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Commit 2507a048 authored by Mark Salyzyn's avatar Mark Salyzyn
Browse files

base: kernel logging get pre-opened /dev/kmsg from environment 

If the environment has an instance of /dev/kmsg pre-opened, pick up.
This happens when an init script has 'file w /dev/kmsg' in the
daemon's recipe.

libcutils android_get_control_file operations are open-coded to
prevent a dependency on libcutils itself.  Also check that /dev/kmsg
file descriptor is valid and open'd for write only.

Test: check to make sure init() kernel logging still works
Bug: 77541952
Bug: 77661605
Change-Id: I007553acd594ef0815d23f32f8aa2867518570ba
parent 0289f35b

base/logging.cpp

+19 −1
Original line number Diff line number Diff line
@@ -54,6 +54,7 @@ 
#endif



#include <android-base/macros.h>

#include <android-base/parseint.h>

#include <android-base/strings.h>

#include <android-base/threads.h>
@@ -82,6 +83,23 @@ const char* getprogname() { 
  return progname;

}

#endif



#if defined(__linux__)

int OpenKmsg() {

#if defined(__ANDROID__)

  // pick up 'file w /dev/kmsg' environment from daemon's init rc file

  const auto val = getenv("ANDROID_FILE__dev_kmsg");

  if (val != nullptr) {

    int fd;

    if (android::base::ParseInt(val, &fd, 0)) {

      auto flags = fcntl(fd, F_GETFL);

      if ((flags != -1) && ((flags & O_ACCMODE) == O_WRONLY)) return fd;

    }

  }

#endif

  return TEMP_FAILURE_RETRY(open("/dev/kmsg", O_WRONLY | O_CLOEXEC));

}

#endif

} // namespace



namespace android {
@@ -150,7 +168,7 @@ void KernelLogger(android::base::LogId, android::base::LogSeverity severity, 
  static_assert(arraysize(kLogSeverityToKernelLogLevel) == android::base::FATAL + 1,

                "Mismatch in size of kLogSeverityToKernelLogLevel and values in LogSeverity");



  static int klog_fd = TEMP_FAILURE_RETRY(open("/dev/kmsg", O_WRONLY | O_CLOEXEC));

  static int klog_fd = OpenKmsg();

  if (klog_fd == -1) return;



  int level = kLogSeverityToKernelLogLevel[severity];