Re: [PATCH v2 5/7] selftests/mm: Fix child process exit codes in ksm_functional_tests

[Donet Tom]

Hi David

On 7/3/25 2:03 PM, David Hildenbrand wrote:
> On 03.07.25 08:06, Aboorva Devarajan wrote:
> > In ksm_functional_tests, test_child_ksm() returned negative values
> > to indicate errors. However, when passed to exit(), these were
> > interpreted as large unsigned values (e.g, -2 became 254), leading to
> > incorrect handling in the parent process. As a result, some tests
> > appeared to be skipped or silently failed.
> >
> > This patch changes test_child_ksm() to return positive error codes
> > (1, 2, 3) and updates test_child_ksm_err() to interpret them correctly.
> > This ensures the parent accurately detects and reports child process
> > failures.
> >
> > --------------
> > Before patch:
> > --------------
> > - [RUN] test_unmerge
> > ok 1 Pages were unmerged
> > ...
> > - [RUN] test_prctl_fork
> > - No pages got merged
> > - [RUN] test_prctl_fork_exec
> > ok 7 PR_SET_MEMORY_MERGE value is inherited
> > ...
> > Bail out! 1 out of 8 tests failed
> > - Planned tests != run tests (9 != 8)
> > - Totals: pass:7 fail:1 xfail:0 xpass:0 skip:0 error:0
> >
> > --------------
> > After patch:
> > --------------
> > - [RUN] test_unmerge
> > ok 1 Pages were unmerged
> > ...
> > - [RUN] test_prctl_fork
> > - No pages got merged
> > not ok 7 Merge in child failed
> > - [RUN] test_prctl_fork_exec
> > ok 8 PR_SET_MEMORY_MERGE value is inherited
> > ...
> > Bail out! 2 out of 9 tests failed
> > - Totals: pass:7 fail:2 xfail:0 xpass:0 skip:0 error:0
> >
> > Fixes: 6c47de3be3a0 ("selftest/mm: ksm_functional_tests: extend test 
> > case for ksm fork/exec")
> > Signed-off-by: Aboorva Devarajan <aboorvad@xxxxxxxxxxxxx>
>
> BTW, when I run the test, I get this weird output
>
> TAP version 13
> 1..9
> # [RUN] test_unmerge
> ok 1 Pages were unmerged
> # [RUN] test_unmerge_zero_pages
> ok 2 KSM zero pages were unmerged
> # [RUN] test_unmerge_discarded
> ok 3 Pages were unmerged
> # [RUN] test_unmerge_uffd_wp
> ok 4 Pages were unmerged
> # [RUN] test_prot_none
> ok 5 Pages were unmerged
> # [RUN] test_prctl
> ok 6 Setting/clearing PR_SET_MEMORY_MERGE works
> # [RUN] test_prctl_fork
> ok 7 PR_SET_MEMORY_MERGE value is inherited
> # [RUN] test_prctl_fork_exec
>
> ^ where is the test?
>
> # [RUN] test_prctl_unmerge
> ok 8 Pages were unmerged
> # Planned tests != run tests (9 != 8)
> # Totals: pass:8 fail:0 xfail:0 xpass:0 skip:0 error:0
>
> ^ what?
>
> ok 8 PR_SET_MEMORY_MERGE value is inherited
> # [RUN] test_prctl_unmerge
> ok 9 Pages were unmerged
> # Totals: pass:9 fail:0 xfail:0 xpass:0 skip:0 error:0
>
> ^ huh, what now?

The problem with the exec test is that it uses its own binary to exec.

        } else if (child_pid == 0) {
                char *prg_name = "./ksm_functional_tests";
                char *argv_for_program[] = { prg_name, 
FORK_EXEC_CHILD_PRG_NAME, NULL };

                execv(prg_name, argv_for_program);
                return;
        }

So we should run it on the same directory where the binary present.