/* SPDX-License-Identifier: LGPL-2.1 OR MIT */ /* * MIPS specific definitions for NOLIBC * Copyright (C) 2017-2022 Willy Tarreau */ #ifndef _NOLIBC_ARCH_MIPS_H #define _NOLIBC_ARCH_MIPS_H #include "compiler.h" #include "crt.h" #if !defined(_ABIO32) #error Unsupported MIPS ABI #endif /* Syscalls for MIPS ABI O32 : * - WARNING! there's always a delayed slot! * - WARNING again, the syntax is different, registers take a '$' and numbers * do not. * - registers are 32-bit * - stack is 8-byte aligned * - syscall number is passed in v0 (starts at 0xfa0). * - arguments are in a0, a1, a2, a3, then the stack. The caller needs to * leave some room in the stack for the callee to save a0..a3 if needed. * - Many registers are clobbered, in fact only a0..a2 and s0..s8 are * preserved. See: https://www.linux-mips.org/wiki/Syscall as well as * scall32-o32.S in the kernel sources. * - the system call is performed by calling "syscall" * - syscall return comes in v0, and register a3 needs to be checked to know * if an error occurred, in which case errno is in v0. * - 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", "cc", "at", "v1", "hi", "lo", \ "t0", "t1", "t2", "t3", "t4", "t5", "t6", "t7", "t8", "t9" #define my_syscall0(num) \ ({ \ register long _num __asm__ ("v0") = (num); \ register long _arg4 __asm__ ("a3"); \ \ __asm__ volatile ( \ "addiu $sp, $sp, -32\n" \ "syscall\n" \ "addiu $sp, $sp, 32\n" \ : "=r"(_num), "=r"(_arg4) \ : "r"(_num) \ : _NOLIBC_SYSCALL_CLOBBERLIST \ ); \ _arg4 ? -_num : _num; \ }) #define my_syscall1(num, arg1) \ ({ \ register long _num __asm__ ("v0") = (num); \ register long _arg1 __asm__ ("a0") = (long)(arg1); \ register long _arg4 __asm__ ("a3"); \ \ __asm__ volatile ( \ "addiu $sp, $sp, -32\n" \ "syscall\n" \ "addiu $sp, $sp, 32\n" \ : "=r"(_num), "=r"(_arg4) \ : "0"(_num), \ "r"(_arg1) \ : _NOLIBC_SYSCALL_CLOBBERLIST \ ); \ _arg4 ? -_num : _num; \ }) #define my_syscall2(num, arg1, arg2) \ ({ \ register long _num __asm__ ("v0") = (num); \ register long _arg1 __asm__ ("a0") = (long)(arg1); \ register long _arg2 __asm__ ("a1") = (long)(arg2); \ register long _arg4 __asm__ ("a3"); \ \ __asm__ volatile ( \ "addiu $sp, $sp, -32\n" \ "syscall\n" \ "addiu $sp, $sp, 32\n" \ : "=r"(_num), "=r"(_arg4) \ : "0"(_num), \ "r"(_arg1), "r"(_arg2) \ : _NOLIBC_SYSCALL_CLOBBERLIST \ ); \ _arg4 ? -_num : _num; \ }) #define my_syscall3(num, arg1, arg2, arg3) \ ({ \ register long _num __asm__ ("v0") = (num); \ register long _arg1 __asm__ ("a0") = (long)(arg1); \ register long _arg2 __asm__ ("a1") = (long)(arg2); \ register long _arg3 __asm__ ("a2") = (long)(arg3); \ register long _arg4 __asm__ ("a3"); \ \ __asm__ volatile ( \ "addiu $sp, $sp, -32\n" \ "syscall\n" \ "addiu $sp, $sp, 32\n" \ : "=r"(_num), "=r"(_arg4) \ : "0"(_num), \ "r"(_arg1), "r"(_arg2), "r"(_arg3) \ : _NOLIBC_SYSCALL_CLOBBERLIST \ ); \ _arg4 ? -_num : _num; \ }) #define my_syscall4(num, arg1, arg2, arg3, arg4) \ ({ \ register long _num __asm__ ("v0") = (num); \ register long _arg1 __asm__ ("a0") = (long)(arg1); \ register long _arg2 __asm__ ("a1") = (long)(arg2); \ register long _arg3 __asm__ ("a2") = (long)(arg3); \ register long _arg4 __asm__ ("a3") = (long)(arg4); \ \ __asm__ volatile ( \ "addiu $sp, $sp, -32\n" \ "syscall\n" \ "addiu $sp, $sp, 32\n" \ : "=r" (_num), "=r"(_arg4) \ : "0"(_num), \ "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4) \ : _NOLIBC_SYSCALL_CLOBBERLIST \ ); \ _arg4 ? -_num : _num; \ }) #define my_syscall5(num, arg1, arg2, arg3, arg4, arg5) \ ({ \ register long _num __asm__ ("v0") = (num); \ register long _arg1 __asm__ ("a0") = (long)(arg1); \ register long _arg2 __asm__ ("a1") = (long)(arg2); \ register long _arg3 __asm__ ("a2") = (long)(arg3); \ register long _arg4 __asm__ ("a3") = (long)(arg4); \ register long _arg5 = (long)(arg5); \ \ __asm__ volatile ( \ "addiu $sp, $sp, -32\n" \ "sw %7, 16($sp)\n" \ "syscall\n" \ "addiu $sp, $sp, 32\n" \ : "=r" (_num), "=r"(_arg4) \ : "0"(_num), \ "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4), "r"(_arg5) \ : _NOLIBC_SYSCALL_CLOBBERLIST \ ); \ _arg4 ? -_num : _num; \ }) #define my_syscall6(num, arg1, arg2, arg3, arg4, arg5, arg6) \ ({ \ register long _num __asm__ ("v0") = (num); \ register long _arg1 __asm__ ("a0") = (long)(arg1); \ register long _arg2 __asm__ ("a1") = (long)(arg2); \ register long _arg3 __asm__ ("a2") = (long)(arg3); \ register long _arg4 __asm__ ("a3") = (long)(arg4); \ register long _arg5 = (long)(arg5); \ register long _arg6 = (long)(arg6); \ \ __asm__ volatile ( \ "addiu $sp, $sp, -32\n" \ "sw %7, 16($sp)\n" \ "sw %8, 20($sp)\n" \ "syscall\n" \ "addiu $sp, $sp, 32\n" \ : "=r" (_num), "=r"(_arg4) \ : "0"(_num), \ "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4), "r"(_arg5), \ "r"(_arg6) \ : _NOLIBC_SYSCALL_CLOBBERLIST \ ); \ _arg4 ? -_num : _num; \ }) /* startup code, note that it's called __start on MIPS */ void __attribute__((weak, noreturn, optimize("Os", "omit-frame-pointer"))) __no_stack_protector __start(void) { __asm__ volatile ( ".set push\n" ".set noreorder\n" "bal 1f\n" /* prime $ra for .cpload */ "nop\n" "1:\n" ".cpload $ra\n" "move $a0, $sp\n" /* save stack pointer to $a0, as arg1 of _start_c */ "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 */ "jal _start_c\n" /* transfer to c runtime */ " nop\n" /* delayed slot */ ".set pop\n" ); __builtin_unreachable(); } #endif /* _NOLIBC_ARCH_MIPS_H */