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pkg/aflow: provide better kernel build errors #7007

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1adb3d4
pkg/build: export ExtractRootCause
a-nogikh Mar 26, 2026
740a840
pkg/aflow: provide better kernel build errors
a-nogikh Mar 26, 2026
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6 changes: 5 additions & 1 deletion pkg/aflow/action/kernel/build.go
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Original file line number Diff line number Diff line change
Expand Up @@ -53,7 +53,11 @@ func BuildKernel(buildDir, srcDir, cfg string, cleanup bool) error {
const compileCommands = "compile_commands.json"
makeArgs = append(makeArgs, "-s", path.Base(image), compileCommands)
if _, err := osutil.RunCmd(time.Hour, srcDir, "make", makeArgs...); err != nil {
return aflow.FlowError(err)
buildErr := build.ExtractRootCause(err, targets.Linux, srcDir)
if buildErr == err {
return aflow.FlowError(err)
}
return aflow.FlowError(fmt.Errorf("%w\n\nRoot cause:\n%w", err, buildErr))
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@dvyukov dvyukov Mar 26, 2026

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I think this won't work. The problem is that we truncate errors, see #6896.
At the very least we should print buildErr first, and maybe take the last part of err.

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@a-nogikh a-nogikh Mar 26, 2026

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But the current err should actually be quite small, right?
It doesn't include the full output:

syzkaller/pkg/osutil/osutil.go

Lines 120 to 122 in 50cdcaa

func (err *VerboseError) Error() string {
return err.Err.Error()
}

ExtractRootCause's output should also be reasonably small:

syzkaller/pkg/build/build.go

Lines 136 to 138 in 50cdcaa

func (err *KernelError) Error() string {
return string(err.Report)
}

I think it should fit even without truncation.

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@dvyukov dvyukov Mar 26, 2026

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We may prepend the full output later b/c what you on the dashboard is not the short output, it's full output.

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@a-nogikh a-nogikh Mar 26, 2026

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In the context of #6896, we'd probably want to keep what we keep in Error reasonably short (= do not keep full logs there) for display in the trajectory table and separately store the full log separately (and make it available via some link).

}
if !cleanup {
return nil
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4 changes: 2 additions & 2 deletions pkg/build/build.go
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Expand Up @@ -106,7 +106,7 @@ func Image(params Params) (details ImageDetails, err error) {
} // Try to preserve the build error otherwise.
}
if err != nil {
err = extractRootCause(err, params.TargetOS, params.KernelDir)
err = ExtractRootCause(err, params.TargetOS, params.KernelDir)
return
}
if key := filepath.Join(params.OutputDir, "key"); osutil.IsExist(key) {
Expand Down Expand Up @@ -220,7 +220,7 @@ func compilerIdentity(compiler string) (string, error) {
return "", fmt.Errorf("no output from compiler --version")
}

func extractRootCause(err error, OS, kernelSrc string) error {
func ExtractRootCause(err error, OS, kernelSrc string) error {
if err == nil {
return nil
}
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2 changes: 1 addition & 1 deletion pkg/build/build_test.go
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Expand Up @@ -75,7 +75,7 @@ func TestExtractRootCause(t *testing.T) {
}
}
t.Run(fmt.Sprint(i), func(t *testing.T) {
got := extractRootCause(err, targetOs, test.src)
got := ExtractRootCause(err, targetOs, test.src)
if got != nil {
assert.Equal(t, expected, got)
}
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