On 2025-02-16 10:49:38+0100, Willy Tarreau wrote:
> On Wed, Feb 12, 2025 at 07:49:53PM +0100, Thomas Weißschuh wrote:
> > +#if defined(_ABIO32)
> > +
> > #define _NOLIBC_SYSCALL_CLOBBERLIST \
> > "memory", "cc", "at", "v1", "hi", "lo", \
> > "t0", "t1", "t2", "t3", "t4", "t5", "t6", "t7", "t8", "t9"
> > +#define _NOLIBC_SYSCALL_STACK_RESERVE "addiu $sp, $sp, -32\n"
> > +#define _NOLIBC_SYSCALL_STACK_UNRESERVE "addiu $sp, $sp, 32\n"
> > +
> > +#elif defined(_ABIN32) || defined(_ABI64)
> > +
> > +/* binutils, GCC and clang disagree about register aliases, use numbers
> > instead. */
>
> Is this often encountered despite this ? I guess it can cause portability
> issues :-/
No idea. It's the first time I saw something like this.
> > +#if defined(_ABIO32)
> > +
> > #define my_syscall5(num, arg1, arg2, arg3, arg4, arg5)
> > \
> > ({
> > \
> > register long _num __asm__ ("v0") = (num); \
> (...)
> > @@ -178,6 +201,50 @@
> > _arg4 ? -_num : _num; \
> > })
> >
> > +#else
> > +
>
> Here you should indicate which ABI is covered by this #else, because one
> has to go up to previous definitions to figure it's _ABIN32 and _ABI64.
Ack.
> > +#define my_syscall5(num, arg1, arg2, arg3, arg4, arg5)
> > \
> > +({
> > \
> > + register long _num __asm__ ("v0") = (num); \
> > + register long _arg1 __asm__ ("$4") = (long)(arg1); \
> > + register long _arg2 __asm__ ("$5") = (long)(arg2); \
> > + register long _arg3 __asm__ ("$6") = (long)(arg3); \
> > + register long _arg4 __asm__ ("$7") = (long)(arg4); \
> > + register long _arg5 __asm__ ("$8") = (long)(arg5); \
> (...)
> > @@ -190,13 +257,33 @@ void __attribute__((weak, noreturn))
> > __nolibc_entrypoint __no_stack_protector __
> > "1:\n"
> > ".cpload $ra\n"
> > "move $a0, $sp\n" /* save stack pointer to $a0, as arg1
> > of _start_c */
> > +
> > +#if defined(_ABIO32)
> > "addiu $sp, $sp, -4\n" /* space for .cprestore to store $gp
> > */
> > ".cprestore 0\n"
> > "li $t0, -8\n"
> > "and $sp, $sp, $t0\n" /* $sp must be 8-byte aligned
> > */
> > "addiu $sp, $sp, -16\n" /* the callee expects to save a0..a3
> > there */
> > - "lui $t9, %hi(_start_c)\n" /* ABI requires current function
> > address in $t9 */
> > +#else
>
> So same here. I think you should do it for all #else since you're generally
> grouping 2 ABIs vs one between a #if and a #else and it's not trivial to
> figure what a #else covers, like below.
Ack.
> > + "daddiu $sp, $sp, -8\n" /* space for .cprestore to store $gp
> > */
> > + ".cpsetup $ra, 0, 1b\n"
> > + "li $t0, -16\n"
> > + "and $sp, $sp, $t0\n" /* $sp must be 16-byte aligned
> > */
> > +#endif
> > +
> > + /* ABI requires current function address in $t9 */
> > +#if defined(_ABIO32) || defined(_ABIN32)
> > + "lui $t9, %hi(_start_c)\n"
> > "ori $t9, %lo(_start_c)\n"
> > +#else
>
> This one indeed covers only _ABI64
(That is intentional)
> > + "lui $t9, %highest(_start_c)\n"
> > + "ori $t9, %higher(_start_c)\n"
> > + "dsll $t9, 0x10\n"
> > + "ori $t9, %hi(_start_c)\n"
> > + "dsll $t9, 0x10\n"
> > + "ori $t9, %lo(_start_c)\n"
> > +#endif
>
> With the tiny details above, this looks fine. It's great that syscall
> numbers didn't change so that you can cover an extra arch with only a
> few ifdefs. I have not tested but I guess you did :-) So that's OK for
> me:
The syscall numbers are different, but the UAPI headers also detect the
ABI in use and select the correct numbers.
> Acked-by: Willy Tarreau <w...@1wt.eu>
Thanks!
