Commit: Fix dir[0] in DWARF-5 line tables

Message ID 87a6lqfuzf.fsf@redhat.com
State New
Headers show
Series
  • Commit: Fix dir[0] in DWARF-5 line tables
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Commit Message

Alan Modra via Binutils Aug. 9, 2021, 4:23 p.m.
Hi Guys,

  It was recently reported that when GAS is generating DWARF-5 format
  directory tables the 0'th entry in the table can be a relative path,
  or in fact pretty much anything.  The DWARF standard however requires
  that the entry matches the DW_AT_comp_dir entry in the associated
  .debug_info for the CU.  (See the description of the directories field
  in section 6.2 of the DWARF-5 spec).

  So I am going to apply the patch below to fix the problem.  

Cheers
  Nick

gas/ChangeLog
2021-08-09  Nick Clifton  <nickc@redhat.com>

	* dwarf2dbg.c (get_directory_table_entry): Ensure that dir[0]
	contains current working directory.
	(out_dir_and_file_list): Likewise.
	* testsuite/gas/elf/dwarf-5-dir0.s: New test source file.
	* testsuite/gas/elf/dwarf-5-dir0.d: New test driver.
	* testsuite/gas/elf/elf.exp: Run the new test.
	* testsuite/gas/elf/dwarf-5-file0.d: Adjust expected output.
	* testsuite/gas/i386/dwarf5-line-1.d: Likewise.
	* testsuite/gas/i386/dwarf5-line-2.d: Likewise.

Patch

diff --git a/gas/dwarf2dbg.c b/gas/dwarf2dbg.c
index 460daaa5c0c..8f5248534ad 100644
--- a/gas/dwarf2dbg.c
+++ b/gas/dwarf2dbg.c
@@ -620,7 +620,22 @@  get_directory_table_entry (const char *dirname,
   if (can_use_zero)
     {
       if (dirs == NULL || dirs[0] == NULL)
-	d = 0;
+	{
+	  const char * pwd = getpwd ();
+
+	  if (dwarf_level >= 5 && strcmp (dirname, pwd) != 0)
+	    {
+	      /* In DWARF-5 the 0 entry in the directory table is expected to be
+		 the same as the DW_AT_comp_dir (which is set to the current build
+		 directory).  Since we are about to create a directory entry that
+		 is not the same, allocate the current directory first.
+		 FIXME: Alternatively we could generate an error message here.  */
+	      (void) get_directory_table_entry (pwd, strlen (pwd), true);
+	      d = 1;
+	    }
+	  else
+	    d = 0;
+	}
     }
   else if (d == 0)
     d = 1;
@@ -628,8 +643,8 @@  get_directory_table_entry (const char *dirname,
   if (d >= dirs_allocated)
     {
       unsigned int old = dirs_allocated;
-
-      dirs_allocated = d + 32;
+#define DIR_TABLE_INCREMENT 32
+      dirs_allocated = d + DIR_TABLE_INCREMENT;
       dirs = XRESIZEVEC (char *, dirs, dirs_allocated);
       memset (dirs + old, 0, (dirs_allocated - old) * sizeof (char *));
     }
@@ -779,7 +794,7 @@  allocate_filename_to_slot (const char *dirname,
 	    {
 	      if (dirs == NULL)
 		{
-		  dirs_allocated = files[num].dir + 32;
+		  dirs_allocated = files[num].dir + DIR_TABLE_INCREMENT;
 		  dirs = XCNEWVEC (char *, dirs_allocated);
 		}
 	      
@@ -807,7 +822,7 @@  allocate_filename_to_slot (const char *dirname,
 		{
 		  if (dirs == NULL)
 		    {
-		      dirs_allocated = files[num].dir + 32;
+		      dirs_allocated = files[num].dir + DIR_TABLE_INCREMENT;
 		      dirs = XCNEWVEC (char *, dirs_allocated);
 		    }
 
@@ -840,7 +855,7 @@  allocate_filename_to_slot (const char *dirname,
       dirlen = strlen (dirname);
       file = filename;
     }
-  
+
   d = get_directory_table_entry (dirname, dirlen, num == 0);
   i = num;
 
@@ -2082,7 +2097,12 @@  out_dir_and_file_list (segT line_seg, int sizeof_offset)
 	 Otherwise use pwd as main file directory.  */
       if (dirs_in_use > 0 && dirs != NULL && dirs[0] != NULL)
 	dir = remap_debug_filename (dirs[0]);
-      else if (dirs_in_use > 1 && dirs != NULL && dirs[1] != NULL)
+      else if (dirs_in_use > 1
+	       && dirs != NULL
+	       && dirs[1] != NULL
+	       /* DWARF-5 directory tables expect dir[0] to be the same as
+		  DW_AT_comp_dir, which is the same as pwd.  */
+	       && dwarf_level < 5)
 	dir = remap_debug_filename (dirs[1]);
       else
 	dir = remap_debug_filename (getpwd ());
@@ -2185,8 +2205,8 @@  out_dir_and_file_list (segT line_seg, int sizeof_offset)
 	     uses slot zero, but that is only set explicitly using a
 	     .file 0 directive.  If that isn't used, but file 1 is,
 	     then use that as main file name.  */
-	  if (DWARF2_LINE_VERSION >= 5 && i == 0 && files_in_use >= 1)
-	      files[0].filename = files[1].filename;
+	  if (DWARF2_LINE_VERSION >= 5 && i == 0 && files_in_use >= 1 && files[0].filename == NULL)
+	    files[0].filename = files[1].filename;
 	  else
 	    files[i].filename = "";
 	  if (DWARF2_LINE_VERSION < 5 || i != 0)
diff --git a/gas/testsuite/gas/elf/dwarf-5-file0.d b/gas/testsuite/gas/elf/dwarf-5-file0.d
index 973dc5b9ff3..f60411c8034 100644
--- a/gas/testsuite/gas/elf/dwarf-5-file0.d
+++ b/gas/testsuite/gas/elf/dwarf-5-file0.d
@@ -3,17 +3,18 @@ 
 #readelf: -wl
 
 #...
- The Directory Table \(offset 0x.*, lines 3, columns 1\):
+ The Directory Table \(offset 0x.*, lines 4, columns 1\):
   Entry	Name
-  0	\(indirect line string, offset: 0x.*\): master directory
-  1	\(indirect line string, offset: 0x.*\): secondary directory
-  2	\(indirect line string, offset: 0x.*\): /tmp
+#...
+  1	\(indirect line string, offset: 0x.*\): master directory
+  2	\(indirect line string, offset: 0x.*\): secondary directory
+  3	\(indirect line string, offset: 0x.*\): /tmp
 
  The File Name Table \(offset 0x.*, lines 3, columns 3\):
   Entry	Dir	MD5				Name
-  0	0 0x0	\(indirect line string, offset: 0x.*\): master source file
-  1	1 0x0	\(indirect line string, offset: 0x.*\): secondary source file
-  2	2 0x95828e8bc4f7404dbf7526fb7bd0f192	\(indirect line string, offset: 0x.*\): foo.c
+  0	1 0x0	\(indirect line string, offset: 0x.*\): master source file
+  1	2 0x0	\(indirect line string, offset: 0x.*\): secondary source file
+  2	3 0x95828e8bc4f7404dbf7526fb7bd0f192	\(indirect line string, offset: 0x.*\): foo.c
 #pass
 
 
diff --git a/gas/testsuite/gas/elf/elf.exp b/gas/testsuite/gas/elf/elf.exp
index 23804758c5a..18bc1db8c70 100644
--- a/gas/testsuite/gas/elf/elf.exp
+++ b/gas/testsuite/gas/elf/elf.exp
@@ -297,6 +297,7 @@  if { [is_elf_format] } then {
     run_dump_test "dwarf2-19" $dump_opts
     run_dump_test "dwarf2-20" $dump_opts
     run_dump_test "dwarf-5-file0" $dump_opts
+    run_dump_test "dwarf-5-dir0" $dump_opts
     run_dump_test "dwarf-4-cu" $dump_opts
     run_dump_test "dwarf-5-cu" $dump_opts
     run_dump_test "dwarf-5-nop-for-line-table" $dump_opts
diff --git a/gas/testsuite/gas/i386/dwarf5-line-1.d b/gas/testsuite/gas/i386/dwarf5-line-1.d
index cc90b61fcfd..f57fc47d269 100644
--- a/gas/testsuite/gas/i386/dwarf5-line-1.d
+++ b/gas/testsuite/gas/i386/dwarf5-line-1.d
@@ -33,7 +33,7 @@  Raw dump of debug contents of section \.z?debug_line:
 
  The Directory Table \(offset 0x.*, lines 2, columns 1\):
   Entry	Name
-  0	\(indirect line string, offset: 0x.*\): .*/gas/testsuite/gas/i386
+  0	\(indirect line string, offset: 0x.*\): .*/gas/testsuite
   1	\(indirect line string, offset: 0x.*\): .*/gas/testsuite/gas/i386
 
  The File Name Table \(offset 0x.*, lines 2, columns 3\):
diff --git a/gas/testsuite/gas/i386/dwarf5-line-2.d b/gas/testsuite/gas/i386/dwarf5-line-2.d
index 302a2d8fcc4..2f96df510d0 100644
--- a/gas/testsuite/gas/i386/dwarf5-line-2.d
+++ b/gas/testsuite/gas/i386/dwarf5-line-2.d
@@ -33,7 +33,7 @@  Raw dump of debug contents of section \.z?debug_line:
 
  The Directory Table \(offset 0x.*, lines 2, columns 1\):
   Entry	Name
-  0	\(indirect line string, offset: 0x.*\): .*/gas/testsuite/gas/i386
+  0	\(indirect line string, offset: 0x.*\): .*/gas/testsuite
   1	\(indirect line string, offset: 0x.*\): .*/gas/testsuite/gas/i386
 
  The File Name Table \(offset 0x.*, lines 1, columns 3\):