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am 155e8d1d: Merge "More dynamic linker cleanup."

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* commit '155e8d1df5b8fdfeabda3e7b61d95beb5b8d1467':
  More dynamic linker cleanup.
This commit is contained in:
Elliott Hughes 2012-10-30 16:56:29 -07:00 committed by Android Git Automerger
commit 914112ea21
13 changed files with 336 additions and 405 deletions
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11
linker/Android.mk
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@ -3,20 +3,19 @@ include $(CLEAR_VARS)
LOCAL_SRC_FILES:= \ LOCAL_SRC_FILES:= \
arch/$(TARGET_ARCH)/begin.S \ arch/$(TARGET_ARCH)/begin.S \
debugger.c \ debugger.cpp \
dlfcn.cpp \ dlfcn.cpp \
linker.cpp \ linker.cpp \
linker_environ.c \ linker_environ.cpp \
linker_format.c \ linker_format.cpp \
linker_phdr.c \ linker_phdr.cpp \
rt.c rt.cpp
LOCAL_LDFLAGS := -shared LOCAL_LDFLAGS := -shared
LOCAL_CFLAGS += -fno-stack-protector \ LOCAL_CFLAGS += -fno-stack-protector \
-Wstrict-overflow=5 \ -Wstrict-overflow=5 \
-fvisibility=hidden \ -fvisibility=hidden \
-std=gnu99 \
-Wall -Wextra -Wall -Wextra
# Set LINKER_DEBUG to either 1 or 0 # Set LINKER_DEBUG to either 1 or 0

85
linker/debugger.c → linker/debugger.cpp
View File

@ -26,6 +26,9 @@
* SUCH DAMAGE. * SUCH DAMAGE.
*/ */
#include "linker.h"
#include "linker_format.h"
#include <stdio.h> #include <stdio.h>
#include <stdlib.h> #include <stdlib.h>
#include <unistd.h> #include <unistd.h>
@ -36,45 +39,35 @@
#include <sys/socket.h> #include <sys/socket.h>
#include <sys/un.h> #include <sys/un.h>
extern int tgkill(int tgid, int tid, int sig); #include <private/logd.h>
void notify_gdb_of_libraries(); extern "C" int tgkill(int tgid, int tid, int sig);
#define DEBUGGER_SOCKET_NAME "android:debuggerd" #define DEBUGGER_SOCKET_NAME "android:debuggerd"
typedef enum { enum debugger_action_t {
// dump a crash // dump a crash
DEBUGGER_ACTION_CRASH, DEBUGGER_ACTION_CRASH,
// dump a tombstone file // dump a tombstone file
DEBUGGER_ACTION_DUMP_TOMBSTONE, DEBUGGER_ACTION_DUMP_TOMBSTONE,
// dump a backtrace only back to the socket // dump a backtrace only back to the socket
DEBUGGER_ACTION_DUMP_BACKTRACE, DEBUGGER_ACTION_DUMP_BACKTRACE,
} debugger_action_t; };
/* message sent over the socket */ /* message sent over the socket */
typedef struct { struct debugger_msg_t {
debugger_action_t action; debugger_action_t action;
pid_t tid; pid_t tid;
} debugger_msg_t; };
#define RETRY_ON_EINTR(ret,cond) \
do { \
ret = (cond); \
} while (ret < 0 && errno == EINTR)
// see man(2) prctl, specifically the section about PR_GET_NAME // see man(2) prctl, specifically the section about PR_GET_NAME
#define MAX_TASK_NAME_LEN (16) #define MAX_TASK_NAME_LEN (16)
static int socket_abstract_client(const char *name, int type) static int socket_abstract_client(const char* name, int type) {
{ sockaddr_un addr;
struct sockaddr_un addr;
size_t namelen;
socklen_t alen;
int s, err;
namelen = strlen(name);
// Test with length +1 for the *initial* '\0'. // Test with length +1 for the *initial* '\0'.
size_t namelen = strlen(name);
if ((namelen + 1) > sizeof(addr.sun_path)) { if ((namelen + 1) > sizeof(addr.sun_path)) {
errno = EINVAL; errno = EINVAL;
return -1; return -1;
@ -86,18 +79,20 @@ static int socket_abstract_client(const char *name, int type)
* Note: The path in this case is *not* supposed to be * Note: The path in this case is *not* supposed to be
* '\0'-terminated. ("man 7 unix" for the gory details.) * '\0'-terminated. ("man 7 unix" for the gory details.)
*/ */
memset (&addr, 0, sizeof addr); memset(&addr, 0, sizeof(addr));
addr.sun_family = AF_LOCAL; addr.sun_family = AF_LOCAL;
addr.sun_path[0] = 0; addr.sun_path[0] = 0;
memcpy(addr.sun_path + 1, name, namelen); memcpy(addr.sun_path + 1, name, namelen);
alen = namelen + offsetof(struct sockaddr_un, sun_path) + 1; socklen_t alen = namelen + offsetof(sockaddr_un, sun_path) + 1;
s = socket(AF_LOCAL, type, 0); int s = socket(AF_LOCAL, type, 0);
if(s < 0) return -1; if (s == -1) {
return -1;
}
RETRY_ON_EINTR(err,connect(s, (struct sockaddr *) &addr, alen)); int err = TEMP_FAILURE_RETRY(connect(s, (sockaddr*) &addr, alen));
if (err < 0) { if (err == -1) {
close(s); close(s);
s = -1; s = -1;
} }
@ -105,9 +100,6 @@ static int socket_abstract_client(const char *name, int type)
return s; return s;
} }
#include "linker_format.h"
#include <../libc/private/logd.h>
/* /*
* Writes a summary of the signal to the log file. We do this so that, if * Writes a summary of the signal to the log file. We do this so that, if
* for some reason we're not able to contact debuggerd, there is still some * for some reason we're not able to contact debuggerd, there is still some
@ -116,15 +108,9 @@ static int socket_abstract_client(const char *name, int type)
* We could be here as a result of native heap corruption, or while a * We could be here as a result of native heap corruption, or while a
* mutex is being held, so we don't want to use any libc functions that * mutex is being held, so we don't want to use any libc functions that
* could allocate memory or hold a lock. * could allocate memory or hold a lock.
*
* "info" will be NULL if the siginfo_t information was not available.
*/ */
static void logSignalSummary(int signum, const siginfo_t* info) static void logSignalSummary(int signum, const siginfo_t* info) {
{ const char* signame;
char buffer[128];
char threadname[MAX_TASK_NAME_LEN + 1]; // one more for termination
char* signame;
switch (signum) { switch (signum) {
case SIGILL: signame = "SIGILL"; break; case SIGILL: signame = "SIGILL"; break;
case SIGABRT: signame = "SIGABRT"; break; case SIGABRT: signame = "SIGABRT"; break;
@ -138,6 +124,7 @@ static void logSignalSummary(int signum, const siginfo_t* info)
default: signame = "???"; break; default: signame = "???"; break;
} }
char threadname[MAX_TASK_NAME_LEN + 1]; // one more for termination
if (prctl(PR_GET_NAME, (unsigned long)threadname, 0, 0, 0) != 0) { if (prctl(PR_GET_NAME, (unsigned long)threadname, 0, 0, 0) != 0) {
strcpy(threadname, "<name unknown>"); strcpy(threadname, "<name unknown>");
} else { } else {
@ -145,6 +132,9 @@ static void logSignalSummary(int signum, const siginfo_t* info)
// implies that 16 byte names are not. // implies that 16 byte names are not.
threadname[MAX_TASK_NAME_LEN] = 0; threadname[MAX_TASK_NAME_LEN] = 0;
} }
char buffer[128];
// "info" will be NULL if the siginfo_t information was not available.
if (info != NULL) { if (info != NULL) {
format_buffer(buffer, sizeof(buffer), format_buffer(buffer, sizeof(buffer),
"Fatal signal %d (%s) at 0x%08x (code=%d), thread %d (%s)", "Fatal signal %d (%s) at 0x%08x (code=%d), thread %d (%s)",
@ -161,8 +151,7 @@ static void logSignalSummary(int signum, const siginfo_t* info)
/* /*
* Returns true if the handler for signal "signum" has SA_SIGINFO set. * Returns true if the handler for signal "signum" has SA_SIGINFO set.
*/ */
static bool haveSiginfo(int signum) static bool haveSiginfo(int signum) {
{
struct sigaction oldact, newact; struct sigaction oldact, newact;
memset(&newact, 0, sizeof(newact)); memset(&newact, 0, sizeof(newact));
@ -188,11 +177,8 @@ static bool haveSiginfo(int signum)
* Catches fatal signals so we can ask debuggerd to ptrace us before * Catches fatal signals so we can ask debuggerd to ptrace us before
* we crash. * we crash.
*/ */
void debugger_signal_handler(int n, siginfo_t* info, void* unused __attribute__((unused))) void debugger_signal_handler(int n, siginfo_t* info, void*) {
{
char msgbuf[128]; char msgbuf[128];
unsigned tid;
int s;
/* /*
* It's possible somebody cleared the SA_SIGINFO flag, which would mean * It's possible somebody cleared the SA_SIGINFO flag, which would mean
@ -204,8 +190,8 @@ void debugger_signal_handler(int n, siginfo_t* info, void* unused __attribute__(
logSignalSummary(n, info); logSignalSummary(n, info);
tid = gettid(); pid_t tid = gettid();
s = socket_abstract_client(DEBUGGER_SOCKET_NAME, SOCK_STREAM); int s = socket_abstract_client(DEBUGGER_SOCKET_NAME, SOCK_STREAM);
if (s >= 0) { if (s >= 0) {
/* debugger knows our pid from the credentials on the /* debugger knows our pid from the credentials on the
@ -217,14 +203,14 @@ void debugger_signal_handler(int n, siginfo_t* info, void* unused __attribute__(
debugger_msg_t msg; debugger_msg_t msg;
msg.action = DEBUGGER_ACTION_CRASH; msg.action = DEBUGGER_ACTION_CRASH;
msg.tid = tid; msg.tid = tid;
RETRY_ON_EINTR(ret, write(s, &msg, sizeof(msg))); ret = TEMP_FAILURE_RETRY(write(s, &msg, sizeof(msg)));
if (ret == sizeof(msg)) { if (ret == sizeof(msg)) {
/* if the write failed, there is no point to read on /* if the write failed, there is no point to read on
* the file descriptor. */ * the file descriptor. */
RETRY_ON_EINTR(ret, read(s, &tid, 1)); ret = TEMP_FAILURE_RETRY(read(s, &tid, 1));
int savedErrno = errno; int saved_errno = errno;
notify_gdb_of_libraries(); notify_gdb_of_libraries();
errno = savedErrno; errno = saved_errno;
} }
if (ret < 0) { if (ret < 0) {
@ -266,8 +252,7 @@ void debugger_signal_handler(int n, siginfo_t* info, void* unused __attribute__(
} }
} }
void debugger_init() void debugger_init() {
{
struct sigaction act; struct sigaction act;
memset(&act, 0, sizeof(act)); memset(&act, 0, sizeof(act));
act.sa_sigaction = debugger_signal_handler; act.sa_sigaction = debugger_signal_handler;

73
linker/linker.cpp
View File

@ -93,7 +93,6 @@ static soinfo *sonext = &libdl_info;
static soinfo *somain; /* main process, always the one after libdl_info */ static soinfo *somain; /* main process, always the one after libdl_info */
#endif #endif
static char ldpaths_buf[LDPATH_BUFSIZE]; static char ldpaths_buf[LDPATH_BUFSIZE];
static const char *ldpaths[LDPATH_MAX + 1]; static const char *ldpaths[LDPATH_MAX + 1];
@ -108,9 +107,6 @@ int debug_verbosity;
static int pid; static int pid;
/* This boolean is set if the program being loaded is setuid */
static bool program_is_setuid;
enum RelocationKind { enum RelocationKind {
kRelocAbsolute = 0, kRelocAbsolute = 0,
kRelocRelative, kRelocRelative,
@ -257,8 +253,7 @@ static void notify_gdb_of_unload(soinfo* info) {
rtld_db_dlactivity(); rtld_db_dlactivity();
} }
extern "C" void notify_gdb_of_libraries() void notify_gdb_of_libraries() {
{
_r_debug.r_state = RT_ADD; _r_debug.r_state = RT_ADD;
rtld_db_dlactivity(); rtld_db_dlactivity();
_r_debug.r_state = RT_CONSISTENT; _r_debug.r_state = RT_CONSISTENT;
@ -1689,7 +1684,7 @@ static int soinfo_link_image(soinfo *si)
ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-02:23.stdio.asc ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-02:23.stdio.asc
*/ */
if (program_is_setuid) { if (get_AT_SECURE()) {
nullify_closed_stdio(); nullify_closed_stdio();
} }
notify_gdb_of_load(si); notify_gdb_of_load(si);
@ -1750,11 +1745,6 @@ static unsigned __linker_init_post_relocation(unsigned **elfdata, unsigned linke
int argc = (int) *elfdata; int argc = (int) *elfdata;
char **argv = (char**) (elfdata + 1); char **argv = (char**) (elfdata + 1);
unsigned *vecs = (unsigned*) (argv + argc + 1); unsigned *vecs = (unsigned*) (argv + argc + 1);
unsigned *v;
soinfo *si;
int i;
const char *ldpath_env = NULL;
const char *ldpreload_env = NULL;
/* NOTE: we store the elfdata pointer on a special location /* NOTE: we store the elfdata pointer on a special location
* of the temporary TLS area in order to pass it to * of the temporary TLS area in order to pass it to
@ -1773,53 +1763,36 @@ static unsigned __linker_init_post_relocation(unsigned **elfdata, unsigned linke
gettimeofday(&t0, 0); gettimeofday(&t0, 0);
#endif #endif
/* Initialize environment functions, and get to the ELF aux vectors table */ // Initialize environment functions, and get to the ELF aux vectors table.
vecs = linker_env_init(vecs); vecs = linker_env_init(vecs);
/* Check auxv for AT_SECURE first to see if program is setuid, setgid,
has file caps, or caused a SELinux/AppArmor domain transition. */
for (v = vecs; v[0]; v += 2) {
if (v[0] == AT_SECURE) {
/* kernel told us whether to enable secure mode */
program_is_setuid = v[1];
goto sanitize;
}
}
/* Kernel did not provide AT_SECURE - fall back on legacy test. */
program_is_setuid = (getuid() != geteuid()) || (getgid() != getegid());
sanitize:
/* Sanitize environment if we're loading a setuid program */
if (program_is_setuid) {
linker_env_secure();
}
debugger_init(); debugger_init();
/* Get a few environment variables */ // Get a few environment variables.
{
#if LINKER_DEBUG #if LINKER_DEBUG
const char* env; {
env = linker_env_get("DEBUG"); /* XXX: TODO: Change to LD_DEBUG */ const char* env = linker_env_get("LD_DEBUG");
if (env) if (env != NULL) {
debug_verbosity = atoi(env); debug_verbosity = atoi(env);
}
}
#endif #endif
/* Normally, these are cleaned by linker_env_secure, but the test // Normally, these are cleaned by linker_env_init, but the test
* against program_is_setuid doesn't cost us anything */ // doesn't cost us anything.
if (!program_is_setuid) { const char* ldpath_env = NULL;
ldpath_env = linker_env_get("LD_LIBRARY_PATH"); const char* ldpreload_env = NULL;
ldpreload_env = linker_env_get("LD_PRELOAD"); if (!get_AT_SECURE()) {
} ldpath_env = linker_env_get("LD_LIBRARY_PATH");
ldpreload_env = linker_env_get("LD_PRELOAD");
} }
INFO("[ android linker & debugger ]\n"); INFO("[ android linker & debugger ]\n");
DEBUG("%5d elfdata @ 0x%08x\n", pid, (unsigned)elfdata); DEBUG("%5d elfdata @ 0x%08x\n", pid, (unsigned)elfdata);
si = soinfo_alloc(argv[0]); soinfo* si = soinfo_alloc(argv[0]);
if(si == 0) { if (si == NULL) {
exit(-1); exit(EXIT_FAILURE);
} }
/* bootstrap the link map, the main exe always needs to be first */ /* bootstrap the link map, the main exe always needs to be first */
@ -1858,7 +1831,7 @@ sanitize:
insert_soinfo_into_debug_map(&linker_soinfo); insert_soinfo_into_debug_map(&linker_soinfo);
/* extract information passed from the kernel */ /* extract information passed from the kernel */
while(vecs[0] != 0){ while (vecs[0] != 0){
switch(vecs[0]){ switch(vecs[0]){
case AT_PHDR: case AT_PHDR:
si->phdr = (Elf32_Phdr*) vecs[1]; si->phdr = (Elf32_Phdr*) vecs[1];
@ -1899,12 +1872,12 @@ sanitize:
char errmsg[] = "CANNOT LINK EXECUTABLE\n"; char errmsg[] = "CANNOT LINK EXECUTABLE\n";
write(2, __linker_dl_err_buf, strlen(__linker_dl_err_buf)); write(2, __linker_dl_err_buf, strlen(__linker_dl_err_buf));
write(2, errmsg, sizeof(errmsg)); write(2, errmsg, sizeof(errmsg));
exit(-1); exit(EXIT_FAILURE);
} }
soinfo_call_preinit_constructors(si); soinfo_call_preinit_constructors(si);
for(i = 0; preloads[i] != NULL; i++) { for (size_t i = 0; preloads[i] != NULL; ++i) {
soinfo_call_constructors(preloads[i]); soinfo_call_constructors(preloads[i]);
} }
@ -2049,7 +2022,7 @@ extern "C" unsigned __linker_init(unsigned **elfdata) {
// //
// This situation should never occur unless the linker itself // This situation should never occur unless the linker itself
// is corrupt. // is corrupt.
exit(-1); exit(EXIT_FAILURE);
} }
// We have successfully fixed our own relocations. It's safe to run // We have successfully fixed our own relocations. It's safe to run

12
linker/linker.h
View File

@ -34,9 +34,6 @@
#include <elf.h> #include <elf.h>
#include <sys/exec_elf.h> #include <sys/exec_elf.h>
#ifdef __cplusplus
extern "C" {
#endif
#include <link.h> #include <link.h>
#undef PAGE_MASK #undef PAGE_MASK
@ -89,8 +86,6 @@ struct r_debug
uintptr_t r_ldbase; uintptr_t r_ldbase;
}; };
typedef struct soinfo soinfo;
#define FLAG_LINKED 0x00000001 #define FLAG_LINKED 0x00000001
#define FLAG_ERROR 0x00000002 #define FLAG_ERROR 0x00000002
#define FLAG_EXE 0x00000004 // The main executable #define FLAG_EXE 0x00000004 // The main executable
@ -98,8 +93,7 @@ typedef struct soinfo soinfo;
#define SOINFO_NAME_LEN 128 #define SOINFO_NAME_LEN 128
struct soinfo struct soinfo {
{
char name[SOINFO_NAME_LEN]; char name[SOINFO_NAME_LEN];
const Elf32_Phdr *phdr; const Elf32_Phdr *phdr;
int phnum; int phnum;
@ -232,8 +226,6 @@ Elf32_Sym *soinfo_find_symbol(soinfo* si, const void *addr);
Elf32_Sym *soinfo_lookup(soinfo *si, const char *name); Elf32_Sym *soinfo_lookup(soinfo *si, const char *name);
void soinfo_call_constructors(soinfo *si); void soinfo_call_constructors(soinfo *si);
#ifdef __cplusplus extern "C" void notify_gdb_of_libraries();
};
#endif
#endif #endif

8
linker/linker_debug.h
View File

@ -62,10 +62,6 @@
#if LINKER_DEBUG #if LINKER_DEBUG
#include "linker_format.h" #include "linker_format.h"
#ifdef __cplusplus
extern "C" {
#endif
extern int debug_verbosity; extern int debug_verbosity;
#if LINKER_DEBUG_TO_LOG #if LINKER_DEBUG_TO_LOG
extern int format_log(int, const char *, const char *, ...); extern int format_log(int, const char *, const char *, ...);
@ -81,10 +77,6 @@ extern int format_fd(int, const char *, ...);
} while (0) } while (0)
#endif /* !LINKER_DEBUG_TO_LOG */ #endif /* !LINKER_DEBUG_TO_LOG */
#ifdef __cplusplus
};
#endif
#else /* !LINKER_DEBUG */ #else /* !LINKER_DEBUG */
#define _PRINTVF(v,f,x...) do {} while(0) #define _PRINTVF(v,f,x...) do {} while(0)
#endif /* LINKER_DEBUG */ #endif /* LINKER_DEBUG */

202
linker/linker_environ.c
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@ -1,202 +0,0 @@
/*
* Copyright (C) 2010 The Android Open Source Project
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include "linker_environ.h"
#include <stddef.h>
static char** _envp;
/* Returns 1 if 'str' points to a valid environment variable definition.
* For now, we check that:
* - It is smaller than MAX_ENV_LEN (to detect non-zero terminated strings)
* - It contains at least one equal sign that is not the first character
*/
static int
_is_valid_definition(const char* str)
{
int pos = 0;
int first_equal_pos = -1;
/* According to its sources, the kernel uses 32*PAGE_SIZE by default
* as the maximum size for an env. variable definition.
*/
const int MAX_ENV_LEN = 32*4096;
if (str == NULL)
return 0;
/* Parse the string, looking for the first '=' there, and its size */
do {
if (str[pos] == '\0')
break;
if (str[pos] == '=' && first_equal_pos < 0)
first_equal_pos = pos;
pos++;
} while (pos < MAX_ENV_LEN);
if (pos >= MAX_ENV_LEN) /* Too large */
return 0;
if (first_equal_pos < 1) /* No equal sign, or it is the first character */
return 0;
return 1;
}
unsigned*
linker_env_init(unsigned* vecs)
{
/* Store environment pointer - can't be NULL */
_envp = (char**) vecs;
/* Skip over all definitions */
while (vecs[0] != 0)
vecs++;
/* The end of the environment block is marked by two NULL pointers */
vecs++;
/* As a sanity check, we're going to remove all invalid variable
* definitions from the environment array.
*/
{
char** readp = _envp;
char** writep = _envp;
for ( ; readp[0] != NULL; readp++ ) {
if (!_is_valid_definition(readp[0]))
continue;
writep[0] = readp[0];
writep++;
}
writep[0] = NULL;
}
/* Return the address of the aux vectors table */
return vecs;
}
/* Check if the environment variable definition at 'envstr'
* starts with '<name>=', and if so return the address of the
* first character after the equal sign. Otherwise return NULL.
*/
static char*
env_match(char* envstr, const char* name)
{
size_t cnt = 0;
while (envstr[cnt] == name[cnt] && name[cnt] != '\0')
cnt++;
if (name[cnt] == '\0' && envstr[cnt] == '=')
return envstr + cnt + 1;
return NULL;
}
#define MAX_ENV_LEN (16*4096)
const char*
linker_env_get(const char* name)
{
char** readp = _envp;
if (name == NULL || name[0] == '\0')
return NULL;
for ( ; readp[0] != NULL; readp++ ) {
char* val = env_match(readp[0], name);
if (val != NULL) {
/* Return NULL for empty strings, or if it is too large */
if (val[0] == '\0')
val = NULL;
return val;
}
}
return NULL;
}
void
linker_env_unset(const char* name)
{
char** readp = _envp;
char** writep = readp;
if (name == NULL || name[0] == '\0')
return;
for ( ; readp[0] != NULL; readp++ ) {
if (env_match(readp[0], name))
continue;
writep[0] = readp[0];
writep++;
}
/* end list with a NULL */
writep[0] = NULL;
}
/* Remove unsafe environment variables. This should be used when
* running setuid programs. */
void
linker_env_secure(void)
{
/* The same list than GLibc at this point */
static const char* const unsec_vars[] = {
"GCONV_PATH",
"GETCONF_DIR",
"HOSTALIASES",
"LD_AUDIT",
"LD_DEBUG",
"LD_DEBUG_OUTPUT",
"LD_DYNAMIC_WEAK",
"LD_LIBRARY_PATH",
"LD_ORIGIN_PATH",
"LD_PRELOAD",
"LD_PROFILE",
"LD_SHOW_AUXV",
"LD_USE_LOAD_BIAS",
"LOCALDOMAIN",
"LOCPATH",
"MALLOC_TRACE",
"MALLOC_CHECK_",
"NIS_PATH",
"NLSPATH",
"RESOLV_HOST_CONF",
"RES_OPTIONS",
"TMPDIR",
"TZDIR",
"LD_AOUT_LIBRARY_PATH",
"LD_AOUT_PRELOAD",
NULL
};
int count;
for (count = 0; unsec_vars[count] != NULL; count++) {
linker_env_unset(unsec_vars[count]);
}
}

222
linker/linker_environ.cpp Normal file
View File

@ -0,0 +1,222 @@
/*
* Copyright (C) 2010 The Android Open Source Project
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include "linker_environ.h"
#include <linux/auxvec.h>
#include <stddef.h>
#include <stdlib.h>
#include <unistd.h>
static char** _envp;
static bool _AT_SECURE_value = true;
bool get_AT_SECURE() {
return _AT_SECURE_value;
}
/* Returns 1 if 'str' points to a valid environment variable definition.
* For now, we check that:
* - It is smaller than MAX_ENV_LEN (to detect non-zero terminated strings)
* - It contains at least one equal sign that is not the first character
*/
static int _is_valid_definition(const char* str) {
int pos = 0;
int first_equal_pos = -1;
// According to its sources, the kernel uses 32*PAGE_SIZE by default
// as the maximum size for an env. variable definition.
const int MAX_ENV_LEN = 32*4096;
if (str == NULL) {
return 0;
}
// Parse the string, looking for the first '=' there, and its size.
while (pos < MAX_ENV_LEN) {
if (str[pos] == '\0') {
break;
}
if (str[pos] == '=' && first_equal_pos < 0) {
first_equal_pos = pos;
}
pos++;
}
if (pos >= MAX_ENV_LEN) {
return 0; // Too large.
}
if (first_equal_pos < 1) {
return 0; // No equals sign, or it's the first character.
}
return 1;
}
static void __init_AT_SECURE(unsigned* auxv) {
// Check auxv for AT_SECURE first to see if program is setuid, setgid,
// has file caps, or caused a SELinux/AppArmor domain transition.
for (unsigned* v = auxv; v[0]; v += 2) {
if (v[0] == AT_SECURE) {
// Kernel told us whether to enable secure mode.
_AT_SECURE_value = v[1];
return;
}
}
// We don't support ancient kernels.
const char* msg = "FATAL: kernel did not supply AT_SECURE\n";
write(2, msg, strlen(msg));
exit(EXIT_FAILURE);
}
static void __remove_unsafe_environment_variables() {
// None of these should be allowed in setuid programs.
static const char* const UNSAFE_VARIABLE_NAMES[] = {
"GCONV_PATH",
"GETCONF_DIR",
"HOSTALIASES",
"LD_AOUT_LIBRARY_PATH",
"LD_AOUT_PRELOAD",
"LD_AUDIT",
"LD_DEBUG",
"LD_DEBUG_OUTPUT",
"LD_DYNAMIC_WEAK",
"LD_LIBRARY_PATH",
"LD_ORIGIN_PATH",
"LD_PRELOAD",
"LD_PROFILE",
"LD_SHOW_AUXV",
"LD_USE_LOAD_BIAS",
"LOCALDOMAIN",
"LOCPATH",
"MALLOC_CHECK_",
"MALLOC_TRACE",
"NIS_PATH",
"NLSPATH",
"RESOLV_HOST_CONF",
"RES_OPTIONS",
"TMPDIR",
"TZDIR",
NULL
};
for (size_t i = 0; UNSAFE_VARIABLE_NAMES[i] != NULL; ++i) {
linker_env_unset(UNSAFE_VARIABLE_NAMES[i]);
}
}
static void __remove_invalid_environment_variables() {
char** src = _envp;
char** dst = _envp;
for (; src[0] != NULL; ++src) {
if (!_is_valid_definition(src[0])) {
continue;
}
dst[0] = src[0];
++dst;
}
dst[0] = NULL;
}
unsigned* linker_env_init(unsigned* environment_and_aux_vectors) {
// Store environment pointer - can't be NULL.
_envp = reinterpret_cast<char**>(environment_and_aux_vectors);
// Skip over all environment variable definitions.
// The end of the environment block is marked by two NULL pointers.
unsigned* aux_vectors = environment_and_aux_vectors;
while (aux_vectors[0] != 0) {
++aux_vectors;
}
++aux_vectors;
__remove_invalid_environment_variables();
__init_AT_SECURE(aux_vectors);
// Sanitize environment if we're loading a setuid program.
if (get_AT_SECURE()) {
__remove_unsafe_environment_variables();
}
return aux_vectors;
}
/* Check if the environment variable definition at 'envstr'
* starts with '<name>=', and if so return the address of the
* first character after the equal sign. Otherwise return NULL.
*/
static char* env_match(char* envstr, const char* name) {
size_t i = 0;
while (envstr[i] == name[i] && name[i] != '\0') {
++i;
}
if (name[i] == '\0' && envstr[i] == '=') {
return envstr + i + 1;
}
return NULL;
}
const char* linker_env_get(const char* name) {
if (name == NULL || name[0] == '\0') {
return NULL;
}
for (char** p = _envp; p[0] != NULL; ++p) {
char* val = env_match(p[0], name);
if (val != NULL) {
if (val[0] == '\0') {
return NULL; // Return NULL for empty strings.
}
return val;
}
}
return NULL;
}
void linker_env_unset(const char* name) {
char** readp = _envp;
char** writep = readp;
if (name == NULL || name[0] == '\0') {
return;
}
for ( ; readp[0] != NULL; readp++ ) {
if (env_match(readp[0], name)) {
continue;
}
writep[0] = readp[0];
writep++;
}
/* end list with a NULL */
writep[0] = NULL;
}

41
linker/linker_environ.h
View File

@ -25,38 +25,27 @@
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE. * SUCH DAMAGE.
*/ */
#ifndef LINKER_ENVIRON_H #ifndef LINKER_ENVIRON_H
#define LINKER_ENVIRON_H #define LINKER_ENVIRON_H
#ifdef __cplusplus // Call this function before anything else. 'environment_and_aux_vectors'
extern "C" { // must point to the environment block in the ELF data block. The function
#endif // returns the start of the aux vectors after the environment block.
extern unsigned* linker_env_init(unsigned* environment_and_aux_vectors);
/* Call this function before anything else. 'vecs' must be the pointer // Unset a given environment variable. In case the variable is defined
* to the environment block in the ELF data block. The function returns // multiple times, unset all instances. This modifies the environment
* the start of the aux vectors after the env block. // block, so any pointer returned by linker_env_get() after this call
*/ // might become invalid.
extern unsigned* linker_env_init(unsigned* vecs); extern void linker_env_unset(const char* name);
/* Unset a given environment variable. In case the variable is defined // Returns the value of environment variable 'name' if defined and not
* multiple times, unset all instances. This modifies the environment // empty, or NULL otherwise. Note that the returned pointer may become
* block, so any pointer returned by linker_env_get() after this call // invalid if linker_env_unset() is called after this function.
* might become invalid */
extern void linker_env_unset(const char* name);
/* Returns the value of environment variable 'name' if defined and not
* empty, or NULL otherwise. Note that the returned pointer may become
* invalid if linker_env_unset() or linker_env_secure() are called
* after this function. */
extern const char* linker_env_get(const char* name); extern const char* linker_env_get(const char* name);
/* Remove insecure environment variables. This should be used when // Returns the value of this program's AT_SECURE variable.
* running setuid programs. */ extern bool get_AT_SECURE();
extern void linker_env_secure(void);
#ifdef __cplusplus
};
#endif
#endif /* LINKER_ENVIRON_H */ #endif /* LINKER_ENVIRON_H */

53
linker/linker_format.c → linker/linker_format.cpp
View File

@ -26,6 +26,7 @@
* SUCH DAMAGE. * SUCH DAMAGE.
*/ */
#include <assert.h>
#include <stdarg.h> #include <stdarg.h>
#include <string.h> #include <string.h>
#include <errno.h> #include <errno.h>
@ -43,14 +44,12 @@
/*** Generic output sink /*** Generic output sink
***/ ***/
typedef struct { struct Out {
void *opaque; void *opaque;
void (*send)(void *opaque, const char *data, int len); void (*send)(void *opaque, const char *data, int len);
} Out; };
static void static void out_send(Out *o, const char *data, size_t len) {
out_send(Out *o, const void *data, size_t len)
{
o->send(o->opaque, data, (int)len); o->send(o->opaque, data, (int)len);
} }
@ -72,27 +71,25 @@ out_send_repeat(Out *o, char ch, int count)
} }
/* forward declaration */ /* forward declaration */
static void static void out_vformat(Out* o, const char* format, va_list args);
out_vformat(Out *o, const char *format, va_list args);
/*** Bounded buffer output /*** Bounded buffer output
***/ ***/
typedef struct { struct BufOut {
Out out[1]; Out out[1];
char *buffer; char *buffer;
char *pos; char *pos;
char *end; char *end;
int total; int total;
} BufOut; };
static void static void buf_out_send(void *opaque, const char *data, int len) {
buf_out_send(void *opaque, const char *data, int len) BufOut *bo = reinterpret_cast<BufOut*>(opaque);
{
BufOut *bo = opaque;
if (len < 0) if (len < 0) {
len = strlen(data); len = strlen(data);
}
bo->total += len; bo->total += len;
@ -194,11 +191,11 @@ snprintf(char* buff, size_t bufsize, const char* format, ...)
/*** File descriptor output /*** File descriptor output
***/ ***/
typedef struct { struct FdOut {
Out out[1]; Out out[1];
int fd; int fd;
int total; int total;
} FdOut; };
static void static void
fd_out_send(void *opaque, const char *data, int len) fd_out_send(void *opaque, const char *data, int len)
@ -593,6 +590,10 @@ out_vformat(Out *o, const char *format, va_list args)
slen = strlen(str); slen = strlen(str);
if (sign != '\0' || prec != -1) {
__assert(__FILE__, __LINE__, "sign/precision unsupported");
}
if (slen < width && !padLeft) { if (slen < width && !padLeft) {
char padChar = padZero ? '0' : ' '; char padChar = padZero ? '0' : ' ';
out_send_repeat(o, padChar, width - slen); out_send_repeat(o, padChar, width - slen);

18
linker/linker_format.h
View File

@ -25,25 +25,17 @@
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE. * SUCH DAMAGE.
*/ */
#ifndef _LINKER_FORMAT_H #ifndef _LINKER_FORMAT_H
#define _LINKER_FORMAT_H #define _LINKER_FORMAT_H
#include <stdarg.h> #include <stdarg.h>
#include <stddef.h> #include <stddef.h>
#ifdef __cplusplus // Formatting routines for the dynamic linker's debug traces
extern "C" { // We want to avoid dragging the whole C library fprintf()
#endif // implementation into the dynamic linker since this creates
// issues (it uses malloc()/free()) and increases code size.
/* Formatting routines for the dynamic linker's debug traces */
/* We want to avoid dragging the whole C library fprintf() */
/* implementation into the dynamic linker since this creates */
/* issues (it uses malloc()/free()) and increases code size */
int format_buffer(char *buffer, size_t bufsize, const char *format, ...); int format_buffer(char *buffer, size_t bufsize, const char *format, ...);
#ifdef __cplusplus
};
#endif
#endif /* _LINKER_FORMAT_H */ #endif /* _LINKER_FORMAT_H */

1
linker/linker_phdr.c → linker/linker_phdr.cpp
View File

@ -301,7 +301,6 @@ phdr_table_load_segments(const Elf32_Phdr* phdr_table,
Elf32_Addr file_end = file_start + phdr->p_filesz; Elf32_Addr file_end = file_start + phdr->p_filesz;
Elf32_Addr file_page_start = PAGE_START(file_start); Elf32_Addr file_page_start = PAGE_START(file_start);
Elf32_Addr file_page_end = PAGE_END(file_end);
seg_addr = mmap((void*)seg_page_start, seg_addr = mmap((void*)seg_page_start,
file_end - file_page_start, file_end - file_page_start,

10
linker/linker_phdr.h
View File

@ -37,12 +37,6 @@
#include "linker.h" #include "linker.h"
#ifdef __cplusplus
extern "C" {
#endif
/* See linker_phdr.c for all usage documentation */
int int
phdr_table_load(int fd, phdr_table_load(int fd,
Elf32_Addr phdr_offset, Elf32_Addr phdr_offset,
@ -107,8 +101,4 @@ phdr_table_get_dynamic_section(const Elf32_Phdr* phdr_table,
Elf32_Addr** dynamic, Elf32_Addr** dynamic,
size_t* dynamic_count); size_t* dynamic_count);
#ifdef __cplusplus
};
#endif
#endif /* LINKER_PHDR_H */ #endif /* LINKER_PHDR_H */

5
linker/rt.c → linker/rt.cpp
View File

@ -28,9 +28,8 @@
/* /*
* This function is an empty stub where GDB locates a breakpoint to get notified * This function is an empty stub where GDB locates a breakpoint to get notified
* about linker activity. It canʼt be inlined away, canʼt be hidden. * about linker activity. It canʼt be inlined away, can't be hidden.
*/ */
void __attribute__((noinline)) __attribute__((visibility("default"))) rtld_db_dlactivity(void) extern "C" void __attribute__((noinline)) __attribute__((visibility("default"))) rtld_db_dlactivity() {
{
} }