linux/000init.subx

   1 # Some OS-specific preliminaries for Linux.
   2
   3 # Memory layout
   4 #
   5 #          0 - 0x08047ffff - reserved for the kernel
   6 # 0x08048000 - 0xbffffffff - available for user programs
   7 # 0xc0000000 - 0xfffffffff - reserved for the kernel
   8 == code 0x09000000
   9 == data 0x0a000000
  10
  11 # Syscalls
  12 #
  13 # We don't have libc, so we need to know Linux's precise syscall layout.
  14 # These are not real functions. Pass arguments in specific registers.
  15 == code
  16
  17 # http://man7.org/linux/man-pages/man2/exit.2.html
  18 syscall_exit:  # status/ebx: int
  19     b8/copy-to-eax 1/imm32
  20     cd/syscall 0x80/imm8
  21
  22 # http://man7.org/linux/man-pages/man2/read.2.html
  23 syscall_read:  # fd/ebx: int, buf/ecx: addr, size/edx: int -> nbytes-or-error/eax: int
  24     b8/copy-to-eax 3/imm32
  25     cd/syscall 0x80/imm8
  26     c3/return
  27
  28 # http://man7.org/linux/man-pages/man2/write.2.html
  29 syscall_write:  # fd/ebx: int, buf/ecx: addr, size/edx: int -> nbytes-or-error/eax: int
  30     b8/copy-to-eax 4/imm32
  31     cd/syscall 0x80/imm8
  32     c3/return
  33
  34 # http://man7.org/linux/man-pages/man2/open.2.html
  35 syscall_open:  # filename/ebx: (addr kernel-string), flags/ecx: int, dummy=0x180/edx -> fd-or-error/eax: int
  36     b8/copy-to-eax 5/imm32
  37     cd/syscall 0x80/imm8
  38     c3/return
  39
  40 # http://man7.org/linux/man-pages/man2/close.2.html
  41 syscall_close:  # fd/ebx: int -> status/eax
  42     b8/copy-to-eax 6/imm32
  43     cd/syscall 0x80/imm8
  44     c3/return
  45
  46 # http://man7.org/linux/man-pages/man2/lseek.2.html
  47 syscall_lseek:  # fd/ebx: int, offset/ecx: int, whence/edx: int
  48     b8/copy-to-eax 0x13/imm32
  49     cd/syscall 0x80/imm8
  50     c3/return
  51
  52 # http://man7.org/linux/man-pages/man2/creat.2.html
  53 syscall_creat:  # filename/ebx: (addr kernel-string) -> fd-or-error/eax: int
  54     b8/copy-to-eax 8/imm32
  55     cd/syscall 0x80/imm8
  56     c3/return
  57
  58 # http://man7.org/linux/man-pages/man2/unlink.2.html
  59 syscall_unlink:  # filename/ebx: (addr kernel-string) -> status/eax: int
  60     b8/copy-to-eax 0xa/imm32
  61     cd/syscall 0x80/imm8
  62     c3/return
  63
  64 # http://man7.org/linux/man-pages/man2/rename.2.html
  65 syscall_rename:  # source/ebx: (addr kernel-string), dest/ecx: (addr kernel-string) -> status/eax: int
  66     b8/copy-to-eax 0x26/imm32
  67     cd/syscall 0x80/imm8
  68     c3/return
  69
  70 # https://github.com/torvalds/linux/blob/fa121bb3fed6313b1f0af23952301e06cf6d32ed/mm/nommu.c#L1352
  71 syscall_mmap:  # arg/ebx: (addr mmap_arg_struct) -> status/eax: int
  72     # the important thing: ebx+4 contains the 32-bit size to be allocated
  73     b8/copy-to-eax 0x5a/imm32
  74     cd/syscall 0x80/imm8
  75     c3/return
  76
  77 syscall_ioctl:  # fd/ebx: int, cmd/ecx: int, arg/edx: (addr _)
  78     b8/copy-to-eax 0x36/imm32
  79     cd/syscall 0x80/imm8
  80     c3/return
  81
  82 syscall_nanosleep:  # req/ebx: (addr timespec)
  83     b8/copy-to-eax 0xa2/imm32  # 162
  84     cd/syscall 0x80/imm8
  85     c3/return
  86
  87 syscall_clock_gettime:  # clock/ebx: int, out/ecx: (addr timespec)
  88     b8/copy-to-eax 0x109/imm32  # 265
  89     cd/syscall 0x80/imm8
  90     c3/return