tools/nolibc: move MIPS ABI validation into arch-mips.h

When installing nolibc to a sysroot arch.h is not used so its ABI check
is bypassed. This makes is possible to compile nolibc with a non O32 ABI
which may build but can not run.

Move the check into arch-mips.h so it will always be evaluated.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Acked-by: Willy Tarreau <w@1wt.eu>

tools/nolibc: error out on unsupported architecture

When an architecture is unsupported arch.h would silently continue.
This leads to a lot of followup errors because my_syscallX() is not
defined and the startup code is missing.

Avoid these confusing errors and fail the build early with a clear
error message and location.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Acked-by: Willy Tarreau <w@1wt.eu>

tools/nolibc: add support for powerpc

Both syscall declarations and _start code definition are added for
powerpc to nolibc.

Like mips, powerpc uses a register (exactly, the summary overflow bit)
to record the error occurred, and uses another register to return the
value [1]. So, the return value of every syscall declaration must be
normalized to match the __sysret() helper, return -value when there is
an error, otheriwse, return value directly.

Glibc and musl use different methods to check the summary overflow bit,
glibc (sysdeps/unix/sysv/linux/powerpc/sysdep.h) saves the cr register
to r0 at first, and then check the summary overflow bit in cr0:

mfcr r0
r0 & (1 << 28) ? -r3 : r3

-->

10003c14: 7c 00 00 26 mfcr r0
10003c18: 74 09 10 00 andis. r9,r0,4096
10003c1c: 41 82 00 08 beq 0x10003c24
10003c20: 7c 63 00 d0 neg r3,r3

Musl (arch/powerpc/syscall_arch.h) directly checks the summary overflow
bit with the 'bns' instruction, it is smaller:

/* no summary overflow bit means no error, return value directly */
bns+ 1f
/* otherwise, return negated value */
neg r3, r3
1:

-->

10000418: 40 a3 00 08 bns 0x10000420
1000041c: 7c 63 00 d0 neg r3,r3

Like musl, Linux (arch/powerpc/include/asm/vdso/gettimeofday.h) uses the
same method for do_syscall_2() too.

Here applies the second method to get smaller size.

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

Reviewed-by: Thomas Weißschuh <linux@weissschuh.net>
Signed-off-by: Zhangjin Wu <falcon@tinylab.org>
Signed-off-by: Willy Tarreau <w@1wt.eu>

tools/nolibc: fix typo pint -> point

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Signed-off-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

tools/nolibc: Add support for LoongArch

Add support for LoongArch (32 and 64 bit) to nolibc.

Signed-off-by: Feiyang Chen <chenfeiyang@loongson.cn>
Acked-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

nolibc: add support for s390

Use arch-x86_64 as a template. Not really different, but
we have our own mmap syscall which takes a structure instead
of discrete arguments.

Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Acked-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

tools/nolibc/arch: split arch-specific code into individual files

In order to ease maintenance, this splits the arch-specific code into
one file per architecture. A common file "arch.h" is used to include the
right file among arch-* based on the detected architecture. Projects
which are already split per architecture could simply rename these
files to $arch/arch.h and get rid of the common arch.h. For this
reason, include guards were placed into each arch-specific file.

Signed-off-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>