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More linker cleanup.

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Change-Id: I9fb3c7c0d4b4ffef0eeaf092d4e30ffe63a08671
This commit is contained in:
Elliott Hughes
2013-03-05 18:47:58 -08:00
parent 036f909720
commit 650be4e584
6 changed files with 326 additions and 466 deletions
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222
linker/linker.cpp
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@@ -41,7 +41,6 @@
// Private C library headers.
#include <private/bionic_tls.h>
#include <private/debug_format.h>
#include <private/KernelArgumentBlock.h>
#include <private/logd.h>
#include <private/ScopedPthreadMutexLocker.h>
@@ -105,7 +104,7 @@ static const char* gLdPreloadNames[LDPRELOAD_MAX + 1];
static soinfo* gLdPreloads[LDPRELOAD_MAX + 1];
static int debug_verbosity;
__LIBC_HIDDEN__ int gLdDebugVerbosity;
enum RelocationKind {
kRelocAbsolute = 0,
@@ -158,17 +157,15 @@ DISALLOW_ALLOCATION(void*, calloc, (size_t u1 UNUSED, size_t u2 UNUSED));
static char tmp_err_buf[768];
static char __linker_dl_err_buf[768];
#define DL_ERR(fmt, x...) \
do { \
__libc_format_buffer(__linker_dl_err_buf, sizeof(__linker_dl_err_buf), fmt, ##x); \
/* If LD_DEBUG is set high enough, send every dlerror(3) message to the log. */ \
DEBUG(fmt "\n", ##x); \
} while(0)
const char* linker_get_error() {
char* linker_get_error_buffer() {
return &__linker_dl_err_buf[0];
}
size_t linker_get_error_buffer_size() {
return sizeof(__linker_dl_err_buf);
}
/*
* This function is an empty stub where GDB locates a breakpoint to get notified
* about linker activity.
@@ -706,197 +703,34 @@ static int open_library(const char* name) {
return fd;
}
// Returns 'true' if the library is prelinked or on failure so we error out
// either way. We no longer support prelinking.
static bool is_prelinked(int fd, const char* name)
{
struct prelink_info_t {
long mmap_addr;
char tag[4]; // "PRE ".
};
off_t sz = lseek(fd, -sizeof(prelink_info_t), SEEK_END);
if (sz < 0) {
DL_ERR("lseek failed: %s", strerror(errno));
return true;
}
prelink_info_t info;
int rc = TEMP_FAILURE_RETRY(read(fd, &info, sizeof(info)));
if (rc != sizeof(info)) {
DL_ERR("could not read prelink_info_t structure for \"%s\": %s", name, strerror(errno));
return true;
}
if (memcmp(info.tag, "PRE ", 4) == 0) {
DL_ERR("prelinked libraries no longer supported: %s", name);
return true;
}
return false;
}
/* verify_elf_header
* Verifies the content of an ELF header.
*
* Args:
*
* Returns:
* 0 on success
* -1 if no valid ELF object is found @ base.
*/
static int
verify_elf_header(const Elf32_Ehdr* hdr)
{
if (hdr->e_ident[EI_MAG0] != ELFMAG0) return -1;
if (hdr->e_ident[EI_MAG1] != ELFMAG1) return -1;
if (hdr->e_ident[EI_MAG2] != ELFMAG2) return -1;
if (hdr->e_ident[EI_MAG3] != ELFMAG3) return -1;
if (hdr->e_type != ET_DYN) return -1;
/* TODO: Should we verify anything else in the header? */
#ifdef ANDROID_ARM_LINKER
if (hdr->e_machine != EM_ARM) return -1;
#elif defined(ANDROID_X86_LINKER)
if (hdr->e_machine != EM_386) return -1;
#elif defined(ANDROID_MIPS_LINKER)
if (hdr->e_machine != EM_MIPS) return -1;
#endif
return 0;
}
struct scoped_fd {
~scoped_fd() {
if (fd != -1) {
close(fd);
}
}
int fd;
};
struct soinfo_ptr {
soinfo_ptr(const char* name) {
const char* bname = strrchr(name, '/');
ptr = soinfo_alloc(bname ? bname + 1 : name);
}
~soinfo_ptr() {
soinfo_free(ptr);
}
soinfo* release() {
soinfo* result = ptr;
ptr = NULL;
return result;
}
soinfo* ptr;
};
// TODO: rewrite linker_phdr.h to use a class, then lose this.
struct phdr_ptr {
phdr_ptr() : phdr_mmap(NULL) {}
~phdr_ptr() {
if (phdr_mmap != NULL) {
phdr_table_unload(phdr_mmap, phdr_size);
}
}
void* phdr_mmap;
Elf32_Addr phdr_size;
};
static soinfo* load_library(const char* name) {
// Open the file.
scoped_fd fd;
fd.fd = open_library(name);
if (fd.fd == -1) {
int fd = open_library(name);
if (fd == -1) {
DL_ERR("library \"%s\" not found", name);
return NULL;
}
// Read the ELF header.
Elf32_Ehdr header[1];
int ret = TEMP_FAILURE_RETRY(read(fd.fd, (void*)header, sizeof(header)));
if (ret < 0) {
DL_ERR("can't read file \"%s\": %s", name, strerror(errno));
return NULL;
}
if (ret != (int)sizeof(header)) {
DL_ERR("too small to be an ELF executable: %s", name);
return NULL;
}
if (verify_elf_header(header) < 0) {
DL_ERR("not a valid ELF executable: %s", name);
// Read the ELF header and load the segments.
ElfReader elf_reader(name, fd);
if (!elf_reader.Load()) {
return NULL;
}
// Read the program header table.
const Elf32_Phdr* phdr_table;
phdr_ptr phdr_holder;
ret = phdr_table_load(fd.fd, header->e_phoff, header->e_phnum,
&phdr_holder.phdr_mmap, &phdr_holder.phdr_size, &phdr_table);
if (ret < 0) {
DL_ERR("can't load program header table: %s: %s", name, strerror(errno));
const char* bname = strrchr(name, '/');
soinfo* si = soinfo_alloc(bname ? bname + 1 : name);
if (si == NULL) {
return NULL;
}
size_t phdr_count = header->e_phnum;
// Get the load extents.
Elf32_Addr ext_sz = phdr_table_get_load_size(phdr_table, phdr_count);
TRACE("[ '%s' wants sz=0x%08x ]\n", name, ext_sz);
if (ext_sz == 0) {
DL_ERR("no loadable segments in file: %s", name);
return NULL;
}
// We no longer support pre-linked libraries.
if (is_prelinked(fd.fd, name)) {
return NULL;
}
// Reserve address space for all loadable segments.
void* load_start = NULL;
Elf32_Addr load_size = 0;
Elf32_Addr load_bias = 0;
ret = phdr_table_reserve_memory(phdr_table,
phdr_count,
&load_start,
&load_size,
&load_bias);
if (ret < 0) {
DL_ERR("can't reserve %d bytes in address space for \"%s\": %s",
ext_sz, name, strerror(errno));
return NULL;
}
TRACE("[ allocated memory for %s @ %p (0x%08x) ]\n", name, load_start, load_size);
/* Map all the segments in our address space with default protections */
ret = phdr_table_load_segments(phdr_table,
phdr_count,
load_bias,
fd.fd);
if (ret < 0) {
DL_ERR("can't map loadable segments for \"%s\": %s",
name, strerror(errno));
return NULL;
}
soinfo_ptr si(name);
if (si.ptr == NULL) {
return NULL;
}
si.ptr->base = (Elf32_Addr) load_start;
si.ptr->size = load_size;
si.ptr->load_bias = load_bias;
si.ptr->flags = 0;
si.ptr->entry = 0;
si.ptr->dynamic = NULL;
si.ptr->phnum = phdr_count;
si.ptr->phdr = phdr_table_get_loaded_phdr(phdr_table, phdr_count, load_bias);
if (si.ptr->phdr == NULL) {
DL_ERR("can't find loaded PHDR for \"%s\"", name);
return NULL;
}
return si.release();
si->base = elf_reader.load_start();
si->size = elf_reader.load_size();
si->load_bias = elf_reader.load_bias();
si->flags = 0;
si->entry = 0;
si->dynamic = NULL;
si->phnum = elf_reader.phdr_count();
si->phdr = elf_reader.loaded_phdr();
return si;
}
static soinfo *find_loaded_library(const char *name)
@@ -1686,7 +1520,7 @@ static bool soinfo_link_image(soinfo* si) {
for (size_t i = 0; gLdPreloadNames[i] != NULL; i++) {
soinfo* lsi = find_library(gLdPreloadNames[i]);
if (lsi == NULL) {
strlcpy(tmp_err_buf, linker_get_error(), sizeof(tmp_err_buf));
strlcpy(tmp_err_buf, linker_get_error_buffer(), sizeof(tmp_err_buf));
DL_ERR("could not load library \"%s\" needed by \"%s\"; caused by %s",
gLdPreloadNames[i], si->name, tmp_err_buf);
return false;
@@ -1704,7 +1538,7 @@ static bool soinfo_link_image(soinfo* si) {
DEBUG("%s needs %s\n", si->name, library_name);
soinfo* lsi = find_library(library_name);
if (lsi == NULL) {
strlcpy(tmp_err_buf, linker_get_error(), sizeof(tmp_err_buf));
strlcpy(tmp_err_buf, linker_get_error_buffer(), sizeof(tmp_err_buf));
DL_ERR("could not load library \"%s\" needed by \"%s\"; caused by %s",
library_name, si->name, tmp_err_buf);
return false;
@@ -1804,7 +1638,7 @@ static unsigned __linker_init_post_relocation(KernelArgumentBlock& args, unsigne
// Get a few environment variables.
const char* LD_DEBUG = linker_env_get("LD_DEBUG");
if (LD_DEBUG != NULL) {
debug_verbosity = atoi(LD_DEBUG);
gLdDebugVerbosity = atoi(LD_DEBUG);
}
// Normally, these are cleaned by linker_env_init, but the test
@@ -1890,9 +1724,7 @@ static unsigned __linker_init_post_relocation(KernelArgumentBlock& args, unsigne
somain = si;
if (!soinfo_link_image(si)) {
const char* msg = "CANNOT LINK EXECUTABLE\n";
write(2, __linker_dl_err_buf, strlen(__linker_dl_err_buf));
write(2, msg, strlen(msg));
__libc_format_fd(2, "CANNOT LINK EXECUTABLE: %s\n", linker_get_error_buffer());
exit(EXIT_FAILURE);
}