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elf: Extract command-line/environment variables state from rtld.c

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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.
This commit is contained in:
Florian Weimer 2020-10-08 10:57:09 +02:00
parent 72d36ffd7d
commit 2bf9e641fd
2 changed files with 157 additions and 96 deletions
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98
elf/dl-main.h Normal file
View file

@ -0,0 +1,98 @@
/* 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 rtld_mode
{
rtld_mode_normal, rtld_mode_list, rtld_mode_verify, rtld_mode_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 rtld_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 */

155
elf/rtld.c
View file

@ -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 = rtld_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 = rtld_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 = rtld_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 (__glibc_unlikely (state.mode == rtld_mode_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 (__glibc_likely (state.mode == rtld_mode_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 (__glibc_unlikely (state.mode == rtld_mode_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 == rtld_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 (__glibc_likely (state.mode == rtld_mode_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 == rtld_mode_normal;
args.dotrace = state.mode == rtld_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 (__glibc_unlikely (state.mode != rtld_mode_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 (__glibc_unlikely (state.mode != rtld_mode_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 = rtld_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 = rtld_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 != rtld_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);