Starting March 27, 2025, we recommend using android-latest-release instead of aosp-main to build and contribute to AOSP. For more information, see Changes to AOSP.
Use strace
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Strace enables you to see the system calls a
process makes and what those system calls return.
Build strace
To build strace, run the following:
mmma -j6 external/strace
Attach to a running process
The simplest and most common use case for strace is to attach it to a running
process, which you can do with:
adb shell strace -f -p PID
The -f flag tells strace to attach to all the threads in the
process, plus any new threads spawned later.
A typical process makes a lot of system calls, so you'll want to review the
strace man page
to learn how to collect only data you're actually interested in.
Use on an app
To use strace on an app:
- Set up the device so that you can run strace. You need to be root, disable SELinux, and restart
the runtime to remove the seccomp filter that will otherwise prevent strace from running:
adb root
adb shell setenforce 0
adb shell stop
adb shell start
- Set up a world-writable directory for strace logs, because strace will be running under the
app's uid:
adb shell mkdir -m 777 /data/local/tmp/strace
- Choose the process to trace and launch it:
adb shell setprop wrap.com.android.calendar '"logwrapper strace -f -o /data/local/tmp/strace/strace.com.android.calendar.txt"'
- Launch the process normally.
Use on the zygote
To use strace on the zygote, fix the relevant init.rc zygote
line (requires adb shell setenforce 0):
cd system/core/
patch -p1 <<EOF
--- a/rootdir/init.zygote32.rc
+++ b/rootdir/init.zygote32.rc
@@ -1,4 +1,4 @@
-service zygote /system/bin/app_process -Xzygote /system/bin --zygote --start-system-server
+service zygote /system/bin/strace -o /data/local/tmp/zygote.strace /system/bin/app_process -Xzygote /system/bin --zygote --start-system-server
class main
socket zygote stream 660 root system
onrestart write /sys/android_power/request_state wake
EOF
Get strace logs during Android boot
To get strace logs during Android boot, make the following changes:
- Since the process name changes from
zygote to
strace, the given service may fail to start due to the missing
SELinux file_context for strace. The solution is to
add a new line for strace in system/sepolicy/private/file_contexts
and copy the original file context over. Example:
/dev/socket/zygote u:object_r:zygote_socket:s0
+ /system/bin/strace u:object_r:zygote_socket:s0
- Add kernel or bootconfig parameter, then boot the device in SELinux permissive mode. You can
do this by adding
androidboot.selinux=permissiveto
BOARD_KERNEL_CMDLINE, or to BOARD_BOOTCONFIG in Android
12 with kernel version 5.10 or greater.
(This variable becomes read-only in build/core/Makefile but is always
available under /device/*/BoardConfig.)
Example for the Pixel (sailfish) device in
/device/google/marlin/sailfish/BoardConfig.mk:
- BOARD_KERNEL_CMDLINE := .... androidboot.hardware=sailfish ...
+BOARD_KERNEL_CMDLINE := .... androidboot.hardware=sailfish ... androidboot.selinux=permissive
After making the change, build and flash the boot image and the device will boot
in permissive mode.
Content and code samples on this page are subject to the licenses described in the Content License. Java and OpenJDK are trademarks or registered trademarks of Oracle and/or its affiliates.
Last updated 2025-06-12 UTC.
[[["Easy to understand","easyToUnderstand","thumb-up"],["Solved my problem","solvedMyProblem","thumb-up"],["Other","otherUp","thumb-up"]],[["Missing the information I need","missingTheInformationINeed","thumb-down"],["Too complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-06-12 UTC."],[],[],null,["# Use strace\n\n[Strace](https://strace.io) enables you to see the system calls a\nprocess makes and what those system calls return.\n\nBuild strace\n------------\n\nTo build strace, run the following: \n\n```\nmmma -j6 external/strace\n```\n\nAttach to a running process\n---------------------------\n\nThe simplest and most common use case for strace is to attach it to a running\nprocess, which you can do with: \n\n```\nadb shell strace -f -p PID\n```\n\nThe `-f` flag tells strace to attach to all the threads in the\nprocess, plus any new threads spawned later.\n\nA typical process makes a lot of system calls, so you'll want to review the\n[strace man page](http://man7.org/linux/man-pages/man1/strace.1.html)\nto learn how to collect only data you're actually interested in.\n\nUse on an app\n-------------\n\nTo use strace on an app:\n\n1. Set up the device so that you can run strace. You need to be root, disable SELinux, and restart the runtime to remove the seccomp filter that will otherwise prevent strace from running: \n\n adb root\n adb shell setenforce 0\n adb shell stop\n adb shell start\n\n2. Set up a world-writable directory for strace logs, because strace will be running under the app's uid: \n\n adb shell mkdir -m 777 /data/local/tmp/strace\n\n3. Choose the process to trace and launch it: \n\n ```\n adb shell setprop wrap.com.android.calendar '\"logwrapper strace -f -o /data/local/tmp/strace/strace.com.android.calendar.txt\"'\n ```\n4. Launch the process normally.\n\nUse on the zygote\n-----------------\n\nTo use strace on the zygote, fix the relevant `init.rc` zygote\nline (requires `adb shell setenforce 0`): \n\n cd system/core/\n patch -p1 \u003c\u003cEOF\n --- a/rootdir/init.zygote32.rc\n +++ b/rootdir/init.zygote32.rc\n @@ -1,4 +1,4 @@\n -service zygote /system/bin/app_process -Xzygote /system/bin --zygote --start-system-server\n +service zygote /system/bin/strace -o /data/local/tmp/zygote.strace /system/bin/app_process -Xzygote /system/bin --zygote --start-system-server\n class main\n socket zygote stream 660 root system\n onrestart write /sys/android_power/request_state wake\n EOF\n\nGet strace logs during Android boot\n-----------------------------------\n\nTo get strace logs during Android boot, make the following changes:\n\n- Since the process name changes from `zygote` to `strace`, the given service may fail to start due to the missing SELinux `file_context` for `strace`. The solution is to add a new line for strace in `system/sepolicy/private/file_contexts` and copy the original file context over. Example: \n\n ```\n /dev/socket/zygote u:object_r:zygote_socket:s0\n + /system/bin/strace u:object_r:zygote_socket:s0\n ```\n- Add kernel or bootconfig parameter, then boot the device in SELinux permissive mode. You can do this by adding `androidboot.selinux=permissive`to `BOARD_KERNEL_CMDLINE`, or to `BOARD_BOOTCONFIG` in Android 12 with kernel version 5.10 or greater. (This variable becomes read-only in `build/core/Makefile` but is always available under `/device/*/BoardConfig`.) \n\n Example for the Pixel (sailfish) device in `/device/google/marlin/sailfish/BoardConfig.mk`: \n\n ```\n - BOARD_KERNEL_CMDLINE := .... androidboot.hardware=sailfish ...\n +BOARD_KERNEL_CMDLINE := .... androidboot.hardware=sailfish ... androidboot.selinux=permissive\n ```\n After making the change, build and flash the boot image and the device will boot in permissive mode."]]
