linux-kernel - Re: [PATCH v3 11/12] tools/nolibc: add ptrace support

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Message-ID: <b2f2a592-da69-4fdb-8d84-8354895b3295@t-8ch.de>
Date: Thu, 25 Sep 2025 18:28:41 +0200
From: Thomas Weißschuh <linux@...ssschuh.net>
To: Benjamin Berg <benjamin@...solutions.net>
Cc: linux-um@...ts.infradead.org, Willy Tarreau <w@....eu>, 
	linux-kselftest@...r.kernel.org, Arnaldo Carvalho de Melo <acme@...hat.com>, 
	linux-kernel@...r.kernel.org, Benjamin Berg <benjamin.berg@...el.com>
Subject: Re: [PATCH v3 11/12] tools/nolibc: add ptrace support

On 2025-09-24 16:20:58+0200, Benjamin Berg wrote:
> From: Benjamin Berg <benjamin.berg@...el.com>
> 
> Add ptrace support, as it will be useful in UML.
> 
> Signed-off-by: Benjamin Berg <benjamin.berg@...el.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@....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 */

(...)