CODEWITHSUNDEEP
androidlinuxlinux-kernel
user422595
user422595

Reputation: 31

Obtaining kernel command line parameters of Android Linux kernel

I know when an (Android) bootloader starts loading kernel, it passes some parameters to the kernel (for example androidboot.verifiedbootstate, ...), which can be obtained via reading /proc/cmdline file, but it could be read only on rooted devices. Was I right ? Is there any other way of getting kernel parameters in non rooted Android devices ?

Upvotes: 2

Views: 6116

Answers (2)

Tom Hebb
Tom Hebb

Reputation: 1210

On Android 12 (and likely earlier/later versions, but I haven't tested), you can retrieve the kernel command line by taking a bug report. Bug reports are collected by Android's dumpstate command, which can and does read /proc/cmdline. Here are the three ways I know to collect a bug report:

  1. From the UI: In "Settings > System > Developer options", either tap "Bug report" directly or enable "Bug report shortcut" and then tap "Bug report" in the power off menu.
  2. From ADB shell: Run am bug-report (or am bug-report --progress for an "interactive" report that shows a progress bar) on the device using adb shell.
  3. From ADB directly: Run adb shell bugreport from your computer, optionally specifying a filename to save the report as (defaults to dumpstate-<DATE>.zip).

The device will take several minutes to collect the bug report. Once it's done (and while it's going if you chose an "interactive" report), it will display a notification.

Once you've collected the report, you need to retrieve it for viewing. If you chose option #3, adb has already done that for you and the bug report will be present on your computer as a .zip file. If you chose option #1 or #2, there are two ways to collect the report:

  1. Share it to an app on your device by tapping the "Bug report #X captured" notification.
  2. Copy it to your computer using adb pull. Bug reports are saved in /bugreports/ (which is a symlink to /data/user_de/0/com.android.shell/files/bugreports/) on the device.

Regardless of what you choose, you should end up with a .zip file containing the bug report. Inside that zip file will be a text file named bugreport.txt, dumpstate.txt, or one of the preceding with a date appended. That file will contain a lot of information about the system state, including a line right at the top starting with Command line: . That line shows the kernel command line.

Upvotes: 0

CL.
CL.

Reputation: 180060

In a 'normal' Linux, /proc/cmdline is readable by everyone. Android explicitly removes that read permission from /proc/cmdline.

There is no other way to get at its contents because that would circumvent this protection. (And if somebody were to find a way, it would be quickly closed.)

Upvotes: 3

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