linux-kernel - [PATCH v2 10/11] tools/nolibc: add ptrace support

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Message-ID: <20250919153420.727385-11-benjamin@sipsolutions.net>
Date: Fri, 19 Sep 2025 17:34:19 +0200
From: Benjamin Berg <benjamin@...solutions.net>
To: linux-um@...ts.infradead.org,
	Willy Tarreau <w@....eu>,
	Thomas Weißschuh <linux@...ssschuh.net>,
	linux-kselftest@...r.kernel.org,
	Arnaldo Carvalho de Melo <acme@...hat.com>
Cc: linux-kernel@...r.kernel.org,
	Benjamin Berg <benjamin.berg@...el.com>
Subject: [PATCH v2 10/11] tools/nolibc: add ptrace support

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>
---
 tools/include/nolibc/Makefile                |  1 +
 tools/include/nolibc/nolibc.h                |  1 +
 tools/include/nolibc/sys/ptrace.h            | 52 ++++++++++++++++++++
 tools/testing/selftests/nolibc/nolibc-test.c |  2 +
 4 files changed, 56 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..3119abdeeecb
--- /dev/null
+++ b/tools/include/nolibc/sys/ptrace.h
@@ -0,0 +1,52 @@
+/* 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);
+ *
+ * However, addr may also be an integer in some cases.
+ */
+static __attribute__((unused))
+long sys_vptrace(int op, pid_t pid, va_list args)
+{
+	return my_syscall4(__NR_ptrace, op, pid,
+			   va_arg(args, void *), va_arg(args, void *));
+}
+
+static __attribute__((unused))
+ssize_t sys_ptrace(int op, pid_t pid, ...)
+{
+	va_list args;
+
+	va_start(args, pid);
+	return sys_vptrace(op, pid, args);
+	va_end(args);
+}
+
+static __attribute__((unused))
+ssize_t ptrace(int op, pid_t pid, ...)
+{
+	va_list args;
+
+	va_start(args, pid);
+	return __sysret(sys_vptrace(op, pid, args));
+	va_end(args);
+}
+
+#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