tools/include/nolibc/arch-x86_64.h

   1 /* SPDX-License-Identifier: LGPL-2.1 OR MIT */
   2 /*
   3  * x86_64 specific definitions for NOLIBC
   4  * Copyright (C) 2017-2022 Willy Tarreau <w@1wt.eu>
   5  */
   6
   7 #ifndef _NOLIBC_ARCH_X86_64_H
   8 #define _NOLIBC_ARCH_X86_64_H
   9
  10 #include "compiler.h"
  11 #include "crt.h"
  12
  13 /* Syscalls for x86_64 :
  14  *   - registers are 64-bit
  15  *   - syscall number is passed in rax
  16  *   - arguments are in rdi, rsi, rdx, r10, r8, r9 respectively
  17  *   - the system call is performed by calling the syscall instruction
  18  *   - syscall return comes in rax
  19  *   - rcx and r11 are clobbered, others are preserved.
  20  *   - the arguments are cast to long and assigned into the target registers
  21  *     which are then simply passed as registers to the asm code, so that we
  22  *     don't have to experience issues with register constraints.
  23  *   - the syscall number is always specified last in order to allow to force
  24  *     some registers before (gcc refuses a %-register at the last position).
  25  *   - see also x86-64 ABI section A.2 AMD64 Linux Kernel Conventions, A.2.1
  26  *     Calling Conventions.
  27  *
  28  * Link x86-64 ABI: https://gitlab.com/x86-psABIs/x86-64-ABI/-/wikis/home
  29  *
  30  */
  31
  32 #define my_syscall0(num)                                                      \
  33 ({                                                                            \
  34         long _ret;                                                            \
  35         register long _num  __asm__ ("rax") = (num);                          \
  36                                                                               \
  37         __asm__ volatile (                                                    \
  38                 "syscall\n"                                                   \
  39                 : "=a"(_ret)                                                  \
  40                 : "0"(_num)                                                   \
  41                 : "rcx", "r11", "memory", "cc"                                \
  42         );                                                                    \
  43         _ret;                                                                 \
  44 })
  45
  46 #define my_syscall1(num, arg1)                                                \
  47 ({                                                                            \
  48         long _ret;                                                            \
  49         register long _num  __asm__ ("rax") = (num);                          \
  50         register long _arg1 __asm__ ("rdi") = (long)(arg1);                   \
  51                                                                               \
  52         __asm__ volatile (                                                    \
  53                 "syscall\n"                                                   \
  54                 : "=a"(_ret)                                                  \
  55                 : "r"(_arg1),                                                 \
  56                   "0"(_num)                                                   \
  57                 : "rcx", "r11", "memory", "cc"                                \
  58         );                                                                    \
  59         _ret;                                                                 \
  60 })
  61
  62 #define my_syscall2(num, arg1, arg2)                                          \
  63 ({                                                                            \
  64         long _ret;                                                            \
  65         register long _num  __asm__ ("rax") = (num);                          \
  66         register long _arg1 __asm__ ("rdi") = (long)(arg1);                   \
  67         register long _arg2 __asm__ ("rsi") = (long)(arg2);                   \
  68                                                                               \
  69         __asm__ volatile (                                                    \
  70                 "syscall\n"                                                   \
  71                 : "=a"(_ret)                                                  \
  72                 : "r"(_arg1), "r"(_arg2),                                     \
  73                   "0"(_num)                                                   \
  74                 : "rcx", "r11", "memory", "cc"                                \
  75         );                                                                    \
  76         _ret;                                                                 \
  77 })
  78
  79 #define my_syscall3(num, arg1, arg2, arg3)                                    \
  80 ({                                                                            \
  81         long _ret;                                                            \
  82         register long _num  __asm__ ("rax") = (num);                          \
  83         register long _arg1 __asm__ ("rdi") = (long)(arg1);                   \
  84         register long _arg2 __asm__ ("rsi") = (long)(arg2);                   \
  85         register long _arg3 __asm__ ("rdx") = (long)(arg3);                   \
  86                                                                               \
  87         __asm__ volatile (                                                    \
  88                 "syscall\n"                                                   \
  89                 : "=a"(_ret)                                                  \
  90                 : "r"(_arg1), "r"(_arg2), "r"(_arg3),                         \
  91                   "0"(_num)                                                   \
  92                 : "rcx", "r11", "memory", "cc"                                \
  93         );                                                                    \
  94         _ret;                                                                 \
  95 })
  96
  97 #define my_syscall4(num, arg1, arg2, arg3, arg4)                              \
  98 ({                                                                            \
  99         long _ret;                                                            \
 100         register long _num  __asm__ ("rax") = (num);                          \
 101         register long _arg1 __asm__ ("rdi") = (long)(arg1);                   \
 102         register long _arg2 __asm__ ("rsi") = (long)(arg2);                   \
 103         register long _arg3 __asm__ ("rdx") = (long)(arg3);                   \
 104         register long _arg4 __asm__ ("r10") = (long)(arg4);                   \
 105                                                                               \
 106         __asm__ volatile (                                                    \
 107                 "syscall\n"                                                   \
 108                 : "=a"(_ret)                                                  \
 109                 : "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4),             \
 110                   "0"(_num)                                                   \
 111                 : "rcx", "r11", "memory", "cc"                                \
 112         );                                                                    \
 113         _ret;                                                                 \
 114 })
 115
 116 #define my_syscall5(num, arg1, arg2, arg3, arg4, arg5)                        \
 117 ({                                                                            \
 118         long _ret;                                                            \
 119         register long _num  __asm__ ("rax") = (num);                          \
 120         register long _arg1 __asm__ ("rdi") = (long)(arg1);                   \
 121         register long _arg2 __asm__ ("rsi") = (long)(arg2);                   \
 122         register long _arg3 __asm__ ("rdx") = (long)(arg3);                   \
 123         register long _arg4 __asm__ ("r10") = (long)(arg4);                   \
 124         register long _arg5 __asm__ ("r8")  = (long)(arg5);                   \
 125                                                                               \
 126         __asm__ volatile (                                                    \
 127                 "syscall\n"                                                   \
 128                 : "=a"(_ret)                                                  \
 129                 : "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4), "r"(_arg5), \
 130                   "0"(_num)                                                   \
 131                 : "rcx", "r11", "memory", "cc"                                \
 132         );                                                                    \
 133         _ret;                                                                 \
 134 })
 135
 136 #define my_syscall6(num, arg1, arg2, arg3, arg4, arg5, arg6)                  \
 137 ({                                                                            \
 138         long _ret;                                                            \
 139         register long _num  __asm__ ("rax") = (num);                          \
 140         register long _arg1 __asm__ ("rdi") = (long)(arg1);                   \
 141         register long _arg2 __asm__ ("rsi") = (long)(arg2);                   \
 142         register long _arg3 __asm__ ("rdx") = (long)(arg3);                   \
 143         register long _arg4 __asm__ ("r10") = (long)(arg4);                   \
 144         register long _arg5 __asm__ ("r8")  = (long)(arg5);                   \
 145         register long _arg6 __asm__ ("r9")  = (long)(arg6);                   \
 146                                                                               \
 147         __asm__ volatile (                                                    \
 148                 "syscall\n"                                                   \
 149                 : "=a"(_ret)                                                  \
 150                 : "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4), "r"(_arg5), \
 151                   "r"(_arg6), "0"(_num)                                       \
 152                 : "rcx", "r11", "memory", "cc"                                \
 153         );                                                                    \
 154         _ret;                                                                 \
 155 })
 156
 157 /* startup code */
 158 /*
 159  * x86-64 System V ABI mandates:
 160  * 1) %rsp must be 16-byte aligned right before the function call.
 161  * 2) The deepest stack frame should be zero (the %rbp).
 162  *
 163  */
 164 void __attribute__((weak, noreturn, optimize("Os", "omit-frame-pointer"))) __no_stack_protector _start(void)
 165 {
 166         __asm__ volatile (
 167                 "xor  %ebp, %ebp\n"       /* zero the stack frame                            */
 168                 "mov  %rsp, %rdi\n"       /* save stack pointer to %rdi, as arg1 of _start_c */
 169                 "and  $-16, %rsp\n"       /* %rsp must be 16-byte aligned before call        */
 170                 "call _start_c\n"         /* transfer to c runtime                           */
 171                 "hlt\n"                   /* ensure it does not return                       */
 172         );
 173         __builtin_unreachable();
 174 }
 175
 176 #define NOLIBC_ARCH_HAS_MEMMOVE
 177 void *memmove(void *dst, const void *src, size_t len);
 178
 179 #define NOLIBC_ARCH_HAS_MEMCPY
 180 void *memcpy(void *dst, const void *src, size_t len);
 181
 182 #define NOLIBC_ARCH_HAS_MEMSET
 183 void *memset(void *dst, int c, size_t len);
 184
 185 __asm__ (
 186 ".section .text.nolibc_memmove_memcpy\n"
 187 ".weak memmove\n"
 188 ".weak memcpy\n"
 189 "memmove:\n"
 190 "memcpy:\n"
 191         "movq %rdx, %rcx\n\t"
 192         "movq %rdi, %rax\n\t"
 193         "movq %rdi, %rdx\n\t"
 194         "subq %rsi, %rdx\n\t"
 195         "cmpq %rcx, %rdx\n\t"
 196         "jb   .Lbackward_copy\n\t"
 197         "rep movsb\n\t"
 198         "retq\n"
 199 ".Lbackward_copy:"
 200         "leaq -1(%rdi, %rcx, 1), %rdi\n\t"
 201         "leaq -1(%rsi, %rcx, 1), %rsi\n\t"
 202         "std\n\t"
 203         "rep movsb\n\t"
 204         "cld\n\t"
 205         "retq\n"
 206
 207 ".section .text.nolibc_memset\n"
 208 ".weak memset\n"
 209 "memset:\n"
 210         "xchgl %eax, %esi\n\t"
 211         "movq  %rdx, %rcx\n\t"
 212         "pushq %rdi\n\t"
 213         "rep stosb\n\t"
 214         "popq  %rax\n\t"
 215         "retq\n"
 216 );
 217
 218 #endif /* _NOLIBC_ARCH_X86_64_H */