linux-kernel - [PATCH v2] tools/nolibc: make signature of ioctl() more flexible

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Message-Id: <20250128-nolibc-ioctl-v2-1-4a07e91fd648@weissschuh.net>
Date: Tue, 28 Jan 2025 22:22:46 +0100
From: Thomas Weißschuh <linux@...ssschuh.net>
To: Willy Tarreau <w@....eu>
Cc: linux-kernel@...r.kernel.org, 
 Thomas Weißschuh <linux@...ssschuh.net>
Subject: [PATCH v2] tools/nolibc: make signature of ioctl() more flexible

POSIX defines the signature of ioctl() as follows,
to allow passing a pointer or integer without casting:
	int ioctl(int fildes, int request, ... /* arg */);

Nolibc ioctl() expects a pointer, forcing the user to manually cast.
Using va_arg to make the signature more flexible would work but seems to
prevent inlining of the function. Instead use a macro. "fd" and "req"
will still be typechecked through sys_ioctl().

Signed-off-by: Thomas Weißschuh <linux@...ssschuh.net>
---
Changes in v2:
- Handle integers of arbitrary sizes
- Align with Linux syscall signature
- Link to v1: https://lore.kernel.org/r/20250123-nolibc-ioctl-v1-1-93f8bca99de5@weissschuh.net
---
This is now not directly POSIX compatible. Instead it uses the signature
of the Linux syscall. It should be close enough.
---
 tools/include/nolibc/sys.h | 12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/tools/include/nolibc/sys.h b/tools/include/nolibc/sys.h
index d4a5c2399a66b200ebf7ab249569cce2285481a5..8c0a55bc9dc3aacd110db0195975fe4f85480fc5 100644
--- a/tools/include/nolibc/sys.h
+++ b/tools/include/nolibc/sys.h
@@ -532,20 +532,16 @@ uid_t getuid(void)
 
 
 /*
- * int ioctl(int fd, unsigned long req, void *value);
+ * int ioctl(int fd, unsigned long cmd, ... arg);
  */
 
 static __attribute__((unused))
-int sys_ioctl(int fd, unsigned long req, void *value)
+long sys_ioctl(unsigned int fd, unsigned int cmd, unsigned long arg)
 {
-	return my_syscall3(__NR_ioctl, fd, req, value);
+	return my_syscall3(__NR_ioctl, fd, cmd, arg);
 }
 
-static __attribute__((unused))
-int ioctl(int fd, unsigned long req, void *value)
-{
-	return __sysret(sys_ioctl(fd, req, value));
-}
+#define ioctl(fd, cmd, arg) __sysret(sys_ioctl(fd, cmd, (unsigned long)(arg)))
 
 /*
  * int kill(pid_t pid, int signal);

---
base-commit: cd45f362fc1f2d81fa69a19e7f8eca058db3e320
change-id: 20250123-nolibc-ioctl-03e86c20049a

Best regards,
-- 
Thomas Weißschuh <linux@...ssschuh.net>