#name: SFrame for IBT .plt.got
+
+.*: +file format .*
+
+Contents of the SFrame section .sframe:
+  Header :
+
+    Version: SFRAME_VERSION_2
+    Flags: SFRAME_F_FDE_SORTED
+    CFA fixed RA offset: \-8
+#...
+
+  Function Index :
+
+    func idx \[0\]: pc = 0x1000, size = 16 bytes
+    STARTPC +CFA +FP +RA +
+    0+1000 +sp\+16 +u +f +
+    0+1006 +sp\+24 +u +f +
+
+    func idx \[1\]: pc = 0x1010, size = 64 bytes
+    STARTPC\[m\] +CFA +FP +RA +
+    0+0000 +sp\+16 +u +f +
+
+#...

ld/testsuite/ld-x86-64/sframe-pltgot-1.s

@@ -0,0 +1,15 @@
+        .text
+        .globl foo
+        .type foo, @function
+foo:
+        .cfi_startproc
+        call    func1@plt
+        movq    func1@GOTPCREL(%rip), %rax
+        call    func2@plt
+        movq    func2@GOTPCREL(%rip), %rax
+        call    func3@plt
+        movq    func3@GOTPCREL(%rip), %rax
+        call    func4@plt
+        movq    func4@GOTPCREL(%rip), %rax
+        .cfi_endproc
+	.section	.note.GNU-stack,"",@progbits

ld/testsuite/ld-x86-64/sframe-pltgot-2.d

@@ -0,0 +1,28 @@
+#as: --gsframe
+#source: sframe-pltgot-1.s
+#objdump: --sframe=.sframe
+#ld: -shared --no-rosegment
+#name: SFrame for .plt.got
+
+.*: +file format .*
+
+Contents of the SFrame section .sframe:
+  Header :
+
+    Version: SFRAME_VERSION_2
+    Flags: SFRAME_F_FDE_SORTED
+    CFA fixed RA offset: \-8
+#...
+
+  Function Index :
+
+    func idx \[0\]: pc = 0x1000, size = 16 bytes
+    STARTPC +CFA +FP +RA +
+    0+1000 +sp\+16 +u +f +
+    0+1006 +sp\+24 +u +f +
+
+    func idx \[1\]: pc = 0x1010, size = 32 bytes
+    STARTPC\[m\] +CFA +FP +RA +
+    0+0000 +sp\+16 +u +f +
+
+#...

ld/testsuite/ld-x86-64/x86-64.exp

@@ -547,6 +547,9 @@ run_dump_test "pr32191-x32"
 if { ![skip_sframe_tests] } {
     run_dump_test "sframe-simple-1"
     run_dump_test "sframe-plt-1"
+    run_dump_test "sframe-ibt-plt-1"
+    run_dump_test "sframe-pltgot-1"
+    run_dump_test "sframe-pltgot-2"
 }
 
 if ![istarget "x86_64-*-linux*"] {