[PATCH] readelf: print warning for -sW

[PATCH] readelf: print warning for -sW

[Martin Liška]

The option -s accepts in elfutils (compared to binutils) a positional
argument that is name of a symbol table section which should be printed.

Thus, print a reasonable warning if -sW is used:
./src/readelf -sW a.out
WARNING: cannot find section: 'W'

Ready for master?
Thanks,
Martin

src/ChangeLog:

	* readelf.c (print_symtab): Change signature and return true if
	something is printed.
	(process_elf_file): Use it and print warning.

tests/ChangeLog:

	* run-readelf-s.sh: Test -sW.
---
 src/readelf.c          | 23 ++++++++++++++++++-----
 tests/run-readelf-s.sh |  3 +++
 2 files changed, 21 insertions(+), 5 deletions(-)

diff --git a/src/readelf.c b/src/readelf.c
index 3dafb041..cc3e0229 100644
--- a/src/readelf.c
+++ b/src/readelf.c
@@ -306,7 +306,7 @@ static void handle_relocs_rel (Ebl *ebl, GElf_Ehdr *ehdr, Elf_Scn *scn,
 			       GElf_Shdr *shdr);
 static void handle_relocs_rela (Ebl *ebl, GElf_Ehdr *ehdr, Elf_Scn *scn,
 				GElf_Shdr *shdr);
-static void print_symtab (Ebl *ebl, int type);
+static bool print_symtab (Ebl *ebl, int type);
 static void handle_symtab (Ebl *ebl, Elf_Scn *scn, GElf_Shdr *shdr);
 static void print_verinfo (Ebl *ebl);
 static void handle_verneed (Ebl *ebl, Elf_Scn *scn, GElf_Shdr *shdr);
@@ -1022,6 +1022,8 @@ process_elf_file (Dwfl_Module *dwflmod, int fd)
 	goto ebl_error;
     }
 
+  bool symtab_printed = false;
+
   if (print_file_header)
     print_ehdr (ebl, ehdr);
   if (print_section_header)
@@ -1037,11 +1039,17 @@ process_elf_file (Dwfl_Module *dwflmod, int fd)
   if (print_histogram)
     handle_hash (ebl);
   if (print_symbol_table || print_dynsym_table)
-    print_symtab (ebl, SHT_DYNSYM);
+    symtab_printed |= print_symtab (ebl, SHT_DYNSYM);
   if (print_version_info)
     print_verinfo (ebl);
   if (print_symbol_table)
-    print_symtab (ebl, SHT_SYMTAB);
+    symtab_printed |= print_symtab (ebl, SHT_SYMTAB);
+
+  if ((print_symbol_table || print_dynsym_table)
+      && !symtab_printed && symbol_table_section != NULL)
+    printf ("WARNING: %s: '%s'\n", _("cannot find section"),
+        symbol_table_section);
+
   if (print_arch)
     print_liblist (ebl);
   if (print_arch)
@@ -2425,13 +2433,15 @@ handle_relocs_rela (Ebl *ebl, GElf_Ehdr *ehdr, Elf_Scn *scn, GElf_Shdr *shdr)
 }
 
 
-/* Print the program header.  */
-static void
+/* Print the program header.  Return true if a symtab is printed,
+   false otherwise.  */
+static bool
 print_symtab (Ebl *ebl, int type)
 {
   /* Find the symbol table(s).  For this we have to search through the
      section table.  */
   Elf_Scn *scn = NULL;
+  bool symtab_printed = false;
 
   while ((scn = elf_nextscn (ebl->elf, scn)) != NULL)
     {
@@ -2467,8 +2477,11 @@ print_symtab (Ebl *ebl, int type)
 			    elf_ndxscn (scn), elf_errmsg (-1));
 	    }
 	  handle_symtab (ebl, scn, shdr);
+	  symtab_printed = true;
 	}
     }
+
+  return symtab_printed;
 }
 
 
diff --git a/tests/run-readelf-s.sh b/tests/run-readelf-s.sh
index ee1c0e82..c150c165 100755
--- a/tests/run-readelf-s.sh
+++ b/tests/run-readelf-s.sh
@@ -395,4 +395,7 @@ Symbol table [27] '.symtab' contains 42 entries:
    41: 00000000004003a8      0 FUNC    GLOBAL DEFAULT       11 _init
 EOF
 
+${abs_top_builddir}/src/readelf --elf-section -sW testfilebaxmin 2>&1 \
+  | grep "WARNING: cannot find section: 'W'" >/dev/null || exit 2
+
 exit 0
-- 
2.38.1

Re: [PATCH] readelf: print warning for -sW

[Mark Wielaard]

Hi Marin,

On Fri, 2022-11-25 at 14:29 +0100, Martin Liška wrote:
> The option -s accepts in elfutils (compared to binutils) a positional
> argument that is name of a symbol table section which should be
> printed.
> 
> Thus, print a reasonable warning if -sW is used:
> ./src/readelf -sW a.out
> WARNING: cannot find section: 'W'
> 
> Ready for master?

Looks good. But one nitpick below.

> src/ChangeLog:
> 
> 	* readelf.c (print_symtab): Change signature and return true if
> 	something is printed.
> 	(process_elf_file): Use it and print warning.

Aha, we are processing the symbol sections twice, once for 
SHT_DYNSYM, then for SHT_SYMTAB. And the named section should be one or
the other. Good.

> tests/ChangeLog:
> 
> 	* run-readelf-s.sh: Test -sW.

Plus a new testcase. Perfect..

> diff --git a/tests/run-readelf-s.sh b/tests/run-readelf-s.sh
> index ee1c0e82..c150c165 100755
> --- a/tests/run-readelf-s.sh
> +++ b/tests/run-readelf-s.sh
> @@ -395,4 +395,7 @@ Symbol table [27] '.symtab' contains 42 entries:
>     41: 00000000004003a8      0 FUNC    GLOBAL DEFAULT       11 _init
>  EOF
>  
> +${abs_top_builddir}/src/readelf --elf-section -sW testfilebaxmin 2>&1 \
> +  | grep "WARNING: cannot find section: 'W'" >/dev/null || exit 2
> +

You need to run a tests with testrun or testrun_compare so they
actually run against the just build libraries (and so they run under
valgrind when configured with --enable-valgrind).

So in this case just add a testrun in front.

-${abs_top_builddir}/src/readelf --elf-section -sW testfilebaxmin 2>&1 \
+testrun ${abs_top_builddir}/src/readelf --elf-section -sW testfilebaxmin 2>&1 \

OK with that change.

Thanks,

Mark