## example showing mmap syscall # Create a new segment using mmap, save the address, write to it. # # To run (from the subx directory): # $ subx translate examples/ex12.subx -o examples/ex12 # $ subx run examples/ex12 # You shouldn't get a segmentation fault. == code # instruction effective address operand displacement immediate # op subop mod rm32 base index scale r32 # 1-3 bytes 3 bits 2 bits 3 bits 3 bits 3 bits 2 bits 2 bits 0/1/2/4 bytes 0/1/2/4 bytes # mmap(0x1000) bb/copy . . . . . . . mmap_new_segment/imm32 # copy to EBX b8/copy . . . . . . . 0x5a/imm32/mmap # copy 8 to EAX cd/syscall 0x80/imm8 # store to *EAX c7/copy 0/mod/direct 0/rm32/EAX . . . . . 0x34/imm32 # copy 0x34 to *EAX # exit(EAX) 89/copy 3/mod/direct 3/rm32/EBX . . . 0/r32/EAX . . # copy EAX to EBX b8/copy . . . . . . . 1/imm32/exit # copy 1 to EAX cd/syscall 0x80/imm8 == data # various constants used here were found in the Linux sources (search for file mman-common.h) mmap_new_segment: # type mmap_arg_struct # addr 00 00 00 00 # null # len 00 01 00 00 # 0x1000 # protection flags 03 00 00 00 # PROT_READ | PROT_WRITE # sharing flags 22 00 00 00 # MAP_PRIVATE | MAP_ANONYMOUS # fd ff ff ff ff # -1 since MAP_ANONYMOUS is specified # offset 00 00 00 00 # 0 since MAP_ANONYMOUS is specified # vim:ft=subx:nowrap:tw&