Re: [PATCH 05/28] elf: Move ld.so error/help output to _dl_usage

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

On 01/10/2020 13:32, Florian Weimer via Libc-alpha wrote:
> Also add a comment to elf/Makefile, explaining why we cannot use
> config.status for autoconf template processing.

LGTM, with just a nit below.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

> ---
>  elf/Makefile   |  9 ++++++++-
>  elf/dl-main.h  |  5 +++++
>  elf/dl-usage.c | 51 ++++++++++++++++++++++++++++++++++++++++++++++++++
>  elf/rtld.c     | 26 +------------------------
>  4 files changed, 65 insertions(+), 26 deletions(-)
>  create mode 100644 elf/dl-usage.c
> 
> diff --git a/elf/Makefile b/elf/Makefile
> index ab792d45c2..71602d04c1 100644
> --- a/elf/Makefile
> +++ b/elf/Makefile
> @@ -59,7 +59,7 @@ elide-routines.os = $(all-dl-routines) dl-support enbl-secure dl-origin \
>  # ld.so uses those routines, plus some special stuff for being the program
>  # interpreter and operating independent of libc.
>  rtld-routines	= rtld $(all-dl-routines) dl-sysdep dl-environ dl-minimal \
> -  dl-error-minimal dl-conflict dl-hwcaps
> +  dl-error-minimal dl-conflict dl-hwcaps dl-usage
>  all-rtld-routines = $(rtld-routines) $(sysdep-rtld-routines)
>  
>  CFLAGS-dl-runtime.c += -fexceptions -fasynchronous-unwind-tables

Ok.

> @@ -618,6 +618,12 @@ ldso_install: $(inst_rtlddir)/$(rtld-installed-name)
>  endif
>  
>  
> +# Workarounds for ${exec_prefix} expansion in configure variables.
> +# config.status cannot be used directly for processing ldd.bash.in or
> +# expanding variables such as sysconfdir because the expansion
> +# contains the literal string ${exec_prefix}, which is not valid in C
> +# headers or installed shell scripts.
> +
>  ldd-rewrite = -e 's%@RTLD@%$(rtlddir)/$(rtld-installed-name)%g' \
>  	      -e 's%@VERSION@%$(version)%g' \
>  	      -e 's|@PKGVERSION@|$(PKGVERSION)|g' \
> @@ -655,6 +661,7 @@ libof-ldconfig = ldconfig
>  CFLAGS-dl-cache.c += $(SYSCONF-FLAGS)
>  CFLAGS-cache.c += $(SYSCONF-FLAGS)
>  CFLAGS-rtld.c += $(SYSCONF-FLAGS)
> +CFLAGS-dl-usage.c += $(SYSCONF-FLAGS)
>  
>  cpp-srcs-left := $(all-rtld-routines:=.os)
>  lib := rtld

Ok.

> diff --git a/elf/dl-main.h b/elf/dl-main.h
> index ad9250171f..681f366871 100644
> --- a/elf/dl-main.h
> +++ b/elf/dl-main.h
> @@ -19,7 +19,9 @@
>  #ifndef _DL_MAIN
>  #define _DL_MAIN
>  
> +#include <ldsodefs.h>
>  #include <limits.h>
> +#include <stdlib.h>
>  
>  /* Length limits for names and paths, to protect the dynamic linker,
>     particularly when __libc_enable_secure is active.  */
> @@ -92,4 +94,7 @@ call_init_paths (const struct dl_main_state *state)
>    _dl_init_paths (state->library_path);
>  }
>  
> +/* Print ld.so usage information and exit.  */
> +void _dl_usage (void) attribute_hidden __attribute__ ((__noreturn__));
> +
>  #endif /* _DL_MAIN */

Why not use C11 _Noreturn?

> diff --git a/elf/dl-usage.c b/elf/dl-usage.c
> new file mode 100644
> index 0000000000..f3d89d22b7
> --- /dev/null
> +++ b/elf/dl-usage.c
> @@ -0,0 +1,51 @@
> +/* Print usage information and help for ld.so.
> +   Copyright (C) 1995-2020 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/>.  */
> +
> +#include <dl-cache.h>
> +#include <dl-main.h>
> +#include <ldsodefs.h>
> +
> +void
> +_dl_usage (void)
> +{
> +  _dl_fatal_printf ("\
> +Usage: ld.so [OPTION]... EXECUTABLE-FILE [ARGS-FOR-PROGRAM...]\n\
> +You have invoked `ld.so', the helper program for shared library executables.\n\
> +This program usually lives in the file `/lib/ld.so', and special directives\n\
> +in executable files using ELF shared libraries tell the system's program\n\
> +loader to load the helper program from this file.  This helper program loads\n\
> +the shared libraries needed by the program executable, prepares the program\n\
> +to run, and runs it.  You may invoke this helper program directly from the\n\
> +command line to load and run an ELF executable file; this is like executing\n\
> +that file itself, but always uses this helper program from the file you\n\
> +specified, instead of the helper program file specified in the executable\n\
> +file you run.  This is mostly of use for maintainers to test new versions\n\
> +of this helper program; chances are you did not intend to run this program.\n\
> +\n\
> +  --list                list all dependencies and how they are resolved\n\
> +  --verify              verify that given object really is a dynamically linked\n\
> +                        object we can handle\n\
> +  --inhibit-cache       Do not use " LD_SO_CACHE "\n\
> +  --library-path PATH   use given PATH instead of content of the environment\n\
> +                        variable LD_LIBRARY_PATH\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\
> +  --argv0 STRING        set argv[0] to STRING before running\n");
> +}

Ok.

> diff --git a/elf/rtld.c b/elf/rtld.c
> index c1153cb627..f3e1791e2f 100644
> --- a/elf/rtld.c
> +++ b/elf/rtld.c
> @@ -1246,31 +1246,7 @@ dl_main (const ElfW(Phdr) *phdr,
>        /* If we have no further argument the program was called incorrectly.
>  	 Grant the user some education.  */
>        if (_dl_argc < 2)
> -	_dl_fatal_printf ("\
> -Usage: ld.so [OPTION]... EXECUTABLE-FILE [ARGS-FOR-PROGRAM...]\n\
> -You have invoked `ld.so', the helper program for shared library executables.\n\
> -This program usually lives in the file `/lib/ld.so', and special directives\n\
> -in executable files using ELF shared libraries tell the system's program\n\
> -loader to load the helper program from this file.  This helper program loads\n\
> -the shared libraries needed by the program executable, prepares the program\n\
> -to run, and runs it.  You may invoke this helper program directly from the\n\
> -command line to load and run an ELF executable file; this is like executing\n\
> -that file itself, but always uses this helper program from the file you\n\
> -specified, instead of the helper program file specified in the executable\n\
> -file you run.  This is mostly of use for maintainers to test new versions\n\
> -of this helper program; chances are you did not intend to run this program.\n\
> -\n\
> -  --list                list all dependencies and how they are resolved\n\
> -  --verify              verify that given object really is a dynamically linked\n\
> -			object we can handle\n\
> -  --inhibit-cache       Do not use " LD_SO_CACHE "\n\
> -  --library-path PATH   use given PATH instead of content of the environment\n\
> -			variable LD_LIBRARY_PATH\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\
> -  --argv0 STRING        set argv[0] to STRING before running\n");
> +	_dl_usage ();
>  
>        ++_dl_skip_args;
>        --_dl_argc;
> 

Ok.