diff mbox series

[04/28] elf: Extract command-line/environment variables state from rtld.c

Message ID 37a8980cbc26bdd47c4e4c7b17e373c4f76b71e0.1601569371.git.fweimer@redhat.com
State Committed
Headers show
Series glibc-hwcaps support | expand

Commit Message

Florian Weimer Oct. 1, 2020, 4:31 p.m. UTC
Introduce struct dl_main_state and move it to <dl-main.h>.

This avoids the need for putting state that is only needed during
startup into the ld.so data segment.
---
 elf/dl-main.h |  95 +++++++++++++++++++++++++++++++
 elf/rtld.c    | 155 +++++++++++++++++++-------------------------------
 2 files changed, 154 insertions(+), 96 deletions(-)
 create mode 100644 elf/dl-main.h

Comments

Adhemerval Zanella Oct. 6, 2020, 8:45 p.m. UTC | #1
On 01/10/2020 13:31, Florian Weimer via Libc-alpha wrote:
> Introduce struct dl_main_state and move it to <dl-main.h>.
> 
> This avoids the need for putting state that is only needed during
> startup into the ld.so data segment.

LGTM, with some nits below.

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

> ---
>  elf/dl-main.h |  95 +++++++++++++++++++++++++++++++
>  elf/rtld.c    | 155 +++++++++++++++++++-------------------------------
>  2 files changed, 154 insertions(+), 96 deletions(-)
>  create mode 100644 elf/dl-main.h
> 
> diff --git a/elf/dl-main.h b/elf/dl-main.h
> new file mode 100644
> index 0000000000..ad9250171f
> --- /dev/null
> +++ b/elf/dl-main.h
> @@ -0,0 +1,95 @@
> +/* Information collection during ld.so startup.
> +   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/>.  */
> +
> +#ifndef _DL_MAIN
> +#define _DL_MAIN
> +
> +#include <limits.h>
> +
> +/* Length limits for names and paths, to protect the dynamic linker,
> +   particularly when __libc_enable_secure is active.  */
> +#ifdef NAME_MAX
> +# define SECURE_NAME_LIMIT NAME_MAX
> +#else
> +# define SECURE_NAME_LIMIT 255
> +#endif
> +#ifdef PATH_MAX
> +# define SECURE_PATH_LIMIT PATH_MAX
> +#else
> +# define SECURE_PATH_LIMIT 1024
> +#endif
> +

Ok.

> +/* Strings containing colon-separated lists of audit modules.  */
> +struct audit_list
> +{
> +  /* Array of strings containing colon-separated path lists.  Each
> +     audit module needs its own namespace, so pre-allocate the largest
> +     possible list.  */
> +  const char *audit_strings[DL_NNS];
> +
> +  /* Number of entries added to audit_strings.  */
> +  size_t length;
> +
> +  /* Index into the audit_strings array (for the iteration phase).  */
> +  size_t current_index;
> +
> +  /* Tail of audit_strings[current_index] which still needs
> +     processing.  */
> +  const char *current_tail;
> +
> +  /* Scratch buffer for returning a name which is part of the strings
> +     in audit_strings.  */
> +  char fname[SECURE_NAME_LIMIT];
> +};
> +

Ok.

> +/* This is a list of all the modes the dynamic loader can be in.  */
> +enum mode { normal, list, verify, trace };
> +

With this enum now outside rtld.c maybe it would be better to use more
explicit identifiers?

> +/* Aggregated state information extracted from environment variables
> +   and the ld.so command line.  */
> +struct dl_main_state
> +{
> +  struct audit_list audit_list;
> +
> +  /* The library search path.  */
> +  const char *library_path;
> +
> +  /* The list preloaded objects from LD_PRELOAD.  */
> +  const char *preloadlist;
> +
> +  /* The preload list passed as a command argument.  */
> +  const char *preloadarg;
> +
> +  enum mode mode;
> +
> +  /* True if any of the debugging options is enabled.  */
> +  bool any_debug;
> +
> +  /* True if information about versions has to be printed.  */
> +  bool version_info;
> +};

Ok.

> +
> +/* Helper function to invoke _dl_init_paths with the right arguments
> +   from *STATE.  */
> +static inline void
> +call_init_paths (const struct dl_main_state *state)
> +{
> +  _dl_init_paths (state->library_path);
> +}
> +
> +#endif /* _DL_MAIN */

Ok.

> diff --git a/elf/rtld.c b/elf/rtld.c
> index 9918fda05e..c1153cb627 100644
> --- a/elf/rtld.c
> +++ b/elf/rtld.c
> @@ -47,6 +47,7 @@
>  #include <not-cancel.h>
>  #include <array_length.h>
>  #include <libc-early-init.h>
> +#include <dl-main.h>
>  
>  #include <assert.h>
>  
> @@ -111,42 +112,6 @@ static void print_missing_version (int errcode, const char *objname,
>  /* Print the various times we collected.  */
>  static void print_statistics (const hp_timing_t *total_timep);
>  
> -/* Length limits for names and paths, to protect the dynamic linker,
> -   particularly when __libc_enable_secure is active.  */
> -#ifdef NAME_MAX
> -# define SECURE_NAME_LIMIT NAME_MAX
> -#else
> -# define SECURE_NAME_LIMIT 255
> -#endif
> -#ifdef PATH_MAX
> -# define SECURE_PATH_LIMIT PATH_MAX
> -#else
> -# define SECURE_PATH_LIMIT 1024
> -#endif
> -

Ok.

> -/* Strings containing colon-separated lists of audit modules.  */
> -struct audit_list
> -{
> -  /* Array of strings containing colon-separated path lists.  Each
> -     audit module needs its own namespace, so pre-allocate the largest
> -     possible list.  */
> -  const char *audit_strings[DL_NNS];
> -
> -  /* Number of entries added to audit_strings.  */
> -  size_t length;
> -
> -  /* Index into the audit_strings array (for the iteration phase).  */
> -  size_t current_index;
> -
> -  /* Tail of audit_strings[current_index] which still needs
> -     processing.  */
> -  const char *current_tail;
> -
> -  /* Scratch buffer for returning a name which is part of the strings
> -     in audit_strings.  */
> -  char fname[SECURE_NAME_LIMIT];
> -};
> -

Ok.

>  /* Creates an empty audit list.  */
>  static void audit_list_init (struct audit_list *);
>  
> @@ -167,13 +132,13 @@ static void audit_list_add_dynamic_tag (struct audit_list *,
>     audit_list_add_dynamic_tags calls.  */
>  static const char *audit_list_next (struct audit_list *);
>  
> -/* This is a list of all the modes the dynamic loader can be in.  */
> -enum mode { normal, list, verify, trace };
> +/* Initialize *STATE with the defaults.  */
> +static void dl_main_state_init (struct dl_main_state *state);
>  
>  /* Process all environments variables the dynamic linker must recognize.
>     Since all of them start with `LD_' we are a bit smarter while finding
>     all the entries.  */
> -static void process_envvars (enum mode *modep, struct audit_list *);
> +static void process_envvars (struct dl_main_state *state);
>  
>  #ifdef DL_ARGV_NOT_RELRO
>  int _dl_argc attribute_hidden;
> @@ -316,6 +281,18 @@ audit_list_count (struct audit_list *list)
>    return naudit;
>  }
>  

Ok.

> +static void
> +dl_main_state_init (struct dl_main_state *state)
> +{
> +  audit_list_init (&state->audit_list);
> +  state->library_path = NULL;
> +  state->preloadlist = NULL;
> +  state->preloadarg = NULL;
> +  state->mode = normal;
> +  state->any_debug = false;
> +  state->version_info = false;
> +}
> +

Ok.

>  #ifndef HAVE_INLINED_SYSCALLS
>  /* Set nonzero during loading and initialization of executable and
>     libraries, cleared before the executable's entry point runs.  This
> @@ -900,15 +877,6 @@ security_init (void)
>  
>  #include <setup-vdso.h>
>  
> -/* The library search path.  */
> -static const char *library_path attribute_relro;
> -/* The list preloaded objects.  */
> -static const char *preloadlist attribute_relro;
> -/* Nonzero if information about versions has to be printed.  */
> -static int version_info attribute_relro;
> -/* The preload list passed as a command argument.  */
> -static const char *preloadarg attribute_relro;
> -

Ok.

>  /* The LD_PRELOAD environment variable gives list of libraries
>     separated by white space or colons that are loaded before the
>     executable's dependencies and prepended to the global scope list.
> @@ -1150,7 +1118,6 @@ dl_main (const ElfW(Phdr) *phdr,
>  	 ElfW(auxv_t) *auxv)
>  {
>    const ElfW(Phdr) *ph;
> -  enum mode mode;
>    struct link_map *main_map;
>    size_t file_size;
>    char *file;
> @@ -1160,8 +1127,8 @@ dl_main (const ElfW(Phdr) *phdr,
>    bool rtld_is_main = false;
>    void *tcbp = NULL;
>  
> -  struct audit_list audit_list;
> -  audit_list_init (&audit_list);
> +  struct dl_main_state state;
> +  dl_main_state_init (&state);
>  
>    GL(dl_init_static_tls) = &_dl_nothread_init_static_tls;
>  

Ok.

> @@ -1176,7 +1143,7 @@ dl_main (const ElfW(Phdr) *phdr,
>    GL(dl_make_stack_executable_hook) = &_dl_make_stack_executable;
>  
>    /* Process the environment variable which control the behaviour.  */
> -  process_envvars (&mode, &audit_list);
> +  process_envvars (&state);
>  
>  #ifndef HAVE_INLINED_SYSCALLS
>    /* Set up a flag which tells we are just starting.  */

Ok.

> @@ -1210,7 +1177,7 @@ dl_main (const ElfW(Phdr) *phdr,
>        while (_dl_argc > 1)
>  	if (! strcmp (_dl_argv[1], "--list"))
>  	  {
> -	    mode = list;
> +	    state.mode = list;
>  	    GLRO(dl_lazy) = -1;	/* This means do no dependency analysis.  */
>  
>  	    ++_dl_skip_args;
> @@ -1219,7 +1186,7 @@ dl_main (const ElfW(Phdr) *phdr,
>  	  }
>  	else if (! strcmp (_dl_argv[1], "--verify"))
>  	  {
> -	    mode = verify;
> +	    state.mode = verify;
>  
>  	    ++_dl_skip_args;
>  	    --_dl_argc;
> @@ -1235,7 +1202,7 @@ dl_main (const ElfW(Phdr) *phdr,
>  	else if (! strcmp (_dl_argv[1], "--library-path")
>  		 && _dl_argc > 2)
>  	  {
> -	    library_path = _dl_argv[2];
> +	    state.library_path = _dl_argv[2];
>  
>  	    _dl_skip_args += 2;
>  	    _dl_argc -= 2;

Ok.

> @@ -1252,7 +1219,7 @@ dl_main (const ElfW(Phdr) *phdr,
>  	  }
>  	else if (! strcmp (_dl_argv[1], "--audit") && _dl_argc > 2)
>  	  {
> -	    audit_list_add_string (&audit_list, _dl_argv[2]);
> +	    audit_list_add_string (&state.audit_list, _dl_argv[2]);
>  
>  	    _dl_skip_args += 2;
>  	    _dl_argc -= 2;
> @@ -1260,7 +1227,7 @@ dl_main (const ElfW(Phdr) *phdr,
>  	  }
>  	else if (! strcmp (_dl_argv[1], "--preload") && _dl_argc > 2)
>  	  {
> -	    preloadarg = _dl_argv[2];
> +	    state.preloadarg = _dl_argv[2];
>  	    _dl_skip_args += 2;
>  	    _dl_argc -= 2;
>  	    _dl_argv += 2;

Ok.

> @@ -1328,7 +1295,7 @@ of this helper program; chances are you did not intend to run this program.\n\
>  	    break;
>  	  }
>  
> -      if (__builtin_expect (mode, normal) == verify)
> +      if (__builtin_expect (state.mode, normal) == verify)
>  	{
>  	  const char *objname;
>  	  const char *err_str = NULL;

Use __glibc_likely here.

> @@ -1357,7 +1324,7 @@ of this helper program; chances are you did not intend to run this program.\n\
>        /* Now the map for the main executable is available.  */
>        main_map = GL(dl_ns)[LM_ID_BASE]._ns_loaded;
>  
> -      if (__builtin_expect (mode, normal) == normal
> +      if (__builtin_expect (state.mode, normal) == normal
>  	  && GL(dl_rtld_map).l_info[DT_SONAME] != NULL
>  	  && main_map->l_info[DT_SONAME] != NULL
>  	  && strcmp ((const char *) D_PTR (&GL(dl_rtld_map), l_info[DT_STRTAB])

Ditto.

> @@ -1604,7 +1571,7 @@ of this helper program; chances are you did not intend to run this program.\n\
>        _dl_setup_hash (main_map);
>      }
>  
> -  if (__builtin_expect (mode, normal) == verify)
> +  if (__builtin_expect (state.mode, normal) == verify)
>      {
>        /* We were called just to verify that this is a dynamic
>  	 executable using us as the program interpreter.  Exit with an

Ditto.

> @@ -1634,7 +1601,7 @@ of this helper program; chances are you did not intend to run this program.\n\
>  
>    /* Initialize the data structures for the search paths for shared
>       objects.  */
> -  _dl_init_paths (library_path);
> +  call_init_paths (&state);
>  
>    /* Initialize _r_debug.  */
>    struct r_debug *r = _dl_debug_initialize (GL(dl_rtld_map).l_addr,

Ok.

> @@ -1699,14 +1666,14 @@ of this helper program; chances are you did not intend to run this program.\n\
>      /* Assign a module ID.  Do this before loading any audit modules.  */
>      GL(dl_rtld_map).l_tls_modid = _dl_next_tls_modid ();
>  
> -  audit_list_add_dynamic_tag (&audit_list, main_map, DT_AUDIT);
> -  audit_list_add_dynamic_tag (&audit_list, main_map, DT_DEPAUDIT);
> +  audit_list_add_dynamic_tag (&state.audit_list, main_map, DT_AUDIT);
> +  audit_list_add_dynamic_tag (&state.audit_list, main_map, DT_DEPAUDIT);
>  
>    /* If we have auditing DSOs to load, do it now.  */
>    bool need_security_init = true;
> -  if (audit_list.length > 0)
> +  if (state.audit_list.length > 0)
>      {
> -      size_t naudit = audit_list_count (&audit_list);
> +      size_t naudit = audit_list_count (&state.audit_list);
>  
>        /* Since we start using the auditing DSOs right away we need to
>  	 initialize the data structures now.  */
> @@ -1719,7 +1686,7 @@ of this helper program; chances are you did not intend to run this program.\n\
>        security_init ();
>        need_security_init = false;
>  
> -      load_audit_modules (main_map, &audit_list);
> +      load_audit_modules (main_map, &state.audit_list);
>  
>        /* The count based on audit strings may overestimate the number
>  	 of audit modules that got loaded, but not underestimate.  */

Ok.

> @@ -1774,19 +1741,21 @@ of this helper program; chances are you did not intend to run this program.\n\
>    struct link_map **preloads = NULL;
>    unsigned int npreloads = 0;
>  
> -  if (__glibc_unlikely (preloadlist != NULL))
> +  if (__glibc_unlikely (state.preloadlist != NULL))
>      {
>        RTLD_TIMING_VAR (start);
>        rtld_timer_start (&start);
> -      npreloads += handle_preload_list (preloadlist, main_map, "LD_PRELOAD");
> +      npreloads += handle_preload_list (state.preloadlist, main_map,
> +					"LD_PRELOAD");
>        rtld_timer_accum (&load_time, start);
>      }
>  
> -  if (__glibc_unlikely (preloadarg != NULL))
> +  if (__glibc_unlikely (state.preloadarg != NULL))
>      {
>        RTLD_TIMING_VAR (start);
>        rtld_timer_start (&start);
> -      npreloads += handle_preload_list (preloadarg, main_map, "--preload");
> +      npreloads += handle_preload_list (state.preloadarg, main_map,
> +					"--preload");
>        rtld_timer_accum (&load_time, start);
>      }
>  

Ok.

> @@ -1893,7 +1862,8 @@ of this helper program; chances are you did not intend to run this program.\n\
>    {
>      RTLD_TIMING_VAR (start);
>      rtld_timer_start (&start);
> -    _dl_map_object_deps (main_map, preloads, npreloads, mode == trace, 0);
> +    _dl_map_object_deps (main_map, preloads, npreloads,
> +			 state.mode == trace, 0);
>      rtld_timer_accum (&load_time, start);
>    }
>  
> @@ -1920,7 +1890,7 @@ of this helper program; chances are you did not intend to run this program.\n\
>        rtld_multiple_ref = true;
>  
>        GL(dl_rtld_map).l_prev = main_map->l_searchlist.r_list[i - 1];
> -      if (__builtin_expect (mode, normal) == normal)
> +      if (__builtin_expect (state.mode, normal) == normal)
>  	{
>  	  GL(dl_rtld_map).l_next = (i + 1 < main_map->l_searchlist.r_nlist
>  				    ? main_map->l_searchlist.r_list[i + 1]

Ok.

> @@ -1953,8 +1923,8 @@ of this helper program; chances are you did not intend to run this program.\n\
>       versions we need.  */
>    {
>      struct version_check_args args;
> -    args.doexit = mode == normal;
> -    args.dotrace = mode == trace;
> +    args.doexit = state.mode == normal;
> +    args.dotrace = state.mode == trace;
>      _dl_receive_error (print_missing_version, version_check_doit, &args);
>    }
>  

Ok.

> @@ -1974,7 +1944,7 @@ of this helper program; chances are you did not intend to run this program.\n\
>         earlier.  */
>      security_init ();
>  
> -  if (__builtin_expect (mode, normal) != normal)
> +  if (__builtin_expect (state.mode, normal) != normal)
>      {
>        /* We were run just to list the shared libraries.  It is
>  	 important that we do this before real relocation, because the

Use __glibc_likely.

> @@ -2076,7 +2046,7 @@ of this helper program; chances are you did not intend to run this program.\n\
>  			  (size_t) l->l_map_start);
>  	}
>  
> -      if (__builtin_expect (mode, trace) != trace)
> +      if (__builtin_expect (state.mode, trace) != trace)
>  	for (i = 1; i < (unsigned int) _dl_argc; ++i)
>  	  {
>  	    const ElfW(Sym) *ref = NULL;
> @@ -2130,7 +2100,7 @@ of this helper program; chances are you did not intend to run this program.\n\
>  		}
>  	    }
>  #define VERNEEDTAG (DT_NUM + DT_THISPROCNUM + DT_VERSIONTAGIDX (DT_VERNEED))
> -	  if (version_info)
> +	  if (state.version_info)
>  	    {
>  	      /* Print more information.  This means here, print information
>  		 about the versions needed.  */
> @@ -2492,13 +2462,10 @@ print_missing_version (int errcode __attribute__ ((unused)),
>  		    objname, errstring);
>  }
>  
> -/* Nonzero if any of the debugging options is enabled.  */
> -static int any_debug attribute_relro;
> -
>  /* Process the string given as the parameter which explains which debugging
>     options are enabled.  */
>  static void
> -process_dl_debug (const char *dl_debug)
> +process_dl_debug (struct dl_main_state *state, const char *dl_debug)
>  {
>    /* When adding new entries make sure that the maximal length of a name
>       is correctly handled in the LD_DEBUG_HELP code below.  */

Ok.

> @@ -2555,7 +2522,7 @@ process_dl_debug (const char *dl_debug)
>  		&& memcmp (dl_debug, debopts[cnt].name, len) == 0)
>  	      {
>  		GLRO(dl_debug_mask) |= debopts[cnt].mask;
> -		any_debug = 1;
> +		state->any_debug = true;
>  		break;
>  	      }
>  
> @@ -2609,11 +2576,10 @@ extern char **_environ attribute_hidden;
>  
>  
>  static void
> -process_envvars (enum mode *modep, struct audit_list *audit_list)
> +process_envvars (struct dl_main_state *state)
>  {
>    char **runp = _environ;
>    char *envline;
> -  enum mode mode = normal;
>    char *debug_output = NULL;
>  
>    /* This is the default place for profiling data file.  */
> @@ -2645,25 +2611,25 @@ process_envvars (enum mode *modep, struct audit_list *audit_list)
>  	  /* Debugging of the dynamic linker?  */
>  	  if (memcmp (envline, "DEBUG", 5) == 0)
>  	    {
> -	      process_dl_debug (&envline[6]);
> +	      process_dl_debug (state, &envline[6]);
>  	      break;
>  	    }
>  	  if (memcmp (envline, "AUDIT", 5) == 0)
> -	    audit_list_add_string (audit_list, &envline[6]);
> +	    audit_list_add_string (&state->audit_list, &envline[6]);
>  	  break;
>  
>  	case 7:
>  	  /* Print information about versions.  */
>  	  if (memcmp (envline, "VERBOSE", 7) == 0)
>  	    {
> -	      version_info = envline[8] != '\0';
> +	      state->version_info = envline[8] != '\0';
>  	      break;
>  	    }
>  
>  	  /* List of objects to be preloaded.  */
>  	  if (memcmp (envline, "PRELOAD", 7) == 0)
>  	    {
> -	      preloadlist = &envline[8];
> +	      state->preloadlist = &envline[8];
>  	      break;
>  	    }
>  

Ok.

> @@ -2712,7 +2678,7 @@ process_envvars (enum mode *modep, struct audit_list *audit_list)
>  	  if (!__libc_enable_secure
>  	      && memcmp (envline, "LIBRARY_PATH", 12) == 0)
>  	    {
> -	      library_path = &envline[13];
> +	      state->library_path = &envline[13];
>  	      break;
>  	    }
>  
> @@ -2754,7 +2720,7 @@ process_envvars (enum mode *modep, struct audit_list *audit_list)
>  	  /* The mode of the dynamic linker can be set.  */
>  	  if (memcmp (envline, "TRACE_PRELINKING", 16) == 0)
>  	    {
> -	      mode = trace;
> +	      state->mode = trace;
>  	      GLRO(dl_verbose) = 1;
>  	      GLRO(dl_debug_mask) |= DL_DEBUG_PRELINK;
>  	      GLRO(dl_trace_prelink) = &envline[17];
> @@ -2764,7 +2730,7 @@ process_envvars (enum mode *modep, struct audit_list *audit_list)
>  	case 20:
>  	  /* The mode of the dynamic linker can be set.  */
>  	  if (memcmp (envline, "TRACE_LOADED_OBJECTS", 20) == 0)
> -	    mode = trace;
> +	    state->mode = trace;
>  	  break;
>  
>  	  /* We might have some extra environment variable to handle.  This
> @@ -2777,9 +2743,6 @@ process_envvars (enum mode *modep, struct audit_list *audit_list)
>  	}
>      }
>  
> -  /* The caller wants this information.  */
> -  *modep = mode;
> -
>    /* Extra security for SUID binaries.  Remove all dangerous environment
>       variables.  */
>    if (__builtin_expect (__libc_enable_secure, 0))
> @@ -2808,13 +2771,13 @@ process_envvars (enum mode *modep, struct audit_list *audit_list)
>  	  GLRO(dl_debug_mask) = 0;
>  	}
>  
> -      if (mode != normal)
> +      if (state->mode != normal)
>  	_exit (5);
>      }
>    /* If we have to run the dynamic linker in debugging mode and the
>       LD_DEBUG_OUTPUT environment variable is given, we write the debug
>       messages to this file.  */
> -  else if (any_debug && debug_output != NULL)
> +  else if (state->any_debug && debug_output != NULL)
>      {
>        const int flags = O_WRONLY | O_APPEND | O_CREAT | O_NOFOLLOW;
>        size_t name_len = strlen (debug_output);
> 

Ok.
Florian Weimer Oct. 8, 2020, 11:32 a.m. UTC | #2
* Adhemerval Zanella via Libc-alpha:

>> +/* This is a list of all the modes the dynamic loader can be in.  */
>> +enum mode { normal, list, verify, trace };
>> +
>
> With this enum now outside rtld.c maybe it would be better to use more
> explicit identifiers?

I pushed this with this suggested change as:

commit 2bf9e641fd50ec34b04b70829679abf64fc0ed78
Author: Florian Weimer <fweimer@redhat.com>
Date:   Thu Oct 8 10:57:09 2020 +0200

    elf: Extract command-line/environment variables state from rtld.c
    
    Introduce struct dl_main_state and move it to <dl-main.h>.  Rename
    enum mode to enum rtld_mode and add the rtld_mode_ prefix to the enum
    constants.
    
    This avoids the need for putting state that is only needed during
    startup into the ld.so data segment.

It also includes the __glibc_likely/__glibc_unlikely changes.

Thanks,
Florian
diff mbox series

Patch

diff --git a/elf/dl-main.h b/elf/dl-main.h
new file mode 100644
index 0000000000..ad9250171f
--- /dev/null
+++ b/elf/dl-main.h
@@ -0,0 +1,95 @@ 
+/* Information collection during ld.so startup.
+   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/>.  */
+
+#ifndef _DL_MAIN
+#define _DL_MAIN
+
+#include <limits.h>
+
+/* Length limits for names and paths, to protect the dynamic linker,
+   particularly when __libc_enable_secure is active.  */
+#ifdef NAME_MAX
+# define SECURE_NAME_LIMIT NAME_MAX
+#else
+# define SECURE_NAME_LIMIT 255
+#endif
+#ifdef PATH_MAX
+# define SECURE_PATH_LIMIT PATH_MAX
+#else
+# define SECURE_PATH_LIMIT 1024
+#endif
+
+/* Strings containing colon-separated lists of audit modules.  */
+struct audit_list
+{
+  /* Array of strings containing colon-separated path lists.  Each
+     audit module needs its own namespace, so pre-allocate the largest
+     possible list.  */
+  const char *audit_strings[DL_NNS];
+
+  /* Number of entries added to audit_strings.  */
+  size_t length;
+
+  /* Index into the audit_strings array (for the iteration phase).  */
+  size_t current_index;
+
+  /* Tail of audit_strings[current_index] which still needs
+     processing.  */
+  const char *current_tail;
+
+  /* Scratch buffer for returning a name which is part of the strings
+     in audit_strings.  */
+  char fname[SECURE_NAME_LIMIT];
+};
+
+/* This is a list of all the modes the dynamic loader can be in.  */
+enum mode { normal, list, verify, trace };
+
+/* Aggregated state information extracted from environment variables
+   and the ld.so command line.  */
+struct dl_main_state
+{
+  struct audit_list audit_list;
+
+  /* The library search path.  */
+  const char *library_path;
+
+  /* The list preloaded objects from LD_PRELOAD.  */
+  const char *preloadlist;
+
+  /* The preload list passed as a command argument.  */
+  const char *preloadarg;
+
+  enum mode mode;
+
+  /* True if any of the debugging options is enabled.  */
+  bool any_debug;
+
+  /* True if information about versions has to be printed.  */
+  bool version_info;
+};
+
+/* Helper function to invoke _dl_init_paths with the right arguments
+   from *STATE.  */
+static inline void
+call_init_paths (const struct dl_main_state *state)
+{
+  _dl_init_paths (state->library_path);
+}
+
+#endif /* _DL_MAIN */
diff --git a/elf/rtld.c b/elf/rtld.c
index 9918fda05e..c1153cb627 100644
--- a/elf/rtld.c
+++ b/elf/rtld.c
@@ -47,6 +47,7 @@ 
 #include <not-cancel.h>
 #include <array_length.h>
 #include <libc-early-init.h>
+#include <dl-main.h>
 
 #include <assert.h>
 
@@ -111,42 +112,6 @@  static void print_missing_version (int errcode, const char *objname,
 /* Print the various times we collected.  */
 static void print_statistics (const hp_timing_t *total_timep);
 
-/* Length limits for names and paths, to protect the dynamic linker,
-   particularly when __libc_enable_secure is active.  */
-#ifdef NAME_MAX
-# define SECURE_NAME_LIMIT NAME_MAX
-#else
-# define SECURE_NAME_LIMIT 255
-#endif
-#ifdef PATH_MAX
-# define SECURE_PATH_LIMIT PATH_MAX
-#else
-# define SECURE_PATH_LIMIT 1024
-#endif
-
-/* Strings containing colon-separated lists of audit modules.  */
-struct audit_list
-{
-  /* Array of strings containing colon-separated path lists.  Each
-     audit module needs its own namespace, so pre-allocate the largest
-     possible list.  */
-  const char *audit_strings[DL_NNS];
-
-  /* Number of entries added to audit_strings.  */
-  size_t length;
-
-  /* Index into the audit_strings array (for the iteration phase).  */
-  size_t current_index;
-
-  /* Tail of audit_strings[current_index] which still needs
-     processing.  */
-  const char *current_tail;
-
-  /* Scratch buffer for returning a name which is part of the strings
-     in audit_strings.  */
-  char fname[SECURE_NAME_LIMIT];
-};
-
 /* Creates an empty audit list.  */
 static void audit_list_init (struct audit_list *);
 
@@ -167,13 +132,13 @@  static void audit_list_add_dynamic_tag (struct audit_list *,
    audit_list_add_dynamic_tags calls.  */
 static const char *audit_list_next (struct audit_list *);
 
-/* This is a list of all the modes the dynamic loader can be in.  */
-enum mode { normal, list, verify, trace };
+/* Initialize *STATE with the defaults.  */
+static void dl_main_state_init (struct dl_main_state *state);
 
 /* Process all environments variables the dynamic linker must recognize.
    Since all of them start with `LD_' we are a bit smarter while finding
    all the entries.  */
-static void process_envvars (enum mode *modep, struct audit_list *);
+static void process_envvars (struct dl_main_state *state);
 
 #ifdef DL_ARGV_NOT_RELRO
 int _dl_argc attribute_hidden;
@@ -316,6 +281,18 @@  audit_list_count (struct audit_list *list)
   return naudit;
 }
 
+static void
+dl_main_state_init (struct dl_main_state *state)
+{
+  audit_list_init (&state->audit_list);
+  state->library_path = NULL;
+  state->preloadlist = NULL;
+  state->preloadarg = NULL;
+  state->mode = normal;
+  state->any_debug = false;
+  state->version_info = false;
+}
+
 #ifndef HAVE_INLINED_SYSCALLS
 /* Set nonzero during loading and initialization of executable and
    libraries, cleared before the executable's entry point runs.  This
@@ -900,15 +877,6 @@  security_init (void)
 
 #include <setup-vdso.h>
 
-/* The library search path.  */
-static const char *library_path attribute_relro;
-/* The list preloaded objects.  */
-static const char *preloadlist attribute_relro;
-/* Nonzero if information about versions has to be printed.  */
-static int version_info attribute_relro;
-/* The preload list passed as a command argument.  */
-static const char *preloadarg attribute_relro;
-
 /* The LD_PRELOAD environment variable gives list of libraries
    separated by white space or colons that are loaded before the
    executable's dependencies and prepended to the global scope list.
@@ -1150,7 +1118,6 @@  dl_main (const ElfW(Phdr) *phdr,
 	 ElfW(auxv_t) *auxv)
 {
   const ElfW(Phdr) *ph;
-  enum mode mode;
   struct link_map *main_map;
   size_t file_size;
   char *file;
@@ -1160,8 +1127,8 @@  dl_main (const ElfW(Phdr) *phdr,
   bool rtld_is_main = false;
   void *tcbp = NULL;
 
-  struct audit_list audit_list;
-  audit_list_init (&audit_list);
+  struct dl_main_state state;
+  dl_main_state_init (&state);
 
   GL(dl_init_static_tls) = &_dl_nothread_init_static_tls;
 
@@ -1176,7 +1143,7 @@  dl_main (const ElfW(Phdr) *phdr,
   GL(dl_make_stack_executable_hook) = &_dl_make_stack_executable;
 
   /* Process the environment variable which control the behaviour.  */
-  process_envvars (&mode, &audit_list);
+  process_envvars (&state);
 
 #ifndef HAVE_INLINED_SYSCALLS
   /* Set up a flag which tells we are just starting.  */
@@ -1210,7 +1177,7 @@  dl_main (const ElfW(Phdr) *phdr,
       while (_dl_argc > 1)
 	if (! strcmp (_dl_argv[1], "--list"))
 	  {
-	    mode = list;
+	    state.mode = list;
 	    GLRO(dl_lazy) = -1;	/* This means do no dependency analysis.  */
 
 	    ++_dl_skip_args;
@@ -1219,7 +1186,7 @@  dl_main (const ElfW(Phdr) *phdr,
 	  }
 	else if (! strcmp (_dl_argv[1], "--verify"))
 	  {
-	    mode = verify;
+	    state.mode = verify;
 
 	    ++_dl_skip_args;
 	    --_dl_argc;
@@ -1235,7 +1202,7 @@  dl_main (const ElfW(Phdr) *phdr,
 	else if (! strcmp (_dl_argv[1], "--library-path")
 		 && _dl_argc > 2)
 	  {
-	    library_path = _dl_argv[2];
+	    state.library_path = _dl_argv[2];
 
 	    _dl_skip_args += 2;
 	    _dl_argc -= 2;
@@ -1252,7 +1219,7 @@  dl_main (const ElfW(Phdr) *phdr,
 	  }
 	else if (! strcmp (_dl_argv[1], "--audit") && _dl_argc > 2)
 	  {
-	    audit_list_add_string (&audit_list, _dl_argv[2]);
+	    audit_list_add_string (&state.audit_list, _dl_argv[2]);
 
 	    _dl_skip_args += 2;
 	    _dl_argc -= 2;
@@ -1260,7 +1227,7 @@  dl_main (const ElfW(Phdr) *phdr,
 	  }
 	else if (! strcmp (_dl_argv[1], "--preload") && _dl_argc > 2)
 	  {
-	    preloadarg = _dl_argv[2];
+	    state.preloadarg = _dl_argv[2];
 	    _dl_skip_args += 2;
 	    _dl_argc -= 2;
 	    _dl_argv += 2;
@@ -1328,7 +1295,7 @@  of this helper program; chances are you did not intend to run this program.\n\
 	    break;
 	  }
 
-      if (__builtin_expect (mode, normal) == verify)
+      if (__builtin_expect (state.mode, normal) == verify)
 	{
 	  const char *objname;
 	  const char *err_str = NULL;
@@ -1357,7 +1324,7 @@  of this helper program; chances are you did not intend to run this program.\n\
       /* Now the map for the main executable is available.  */
       main_map = GL(dl_ns)[LM_ID_BASE]._ns_loaded;
 
-      if (__builtin_expect (mode, normal) == normal
+      if (__builtin_expect (state.mode, normal) == normal
 	  && GL(dl_rtld_map).l_info[DT_SONAME] != NULL
 	  && main_map->l_info[DT_SONAME] != NULL
 	  && strcmp ((const char *) D_PTR (&GL(dl_rtld_map), l_info[DT_STRTAB])
@@ -1604,7 +1571,7 @@  of this helper program; chances are you did not intend to run this program.\n\
       _dl_setup_hash (main_map);
     }
 
-  if (__builtin_expect (mode, normal) == verify)
+  if (__builtin_expect (state.mode, normal) == verify)
     {
       /* We were called just to verify that this is a dynamic
 	 executable using us as the program interpreter.  Exit with an
@@ -1634,7 +1601,7 @@  of this helper program; chances are you did not intend to run this program.\n\
 
   /* Initialize the data structures for the search paths for shared
      objects.  */
-  _dl_init_paths (library_path);
+  call_init_paths (&state);
 
   /* Initialize _r_debug.  */
   struct r_debug *r = _dl_debug_initialize (GL(dl_rtld_map).l_addr,
@@ -1699,14 +1666,14 @@  of this helper program; chances are you did not intend to run this program.\n\
     /* Assign a module ID.  Do this before loading any audit modules.  */
     GL(dl_rtld_map).l_tls_modid = _dl_next_tls_modid ();
 
-  audit_list_add_dynamic_tag (&audit_list, main_map, DT_AUDIT);
-  audit_list_add_dynamic_tag (&audit_list, main_map, DT_DEPAUDIT);
+  audit_list_add_dynamic_tag (&state.audit_list, main_map, DT_AUDIT);
+  audit_list_add_dynamic_tag (&state.audit_list, main_map, DT_DEPAUDIT);
 
   /* If we have auditing DSOs to load, do it now.  */
   bool need_security_init = true;
-  if (audit_list.length > 0)
+  if (state.audit_list.length > 0)
     {
-      size_t naudit = audit_list_count (&audit_list);
+      size_t naudit = audit_list_count (&state.audit_list);
 
       /* Since we start using the auditing DSOs right away we need to
 	 initialize the data structures now.  */
@@ -1719,7 +1686,7 @@  of this helper program; chances are you did not intend to run this program.\n\
       security_init ();
       need_security_init = false;
 
-      load_audit_modules (main_map, &audit_list);
+      load_audit_modules (main_map, &state.audit_list);
 
       /* The count based on audit strings may overestimate the number
 	 of audit modules that got loaded, but not underestimate.  */
@@ -1774,19 +1741,21 @@  of this helper program; chances are you did not intend to run this program.\n\
   struct link_map **preloads = NULL;
   unsigned int npreloads = 0;
 
-  if (__glibc_unlikely (preloadlist != NULL))
+  if (__glibc_unlikely (state.preloadlist != NULL))
     {
       RTLD_TIMING_VAR (start);
       rtld_timer_start (&start);
-      npreloads += handle_preload_list (preloadlist, main_map, "LD_PRELOAD");
+      npreloads += handle_preload_list (state.preloadlist, main_map,
+					"LD_PRELOAD");
       rtld_timer_accum (&load_time, start);
     }
 
-  if (__glibc_unlikely (preloadarg != NULL))
+  if (__glibc_unlikely (state.preloadarg != NULL))
     {
       RTLD_TIMING_VAR (start);
       rtld_timer_start (&start);
-      npreloads += handle_preload_list (preloadarg, main_map, "--preload");
+      npreloads += handle_preload_list (state.preloadarg, main_map,
+					"--preload");
       rtld_timer_accum (&load_time, start);
     }
 
@@ -1893,7 +1862,8 @@  of this helper program; chances are you did not intend to run this program.\n\
   {
     RTLD_TIMING_VAR (start);
     rtld_timer_start (&start);
-    _dl_map_object_deps (main_map, preloads, npreloads, mode == trace, 0);
+    _dl_map_object_deps (main_map, preloads, npreloads,
+			 state.mode == trace, 0);
     rtld_timer_accum (&load_time, start);
   }
 
@@ -1920,7 +1890,7 @@  of this helper program; chances are you did not intend to run this program.\n\
       rtld_multiple_ref = true;
 
       GL(dl_rtld_map).l_prev = main_map->l_searchlist.r_list[i - 1];
-      if (__builtin_expect (mode, normal) == normal)
+      if (__builtin_expect (state.mode, normal) == normal)
 	{
 	  GL(dl_rtld_map).l_next = (i + 1 < main_map->l_searchlist.r_nlist
 				    ? main_map->l_searchlist.r_list[i + 1]
@@ -1953,8 +1923,8 @@  of this helper program; chances are you did not intend to run this program.\n\
      versions we need.  */
   {
     struct version_check_args args;
-    args.doexit = mode == normal;
-    args.dotrace = mode == trace;
+    args.doexit = state.mode == normal;
+    args.dotrace = state.mode == trace;
     _dl_receive_error (print_missing_version, version_check_doit, &args);
   }
 
@@ -1974,7 +1944,7 @@  of this helper program; chances are you did not intend to run this program.\n\
        earlier.  */
     security_init ();
 
-  if (__builtin_expect (mode, normal) != normal)
+  if (__builtin_expect (state.mode, normal) != normal)
     {
       /* We were run just to list the shared libraries.  It is
 	 important that we do this before real relocation, because the
@@ -2076,7 +2046,7 @@  of this helper program; chances are you did not intend to run this program.\n\
 			  (size_t) l->l_map_start);
 	}
 
-      if (__builtin_expect (mode, trace) != trace)
+      if (__builtin_expect (state.mode, trace) != trace)
 	for (i = 1; i < (unsigned int) _dl_argc; ++i)
 	  {
 	    const ElfW(Sym) *ref = NULL;
@@ -2130,7 +2100,7 @@  of this helper program; chances are you did not intend to run this program.\n\
 		}
 	    }
 #define VERNEEDTAG (DT_NUM + DT_THISPROCNUM + DT_VERSIONTAGIDX (DT_VERNEED))
-	  if (version_info)
+	  if (state.version_info)
 	    {
 	      /* Print more information.  This means here, print information
 		 about the versions needed.  */
@@ -2492,13 +2462,10 @@  print_missing_version (int errcode __attribute__ ((unused)),
 		    objname, errstring);
 }
 
-/* Nonzero if any of the debugging options is enabled.  */
-static int any_debug attribute_relro;
-
 /* Process the string given as the parameter which explains which debugging
    options are enabled.  */
 static void
-process_dl_debug (const char *dl_debug)
+process_dl_debug (struct dl_main_state *state, const char *dl_debug)
 {
   /* When adding new entries make sure that the maximal length of a name
      is correctly handled in the LD_DEBUG_HELP code below.  */
@@ -2555,7 +2522,7 @@  process_dl_debug (const char *dl_debug)
 		&& memcmp (dl_debug, debopts[cnt].name, len) == 0)
 	      {
 		GLRO(dl_debug_mask) |= debopts[cnt].mask;
-		any_debug = 1;
+		state->any_debug = true;
 		break;
 	      }
 
@@ -2609,11 +2576,10 @@  extern char **_environ attribute_hidden;
 
 
 static void
-process_envvars (enum mode *modep, struct audit_list *audit_list)
+process_envvars (struct dl_main_state *state)
 {
   char **runp = _environ;
   char *envline;
-  enum mode mode = normal;
   char *debug_output = NULL;
 
   /* This is the default place for profiling data file.  */
@@ -2645,25 +2611,25 @@  process_envvars (enum mode *modep, struct audit_list *audit_list)
 	  /* Debugging of the dynamic linker?  */
 	  if (memcmp (envline, "DEBUG", 5) == 0)
 	    {
-	      process_dl_debug (&envline[6]);
+	      process_dl_debug (state, &envline[6]);
 	      break;
 	    }
 	  if (memcmp (envline, "AUDIT", 5) == 0)
-	    audit_list_add_string (audit_list, &envline[6]);
+	    audit_list_add_string (&state->audit_list, &envline[6]);
 	  break;
 
 	case 7:
 	  /* Print information about versions.  */
 	  if (memcmp (envline, "VERBOSE", 7) == 0)
 	    {
-	      version_info = envline[8] != '\0';
+	      state->version_info = envline[8] != '\0';
 	      break;
 	    }
 
 	  /* List of objects to be preloaded.  */
 	  if (memcmp (envline, "PRELOAD", 7) == 0)
 	    {
-	      preloadlist = &envline[8];
+	      state->preloadlist = &envline[8];
 	      break;
 	    }
 
@@ -2712,7 +2678,7 @@  process_envvars (enum mode *modep, struct audit_list *audit_list)
 	  if (!__libc_enable_secure
 	      && memcmp (envline, "LIBRARY_PATH", 12) == 0)
 	    {
-	      library_path = &envline[13];
+	      state->library_path = &envline[13];
 	      break;
 	    }
 
@@ -2754,7 +2720,7 @@  process_envvars (enum mode *modep, struct audit_list *audit_list)
 	  /* The mode of the dynamic linker can be set.  */
 	  if (memcmp (envline, "TRACE_PRELINKING", 16) == 0)
 	    {
-	      mode = trace;
+	      state->mode = trace;
 	      GLRO(dl_verbose) = 1;
 	      GLRO(dl_debug_mask) |= DL_DEBUG_PRELINK;
 	      GLRO(dl_trace_prelink) = &envline[17];
@@ -2764,7 +2730,7 @@  process_envvars (enum mode *modep, struct audit_list *audit_list)
 	case 20:
 	  /* The mode of the dynamic linker can be set.  */
 	  if (memcmp (envline, "TRACE_LOADED_OBJECTS", 20) == 0)
-	    mode = trace;
+	    state->mode = trace;
 	  break;
 
 	  /* We might have some extra environment variable to handle.  This
@@ -2777,9 +2743,6 @@  process_envvars (enum mode *modep, struct audit_list *audit_list)
 	}
     }
 
-  /* The caller wants this information.  */
-  *modep = mode;
-
   /* Extra security for SUID binaries.  Remove all dangerous environment
      variables.  */
   if (__builtin_expect (__libc_enable_secure, 0))
@@ -2808,13 +2771,13 @@  process_envvars (enum mode *modep, struct audit_list *audit_list)
 	  GLRO(dl_debug_mask) = 0;
 	}
 
-      if (mode != normal)
+      if (state->mode != normal)
 	_exit (5);
     }
   /* If we have to run the dynamic linker in debugging mode and the
      LD_DEBUG_OUTPUT environment variable is given, we write the debug
      messages to this file.  */
-  else if (any_debug && debug_output != NULL)
+  else if (state->any_debug && debug_output != NULL)
     {
       const int flags = O_WRONLY | O_APPEND | O_CREAT | O_NOFOLLOW;
       size_t name_len = strlen (debug_output);