tools/nolibc: add __nolibc_arg_to_reg()

In the architecture specific system call glue, all arguments are
currently casted to 'long' to fit into registers. This works for
pointers as 'long' has the same size as pointers.
However the system call registers for X32 and MIPS N32 need to be
'long long' to work correctly for 64-bit values expected by the system
call ABI. Casting a pointer to a 'long long' will produce a compiler
warning while casting 64-bit integers to 'long' will truncate those.

Add a helper which can be used to correctly cast both pointers and
integers into 'long long' registers. Cast the pointers through
'unsigned' to avoid any sign extensions.

Both builtins have been available since at least GCC 3 and clang 3.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Acked-by: Willy Tarreau <w@1wt.eu>
Link: https://patch.msgid.link/20260418-nolibc-largefile-v1-2-b91f0775bac3@weissschuh.net

diff --git a/tools/include/nolibc/crt.h b/tools/include/nolibc/crt.h
index 78124b6598a7291d5ba427ba0226bb5154426dc3..714256228914e98ecd75eaf1ba44cac2dfadd2bb 100644 (file)
--- a/tools/include/nolibc/crt.h
+++ b/tools/include/nolibc/crt.h
@@ -7,6 +7,10 @@
 #ifndef _NOLIBC_CRT_H
 #define _NOLIBC_CRT_H
 
+#define __nolibc_arg_to_reg(_a)                                                                        \
+       __builtin_choose_expr(__builtin_classify_type(_a) == __builtin_classify_type(NULL),     \
+                             (unsigned long)(_a), (_a))
+
 #ifndef NOLIBC_NO_RUNTIME
 
 #include "compiler.h"