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Snapshot at a random moment, showing a new debugging trick: hacking on
the C++ level to dump memory contents on specific labels.

For some reason label 'x' doesn't have a segment assigned by the time we
get to compute-addresses.
This commit is contained in:
Kartik Agaram 2019-07-12 23:14:13 -07:00
parent 94f2de6d06
commit 8ba17d839e
2 changed files with 70 additions and 2 deletions
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15
subx/039debug.cc
View File

@ -91,6 +91,21 @@ if (!Watch_this_effective_address.empty()) {
put(Watch_points, Watch_this_effective_address, addr);
}
//: Special label that dumps regions of memory.
//: Not a general mechanism; by the time you get here you're willing to hack
//: on the emulator.
:(after "Run One Instruction")
if (contains_key(Symbol_name, EIP) && get(Symbol_name, EIP) == "$dump-stream-at-ESI")
dump_stream_at_ESI();
:(code)
void dump_stream_at_ESI() {
uint32_t stream_start = Reg[ESI].i;
int32_t stream_length = read_mem_i32(stream_start + 8);
dbg << "stream length: " << std::dec << stream_length << end();
for (int i = 0; i < stream_length + 12; ++i)
dbg << "0x" << HEXWORD << (stream_start+i) << ": " << HEXBYTE << NUM(read_mem_u8(stream_start+i)) << end();
}
//: helpers
:(code)

57
subx/apps/survey.subx
View File

@ -1174,6 +1174,7 @@ $compute-addresses:segment-loop:
$compute-addresses:segment-break:
# ESI = labels
8b/copy 1/mod/*+disp8 5/rm32/EBP . . . 6/r32/ESI 0xc/disp8 . # copy *(EBP+12) to ESI
#? $dump-stream-at-ESI:
# lrow/EAX = labels->data
8d/copy-address 1/mod/*+disp8 6/rm32/ESI . . . 0/r32/EAX 0xc/disp8 . # copy ESI+12 to EAX
# max/ECX = labels->data + labels->write
@ -1182,9 +1183,61 @@ $compute-addresses:segment-break:
$compute-addresses:label-loop:
# if (lrow >= max) break
39/compare 3/mod/direct 0/rm32/EAX . . . 1/r32/ECX . . # compare EAX with ECX
73/jump-if-greater-or-equal-unsigned $compute-addresses:end/disp8
0f 83/jump-if-greater-or-equal-unsigned $compute-addresses:end/disp32
# dump lrow->key {{{
# . write(2/stderr, "label: ")
# . . push args
68/push "label: "/imm32
68/push 2/imm32/stderr
# . . call
e8/call write/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add to ESP
# . write(2/stderr, lrow->key)
# . . push args
ff 6/subop/push 0/mod/indirect 0/rm32/EAX . . . . . . # push *EAX
68/push 2/imm32/stderr
# . . call
e8/call write/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add to ESP
# . write(2/stderr, "$\n")
# . . push args
68/push "$\n"/imm32
68/push 2/imm32/stderr
# . . call
e8/call write/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add to ESP
# }}}
# seg-name/EDX = lrow->segment-name
8b/copy 1/mod/*+disp8 0/rm32/EAX . . . 2/r32/EDX 4/disp8 . # copy *EAX to EDX
# dump seg-name {{{
# . write(2/stderr, "compute-addresses: seg-name: ")
# . . push args
68/push "seg-name: "/imm32
68/push 2/imm32/stderr
# . . call
e8/call write/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add to ESP
# . write(2/stderr, seg-name)
# . . push args
52/push-EDX
68/push 2/imm32/stderr
# . . call
e8/call write/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add to ESP
# . write(2/stderr, "$\n")
# . . push args
68/push "$\n"/imm32
68/push 2/imm32/stderr
# . . call
e8/call write/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add to ESP
# }}}
# label-seg/EDX : (address segment-info) = get(segments, seg-name, row-size=16)
# . save EAX
50/push-EAX
@ -1220,7 +1273,7 @@ $compute-addresses:label-loop:
81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 0x14/imm32 # add to ESP
# lrow += 16 # size of row
05/add-to-EAX 0x10/imm32
eb/jump $compute-addresses:label-loop/disp8
e9/jump $compute-addresses:label-loop/disp32
$compute-addresses:end:
# . restore registers
5f/pop-to-EDI