From 38395c77d7619fb32885468f52edf566ab84d411 Mon Sep 17 00:00:00 2001
From: Mark Harmstone <mark@harmstone.com>
Date: Mon, 20 Feb 2023 14:10:05 +0000
Subject: [PATCH] ld: Sort section contributions in PDB files

Microsoft's DIA library, and thus also MSVC and WinDbg, expects section
contributions to be ordered by section number and offset, otherwise it's
unable to resolve line numbers.
---
 ld/pdb.c                                  | 82 +++++++++++++++++------
 ld/testsuite/ld-pe/pdb2-section-contrib.d |  6 +-
 2 files changed, 66 insertions(+), 22 deletions(-)

diff --git a/ld/pdb.c b/ld/pdb.c
index 12c4ac4b112..5e85f999c6b 100644
--- a/ld/pdb.c
+++ b/ld/pdb.c
@@ -107,6 +107,13 @@ struct globals
   htab_t hashmap;
 };
 
+struct in_sc
+{
+  asection *s;
+  uint16_t sect_num;
+  uint16_t mod_index;
+};
+
 static const uint32_t crc_table[] =
 {
   0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419, 0x706af48f,
@@ -4118,6 +4125,27 @@ find_section_number (bfd *abfd, asection *sect)
   return 0;
 }
 
+/* Used as parameter to qsort, to sort section contributions by section and
+   offset.  */
+static int
+section_contribs_compare (const void *p1, const void *p2)
+{
+  const struct in_sc *sc1 = p1;
+  const struct in_sc *sc2 = p2;
+
+  if (sc1->sect_num < sc2->sect_num)
+    return -1;
+  if (sc1->sect_num > sc2->sect_num)
+    return 1;
+
+  if (sc1->s->output_offset < sc2->s->output_offset)
+    return -1;
+  if (sc1->s->output_offset > sc2->s->output_offset)
+    return 1;
+
+  return 0;
+}
+
 /* Create the substream which maps addresses in the image file to locations
    in the original object files.  */
 static bool
@@ -4128,6 +4156,8 @@ create_section_contrib_substream (bfd *abfd, void **data, uint32_t *size)
   uint16_t mod_index;
   char *sect_flags;
   file_ptr offset;
+  struct in_sc *sc_in, *sc2;
+  uint32_t *ptr;
 
   for (bfd *in = coff_data (abfd)->link_info->input_bfds; in;
        in = in->link.next)
@@ -4168,8 +4198,11 @@ create_section_contrib_substream (bfd *abfd, void **data, uint32_t *size)
       offset += sizeof (struct external_scnhdr);
     }
 
-  sc =
-    (struct section_contribution *) ((uint8_t *) *data + sizeof (uint32_t));
+  /* Microsoft's DIA expects section contributions to be sorted by section
+     number and offset, otherwise it will be unable to resolve line numbers.  */
+
+  sc_in = xmalloc (num_sc * sizeof (* sc_in));
+  sc2 = sc_in;
 
   mod_index = 0;
   for (bfd *in = coff_data (abfd)->link_info->input_bfds; in;
@@ -4177,32 +4210,43 @@ create_section_contrib_substream (bfd *abfd, void **data, uint32_t *size)
     {
       for (asection *s = in->sections; s; s = s->next)
 	{
-	  uint16_t sect_num;
-
 	  if (s->size == 0 || discarded_section (s))
 	    continue;
 
-	  sect_num = find_section_number (abfd, s->output_section);
-
-	  memcpy (&sc->characteristics,
-		  sect_flags + ((sect_num - 1) * sizeof (uint32_t)),
-		  sizeof (uint32_t));
-
-	  bfd_putl16 (sect_num, &sc->section);
-	  bfd_putl16 (0, &sc->padding1);
-	  bfd_putl32 (s->output_offset, &sc->offset);
-	  bfd_putl32 (s->size, &sc->size);
-	  bfd_putl16 (mod_index, &sc->module_index);
-	  bfd_putl16 (0, &sc->padding2);
-	  bfd_putl32 (0, &sc->data_crc);
-	  bfd_putl32 (0, &sc->reloc_crc);
+	  sc2->s = s;
+	  sc2->sect_num = find_section_number (abfd, s->output_section);
+	  sc2->mod_index = mod_index;
 
-	  sc++;
+	  sc2++;
 	}
 
       mod_index++;
     }
 
+  qsort (sc_in, num_sc, sizeof (* sc_in), section_contribs_compare);
+
+  ptr = *data;
+  sc = (struct section_contribution *) (ptr + 1); /* Skip the version word.  */
+
+  for (unsigned int i = 0; i < num_sc; i++)
+    {
+      memcpy (&sc->characteristics,
+	      sect_flags + ((sc_in[i].sect_num - 1) * sizeof (uint32_t)),
+	      sizeof (uint32_t));
+
+      bfd_putl16 (sc_in[i].sect_num, &sc->section);
+      bfd_putl16 (0, &sc->padding1);
+      bfd_putl32 (sc_in[i].s->output_offset, &sc->offset);
+      bfd_putl32 (sc_in[i].s->size, &sc->size);
+      bfd_putl16 (sc_in[i].mod_index, &sc->module_index);
+      bfd_putl16 (0, &sc->padding2);
+      bfd_putl32 (0, &sc->data_crc);
+      bfd_putl32 (0, &sc->reloc_crc);
+
+      sc++;
+    }
+
+  free (sc_in);
   free (sect_flags);
 
   return true;
diff --git a/ld/testsuite/ld-pe/pdb2-section-contrib.d b/ld/testsuite/ld-pe/pdb2-section-contrib.d
index dd9437214bb..65ed76dafdc 100644
--- a/ld/testsuite/ld-pe/pdb2-section-contrib.d
+++ b/ld/testsuite/ld-pe/pdb2-section-contrib.d
@@ -4,9 +4,9 @@ tmpdir/pdb2-sc:     file format binary
 Contents of section .data:
  0000 2dba2ef1 01000000 00000000 10000000  -...............
  0010 20000060 00000000 00000000 00000000   ..`............
- 0020 02000000 00000000 3d000000 40000040  ........=...@..@
- 0030 00000000 00000000 00000000 01000000  ................
- 0040 10000000 10000000 20000060 01000000  ........ ..`....
+ 0020 01000000 10000000 10000000 20000060  ............ ..`
+ 0030 01000000 00000000 00000000 02000000  ................
+ 0040 00000000 3d000000 40000040 00000000  ....=...@..@....
  0050 00000000 00000000 04000000 00000000  ................
  0060 0c000000 40000042 02000000 00000000  ....@..B........
  0070 00000000                             ....            
\ No newline at end of file
-- 
2.30.2