linux-kernel - [PATCH v3 1/3] tools/nolibc: sys.h: add a syscall return helper

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Message-Id: <7cad207c4c4deb41151bd12fa658fb3fc64a5bf1.1686135913.git.falcon@tinylab.org>
Date:   Wed,  7 Jun 2023 19:30:09 +0800
From:   Zhangjin Wu <falcon@...ylab.org>
To:     thomas@...ch.de, w@....eu
Cc:     falcon@...ylab.org, arnd@...db.de, linux-kernel@...r.kernel.org,
        linux-kselftest@...r.kernel.org, linux-riscv@...ts.infradead.org,
        Thomas Weißschuh <linux@...ssschuh.net>
Subject: [PATCH v3 1/3] tools/nolibc: sys.h: add a syscall return helper

Most of the library routines share the same syscall return logic:

  In general, a 0 return value indicates success.  A -1 return value
  indicates an error, and an error number is stored in errno. [1]

Let's add a __sysret() helper for the above logic to simplify the coding
and shrink the code lines too.

Thomas suggested to use inline function instead of macro for __sysret().

Willy suggested to make __sysret() be always inline.

[1]: https://man7.org/linux/man-pages/man2/syscall.2.html

Suggested-by: Willy Tarreau <w@....eu>
Link: https://lore.kernel.org/linux-riscv/ZH1+hkhiA2+ItSvX@1wt.eu/
Suggested-by: Thomas Weißschuh <linux@...ssschuh.net>
Link: https://lore.kernel.org/linux-riscv/ea4e7442-7223-4211-ba29-70821e907888@t-8ch.de/
Signed-off-by: Zhangjin Wu <falcon@...ylab.org>
---
 tools/include/nolibc/sys.h | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/tools/include/nolibc/sys.h b/tools/include/nolibc/sys.h
index 856249a11890..150777207468 100644
--- a/tools/include/nolibc/sys.h
+++ b/tools/include/nolibc/sys.h
@@ -28,6 +28,16 @@
 #include "errno.h"
 #include "types.h"
 
+/* Syscall return helper, set errno as -ret when ret < 0 */
+static __inline__ __attribute__((unused, always_inline))
+long __sysret(long ret)
+{
+	if (ret < 0) {
+		SET_ERRNO(-ret);
+		ret = -1;
+	}
+	return ret;
+}
 
 /* Functions in this file only describe syscalls. They're declared static so
  * that the compiler usually decides to inline them while still being allowed
-- 
2.25.1