Commit beb6abed authored Jul 29, 2019 by Mark Salyzyn

init: first stage init tie stdout and stderr to /dev/kmsg

It is exceedingly difficult to debug I/O and filesystem corruption
issues during first and selinux initialization stage init.  By
redirecting stderr, and for good measure stdout, to /dev/kmsg in
first stage init before it exec's "/system/bin/init" we can see
the filesystem corruption errors more clearly.

Before this we would see:

init: Skipped setting INIT_AVB_VERSION (not in recovery mode)
Kernel panic - not syncing: Attempted to kill init! exitcode=0x...

and then wonder why?

After this change we can see:

init: Skipped setting INIT_AVB_VERSION (not in recovery mode)
libc: Fatal signal 5 (SIGTRAP), code 128 (SI_KERNEL), fault addr...
Kernel panic - not syncing: Attempted to kill init! exitcode=0x...

-or-

init: Skipped setting INIT_AVB_VERSION (not in recovery mode)
linker: CANNOT LINK EXECUTABLE "/system/bin/init": cannot locate symbol...
Kernel panic - not syncing: Attempted to kill init! exitcode=0x...

(NB: with stutter removed because of stdout and stderr)

Silence from these sources otherwise on successful execution.

Test: boot
Bug: 138459777
Change-Id: I4200b24baeaa6e408a5e0a2c890561bda1e2f1f4

parent 244d9b8f

init/first_stage_init.cpp

+7 −3

Original line number	Diff line number	Diff line
		@@ -121,9 +121,9 @@ void StartConsole() {
		_exit(127);
		}
		ioctl(fd, TIOCSCTTY, 0);
		dup2(fd, 0);
		dup2(fd, 1);
		dup2(fd, 2);
		dup2(fd, STDIN_FILENO);
		dup2(fd, STDOUT_FILENO);
		dup2(fd, STDERR_FILENO);
		close(fd);

		const char* path = "/system/bin/sh";
		@@ -291,6 +291,10 @@ int FirstStageMain(int argc, char** argv) {

		const char* path = "/system/bin/init";
		const char* args[] = {path, "selinux_setup", nullptr};
		auto fd = open("/dev/kmsg", O_WRONLY \| O_CLOEXEC);
		dup2(fd, STDOUT_FILENO);
		dup2(fd, STDERR_FILENO);
		close(fd);
		execv(path, const_cast<char**>(args));

		// execv() only returns if an error happened, in which case we

init/selinux.cpp

+1 −0

Original line number	Diff line number	Diff line
		@@ -519,6 +519,7 @@ int SelinuxGetVendorAndroidVersion() {

		// This function initializes SELinux then execs init to run in the init SELinux context.
		int SetupSelinux(char** argv) {
		SetStdioToDevNull(argv);
		InitKernelLogging(argv);

		if (REBOOT_BOOTLOADER_ON_PANIC) {