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 easier 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:
/* 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
The later one is smaller, here applies it.
arch/powerpc/include/asm/vdso/gettimeofday.h file uses the smaller method for do_syscall_2() too.
[1]: https://man7.org/linux/man-pages/man2/syscall.2.html
Signed-off-by: Zhangjin Wu falcon@tinylab.org --- tools/include/nolibc/arch-powerpc.h | 156 ++++++++++++++++++++++++++++ 1 file changed, 156 insertions(+) create mode 100644 tools/include/nolibc/arch-powerpc.h
diff --git a/tools/include/nolibc/arch-powerpc.h b/tools/include/nolibc/arch-powerpc.h new file mode 100644 index 000000000000..100ec0f412dc --- /dev/null +++ b/tools/include/nolibc/arch-powerpc.h @@ -0,0 +1,156 @@ +/* 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", "r9", "r10", "r11", "r12" + +#define my_syscall0(num) \ +({ \ + register long r0 __asm__ ("r0") = (num); \ + register long r3 __asm__ ("r3"); \ + \ + __asm__ volatile ( \ + "sc; bns+ 1f; neg %1, %1; 1:\n" \ + : "+r"(r0), "=r"(r3) \ + :: "r4", "r5", "r6", "r7", "r8", _NOLIBC_SYSCALL_CLOBBERLIST \ + ); \ + r3; \ +}) + +#define my_syscall1(num, arg1) \ +({ \ + register long r0 __asm__ ("r0") = (num); \ + register long r3 __asm__ ("r3") = (long)(arg1); \ + \ + __asm__ volatile ( \ + "sc; bns+ 1f; neg %1, %1; 1:\n" \ + : "+r"(r0), "+r"(r3) \ + :: "r4", "r5", "r6", "r7", "r8", _NOLIBC_SYSCALL_CLOBBERLIST \ + ); \ + r3; \ +}) + + +#define my_syscall2(num, arg1, arg2) \ +({ \ + register long r0 __asm__ ("r0") = (num); \ + register long r3 __asm__ ("r3") = (long)(arg1); \ + register long r4 __asm__ ("r4") = (long)(arg2); \ + \ + __asm__ volatile ( \ + "sc; bns+ 1f; neg %1, %1; 1:\n" \ + : "+r"(r0), "+r"(r3), \ + "+r"(r4) \ + :: "r5", "r6", "r7", "r8", _NOLIBC_SYSCALL_CLOBBERLIST \ + ); \ + r3; \ +}) + + +#define my_syscall3(num, arg1, arg2, arg3) \ +({ \ + register long r0 __asm__ ("r0") = (num); \ + register long r3 __asm__ ("r3") = (long)(arg1); \ + register long r4 __asm__ ("r4") = (long)(arg2); \ + register long r5 __asm__ ("r5") = (long)(arg3); \ + \ + __asm__ volatile ( \ + "sc; bns+ 1f; neg %1, %1; 1:\n" \ + : "+r"(r0), "+r"(r3), \ + "+r"(r4), "+r"(r5) \ + :: "r6", "r7", "r8", _NOLIBC_SYSCALL_CLOBBERLIST \ + ); \ + r3; \ +}) + + +#define my_syscall4(num, arg1, arg2, arg3, arg4) \ +({ \ + register long r0 __asm__ ("r0") = (num); \ + register long r3 __asm__ ("r3") = (long)(arg1); \ + register long r4 __asm__ ("r4") = (long)(arg2); \ + register long r5 __asm__ ("r5") = (long)(arg3); \ + register long r6 __asm__ ("r6") = (long)(arg4); \ + \ + __asm__ volatile ( \ + "sc; bns+ 1f; neg %1, %1; 1:\n" \ + : "+r"(r0), "+r"(r3), \ + "+r"(r4), "+r"(r5), "+r"(r6) \ + :: "r7", "r8", _NOLIBC_SYSCALL_CLOBBERLIST \ + ); \ + r3; \ +}) + + +#define my_syscall5(num, arg1, arg2, arg3, arg4, arg5) \ +({ \ + register long r0 __asm__ ("r0") = (num); \ + register long r3 __asm__ ("r3") = (long)(arg1); \ + register long r4 __asm__ ("r4") = (long)(arg2); \ + register long r5 __asm__ ("r5") = (long)(arg3); \ + register long r6 __asm__ ("r6") = (long)(arg4); \ + register long r7 __asm__ ("r7") = (long)(arg5); \ + \ + __asm__ volatile ( \ + "sc; bns+ 1f; neg %1, %1; 1:\n" \ + : "+r"(r0), "+r"(r3), \ + "+r"(r4), "+r"(r5), "+r"(r6), "+r"(r7) \ + :: "r8", _NOLIBC_SYSCALL_CLOBBERLIST \ + ); \ + r3; \ +}) + +#define my_syscall6(num, arg1, arg2, arg3, arg4, arg5, arg6) \ +({ \ + register long r0 __asm__ ("r0") = (num); \ + register long r3 __asm__ ("r3") = (long)(arg1); \ + register long r4 __asm__ ("r4") = (long)(arg2); \ + register long r5 __asm__ ("r5") = (long)(arg3); \ + register long r6 __asm__ ("r6") = (long)(arg4); \ + register long r7 __asm__ ("r7") = (long)(arg5); \ + register long r8 __asm__ ("r8") = (long)(arg6); \ + \ + __asm__ volatile ( \ + "sc; bns+ 1f; neg %1, %1; 1:\n" \ + : "+r"(r0), "+r"(r3), \ + "+r"(r4), "+r"(r5), "+r"(r6), "+r"(r7), "+r"(r8) \ + :: _NOLIBC_SYSCALL_CLOBBERLIST \ + ); \ + r3; \ +}) + +/* 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 */