[PATCH] selftests: riscv: Bypass libc in inactive vector ptrace test

[PATCH] selftests: riscv: Bypass libc in inactive vector ptrace test

[Andrew Jones]

The ptrace_v_not_enabled test expects the child to reach its ebreak
before it has used the vector extension. That is not guaranteed when
using fork(), because libc may run child atfork handlers before
returning to the test code. In those cases PTRACE_GETREGSET for
NT_RISCV_VECTOR then succeeds instead of returning ENODATA for
inactive vector state.

Use the raw clone syscall with SIGCHLD to keep fork-like semantics
while bypassing libc's fork wrapper and atfork handler chain.

Cc: Andy Chiu <tchiu@tenstorrent.com>
Assisted-by: Claude:claude-sonnet-4-6
Signed-off-by: Andrew Jones <andrew.jones@oss.qualcomm.com>
---
 tools/testing/selftests/riscv/vector/validate_v_ptrace.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/riscv/vector/validate_v_ptrace.c b/tools/testing/selftests/riscv/vector/validate_v_ptrace.c
index 74b6f6bcf067..b038e2175c80 100644
--- a/tools/testing/selftests/riscv/vector/validate_v_ptrace.c
+++ b/tools/testing/selftests/riscv/vector/validate_v_ptrace.c
@@ -1,5 +1,6 @@
 // SPDX-License-Identifier: GPL-2.0-only
 #include <sys/ptrace.h>
+#include <sys/syscall.h>
 #include <sys/types.h>
 #include <sys/wait.h>
 #include <sys/uio.h>
@@ -25,9 +26,9 @@ TEST(ptrace_v_not_enabled)
 		SKIP(return, "Vector not supported");
 
 	chld_lock = 1;
-	pid = fork();
+	pid = (pid_t)syscall(SYS_clone, SIGCHLD, 0, NULL, 0, NULL);
 	ASSERT_LE(0, pid)
-		TH_LOG("fork: %m");
+		TH_LOG("clone: %m");
 
 	if (pid == 0) {
 		while (chld_lock == 1)
-- 
2.43.0


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Re: [PATCH] selftests: riscv: Bypass libc in inactive vector ptrace test

[Paul Walmsley]

On Tue, 7 Jul 2026, Andrew Jones wrote:

> The ptrace_v_not_enabled test expects the child to reach its ebreak
> before it has used the vector extension. That is not guaranteed when
> using fork(), because libc may run child atfork handlers before
> returning to the test code. In those cases PTRACE_GETREGSET for
> NT_RISCV_VECTOR then succeeds instead of returning ENODATA for
> inactive vector state.
> 
> Use the raw clone syscall with SIGCHLD to keep fork-like semantics
> while bypassing libc's fork wrapper and atfork handler chain.
> 
> Cc: Andy Chiu <tchiu@tenstorrent.com>
> Assisted-by: Claude:claude-sonnet-4-6
> Signed-off-by: Andrew Jones <andrew.jones@oss.qualcomm.com>

Thanks, queued for v7.2-rc.

- Paul

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Re: [PATCH] selftests: riscv: Bypass libc in inactive vector ptrace test

[patchwork-bot+linux-riscv]

Hello:

This patch was applied to riscv/linux.git (fixes)
by Paul Walmsley <pjw@kernel.org>:

On Tue,  7 Jul 2026 17:38:27 +0200 you wrote:
> The ptrace_v_not_enabled test expects the child to reach its ebreak
> before it has used the vector extension. That is not guaranteed when
> using fork(), because libc may run child atfork handlers before
> returning to the test code. In those cases PTRACE_GETREGSET for
> NT_RISCV_VECTOR then succeeds instead of returning ENODATA for
> inactive vector state.
> 
> [...]

Here is the summary with links:
  - selftests: riscv: Bypass libc in inactive vector ptrace test
    https://git.kernel.org/riscv/c/70b439e46eff

You are awesome, thank you!
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