diff options
| author | Zhangjin Wu <falcon@tinylab.org> | 2023-08-06 02:39:26 +0800 |
|---|---|---|
| committer | Willy Tarreau <w@1wt.eu> | 2023-08-23 05:17:07 +0200 |
| commit | 0cb0675ec37e1640e0304dc9ff7e4ba0b9ea8965 (patch) | |
| tree | ebf0be2375196855a1f15ec179c398977d9e9bf2 /tools/include/nolibc/arch.h | |
| parent | 024a6c29f0cda622702dcf3a2597607e23431d3c (diff) | |
| download | linux-0cb0675ec37e1640e0304dc9ff7e4ba0b9ea8965.tar.gz linux-0cb0675ec37e1640e0304dc9ff7e4ba0b9ea8965.tar.bz2 linux-0cb0675ec37e1640e0304dc9ff7e4ba0b9ea8965.zip | |
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>
Diffstat (limited to 'tools/include/nolibc/arch.h')
| -rw-r--r-- | tools/include/nolibc/arch.h | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/tools/include/nolibc/arch.h b/tools/include/nolibc/arch.h index 82b43935650f..e276fb0680af 100644 --- a/tools/include/nolibc/arch.h +++ b/tools/include/nolibc/arch.h @@ -25,6 +25,8 @@ #include "arch-aarch64.h" #elif defined(__mips__) && defined(_ABIO32) #include "arch-mips.h" +#elif defined(__powerpc__) +#include "arch-powerpc.h" #elif defined(__riscv) #include "arch-riscv.h" #elif defined(__s390x__) |