Re: [PATCH] objdump: Implement short name search

[Alan Modra <amodra@gmail.com>]

On Wed, Feb 28, 2024 at 06:46:18PM +0100, Mikołaj Piróg wrote:
> This patch introduces the "--short-name-search" option to objdump. When
> this option is used like so: objdump --disassemble=ns::foo
> --short-name-search -C file The objdump will then output disassembled
> output for functions that match the name "ns::foo". The current behaviour
> of objdump in this context is to match the whole function signature, not
> only the name (like so: "ns::foo(int, char const*)"). Option
> "--short-name-search" works only in conjunction with demangling ("-C"). The
> motivation behind this change is to ease a process of a quick disassembly
> of a given function in a binary, since providing the whole function
> signature isn't comfortable. I am not particularly happy with the name for
> this option, but I couldn't come up with anything better. If the
> functionality provided by this patch is desired in objdump, I am happy to
> listen for suggestions for a better name.

I like the idea.  It sounds useful.  Hmm, I wonder could you provide
this functionality without a new option.  ie. When demamgling
automatically detect that the user has specified a function name
without args.

If you do need a new option then the patch needs changes to
doc/binutils.texi, describing what the new objdump option does.

> diff --git a/binutils/objdump.c b/binutils/objdump.c
> index 7beb221cb2f..a013eee3c12 100644
> --- a/binutils/objdump.c
> +++ b/binutils/objdump.c
> @@ -138,6 +138,7 @@ static bool extended_color_output = false; /* --visualize-jumps=extended-color.
>  static int process_links = false;       /* --process-links.  */
>  static int show_all_symbols;            /* --show-all-symbols.  */
>  static bool decompressed_dumps = false; /* -Z, --decompress.  */
> +static bool short_name_search = false; /* --short-name-search */
>  
>  static enum color_selection
>    {
> @@ -272,6 +273,8 @@ usage (FILE *stream, int status)
>    -D, --disassemble-all    Display assembler contents of all sections\n"));
>    fprintf (stream, _("\
>        --disassemble=<sym>  Display assembler contents from <sym>\n"));
> +  fprintf (stream, _("\
> +      --short-name-search  When searching for <sym>, compare functions names, not signatures\n"));
>    fprintf (stream, _("\
>    -S, --source             Intermix source code with disassembly\n"));
>    fprintf (stream, _("\
> @@ -488,7 +491,8 @@ enum option_values
>  #endif
>      OPTION_SFRAME,
>      OPTION_VISUALIZE_JUMPS,
> -    OPTION_DISASSEMBLER_COLOR
> +    OPTION_DISASSEMBLER_COLOR,
> +    OPTION_SYMBOL_SHORT_NAME_SEARCH
>    };
>  
>  static struct option long_options[]=
> @@ -543,6 +547,7 @@ static struct option long_options[]=
>    {"section", required_argument, NULL, 'j'},
>    {"section-headers", no_argument, NULL, 'h'},
>    {"sframe", optional_argument, NULL, OPTION_SFRAME},
> +  {"short-name-search", no_argument, NULL, OPTION_SYMBOL_SHORT_NAME_SEARCH},
>    {"show-all-symbols", no_argument, &show_all_symbols, 1},
>    {"show-raw-insn", no_argument, &show_raw_insn, 1},
>    {"source", no_argument, NULL, 'S'},
> @@ -3905,7 +3910,11 @@ disassemble_section (bfd *abfd, asection *section, void *inf)
>  	      if (do_demangle && name[0] != '\0')
>  		{
>  		  /* Demangle the name.  */
> -		  alloc = bfd_demangle (abfd, name, demangle_flags);
> +		  if (short_name_search)
> +		    alloc = bfd_demangle (abfd, name, DMGL_NO_OPTS);
> +		  else
> +		    alloc = bfd_demangle (abfd, name, demangle_flags);
> +
>  		  if (alloc != NULL)
>  		    name = alloc;
>  		}
> @@ -3923,7 +3932,7 @@ disassemble_section (bfd *abfd, asection *section, void *inf)
>  		   (*rel_pp)->address - rel_offset < sym_offset)
>  			  ++rel_pp;
>  
> -		  if (sym->flags & BSF_FUNCTION)
> +		  if (sym->flags & BSF_FUNCTION && !(short_name_search && do_demangle))
>  		    {
>  		      if (bfd_get_flavour (abfd) == bfd_target_elf_flavour
>  			  && ((elf_symbol_type *) sym)->internal_elf_sym.st_size > 0)

I think this should be moved a little lower, so that loop_until is
function_sym, but I haven't checked fully that this won't exit the
loop prematurely.  Obviously you want to disassemble the entire
function, but also continue looking for another occurrence of the same
function name (with a different signature).

> @@ -6200,6 +6209,9 @@ main (int argc, char **argv)
>  	    dump_sframe_section_name = xstrdup (optarg);
>  	  seenflag = true;
>  	  break;
> +	case OPTION_SYMBOL_SHORT_NAME_SEARCH:
> +	  short_name_search = true;
> +	  break;
>  	case 'G':
>  	  dump_stab_section_info = true;
>  	  seenflag = true;
> @@ -6287,6 +6299,5 @@ main (int argc, char **argv)
>    free (dump_ctf_section_name);
>    free (dump_ctf_parent_name);
>    free ((void *) source_comment);
> -
>    return exit_status;
>  }


-- 
Alan Modra
Australia Development Lab, IBM