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fuzz: double the IOs to remove for every loop

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Instead of removing IO instructions one by one, we can try deleting multiple
instructions at once. According to the locality of reference, we double the
number of instructions to remove for the next round and recover it to one
once we fail.

This patch is usually significant for large input.

Test with quadrupled trace input at:
  https://bugs.launchpad.net/qemu/+bug/1890333/comments/1

Patched 1/6 version:
  real  0m45.904s
  user  0m16.874s
  sys   0m10.042s

Refined version:
  real  0m11.412s
  user  0m6.888s
  sys   0m3.325s

Signed-off-by: Qiuhao Li <Qiuhao.Li@outlook.com>
Reviewed-by: Alexander Bulekov <alxndr@bu.edu>
Tested-by: Alexander Bulekov <alxndr@bu.edu>
Message-Id: <SYCPR01MB350280A67BB55C3FADF173E3FCAB0@SYCPR01MB3502.ausprd01.prod.outlook.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
This commit is contained in:
Qiuhao Li 2021-01-11 14:11:47 +08:00 committed by Thomas Huth
parent 22ec0c696f
commit 7b339f287f
1 changed files with 21 additions and 12 deletions
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33
scripts/oss-fuzz/minimize_qtest_trace.py
View File

@ -88,19 +88,28 @@ def minimize_trace(inpath, outpath):
i = 0
newtrace = trace[:]
# For each line
remove_step = 1
while i < len(newtrace):
# 1.) Try to remove it completely and reproduce the crash. If it works,
# we're done.
prior = newtrace[i]
print("Trying to remove {}".format(newtrace[i]))
# Try to remove the line completely
newtrace[i] = ""
# 1.) Try to remove lines completely and reproduce the crash.
# If it works, we're done.
if (i+remove_step) >= len(newtrace):
remove_step = 1
prior = newtrace[i:i+remove_step]
for j in range(i, i+remove_step):
newtrace[j] = ""
print("Removing {lines} ...".format(lines=prior))
if check_if_trace_crashes(newtrace, outpath):
i += 1
i += remove_step
# Double the number of lines to remove for next round
remove_step *= 2
continue
newtrace[i] = prior
# Failed to remove multiple IOs, fast recovery
if remove_step > 1:
for j in range(i, i+remove_step):
newtrace[j] = prior[j-i]
remove_step = 1
continue
newtrace[i] = prior[0] # remove_step = 1
# 2.) Try to replace write{bwlq} commands with a write addr, len
# command. Since this can require swapping endianness, try both LE and
# BE options. We do this, so we can "trim" the writes in (3)
@ -121,7 +130,7 @@ def minimize_trace(inpath, outpath):
if(check_if_trace_crashes(newtrace, outpath)):
break
else:
newtrace[i] = prior
newtrace[i] = prior[0]
# 3.) If it is a qtest write command: write addr len data, try to split
# it into two separate write commands. If splitting the write down the
@ -154,7 +163,7 @@ def minimize_trace(inpath, outpath):
if check_if_trace_crashes(newtrace, outpath):
i -= 1
else:
newtrace[i] = prior
newtrace[i] = prior[0]
del newtrace[i+1]
i += 1
check_if_trace_crashes(newtrace, outpath)