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flushing [0,-1] results in failing to identify whether code was executed #4097

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derekbruening opened this issue Feb 14, 2020 · 1 comment · Fixed by #4101
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flushing [0,-1] results in failing to identify whether code was executed #4097

derekbruening opened this issue Feb 14, 2020 · 1 comment · Fixed by #4101
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@derekbruening

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@derekbruening
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A vmareas assert hit on Mac (#1979 (comment)) made me think of #4031. I added a check and it did not match Mac but it did fire on the drcachesim.delay-simple test, here:

#0  binary_search (v=0x7fff33c33c58, start=0x0, end=0x0, area=0x7fff33c02638, index=0x0, first=true) at /home/bruening/dr/git/src/core/vmareas.c:1508
#1  0x00007ffff7d1527a in executable_areas_match_flags (addr_start=0x0, 
    addr_end=0xffffffffffffffff <error: Cannot access memory at address 0xffffffffffffffff>, found_area=0x0, first_match_start=0x0, are_all_matching=false, 
    match_vm_flags=2048, match_frag_flags=0) at /home/bruening/dr/git/src/core/vmareas.c:3186
#2  0x00007ffff7d155b3 in executable_vm_area_executed_from (start=0x0, end=0xffffffffffffffff <error: Cannot access memory at address 0xffffffffffffffff>)
    at /home/bruening/dr/git/src/core/vmareas.c:3303
#3  0x00007ffff7d71658 in dr_unlink_flush_region (start=0x0, size=18446744073709551615) at /home/bruening/dr/git/src/core/lib/instrument.c:7082
#4  0x00007fffb3b911cc in hit_instr_count_threshold () at /home/bruening/dr/git/src/clients/drcachesim/tracer/tracer.cpp:1347

The assert doesn't fire b/c end is NULL. However, this is a bug in executable_areas_match_flags() b/c it doesn't iterate over anything!
@derekbruening derekbruening self-assigned this Feb 14, 2020
@derekbruening derekbruening mentioned this issue Feb 14, 2020
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@derekbruening
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Prior to PR #4098 a binary_search of 0..0 would return the 1st area every time.

derekbruening added a commit that referenced this issue Feb 14, 2020
@derekbruening
i#4097: Fix flush-the-world code region locating
c1c3bce 
Fixes a bug where flushing 0..-1 found only the very first code
region, due to passing 0..0 to binary_search.

Adds a unit test and an assert on passing 0..0 in the future.

Fixes #4097
@derekbruening derekbruening mentioned this issue Feb 14, 2020
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derekbruening added a commit that referenced this issue Feb 14, 2020
@derekbruening
i#4097: Fix flush-the-world code region locating (#4101)
bb93936 
Fixes a bug where flushing 0..-1 found only the very first code
region, due to passing 0..0 to binary_search.

Adds a unit test and an assert on passing 0..0 in the future.

Fixes #4097
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i#4097: Fix flush-the-world code region locating DynamoRIO/dynamorio
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