readelf: Add optional --symbols[=SECTION] argument to select section name.

Make it possible to display just the symbols from a named symbol section
instead of always displaying all symbol sections.

https://bugzilla.redhat.com/show_bug.cgi?id=1396092

Signed-off-by: Mark Wielaard <[email protected]>

Author: Mark Wielaard

src/ChangeLog

@@ -1,3 +1,10 @@
+2016-11-17  Mark Wielaard  <[email protected]>
+
+	* readelf.c (options): Add optional arg SECTION for symbols.
+	(symbol_table_section): New static variable.
+	(parse_opt): Set symbol_table_section on 's'.
+	(print_symtab): Filter on symbol_table_section name is set.
+
 2016-11-10  Mark Wielaard  <[email protected]>
 
 	* ar.c (write_member): Make sure tmpbuf is large enough to contain

src/readelf.c

@@ -85,7 +85,8 @@ static const struct argp_option options[] =
   { "relocs", 'r', NULL, 0, N_("Display relocations"), 0 },
   { "section-headers", 'S', NULL, 0, N_("Display the sections' headers"), 0 },
   { "sections", 'S', NULL, OPTION_ALIAS | OPTION_HIDDEN, NULL, 0 },
-  { "symbols", 's', NULL, 0, N_("Display the symbol table"), 0 },
+  { "symbols", 's', "SECTION", OPTION_ARG_OPTIONAL,
+    N_("Display the symbol table sections"), 0 },
   { "version-info", 'V', NULL, 0, N_("Display versioning information"), 0 },
   { "notes", 'n', NULL, 0, N_("Display the ELF notes"), 0 },
   { "arch-specific", 'A', NULL, 0,
@@ -157,6 +158,9 @@ static bool print_section_header;
 /* True if the symbol table should be printed.  */
 static bool print_symbol_table;
 
+/* A specific section name, or NULL to print all symbol tables.  */
+static char *symbol_table_section;
+
 /* True if the version information should be printed.  */
 static bool print_version_info;
 
@@ -389,6 +393,7 @@ parse_opt (int key, char *arg,
     case 's':
       print_symbol_table = true;
       any_control_option = true;
+      symbol_table_section = arg;
       break;
     case 'V':
       print_version_info = true;
@@ -2236,6 +2241,19 @@ print_symtab (Ebl *ebl, int type)
 
       if (shdr != NULL && shdr->sh_type == (GElf_Word) type)
 	{
+	  if (symbol_table_section != NULL)
+	    {
+	      /* Get the section header string table index.  */
+	      size_t shstrndx;
+	      const char *sname;
+	      if (unlikely (elf_getshdrstrndx (ebl->elf, &shstrndx) < 0))
+		error (EXIT_FAILURE, 0,
+		       gettext ("cannot get section header string table index"));
+	      sname = elf_strptr (ebl->elf, shstrndx, shdr->sh_name);
+	      if (sname == NULL || strcmp (sname, symbol_table_section) != 0)
+		continue;
+	    }
+
 	  if ((shdr->sh_flags & SHF_COMPRESSED) != 0)
 	    {
 	      if (elf_compress (scn, 0, 0) < 0)

tests/ChangeLog

@@ -1,3 +1,7 @@
+2016-11-17  Mark Wielaard  <[email protected]>
+
+	* run-readelf-s.sh: Add --symbols=.dynsym and --symbols=.symtab tests.
+
 2016-11-02  Mark Wielaard  <[email protected]>
 
 	* backtrace-data.c (thread_callback): Add explicit break after error.

tests/run-readelf-s.sh

@@ -273,9 +273,20 @@ Symbol table [28] '.symtab' contains 40 entries:
    39: 0000000000000680      0 FUNC    GLOBAL DEFAULT       11 _init
 EOF
 
+# Display all symbol tables.
 cat testfile.dynsym.in testfile.symtab.in \
   | testrun_compare ${abs_top_builddir}/src/readelf -s testfilebaztab
 
+# Display just .dynsym
+cat testfile.dynsym.in \
+  | testrun_compare ${abs_top_builddir}/src/readelf \
+    --symbols=.dynsym testfilebaztab
+
+# Display just .symtab
+cat testfile.symtab.in \
+  | testrun_compare ${abs_top_builddir}/src/readelf \
+    --symbols=.symtab testfilebaztab
+
 cat testfile.dynsym.in \
   | testrun_compare ${abs_top_builddir}/src/readelf -s testfilebazdbg