linux-kernel - [PATCH 3/3] selftests/clone3: Add sys

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Message-Id: <20260116153051.21678-4-ludwig.rydberg@gaisler.com>
Date: Fri, 16 Jan 2026 16:30:51 +0100
From: Ludwig Rydberg <ludwig.rydberg@...sler.com>
To: davem@...emloft.net,
	andreas@...sler.com,
	brauner@...nel.org,
	shuah@...nel.org
Cc: sparclinux@...r.kernel.org,
	linux-kselftest@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	arnd@...db.de,
	glaubitz@...sik.fu-berlin.de,
	geert@...ux-m68k.org,
	schuster.simon@...mens-energy.com
Subject: [PATCH 3/3] selftests/clone3: Add sys_clone3 wrapper for SPARC

Add a sys_clone3 wrapper (based on the INLINE_CLONE_SYSCALL macro
in glibc) for SPARC to handle its unique return call convention.

The needed handling is described in arch/sparc/kernel/process_{32|64}.c:

Parent -->  %o0 == child's  pid, %o1 == 0
Child  -->  %o0 == parent's pid, %o1 == 1

Signed-off-by: Ludwig Rydberg <ludwig.rydberg@...sler.com>
---
 .../selftests/clone3/clone3_selftests.h       | 75 +++++++++++++++++++
 1 file changed, 75 insertions(+)

diff --git a/tools/testing/selftests/clone3/clone3_selftests.h b/tools/testing/selftests/clone3/clone3_selftests.h
index a0593e8950f0..5fa33294227d 100644
--- a/tools/testing/selftests/clone3/clone3_selftests.h
+++ b/tools/testing/selftests/clone3/clone3_selftests.h
@@ -33,12 +33,87 @@ struct __clone_args {
 	__aligned_u64 cgroup;
 };
 
+#if defined(__sparc__)
+#include <errno.h>
+
+#if	defined(__arch64__)
+#define __SYSCALL_STRING						\
+	"mov	%[scn], %%g1;"						\
+	"ta	0x6d;"							\
+	"bcc,pt	%%xcc, 1f;"						\
+	" nop;"								\
+	"sub	%%g0, %%o0, %%o0;"					\
+	"1:"
+
+#define __SYSCALL_CLOBBERS						\
+	"g1", "f0", "f1", "f2", "f3", "f4", "f5", "f6", "f7",		\
+	"f8", "f9", "f10", "f11", "f12", "f13", "f14", "f15",		\
+	"f16", "f17", "f18", "f19", "f20", "f21", "f22", "f23",		\
+	"f24", "f25", "f26", "f27", "f28", "f29", "f30", "f31",		\
+	"f32", "f34", "f36", "f38", "f40", "f42", "f44", "f46",		\
+	"f48", "f50", "f52", "f54", "f56", "f58", "f60", "f62",		\
+	"cc", "memory"
+#else
+#define __SYSCALL_STRING						\
+	"mov	%[scn], %%g1;"						\
+	"ta	0x10;"							\
+	"bcc	1f;"							\
+	" nop;"								\
+	"sub	%%g0, %%o0, %%o0;"					\
+	"1:"
+
+#define __SYSCALL_CLOBBERS						\
+	"g1", "f0", "f1", "f2", "f3", "f4", "f5", "f6", "f7",		\
+	"f8", "f9", "f10", "f11", "f12", "f13", "f14", "f15",		\
+	"f16", "f17", "f18", "f19", "f20", "f21", "f22", "f23",		\
+	"f24", "f25", "f26", "f27", "f28", "f29", "f30", "f31",		\
+	"cc", "memory"
+#endif
+
+/* A special wrapper is required to handle the return call convention
+ * on SPARC and is based on the INLINE_CLONE_SYSCALL macro in glibc.
+ *
+ * Parent -->  %o0 == child's  pid, %o1 == 0
+ * Child  -->  %o0 == parent's pid, %o1 == 1
+ */
+static inline pid_t sparc_clone3(struct __clone_args *args, size_t size)
+{
+	long _cl_args = (long) (args);
+	long _size = (long) (size);
+	long _scn = __NR_clone3;
+
+	register long o0 __asm__ ("o0") = _cl_args;
+	register long o1 __asm__ ("o1") = _size;
+
+	asm volatile (__SYSCALL_STRING
+			: "=r" (o0), "=r" (o1)
+			: [scn] "r" (_scn), "0" (o0), "1" (o1)
+			: __SYSCALL_CLOBBERS);
+
+	if ((unsigned long) (o0) > -4096UL) {
+		errno = -o0;
+		o0 = -1L;
+	} else {
+		o0 &= (o1 - 1);
+	}
+
+	return o0;
+}
+
+static pid_t sys_clone3(struct __clone_args *args, size_t size)
+{
+	fflush(stdout);
+	fflush(stderr);
+	return sparc_clone3(args, size);
+}
+#else
 static pid_t sys_clone3(struct __clone_args *args, size_t size)
 {
 	fflush(stdout);
 	fflush(stderr);
 	return syscall(__NR_clone3, args, size);
 }
+#endif
 
 static inline void test_clone3_supported(void)
 {
-- 
2.35.3