From: Benjamin Berg <benjamin.berg@intel.com>

Add ptrace support, as it will be useful in UML.

Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>

---
v3:
- Only use variardic for ptrace and not for sys_ptrace
---
 tools/include/nolibc/Makefile                |  1 +
 tools/include/nolibc/nolibc.h                |  1 +
 tools/include/nolibc/sys/ptrace.h            | 44 ++++++++++++++++++++
 tools/testing/selftests/nolibc/nolibc-test.c |  2 +
 4 files changed, 48 insertions(+)
 create mode 100644 tools/include/nolibc/sys/ptrace.h

diff --git a/tools/include/nolibc/Makefile b/tools/include/nolibc/Makefile
index 9bbbba32dac6..8e0cac3ac522 100644
--- a/tools/include/nolibc/Makefile
+++ b/tools/include/nolibc/Makefile
@@ -53,6 +53,7 @@ all_files := \
 		sys/mman.h \
 		sys/mount.h \
 		sys/prctl.h \
+		sys/ptrace.h \
 		sys/random.h \
 		sys/reboot.h \
 		sys/resource.h \
diff --git a/tools/include/nolibc/nolibc.h b/tools/include/nolibc/nolibc.h
index b4bc1c9b883d..590eef545ca6 100644
--- a/tools/include/nolibc/nolibc.h
+++ b/tools/include/nolibc/nolibc.h
@@ -101,6 +101,7 @@
 #include "sys/mman.h"
 #include "sys/mount.h"
 #include "sys/prctl.h"
+#include "sys/ptrace.h"
 #include "sys/random.h"
 #include "sys/reboot.h"
 #include "sys/resource.h"
diff --git a/tools/include/nolibc/sys/ptrace.h b/tools/include/nolibc/sys/ptrace.h
new file mode 100644
index 000000000000..5d1e52965878
--- /dev/null
+++ b/tools/include/nolibc/sys/ptrace.h
@@ -0,0 +1,44 @@
+/* SPDX-License-Identifier: LGPL-2.1 OR MIT */
+/*
+ * ptrace for NOLIBC
+ * Copyright (C) 2017-2021 Willy Tarreau <w@1wt.eu>
+ * Copyright (C) 2025 Intel Corporation
+ */
+
+/* make sure to include all global symbols */
+#include "../nolibc.h"
+
+#ifndef _NOLIBC_SYS_PTRACE_H
+#define _NOLIBC_SYS_PTRACE_H
+
+#include "../sys.h"
+#include "uio.h"
+
+
+#include <linux/ptrace.h>
+
+/*
+ * long ptrace(int op, pid_t pid, void *addr, void *data);
+ */
+static __attribute__((unused))
+long sys_ptrace(int op, pid_t pid, void *addr, void *data)
+{
+	return my_syscall4(__NR_ptrace, op, pid, addr, data);
+}
+
+static __attribute__((unused))
+ssize_t ptrace(int op, pid_t pid, ...)
+{
+	ssize_t ret;
+	va_list args;
+
+	va_start(args, pid);
+	ret = __sysret(sys_ptrace(op, pid,
+				  va_arg(args, void *),
+				  va_arg(args, void *)));
+	va_end(args);
+
+	return ret;
+}
+
+#endif /* _NOLIBC_SYS_PTRACE_H */
diff --git a/tools/testing/selftests/nolibc/nolibc-test.c b/tools/testing/selftests/nolibc/nolibc-test.c
index 1907128bc3f6..4c1b9ee32b7d 100644
--- a/tools/testing/selftests/nolibc/nolibc-test.c
+++ b/tools/testing/selftests/nolibc/nolibc-test.c
@@ -17,6 +17,7 @@
 #include <sys/mman.h>
 #include <sys/mount.h>
 #include <sys/prctl.h>
+#include <sys/ptrace.h>
 #include <sys/random.h>
 #include <sys/reboot.h>
 #include <sys/resource.h>
@@ -1404,6 +1405,7 @@ int run_syscall(int min, int max)
 		CASE_TEST(readv_zero);        EXPECT_SYSZR(1, readv(1, NULL, 0)); break;
 		CASE_TEST(writev_badf);       EXPECT_SYSER(1, writev(-1, &iov_one, 1), -1, EBADF); break;
 		CASE_TEST(writev_zero);       EXPECT_SYSZR(1, writev(1, NULL, 0)); break;
+		CASE_TEST(ptrace);            EXPECT_SYSER(1, ptrace(PTRACE_CONT, getpid(), NULL, NULL), -1, ESRCH); break;
 		CASE_TEST(syscall_noargs);    EXPECT_SYSEQ(1, syscall(__NR_getpid), getpid()); break;
 		CASE_TEST(syscall_args);      EXPECT_SYSER(1, syscall(__NR_statx, 0, NULL, 0, 0, NULL), -1, EFAULT); break;
 		CASE_TEST(namespace);         EXPECT_SYSZR(euid0 && proc, test_namespace()); break;
-- 
2.51.0

On 2025-09-24 16:20:58+0200, Benjamin Berg wrote:
> From: Benjamin Berg <benjamin.berg@intel.com>
> 
> Add ptrace support, as it will be useful in UML.
> 
> Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
> 
> ---
> v3:
> - Only use variardic for ptrace and not for sys_ptrace
> ---
>  tools/include/nolibc/Makefile                |  1 +
>  tools/include/nolibc/nolibc.h                |  1 +
>  tools/include/nolibc/sys/ptrace.h            | 44 ++++++++++++++++++++
>  tools/testing/selftests/nolibc/nolibc-test.c |  2 +
>  4 files changed, 48 insertions(+)
>  create mode 100644 tools/include/nolibc/sys/ptrace.h

(...)

> diff --git a/tools/include/nolibc/sys/ptrace.h b/tools/include/nolibc/sys/ptrace.h
> new file mode 100644
> index 000000000000..5d1e52965878
> --- /dev/null
> +++ b/tools/include/nolibc/sys/ptrace.h
> @@ -0,0 +1,44 @@
> +/* SPDX-License-Identifier: LGPL-2.1 OR MIT */
> +/*
> + * ptrace for NOLIBC
> + * Copyright (C) 2017-2021 Willy Tarreau <w@1wt.eu>
> + * Copyright (C) 2025 Intel Corporation
> + */
> +
> +/* make sure to include all global symbols */
> +#include "../nolibc.h"
> +
> +#ifndef _NOLIBC_SYS_PTRACE_H
> +#define _NOLIBC_SYS_PTRACE_H
> +
> +#include "../sys.h"
> +#include "uio.h"
> +
> +
> +#include <linux/ptrace.h>
> +
> +/*
> + * long ptrace(int op, pid_t pid, void *addr, void *data);
> + */
> +static __attribute__((unused))
> +long sys_ptrace(int op, pid_t pid, void *addr, void *data)
> +{
> +	return my_syscall4(__NR_ptrace, op, pid, addr, data);
> +}
> +
> +static __attribute__((unused))
> +ssize_t ptrace(int op, pid_t pid, ...)
> +{
> +	ssize_t ret;
> +	va_list args;
> +
> +	va_start(args, pid);
> +	ret = __sysret(sys_ptrace(op, pid,
> +				  va_arg(args, void *),
> +				  va_arg(args, void *)));
> +	va_end(args);

My understanding of the last discussion was not to use varargs here
either. Instead I wanted to stick to the prototype from the manpage.

> +
> +	return ret;
> +}
> +
> +#endif /* _NOLIBC_SYS_PTRACE_H */

(...)