Re: [PATCH v2] ld.so: add an --argv0 option

[Adhemerval Zanella via Libc-alpha <libc-alpha@sourceware.org>]

On 26/08/2020 08:53, vmihalko--- via Libc-alpha wrote:
> From: Vincent Mihalkovic <vmihalko@redhat.com>

The testcase still misses some pieces (copyright headers, indentation, libsupport
usage).

> 
> ---
>  elf/Makefile          | 13 +++++++++++--
>  elf/argv0test.c       | 18 ++++++++++++++++++
>  elf/rtld.c            | 17 ++++++++++++++++-
>  elf/tst-rtld-argv0.sh | 37 +++++++++++++++++++++++++++++++++++++
>  4 files changed, 82 insertions(+), 3 deletions(-)
>  create mode 100644 elf/argv0test.c
>  create mode 100755 elf/tst-rtld-argv0.sh
> 
> diff --git a/elf/Makefile b/elf/Makefile
> index 0b787218..f38904d8 100644
> --- a/elf/Makefile
> +++ b/elf/Makefile
> @@ -210,7 +210,8 @@ tests += restest1 preloadtest loadfail multiload origtest resolvfail \
>  	 tst-filterobj tst-filterobj-dlopen tst-auxobj tst-auxobj-dlopen \
>  	 tst-audit14 tst-audit15 tst-audit16 \
>  	 tst-single_threaded tst-single_threaded-pthread \
> -	 tst-tls-ie tst-tls-ie-dlmopen
> +	 tst-tls-ie tst-tls-ie-dlmopen \
> +	 argv0test
>  #	 reldep9
>  tests-internal += loadtest unload unload2 circleload1 \
>  	 neededtest neededtest2 neededtest3 neededtest4 \
> @@ -414,7 +415,7 @@ endif
>  ifeq (yes,$(build-shared))
>  ifeq ($(run-built-tests),yes)
>  tests-special += $(objpfx)tst-pathopt.out $(objpfx)tst-rtld-load-self.out \
> -		 $(objpfx)tst-rtld-preload.out
> +		 $(objpfx)tst-rtld-preload.out $(objpfx)argv0test.out
>  endif
>  tests-special += $(objpfx)check-textrel.out $(objpfx)check-execstack.out \
>  		 $(objpfx)check-wx-segment.out \
> @@ -1796,3 +1797,11 @@ $(objpfx)tst-tls-ie-dlmopen.out: \
>    $(objpfx)tst-tls-ie-mod6.so
>  
>  $(objpfx)tst-tls-surplus: $(libdl)
> +
> +ARGV0 = test-argv0
> +$(objpfx)argv0test.out: tst-rtld-argv0.sh $(objpfx)ld.so \
> +			$(objpfx)argv0test
> +	$(SHELL) $< $(objpfx)ld.so $(objpfx)argv0test \
> +            '$(test-wrapper-env)' '$(run_program_env)' \
> +            '$(rpath-link)' '$(ARGV0)' > $@; \
> +    $(evaluate-test)
> diff --git a/elf/argv0test.c b/elf/argv0test.c
> new file mode 100644
> index 00000000..137ced8d
> --- /dev/null
> +++ b/elf/argv0test.c
> @@ -0,0 +1,18 @@

It misses the GPL copyright header.

> +#include <stdio.h>   // for printf
> +#include <string.h>  // for strcmp

Afaik the style prefer C-style comments over C++ one, even though they are
added on C99.

> +
> +static int
> +do_test (int argc, char **argv)
> +{
> +	int result = strcmp (argv[0], "test-argv0");
> +
> +	printf ("argv[0] = %s, strcmp (argv[0], \"test-argv0\") = %d, %s\n",
> +					argv[0], result, !result ? "ok" : "wrong");
> +
> +	return result;
> +
> +}
> +
> +
> +#define TEST_FUNCTION_ARGV do_test
> +#include <support/test-driver.c>

The indentation it still off, it should be use double space not four space.
Also a simple implementation using libsupport would be:

  #include <support/check.h>

  static int
  do_test (int argc, char **argv)
  {
     TEST_COMPARE_BLOB (argv[0], strlen (argv[0]),
			"test-argv0", strlen ("test-argv0"));
     return 0;
  }

  #define TEST_FUNCTION_ARGV do_test
  #include <support/test-driver.c>

> diff --git a/elf/rtld.c b/elf/rtld.c
> index 5b882163..e66e033c 100644
> --- a/elf/rtld.c
> +++ b/elf/rtld.c
> @@ -1202,6 +1202,8 @@ dl_main (const ElfW(Phdr) *phdr,
>  	 installing it.  */
>        rtld_is_main = true;
>  
> +      char *argv0 = NULL;
> +
>        /* Note the place where the dynamic linker actually came from.  */
>        GL(dl_rtld_map).l_name = rtld_progname;
>  
> @@ -1259,6 +1261,14 @@ dl_main (const ElfW(Phdr) *phdr,
>  	else if (! strcmp (_dl_argv[1], "--preload") && _dl_argc > 2)
>  	  {
>  	    preloadarg = _dl_argv[2];
> +	    _dl_skip_args += 2;
> +	    _dl_argc -= 2;
> +	    _dl_argv += 2;
> +	  }
> +	else if (! strcmp (_dl_argv[1], "--argv0") && _dl_argc > 2)
> +	  {
> +	    argv0 = _dl_argv[2];
> +
>  	    _dl_skip_args += 2;
>  	    _dl_argc -= 2;
>  	    _dl_argv += 2;
> @@ -1292,7 +1302,8 @@ of this helper program; chances are you did not intend to run this program.\n\
>    --inhibit-rpath LIST  ignore RUNPATH and RPATH information in object names\n\
>  			in LIST\n\
>    --audit LIST          use objects named in LIST as auditors\n\
> -  --preload LIST        preload objects named in LIST\n");
> +  --preload LIST        preload objects named in LIST\n\
> +  --argv0 STRING        set argv[0] to STRING before running\n");
>  
>        ++_dl_skip_args;
>        --_dl_argc;
> @@ -1384,6 +1395,10 @@ of this helper program; chances are you did not intend to run this program.\n\
>  	    break;
>  	  }
>  #endif
> +
> +      /* Set the argv[0] string now that we've processed the executable.  */
> +      if (argv0 != NULL)
> +		_dl_argv[0] = argv0;
>      }
>    else
>      {
> diff --git a/elf/tst-rtld-argv0.sh b/elf/tst-rtld-argv0.sh
> new file mode 100755
> index 00000000..5f873b6c
> --- /dev/null
> +++ b/elf/tst-rtld-argv0.sh
> @@ -0,0 +1,37 @@
> +#!/bin/sh
> +# Test --argv0 argument ld.so.
> +# Copyright (C) 2019-2020 Free Software Foundation, Inc.
> +# This file is part of the GNU C Library.
> +#
> +# The GNU C Library is free software; you can redistribute it and/or
> +# modify it under the terms of the GNU Lesser General Public
> +# License as published by the Free Software Foundation; either
> +# version 2.1 of the License, or (at your option) any later version.
> +#
> +# The GNU C Library is distributed in the hope that it will be useful,
> +# but WITHOUT ANY WARRANTY; without even the implied warranty of
> +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +# Lesser General Public License for more details.
> +#
> +# You should have received a copy of the GNU Lesser General Public
> +# License along with the GNU C Library; if not, see
> +# <https://www.gnu.org/licenses/>.
> +
> +set -e
> +
> +rtld=$1
> +test_program=$2
> +test_wrapper_env=$3
> +run_program_env=$4
> +library_path=$5
> +argv0=$6
> +
> +echo "# [${test_wrapper_env}] [${run_program_env}] [$rtld] [--library-path]" \
> +     "[$library_path] [--argv0] [$argv0] [$test_program]"
> +${test_wrapper_env} \
> +${run_program_env} \
> +$rtld --library-path "$library_path" \
> +  --argv0 "$argv0" $test_program 2>&1 && rc=0 || rc=$?
> +echo "# exit status $rc"
> +
> +exit $rc
>