103 lines
3.4 KiB
Plaintext
103 lines
3.4 KiB
Plaintext
# Helper to check an array's bounds, and to abort if they're violated.
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# Really only intended to be called from code generated by mu.subx.
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== code
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__check-mu-array-bounds: # index: int, elem-size: int, arr-size: int, function-name: (addr array byte), array-name: (addr array byte)
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# . prologue
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55/push-ebp
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89/<- %ebp 4/r32/esp
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# . save registers
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50/push-eax
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51/push-ecx
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52/push-edx
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# . not bothering saving ebx; it's only clobbered if we're going to abort
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# ecx = arr-size
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8b/-> *(ebp+0x10) 1/r32/ecx
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# var overflow/edx: int = 0
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ba/copy-to-edx 0/imm32
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# var offset/eax: int = index * elem-size
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8b/-> *(ebp+8) 0/r32/eax
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f7 4/subop/multiply-eax-with *(ebp+0xc)
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# check for overflow
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81 7/subop/compare %edx 0/imm32
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0f 85/jump-if-!= __check-mu-array-bounds:overflow/disp32
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# check bounds
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39/compare %eax 1/r32/ecx
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0f 82/jump-if-unsigned< $__check-mu-array-bounds:end/disp32 # negative index should always abort
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# abort if necessary
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(write-buffered Stderr "fn ")
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(write-buffered Stderr *(ebp+0x14))
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(write-buffered Stderr ": offset ")
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(write-int32-hex-buffered Stderr %eax)
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(write-buffered Stderr " is too large for array '")
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(write-buffered Stderr *(ebp+0x18))
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(write-buffered Stderr "'\n")
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(flush Stderr)
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# exit(1)
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bb/copy-to-ebx 1/imm32
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e8/call syscall_exit/disp32
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# never gets here
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$__check-mu-array-bounds:end:
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# . restore registers
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5a/pop-to-edx
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59/pop-to-ecx
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58/pop-to-eax
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# . epilogue
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89/<- %esp 5/r32/ebp
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5d/pop-to-ebp
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c3/return
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__check-mu-array-bounds:overflow:
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# "fn " function-name ": offset to array '" array-name "' overflowed 32 bits\n"
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(write-buffered Stderr "fn ")
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(write-buffered Stderr *(ebp+0x14))
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(write-buffered Stderr ": offset to array '")
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(write-buffered Stderr *(ebp+0x18))
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(write-buffered Stderr "' overflowed 32 bits\n")
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(flush Stderr)
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# exit(1)
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bb/copy-to-ebx 1/imm32
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e8/call syscall_exit/disp32
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# never gets here
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# potential alternative
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#? __bounds-check: # msg: (addr array byte)
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#? (write-buffered Stderr "abort: array bounds exceeded in fn ")
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#? 8b/-> *(esp+4) 0/r32/eax # we're going to abort, so just clobber away
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#? (write-buffered Stderr %eax)
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#? (write-buffered Stderr Newline)
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#? # exit(1)
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#? bb/copy-to-ebx 1/imm32
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#? e8/call syscall_exit/disp32
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# to be called as follows:
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# var/reg <- index arr/rega: (addr array T), idx/regi: int
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# | if size-of(T) is 1, 2, 4 or 8
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# => # temporarily save array size to reg to check bounds
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# "8b/-> *" rega " " reg "/r32"
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# "c1/shift 5/subop/right %" reg " " log2(size-of(T)) "/imm32"
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# "3b/compare " reg "/r32 *" rega
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# "68/push \"" function "\"/imm32" # pass function name to error message
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# "0f 8d/jump-if->= __bounds_check/disp32"
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# "81 0/subop/add %esp 4/imm32" # drop function name
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# # actually save the index addr in reg
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# "8d/copy-address *(" rega "+" regi "<<" log2(size-of(T)) "+4) " reg "/r32"
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__mu-abort-null-index-base-address:
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(write-buffered Stderr "null address in 'index'\n")
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(flush Stderr)
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# exit(1)
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bb/copy-to-ebx 1/imm32
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e8/call syscall_exit/disp32
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# never gets here
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__mu-abort-null-get-base-address:
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(write-buffered Stderr "null address in 'get'\n")
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(flush Stderr)
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# exit(1)
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bb/copy-to-ebx 1/imm32
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e8/call syscall_exit/disp32
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# never gets here
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