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linker: Fallback to argv[0] to get the executable info 

Enable linking on a system without /proc mounted by falling back to
reading the executable paths from argv[0] when /proc/exe/self can't be
found.

Bug: 254835242
Change-Id: I0735e873fa4e2f439688722c4a846fb70ff398a5
This commit is contained in:
Vincent Donnefort 2023-01-24 18:00:03 +00:00
parent 98c641b096
commit 2efa017409
1 changed files with 20 additions and 26 deletions
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46
linker/linker_main.cpp
View File

@ -203,35 +203,29 @@ struct ExecutableInfo {
ElfW(Addr) entry_point;
};
static ExecutableInfo get_executable_info() {
static ExecutableInfo get_executable_info(const char* arg_path) {
ExecutableInfo result = {};
char const* exe_path = "/proc/self/exe";
if (is_first_stage_init()) {
// /proc fs is not mounted when first stage init starts. Therefore we can't
// use /proc/self/exe for init.
stat("/init", &result.file_stat);
// /init may be a symlink, so try to read it as such.
char path[PATH_MAX];
ssize_t path_len = readlink("/init", path, sizeof(path));
if (path_len == -1 || path_len >= static_cast<ssize_t>(sizeof(path))) {
result.path = "/init";
} else {
result.path = std::string(path, path_len);
// Stat "/proc/self/exe" instead of executable_path because
// the executable could be unlinked by this point and it should
// not cause a crash (see http://b/31084669)
if (TEMP_FAILURE_RETRY(stat(exe_path, &result.file_stat) == -1)) {
// Fallback to argv[0] for the case where /proc isn't available
if (TEMP_FAILURE_RETRY(stat(arg_path, &result.file_stat) == -1)) {
async_safe_fatal("unable to stat either \"/proc/self/exe\" or \"%s\": %s",
arg_path, strerror(errno));
}
exe_path = arg_path;
}
// Path might be a symlink
char sym_path[PATH_MAX];
ssize_t sym_path_len = readlink(exe_path, sym_path, sizeof(sym_path));
if (sym_path_len > 0 && sym_path_len < static_cast<ssize_t>(sizeof(sym_path))) {
result.path = std::string(sym_path, sym_path_len);
} else {
// Stat "/proc/self/exe" instead of executable_path because
// the executable could be unlinked by this point and it should
// not cause a crash (see http://b/31084669)
if (TEMP_FAILURE_RETRY(stat("/proc/self/exe", &result.file_stat)) != 0) {
async_safe_fatal("unable to stat \"/proc/self/exe\": %s", strerror(errno));
}
char path[PATH_MAX];
ssize_t path_len = readlink("/proc/self/exe", path, sizeof(path));
if (path_len == -1 || path_len >= static_cast<ssize_t>(sizeof(path))) {
async_safe_fatal("readlink('/proc/self/exe') failed: %s", strerror(errno));
}
result.path = std::string(path, path_len);
result.path = std::string(exe_path, strlen(exe_path));
}
result.phdr = reinterpret_cast<const ElfW(Phdr)*>(getauxval(AT_PHDR));
@ -359,7 +353,7 @@ static ElfW(Addr) linker_main(KernelArgumentBlock& args, const char* exe_to_load
}
const ExecutableInfo exe_info = exe_to_load ? load_executable(exe_to_load) :
get_executable_info();
get_executable_info(args.argv[0]);
INFO("[ Linking executable \"%s\" ]", exe_info.path.c_str());