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Copy snapuserd to first_stage_ramdisk

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Certain binaries, such as snapuserd, are only available under
/system/bin. To make them accessible by first stage init, we copy
/system/bin/snapuserd to /first_stage_ramdisk/system/bin/snapuserd .

Test: th
Bug: 219841787
Change-Id: I913425a82905c745a05ac32d488f08506dc264ff
This commit is contained in:
Kelvin Zhang 2022-03-17 15:18:36 -07:00
parent 1821237a1e
commit 22929da287
2 changed files with 39 additions and 4 deletions
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40
init/first_stage_init.cpp
View file

@ -27,6 +27,7 @@
#include <sys/utsname.h>
#include <unistd.h>
#include <chrono>
#include <filesystem>
#include <string>
#include <vector>
@ -107,6 +108,39 @@ bool ForceNormalBoot(const std::string& cmdline, const std::string& bootconfig)
cmdline.find("androidboot.force_normal_boot=1") != std::string::npos;
}
static void Copy(const char* src, const char* dst) {
if (link(src, dst) == 0) {
LOG(INFO) << "hard linking " << src << " to " << dst << " succeeded";
return;
}
PLOG(FATAL) << "hard linking " << src << " to " << dst << " failed, falling back to copy.";
}
// Move e2fsck before switching root, so that it is available at the same path
// after switching root.
void PrepareSwitchRoot() {
constexpr const char* src = "/system/bin/snapuserd";
constexpr const char* dst = "/first_stage_ramdisk/system/bin/snapuserd";
if (access(dst, X_OK) == 0) {
LOG(INFO) << dst << " already exists and it can be executed";
return;
}
if (access(src, F_OK) != 0) {
PLOG(INFO) << "Not moving " << src << " because it cannot be accessed";
return;
}
auto dst_dir = android::base::Dirname(dst);
std::error_code ec;
if (access(dst_dir.c_str(), F_OK) != 0) {
if (!fs::create_directories(dst_dir, ec)) {
LOG(FATAL) << "Cannot create " << dst_dir << ": " << ec.message();
}
}
Copy(src, dst);
}
} // namespace
std::string GetModuleLoadList(bool recovery, const std::string& dir_path) {
@ -304,12 +338,11 @@ int FirstStageMain(int argc, char** argv) {
<< module_elapse_time.count() << " ms";
}
bool created_devices = false;
if (want_console == FirstStageConsoleParam::CONSOLE_ON_FAILURE) {
if (!IsRecoveryMode()) {
created_devices = DoCreateDevices();
if (!created_devices){
if (!created_devices) {
LOG(ERROR) << "Failed to create device nodes early";
}
}
@ -352,10 +385,11 @@ int FirstStageMain(int argc, char** argv) {
if (ForceNormalBoot(cmdline, bootconfig)) {
mkdir("/first_stage_ramdisk", 0755);
PrepareSwitchRoot();
// SwitchRoot() must be called with a mount point as the target, so we bind mount the
// target directory to itself here.
if (mount("/first_stage_ramdisk", "/first_stage_ramdisk", nullptr, MS_BIND, nullptr) != 0) {
LOG(FATAL) << "Could not bind mount /first_stage_ramdisk to itself";
PLOG(FATAL) << "Could not bind mount /first_stage_ramdisk to itself";
}
SwitchRoot("/first_stage_ramdisk");
}

3
init/switch_root.cpp
View file

@ -78,7 +78,8 @@ void SwitchRoot(const std::string& new_root) {
auto new_mount_path = new_root + mount_path;
mkdir(new_mount_path.c_str(), 0755);
if (mount(mount_path.c_str(), new_mount_path.c_str(), nullptr, MS_MOVE, nullptr) != 0) {
PLOG(FATAL) << "Unable to move mount at '" << mount_path << "'";
PLOG(FATAL) << "Unable to move mount at '" << mount_path << "' to "
<< "'" << new_mount_path << "'";
}
}