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Issue 823629 link

Starred by 1 user
Status: Verified
Owner:
█ mka@chromium.org
Last visit > 30 days ago
Closed: Mar 2018
Cc:
drinkcat@chromium.org
groeck@chromium.org
manojgupta@chromium.org
Components:
EstimatedDays: ----
NextAction: ----
OS: Chrome
Pri: 1
Type: Bug
Build-Toolchain



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kernel-4.4: ftrace broken with USE=clang

Project Member Reported by drinkcat@chromium.org, Mar 20 2018 
Chrome OS 4.4 kernel at: a3a043ba69d2767100325d2f5e0e27c9e79be4bf8

Build kernel and deploy using:
cros_workon_make --board=poppy --install chromeos-kernel-4_4 && ./update_kernel.sh --remote=100.102.196.44 --remote_bootargs

cd /sys/kernel/debug/tracing/
echo "function" > current_tracer

system immediately reboots, nothing interesting in console-ramoops.

Building the kernel with USE=-clang fixes the issue.

Comment 1 by drinkcat@chromium.org, Mar 20 2018 

bebc6082da0a9 (upstream v4.14) has the same problem.

So does:
42b96e19dddd6 Linux 4.14.28

Comment 2 by mka@chromium.org, Mar 20 2018 

This seems to affect 'only' x86, it does not occur on scarlet/dru (arm64). Will have a look.

Comment 3 by mka@chromium.org, Mar 20 2018

Cc: manojgupta@chromium.org
The prod-kernel team ran into the same issue recently (b/73891158), a new LLVM version including a fix has just been rolled out for CrOS.

I verified that ftrace works (at least generally) on x86 (eve) with a kernel built with the lasted version of clang.

drinkcat@: Could you sync your workspace and confirm that the issue is also fixed for you with the latest LLVM? The version should be "Chromium OS 7.0_pre326829_p20180318 clang version 7.0.0"

Comment 4 by manojgupta@chromium.org, Mar 20 2018

Components: Tools>ChromeOS-Toolchain

Comment 5 by drinkcat@chromium.org, Mar 21 2018

Status: Verified (was: Assigned)
#3: Thanks, looking good with latest compiler.
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