From: Mark Wielaard <mark@klomp.org>
Date: Mon, 29 Jun 2026 20:43:39 +0000 (+0200)
Subject: readelf: Fix interpretation of offset_size_flag in print_cu_index_section
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=bdd83a9102c0bc92b4e043417f0d3d0b3351d3a3;p=thirdparty%2Felfutils.git

readelf: Fix interpretation of offset_size_flag in print_cu_index_section

The offset_size_flag is an DWARF 6 extension described in
https://dwarfstd.org/issues/220708.2.html

While writing tests for eu-dwp some issues with the eu-readelf display
of the .debug_cu_index were found. The offset_size_flag was only used
for the offsets table, not the size (lengths) table. And if the flag
was set only 4 bytes of the offset were read (instead of 8 bytes).

	* src/readelf.c (print_cu_index_section): Calculate
        lengths_end using off_bytes, use read_8ubyte_unaligned to
        read offsets when offset_size_flag is set, calculate prow
        using off_bytes, read and print sizes based on off_bytes.

Signed-off-by: Mark Wielaard <mark@klomp.org>
---

diff --git a/src/readelf.c b/src/readelf.c
index 8d7950d3..9d3bbbf6 100644
--- a/src/readelf.c
+++ b/src/readelf.c
@@ -12290,6 +12290,7 @@ print_cu_index_section (Dwfl_Module *dwflmod __attribute__ ((unused)),
       readp++;
     }
 
+  /* Both offsets and sizes are either 32 or 64 bits (4 or 8 bytes).  */
   const unsigned char off_bytes = offset_size_flag == 0 ? 4 : 8;
 
   if (unlikely (readp > dataend - 4))
@@ -12325,17 +12326,17 @@ print_cu_index_section (Dwfl_Module *dwflmod __attribute__ ((unused)),
      the hash table (ids of 8 bytes).  */
   const unsigned char *indices = hash_table + slot_count * 8;
   /* Sections used starts after the indices, indices and hash table
-     have the same number of slots, indeces are 4 bytes each, */
+     have the same number of slots, indices are 4 bytes each, */
   const unsigned char *sections = indices + slot_count * 4;
   /* Offset slots for each section follow the one row of sections.  */
   const unsigned char *offsets = sections + section_count * 4;
   /* Size slots for each section follow the offsets (used rows).  */
   const unsigned char *lengths = (offsets +
 				  unit_count * section_count * off_bytes);
-  /* The size table has one row of section_count 4-byte slots per unit,
+  /* The size table has one row of section_count slots per unit,
      just like the offset table, so it spans unit_count rows (not one).  */
   const unsigned char *lengths_end = (lengths +
-				      unit_count * section_count * 4);
+				      unit_count * section_count * off_bytes);
 
   /* Sanity check the above against dataend.  */
   if ((slot_count > UINT32_MAX / 8)
@@ -12395,7 +12396,7 @@ print_cu_index_section (Dwfl_Module *dwflmod __attribute__ ((unused)),
 	  else
 	    for (size_t j = 0; j < section_count; j++)
 	      {
-		uint64_t off = read_4ubyte_unaligned (dbg, prow + j * 8);
+		uint64_t off = read_8ubyte_unaligned (dbg, prow + j * 8);
 		fprintf (out, " %6" PRIu64, off);
 	      }
 	  fprintf (out, "\n");
@@ -12433,12 +12434,20 @@ print_cu_index_section (Dwfl_Module *dwflmod __attribute__ ((unused)),
 	      continue;
 	    }
 	  /* Note row is one based, not zero based.  */
-	  const unsigned char *prow = lengths + (row - 1) * section_count * 4;
-	  for (size_t j = 0; j < section_count; j++)
-	    {
-	      uint32_t off = read_4ubyte_unaligned (dbg, prow + j * 4);
-	      fprintf (out, " %6" PRIu32, off);
-	    }
+	  const unsigned char *prow = (lengths
+				       + (row - 1) * section_count * off_bytes);
+	  if (off_bytes == 4)
+	    for (size_t j = 0; j < section_count; j++)
+	      {
+		uint32_t sz = read_4ubyte_unaligned (dbg, prow + j * 4);
+		fprintf (out, " %6" PRIu32, sz);
+	      }
+	  else
+	    for (size_t j = 0; j < section_count; j++)
+	      {
+		uint64_t sz = read_8ubyte_unaligned (dbg, prow + j * 8);
+		fprintf (out, " %6" PRIu64, sz);
+	      }
 	  fprintf (out, "\n");
 	}
     }