linux-kernel - [PATCH 1/2] tools/nolibc: add support for sys

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Message-Id: <20250130-nolibc-dir-v1-1-ea9950b52e29@weissschuh.net>
Date: Thu, 30 Jan 2025 20:54:02 +0100
From: Thomas Weißschuh <linux@...ssschuh.net>
To: Willy Tarreau <w@....eu>, Shuah Khan <shuah@...nel.org>
Cc: linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org, 
 Thomas Weißschuh <thomas.weissschuh@...utronix.de>, 
 Thomas Weißschuh <linux@...ssschuh.net>
Subject: [PATCH 1/2] tools/nolibc: add support for sys_llseek()

From: Thomas Weißschuh <thomas.weissschuh@...utronix.de>

Not all architectures have the old sys_lseek(), notably riscv32.
Implement lseek() in terms of sys_llseek() in that case.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
Signed-off-by: Thomas Weißschuh <linux@...ssschuh.net>
---
 tools/include/nolibc/sys.h | 29 ++++++++++++++++++++++++++++-
 1 file changed, 28 insertions(+), 1 deletion(-)

diff --git a/tools/include/nolibc/sys.h b/tools/include/nolibc/sys.h
index d4a5c2399a66b200ebf7ab249569cce2285481a5..cf8d72f99c87c99622eca410cf80b0c5c1aab8f0 100644
--- a/tools/include/nolibc/sys.h
+++ b/tools/include/nolibc/sys.h
@@ -601,10 +601,37 @@ off_t sys_lseek(int fd, off_t offset, int whence)
 #endif
 }
 
+static __attribute__((unused))
+int sys_llseek(int fd, unsigned long offset_high, unsigned long offset_low,
+	       __kernel_loff_t *result, int whence)
+{
+#ifdef __NR_llseek
+	return my_syscall5(__NR_llseek, fd, offset_high, offset_low, result, whence);
+#else
+	return __nolibc_enosys(__func__, fd, offset_high, offset_low, result, whence);
+#endif
+}
+
 static __attribute__((unused))
 off_t lseek(int fd, off_t offset, int whence)
 {
-	return __sysret(sys_lseek(fd, offset, whence));
+	__kernel_loff_t loff = 0;
+	off_t result;
+	int ret;
+
+	result = sys_lseek(fd, offset, whence);
+	if (result == -ENOSYS) {
+		/* Only exists on 32bit where nolibc off_t is also 32bit */
+		ret = sys_llseek(fd, 0, offset, &loff, whence);
+		if (ret < 0)
+			result = ret;
+		else if (loff != (off_t)loff)
+			result = -EOVERFLOW;
+		else
+			result = loff;
+	}
+
+	return __sysret(result);
 }
 
 

-- 
2.48.1