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selftests/mm: fix child process exit codes in ksm_functional_tests

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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. 
Additionally, test_prctl_fork_exec() now uses exit(4) after a failed
execv() to clearly signal exec failures.  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

Link: https://lkml.kernel.org/r/20250816040113.760010-6-aboorvad@linux.ibm.com
Fixes: 6c47de3be3 ("selftest/mm: ksm_functional_tests: extend test case for ksm fork/exec")
Co-developed-by: Donet Tom <donettom@linux.ibm.com>
Signed-off-by: Donet Tom <donettom@linux.ibm.com>
Signed-off-by: Aboorva Devarajan <aboorvad@linux.ibm.com>
Acked-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Wei Yang <richard.weiyang@gmail.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Mariano Pache <npache@redhat.com>
Cc: "Ritesh Harjani (IBM)" <ritesh.list@gmail.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Aboorva Devarajan 2025-08-16 09:31:11 +05:30 committed by Andrew Morton
parent 7bc857ddee
commit 2d941088f4
1 changed files with 9 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

16
tools/testing/selftests/mm/ksm_functional_tests.c
View File

@ -512,14 +512,14 @@ static int test_child_ksm(void)
/* Test if KSM is enabled for the process. */
if (prctl(PR_GET_MEMORY_MERGE, 0, 0, 0, 0) != 1)
return -1;
return 1;
/* Test if merge could really happen. */
map = __mmap_and_merge_range(0xcf, size, PROT_READ | PROT_WRITE, KSM_MERGE_NONE);
if (map == MAP_MERGE_FAIL)
return -2;
return 2;
else if (map == MAP_MERGE_SKIP)
return -3;
return 3;
ksm_unmerge();
munmap(map, size);
@ -528,12 +528,14 @@ static int test_child_ksm(void)
static void test_child_ksm_err(int status)
{
if (status == -1)
if (status == 1)
ksft_test_result_fail("unexpected PR_GET_MEMORY_MERGE result in child\n");
else if (status == -2)
else if (status == 2)
ksft_test_result_fail("Merge in child failed\n");
else if (status == -3)
else if (status == 3)
ksft_test_result_skip("Merge in child skipped\n");
else if (status == 4)
ksft_test_result_fail("Binary not found\n");
}
/* Verify that prctl ksm flag is inherited. */
@ -606,7 +608,7 @@ static void test_prctl_fork_exec(void)
char *argv_for_program[] = { prg_name, FORK_EXEC_CHILD_PRG_NAME, NULL };
execv(prg_name, argv_for_program);
return;
exit(4);
}
if (waitpid(child_pid, &status, 0) > 0) {