2022-02-07 19:23:17 +03:00
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/* SPDX-License-Identifier: LGPL-2.1 OR MIT */
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/*
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* MIPS specific definitions for NOLIBC
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* Copyright (C) 2017-2022 Willy Tarreau <w@1wt.eu>
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*/
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#ifndef _NOLIBC_ARCH_MIPS_H
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#define _NOLIBC_ARCH_MIPS_H
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/* The struct returned by the stat() syscall. 88 bytes are returned by the
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* syscall.
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*/
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struct sys_stat_struct {
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unsigned int st_dev;
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long st_pad1[3];
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unsigned long st_ino;
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unsigned int st_mode;
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unsigned int st_nlink;
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unsigned int st_uid;
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unsigned int st_gid;
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unsigned int st_rdev;
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long st_pad2[2];
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long st_size;
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long st_pad3;
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long st_atime;
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long st_atime_nsec;
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long st_mtime;
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long st_mtime_nsec;
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long st_ctime;
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long st_ctime_nsec;
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long st_blksize;
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long st_blocks;
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long st_pad4[14];
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};
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/* Syscalls for MIPS ABI O32 :
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* - WARNING! there's always a delayed slot!
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* - WARNING again, the syntax is different, registers take a '$' and numbers
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* do not.
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* - registers are 32-bit
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* - stack is 8-byte aligned
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* - syscall number is passed in v0 (starts at 0xfa0).
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* - arguments are in a0, a1, a2, a3, then the stack. The caller needs to
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* leave some room in the stack for the callee to save a0..a3 if needed.
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* - Many registers are clobbered, in fact only a0..a2 and s0..s8 are
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* preserved. See: https://www.linux-mips.org/wiki/Syscall as well as
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* scall32-o32.S in the kernel sources.
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* - the system call is performed by calling "syscall"
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* - syscall return comes in v0, and register a3 needs to be checked to know
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* if an error occurred, in which case errno is in v0.
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* - the arguments are cast to long and assigned into the target registers
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* which are then simply passed as registers to the asm code, so that we
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* don't have to experience issues with register constraints.
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*/
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#define my_syscall0(num) \
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({ \
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2022-03-29 13:17:30 +03:00
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register long _num __asm__ ("v0") = (num); \
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register long _arg4 __asm__ ("a3"); \
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2022-02-07 19:23:17 +03:00
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\
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2022-03-29 13:17:30 +03:00
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__asm__ volatile ( \
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2022-02-07 19:23:17 +03:00
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"addiu $sp, $sp, -32\n" \
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"syscall\n" \
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"addiu $sp, $sp, 32\n" \
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: "=r"(_num), "=r"(_arg4) \
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: "r"(_num) \
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: "memory", "cc", "at", "v1", "hi", "lo", \
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"t0", "t1", "t2", "t3", "t4", "t5", "t6", "t7", "t8", "t9" \
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); \
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_arg4 ? -_num : _num; \
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})
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#define my_syscall1(num, arg1) \
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({ \
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2022-03-29 13:17:30 +03:00
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register long _num __asm__ ("v0") = (num); \
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register long _arg1 __asm__ ("a0") = (long)(arg1); \
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register long _arg4 __asm__ ("a3"); \
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2022-02-07 19:23:17 +03:00
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\
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2022-03-29 13:17:30 +03:00
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__asm__ volatile ( \
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2022-02-07 19:23:17 +03:00
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"addiu $sp, $sp, -32\n" \
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"syscall\n" \
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"addiu $sp, $sp, 32\n" \
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: "=r"(_num), "=r"(_arg4) \
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: "0"(_num), \
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"r"(_arg1) \
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: "memory", "cc", "at", "v1", "hi", "lo", \
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"t0", "t1", "t2", "t3", "t4", "t5", "t6", "t7", "t8", "t9" \
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); \
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_arg4 ? -_num : _num; \
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})
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#define my_syscall2(num, arg1, arg2) \
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({ \
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2022-03-29 13:17:30 +03:00
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register long _num __asm__ ("v0") = (num); \
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register long _arg1 __asm__ ("a0") = (long)(arg1); \
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register long _arg2 __asm__ ("a1") = (long)(arg2); \
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register long _arg4 __asm__ ("a3"); \
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2022-02-07 19:23:17 +03:00
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\
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2022-03-29 13:17:30 +03:00
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__asm__ volatile ( \
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2022-02-07 19:23:17 +03:00
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"addiu $sp, $sp, -32\n" \
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"syscall\n" \
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"addiu $sp, $sp, 32\n" \
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: "=r"(_num), "=r"(_arg4) \
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: "0"(_num), \
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"r"(_arg1), "r"(_arg2) \
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: "memory", "cc", "at", "v1", "hi", "lo", \
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"t0", "t1", "t2", "t3", "t4", "t5", "t6", "t7", "t8", "t9" \
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); \
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_arg4 ? -_num : _num; \
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})
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#define my_syscall3(num, arg1, arg2, arg3) \
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({ \
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2022-03-29 13:17:30 +03:00
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register long _num __asm__ ("v0") = (num); \
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register long _arg1 __asm__ ("a0") = (long)(arg1); \
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register long _arg2 __asm__ ("a1") = (long)(arg2); \
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register long _arg3 __asm__ ("a2") = (long)(arg3); \
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register long _arg4 __asm__ ("a3"); \
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2022-02-07 19:23:17 +03:00
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\
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2022-03-29 13:17:30 +03:00
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__asm__ volatile ( \
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2022-02-07 19:23:17 +03:00
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"addiu $sp, $sp, -32\n" \
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"syscall\n" \
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"addiu $sp, $sp, 32\n" \
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: "=r"(_num), "=r"(_arg4) \
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: "0"(_num), \
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"r"(_arg1), "r"(_arg2), "r"(_arg3) \
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: "memory", "cc", "at", "v1", "hi", "lo", \
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"t0", "t1", "t2", "t3", "t4", "t5", "t6", "t7", "t8", "t9" \
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); \
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_arg4 ? -_num : _num; \
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})
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#define my_syscall4(num, arg1, arg2, arg3, arg4) \
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({ \
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2022-03-29 13:17:30 +03:00
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register long _num __asm__ ("v0") = (num); \
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register long _arg1 __asm__ ("a0") = (long)(arg1); \
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register long _arg2 __asm__ ("a1") = (long)(arg2); \
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register long _arg3 __asm__ ("a2") = (long)(arg3); \
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register long _arg4 __asm__ ("a3") = (long)(arg4); \
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2022-02-07 19:23:17 +03:00
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\
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2022-03-29 13:17:30 +03:00
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__asm__ volatile ( \
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2022-02-07 19:23:17 +03:00
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"addiu $sp, $sp, -32\n" \
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"syscall\n" \
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"addiu $sp, $sp, 32\n" \
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: "=r" (_num), "=r"(_arg4) \
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: "0"(_num), \
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"r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4) \
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: "memory", "cc", "at", "v1", "hi", "lo", \
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"t0", "t1", "t2", "t3", "t4", "t5", "t6", "t7", "t8", "t9" \
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); \
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_arg4 ? -_num : _num; \
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})
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#define my_syscall5(num, arg1, arg2, arg3, arg4, arg5) \
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({ \
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2022-03-29 13:17:30 +03:00
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register long _num __asm__ ("v0") = (num); \
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register long _arg1 __asm__ ("a0") = (long)(arg1); \
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register long _arg2 __asm__ ("a1") = (long)(arg2); \
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register long _arg3 __asm__ ("a2") = (long)(arg3); \
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register long _arg4 __asm__ ("a3") = (long)(arg4); \
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2022-02-07 19:23:17 +03:00
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register long _arg5 = (long)(arg5); \
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\
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2022-03-29 13:17:30 +03:00
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__asm__ volatile ( \
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2022-02-07 19:23:17 +03:00
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"addiu $sp, $sp, -32\n" \
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"sw %7, 16($sp)\n" \
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"syscall\n " \
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"addiu $sp, $sp, 32\n" \
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: "=r" (_num), "=r"(_arg4) \
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: "0"(_num), \
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"r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4), "r"(_arg5) \
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: "memory", "cc", "at", "v1", "hi", "lo", \
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"t0", "t1", "t2", "t3", "t4", "t5", "t6", "t7", "t8", "t9" \
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); \
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_arg4 ? -_num : _num; \
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})
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2023-01-10 10:24:22 +03:00
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char **environ __attribute__((weak));
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2023-01-10 10:24:30 +03:00
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const unsigned long *_auxv __attribute__((weak));
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2023-01-10 10:24:22 +03:00
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2022-02-07 19:23:17 +03:00
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/* startup code, note that it's called __start on MIPS */
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tools/nolibc: make compiler and assembler agree on the section around _start
The out-of-block asm() statement carrying _start does not allow the
compiler to know what section the assembly code is being emitted to,
and there's no easy way to push/pop the current section and restore
it. It sometimes causes issues depending on the include files ordering
and compiler optimizations. For example if a variable is declared
immediately before the asm() block and another one after, the compiler
assumes that the current section is still .bss and doesn't re-emit it,
making the second variable appear inside the .text section instead.
Forcing .bss at the end of the _start block doesn't work either because
at certain optimizations the compiler may reorder blocks and will make
some real code appear just after this block.
A significant number of solutions were attempted, but many of them were
still sensitive to section reordering. In the end, the best way to make
sure the compiler and assembler agree on the current section is to place
this code inside a function. Here the function is directly called _start
and configured not to emit a frame-pointer, hence to have no prologue.
If some future architectures would still emit some prologue, another
working approach consists in naming the function differently and placing
the _start label inside the asm statement. But the current solution is
simpler.
It was tested with nolibc-test at -O,-O0,-O2,-O3,-Os for arm,arm64,i386,
mips,riscv,s390 and x86_64.
Signed-off-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2023-01-10 10:24:13 +03:00
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void __attribute__((weak,noreturn,optimize("omit-frame-pointer"))) __start(void)
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{
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__asm__ volatile (
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//".set nomips16\n"
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".set push\n"
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".set noreorder\n"
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".option pic0\n"
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//".ent __start\n"
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//"__start:\n"
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"lw $a0,($sp)\n" // argc was in the stack
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"addiu $a1, $sp, 4\n" // argv = sp + 4
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"sll $a2, $a0, 2\n" // a2 = argc * 4
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"add $a2, $a2, $a1\n" // envp = argv + 4*argc ...
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"addiu $a2, $a2, 4\n" // ... + 4
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2023-01-10 10:24:22 +03:00
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"lui $a3, %hi(environ)\n" // load environ into a3 (hi)
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"addiu $a3, %lo(environ)\n" // load environ into a3 (lo)
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"sw $a2,($a3)\n" // store envp(a2) into environ
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2023-01-10 10:24:30 +03:00
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"move $t0, $a2\n" // iterate t0 over envp, look for NULL
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"0:" // do {
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"lw $a3, ($t0)\n" // a3=*(t0);
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"bne $a3, $0, 0b\n" // } while (a3);
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"addiu $t0, $t0, 4\n" // delayed slot: t0+=4;
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"lui $a3, %hi(_auxv)\n" // load _auxv into a3 (hi)
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"addiu $a3, %lo(_auxv)\n" // load _auxv into a3 (lo)
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"sw $t0, ($a3)\n" // store t0 into _auxv
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tools/nolibc: make compiler and assembler agree on the section around _start
The out-of-block asm() statement carrying _start does not allow the
compiler to know what section the assembly code is being emitted to,
and there's no easy way to push/pop the current section and restore
it. It sometimes causes issues depending on the include files ordering
and compiler optimizations. For example if a variable is declared
immediately before the asm() block and another one after, the compiler
assumes that the current section is still .bss and doesn't re-emit it,
making the second variable appear inside the .text section instead.
Forcing .bss at the end of the _start block doesn't work either because
at certain optimizations the compiler may reorder blocks and will make
some real code appear just after this block.
A significant number of solutions were attempted, but many of them were
still sensitive to section reordering. In the end, the best way to make
sure the compiler and assembler agree on the current section is to place
this code inside a function. Here the function is directly called _start
and configured not to emit a frame-pointer, hence to have no prologue.
If some future architectures would still emit some prologue, another
working approach consists in naming the function differently and placing
the _start label inside the asm statement. But the current solution is
simpler.
It was tested with nolibc-test at -O,-O0,-O2,-O3,-Os for arm,arm64,i386,
mips,riscv,s390 and x86_64.
Signed-off-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2023-01-10 10:24:13 +03:00
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"li $t0, -8\n"
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"and $sp, $sp, $t0\n" // sp must be 8-byte aligned
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"addiu $sp,$sp,-16\n" // the callee expects to save a0..a3 there!
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"jal main\n" // main() returns the status code, we'll exit with it.
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"nop\n" // delayed slot
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"move $a0, $v0\n" // retrieve 32-bit exit code from v0
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"li $v0, 4001\n" // NR_exit == 4001
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"syscall\n"
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//".end __start\n"
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".set pop\n"
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);
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__builtin_unreachable();
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}
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2022-02-07 19:23:17 +03:00
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#endif // _NOLIBC_ARCH_MIPS_H
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