From: Wake Liu wakel@google.com
[ Upstream commit bc4c0a48bdad7f225740b8e750fdc1da6d85e1eb ]
The get_next_frame() function in psock_tpacket.c was missing a return statement in its default switch case, leading to a compiler warning.
This was caused by a `bug_on(1)` call, which is defined as an `assert()`, being compiled out because NDEBUG is defined during the build.
Instead of adding a `return NULL;` which would silently hide the error and could lead to crashes later, this change restores the original author's intent. By adding `#undef NDEBUG` before including <assert.h>, we ensure the assertion is active and will cause the test to abort if this unreachable code is ever executed.
Signed-off-by: Wake Liu wakel@google.com Link: https://patch.msgid.link/20250809062013.2407822-1-wakel@google.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org ---
LLM Generated explanations, may be completely bogus:
YES
- What changed - Adds `#undef NDEBUG` before including `assert.h` in tools/testing/selftests/net/psock_tpacket.c:24 so that `assert()` (and the local `bug_on()` wrapper) are active during kselftest builds.
- Why it matters - The function `get_next_frame()` lacks a return in the `default` switch case (tools/testing/selftests/net/psock_tpacket.c:365). That case currently only calls `bug_on(1);` which is defined as `assert(!(cond))`. If `NDEBUG` is defined, `assert()` compiles to a no-op, leaving the function without a return statement on that path, triggering a compiler warning (and theoretically undefined behavior if ever executed). - Other functions that use `bug_on(1)` already append a dummy `return 0;` for the `NDEBUG` case, e.g. tools/testing/selftests/net/psock_tpacket.c:203 and tools/testing/selftests/net/psock_tpacket.c:322. `get_next_frame()` is the outlier.
- Correctness and intent - With `#undef NDEBUG`, `bug_on(1)` expands to an `assert(false)` which calls a `noreturn` failure path, so the compiler no longer warns about a missing return. More importantly, the test will abort if unreachable code is ever hit, matching the original author’s fail-fast intent rather than silently proceeding. - This is a common kselftest pattern; several selftests explicitly `#undef NDEBUG` to ensure assertions fire (for example, tools/testing/selftests/proc/read.c:22).
- Scope and risk - Selftests-only change; no in-kernel code or ABI touched. - Very small, localized change with no architectural implications. - Improves test reliability and eliminates a build warning that can be promoted to an error in stricter build environments. - No behavioral change in normal paths: `ring->version` is set to one of TPACKET_V1/V2/V3, so the `default` path should never be taken. If it is, failing loudly is desirable for a test.
- Stable backport criteria - Fixes a real issue for users of the stable kselftest suite (warning/possible -Werror build failure and loss of assert coverage). - Minimal risk and fully contained to `tools/testing/selftests/net/psock_tpacket.c`. - Does not introduce features or architectural changes; purely a test robustness fix.
Given the above, this is a low-risk, test-only fix that improves correctness and build reliability, and is appropriate for stable backporting.
tools/testing/selftests/net/psock_tpacket.c | 1 + 1 file changed, 1 insertion(+)
diff --git a/tools/testing/selftests/net/psock_tpacket.c b/tools/testing/selftests/net/psock_tpacket.c index 0dd909e325d93..2938045c5cf97 100644 --- a/tools/testing/selftests/net/psock_tpacket.c +++ b/tools/testing/selftests/net/psock_tpacket.c @@ -22,6 +22,7 @@ * - TPACKET_V3: RX_RING */
+#undef NDEBUG #include <stdio.h> #include <stdlib.h> #include <sys/types.h>