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
diff --git a/init/first_stage_init.cpp b/init/first_stage_init.cpp
index b60c450..fd2d766 100644
--- a/init/first_stage_init.cpp
+++ b/init/first_stage_init.cpp
@@ -121,9 +121,9 @@
_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 @@
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
diff --git a/init/selinux.cpp b/init/selinux.cpp
index 54be086..309fcc1 100644
--- a/init/selinux.cpp
+++ b/init/selinux.cpp
@@ -519,6 +519,7 @@
// 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) {