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# Example showing mmap syscall.
# Create a new segment using mmap, save the address, write to it.
#
# To run:
# $ ./translate_subx 000init.subx apps/ex12.subx
# $ ./a.elf
# You shouldn't get a segmentation fault.
== code
# instruction effective address register 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
Entry:
# mmap(Mmap-new-segment->len)
bb/copy-to-ebx Mmap-new-segment/imm32
e8/call syscall_mmap/disp32
# write to *eax to check that we have access to the newly-allocated segment
c7 0/subop/copy 0/mod/direct 0/rm32/eax . . . . . 0x34/imm32 # copy to *eax
# exit(eax)
89/copy 3/mod/direct 3/rm32/ebx . . . 0/r32/eax . . # copy eax to ebx
e8/call syscall_exit/disp32
== 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
0/imm32
# len
0x100/imm32
# protection flags
3/imm32 # PROT_READ | PROT_WRITE
# sharing flags
0x22/imm32 # MAP_PRIVATE | MAP_ANONYMOUS
# fd
-1/imm32 # since MAP_ANONYMOUS is specified
# offset
0/imm32 # since MAP_ANONYMOUS is specified
# . . vim:nowrap:textwidth=0
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