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tools/nolibc: add support for powerpc

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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>
This commit is contained in:
Zhangjin Wu 2023-08-06 02:39:26 +08:00 • committed by Willy Tarreau
parent 024a6c29f0
commit 0cb0675ec3
2 changed files with 199 additions and 0 deletions
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197
tools/include/nolibc/arch-powerpc.h Normal file
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@ -0,0 +1,197 @@
/* SPDX-License-Identifier: LGPL-2.1 OR MIT */
/*
* PowerPC specific definitions for NOLIBC
* Copyright (C) 2023 Zhangjin Wu <falcon@tinylab.org>
*/
#ifndef _NOLIBC_ARCH_POWERPC_H
#define _NOLIBC_ARCH_POWERPC_H
#include "compiler.h"
#include "crt.h"
/* Syscalls for PowerPC :
* - stack is 16-byte aligned
* - syscall number is passed in r0
* - arguments are in r3, r4, r5, r6, r7, r8, r9
* - the system call is performed by calling "sc"
* - syscall return comes in r3, and the summary overflow bit is checked
* to know if an error occurred, in which case errno is in r3.
* - the arguments are cast to long and assigned into the target
* registers which are then simply passed as registers to the asm code,
* so that we don't have to experience issues with register constraints.
*/
#define _NOLIBC_SYSCALL_CLOBBERLIST \
"memory", "cr0", "r12", "r11", "r10", "r9"
#define my_syscall0(num) \
({ \
register long _ret __asm__ ("r3"); \
register long _num __asm__ ("r0") = (num); \
\
__asm__ volatile ( \
" sc\n" \
" bns+ 1f\n" \
" neg %0, %0\n" \
"1:\n" \
: "=r"(_ret), "+r"(_num) \
: \
: _NOLIBC_SYSCALL_CLOBBERLIST, "r8", "r7", "r6", "r5", "r4" \
); \
_ret; \
})
#define my_syscall1(num, arg1) \
({ \
register long _ret __asm__ ("r3"); \
register long _num __asm__ ("r0") = (num); \
register long _arg1 __asm__ ("r3") = (long)(arg1); \
\
__asm__ volatile ( \
" sc\n" \
" bns+ 1f\n" \
" neg %0, %0\n" \
"1:\n" \
: "=r"(_ret), "+r"(_num) \
: "0"(_arg1) \
: _NOLIBC_SYSCALL_CLOBBERLIST, "r8", "r7", "r6", "r5", "r4" \
); \
_ret; \
})
#define my_syscall2(num, arg1, arg2) \
({ \
register long _ret __asm__ ("r3"); \
register long _num __asm__ ("r0") = (num); \
register long _arg1 __asm__ ("r3") = (long)(arg1); \
register long _arg2 __asm__ ("r4") = (long)(arg2); \
\
__asm__ volatile ( \
" sc\n" \
" bns+ 1f\n" \
" neg %0, %0\n" \
"1:\n" \
: "=r"(_ret), "+r"(_num), "+r"(_arg2) \
: "0"(_arg1) \
: _NOLIBC_SYSCALL_CLOBBERLIST, "r8", "r7", "r6", "r5" \
); \
_ret; \
})
#define my_syscall3(num, arg1, arg2, arg3) \
({ \
register long _ret __asm__ ("r3"); \
register long _num __asm__ ("r0") = (num); \
register long _arg1 __asm__ ("r3") = (long)(arg1); \
register long _arg2 __asm__ ("r4") = (long)(arg2); \
register long _arg3 __asm__ ("r5") = (long)(arg3); \
\
__asm__ volatile ( \
" sc\n" \
" bns+ 1f\n" \
" neg %0, %0\n" \
"1:\n" \
: "=r"(_ret), "+r"(_num), "+r"(_arg2), "+r"(_arg3) \
: "0"(_arg1) \
: _NOLIBC_SYSCALL_CLOBBERLIST, "r8", "r7", "r6" \
); \
_ret; \
})
#define my_syscall4(num, arg1, arg2, arg3, arg4) \
({ \
register long _ret __asm__ ("r3"); \
register long _num __asm__ ("r0") = (num); \
register long _arg1 __asm__ ("r3") = (long)(arg1); \
register long _arg2 __asm__ ("r4") = (long)(arg2); \
register long _arg3 __asm__ ("r5") = (long)(arg3); \
register long _arg4 __asm__ ("r6") = (long)(arg4); \
\
__asm__ volatile ( \
" sc\n" \
" bns+ 1f\n" \
" neg %0, %0\n" \
"1:\n" \
: "=r"(_ret), "+r"(_num), "+r"(_arg2), "+r"(_arg3), \
"+r"(_arg4) \
: "0"(_arg1) \
: _NOLIBC_SYSCALL_CLOBBERLIST, "r8", "r7" \
); \
_ret; \
})
#define my_syscall5(num, arg1, arg2, arg3, arg4, arg5) \
({ \
register long _ret __asm__ ("r3"); \
register long _num __asm__ ("r0") = (num); \
register long _arg1 __asm__ ("r3") = (long)(arg1); \
register long _arg2 __asm__ ("r4") = (long)(arg2); \
register long _arg3 __asm__ ("r5") = (long)(arg3); \
register long _arg4 __asm__ ("r6") = (long)(arg4); \
register long _arg5 __asm__ ("r7") = (long)(arg5); \
\
__asm__ volatile ( \
" sc\n" \
" bns+ 1f\n" \
" neg %0, %0\n" \
"1:\n" \
: "=r"(_ret), "+r"(_num), "+r"(_arg2), "+r"(_arg3), \
"+r"(_arg4), "+r"(_arg5) \
: "0"(_arg1) \
: _NOLIBC_SYSCALL_CLOBBERLIST, "r8" \
); \
_ret; \
})
#define my_syscall6(num, arg1, arg2, arg3, arg4, arg5, arg6) \
({ \
register long _ret __asm__ ("r3"); \
register long _num __asm__ ("r0") = (num); \
register long _arg1 __asm__ ("r3") = (long)(arg1); \
register long _arg2 __asm__ ("r4") = (long)(arg2); \
register long _arg3 __asm__ ("r5") = (long)(arg3); \
register long _arg4 __asm__ ("r6") = (long)(arg4); \
register long _arg5 __asm__ ("r7") = (long)(arg5); \
register long _arg6 __asm__ ("r8") = (long)(arg6); \
\
__asm__ volatile ( \
" sc\n" \
" bns+ 1f\n" \
" neg %0, %0\n" \
"1:\n" \
: "=r"(_ret), "+r"(_num), "+r"(_arg2), "+r"(_arg3), \
"+r"(_arg4), "+r"(_arg5), "+r"(_arg6) \
: "0"(_arg1) \
: _NOLIBC_SYSCALL_CLOBBERLIST \
); \
_ret; \
})
/* FIXME: For 32-bit PowerPC, with newer gcc compilers (e.g. gcc 13.1.0),
* "omit-frame-pointer" fails with __attribute__((no_stack_protector)) but
* works with __attribute__((__optimize__("-fno-stack-protector")))
*/
#ifdef __no_stack_protector
#undef __no_stack_protector
#define __no_stack_protector __attribute__((__optimize__("-fno-stack-protector")))
#endif
/* startup code */
void __attribute__((weak, noreturn, optimize("Os", "omit-frame-pointer"))) __no_stack_protector _start(void)
{
__asm__ volatile (
"mr 3, 1\n" /* save stack pointer to r3, as arg1 of _start_c */
"clrrwi 1, 1, 4\n" /* align the stack to 16 bytes */
"li 0, 0\n" /* zero the frame pointer */
"stwu 1, -16(1)\n" /* the initial stack frame */
"bl _start_c\n" /* transfer to c runtime */
);
__builtin_unreachable();
}
#endif /* _NOLIBC_ARCH_POWERPC_H */

2
tools/include/nolibc/arch.h
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@ -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__)