Re: [PATCH 5/7] tools/nolibc: handle 64-bit system call arguments on MIPS N32

[Willy Tarreau <w@1wt.eu>]

On Sat, Apr 18, 2026 at 01:54:55PM +0200, Thomas Weißschuh wrote:
> Hey David,
> 
> Apr 18, 2026 13:14:46 David Laight <david.laight.linux@gmail.com>:
> 
> > On Sat, 18 Apr 2026 12:20:00 +0200
> > Thomas Weißschuh <linux@weissschuh.net> wrote:
> >
> >> The N32 system call ABI expects 64-bit values directly in registers.
> >> This does not work on nolibc currently, as a 'long' is only 32 bits
> >> wide. Switch the system call wrappers to use 'long long' instead which
> >> can handle 64-bit values on N32. As on N64 'long' and 'long long' are
> >> the same, this does not change the behavior there.
> >>
> >> Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
> >> ---
> >> tools/include/nolibc/arch-mips.h | 94 +++++++++++++++++++++-------------------
> >> 1 file changed, 49 insertions(+), 45 deletions(-)
> >>
> >> diff --git a/tools/include/nolibc/arch-mips.h b/tools/include/nolibc/arch-mips.h
> >> index bb9d580ea1b1..557ef34d9df8 100644
> >> --- a/tools/include/nolibc/arch-mips.h
> >> +++ b/tools/include/nolibc/arch-mips.h
> >> @@ -55,6 +55,8 @@
> >> #define _NOLIBC_SYSCALL_STACK_RESERVE "addiu $sp, $sp, -32\n"
> >> #define _NOLIBC_SYSCALL_STACK_UNRESERVE "addiu $sp, $sp, 32\n"
> >>
> >> +#define _NOLIBC_SYSCALL_REG register long
> >> +
> >> #else /* _ABIN32 || _ABI64 */
> >>
> >> /* binutils, GCC and clang disagree about register aliases, use numbers instead. */
> >> @@ -66,12 +68,14 @@
> >> #define _NOLIBC_SYSCALL_STACK_RESERVE
> >> #define _NOLIBC_SYSCALL_STACK_UNRESERVE
> >>
> >> +#define _NOLIBC_SYSCALL_REG register long long
> >> +
> >> #endif /* _ABIO32 */
> >
> > Since you need to use a #define, did you think about:
> > #define _NOLIBC_SYSCALL_REG(var, reg) register long long var __asm__ (reg)
> > to shorten the lines and the repetitive pattern.
> 
> I didn't think of this.
> Personally I am fine with both variants.
> The parameterized macro is a bit weird
> is it breaks the normal syntax.
> Let's wait what Willy thinks.

I don't have a strong preference either, however macros make debugging
particularly painful and are only interesting when they save lots of
complicated code, which is not the case here. So I'd say that Thomas'
approach is minimalistic and obfuscates the least. If these were to be
exposed to end users, I think David's proposals would be better, but
since it's only for internal consumption and changed only once every
5 years, maybe better keep the explicit definitions like in Thomas'
approach.

Willy