When decodetree.py was added in commit 568ae7efae, QEMU was
using Python 2 which happily reads UTF-8 files in text mode.
Python 3 requires either UTF-8 locale or an explicit encoding
passed to open(). Now that Python 3 is required, explicit
UTF-8 encoding for decodetree source files.
To avoid further problems with the user locale, also explicit
UTF-8 encoding for the generated C files.
Explicit both input/output are plain text by using the 't' mode.
This fixes:
$ /usr/bin/python3 scripts/decodetree.py test.decode
Traceback (most recent call last):
File "scripts/decodetree.py", line 1397, in <module>
main()
File "scripts/decodetree.py", line 1308, in main
parse_file(f, toppat)
File "scripts/decodetree.py", line 994, in parse_file
for line in f:
File "/usr/lib/python3.6/encodings/ascii.py", line 26, in decode
return codecs.ascii_decode(input, self.errors)[0]
UnicodeDecodeError: 'ascii' codec can't decode byte 0xc3 in position 80:
ordinal not in range(128)
Reported-by: Peter Maydell <peter.maydell@linaro.org>
Suggested-by: Yonggang Luo <luoyonggang@gmail.com>
Reviewed-by: Eduardo Habkost <ehabkost@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <20210110000240.761122-1-f4bug@amsat.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
This script first runs the regular gdb's 'bt' command, and then if we are in a
coroutine it prints the coroutines backtraces in the order in which they
were called.
Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Message-Id: <20201217155436.927320-3-mlevitsk@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
The code that dumps the stack frame works like that:
* save current registers
* overwrite current registers (including rip/rsp) with coroutine snapshot
in the jmpbuf
* print backtrace
* restore the saved registers.
If the user has currently selected a non topmost stack frame in gdb,
the above code will still restore the selected frame registers,
but the gdb will then lose the selected frame index, which makes it impossible
to switch back to frame 0, to continue debugging the executable.
Therefore switch temporarily to the topmost frame of the stack
for the above code.
Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Message-Id: <20201217155436.927320-2-mlevitsk@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Now we use a one-time scan and remove strategy in the minimizer,
which is not suitable for timing dependent instructions.
For example, instruction A will indicate an address where the config
chunk locates, and instruction B will make the configuration active.
If we have the following instruction sequence:
...
A1
B1
A2
B2
...
A2 and B2 are the actual instructions that trigger the bug.
If we scan from top to bottom, after we remove A1, the behavior of B1
might be unknowable, including not to crash the program. But we will
successfully remove B1 later cause A2 and B2 will crash the process
anyway:
...
A1
A2
B2
...
Now one more trimming will remove A1.
In the perfect case, we would need to be able to remove A and B (or C!) at
the same time. But for now, let's just add a loop around the minimizer.
Since we only remove instructions, this iterative algorithm is converging.
Tested with Bug 1908062.
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: <SYCPR01MB350263004448040ACCB9A9F1FCAB0@SYCPR01MB3502.ausprd01.prod.outlook.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
Currently, we split the write commands' data from the middle. If it does not
work, try to move the pivot left by one byte and retry until there is no
space.
But, this method has two flaws:
1. It may fail to trim all unnecessary bytes on the right side.
For example, there is an IO write command:
write addr uuxxxxuu
u is the unnecessary byte for the crash. Unlike ram write commands, in most
case, a split IO write won't trigger the same crash, So if we split from the
middle, we will get:
write addr uu (will be removed in next round)
write addr xxxxuu
For xxxxuu, since split it from the middle and retry to the leftmost byte
won't get the same crash, we will be stopped from removing the last two
bytes.
2. The algorithm complexity is O(n) since we move the pivot byte by byte.
To solve the first issue, we can try a symmetrical position on the right if
we fail on the left. As for the second issue, instead moving by one byte, we
can approach the boundary exponentially, achieving O(log(n)).
Give an example:
xxxxuu len=6
+
|
+
xxx,xuu 6/2=3 fail
+
+--------------+-------------+
| |
+ +
xx,xxuu 6/2^2=1 fail xxxxu,u 6-1=5 success
+ +
+------------------+----+ |
| | +-------------+ u removed
+ +
xx,xxu 5/2=2 fail xxxx,u 6-2=4 success
+
|
+-----------+ u removed
In some rare cases, this algorithm will fail to trim all unnecessary bytes:
xxxxxxxxxuxxxxxx
xxxxxxxx-xuxxxxxx Fail
xxxx-xxxxxuxxxxxx Fail
xxxxxxxxxuxx-xxxx Fail
...
I think the trade-off is worth it.
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: <SYCPR01MB3502D26F1BEB680CBBC169E5FCAB0@SYCPR01MB3502.ausprd01.prod.outlook.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
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>
We spend much time waiting for the timeout program during the minimization
process until it passes a time limit. This patch hacks the CLOSED (indicates
the redirection file closed) notification in QTest's output if it doesn't
crash.
Test with quadrupled trace input at:
https://bugs.launchpad.net/qemu/+bug/1890333/comments/1
Original version:
real 1m37.246s
user 0m13.069s
sys 0m8.399s
Refined version:
real 0m45.904s
user 0m16.874s
sys 0m10.042s
Note:
Sometimes the mutated or the same trace may trigger a different crash
summary (second-to-last line) but indicates the same bug. For example, Bug
1910826 [1], which will trigger a stack overflow, may output summaries
like:
SUMMARY: AddressSanitizer: stack-overflow
/home/qiuhao/hack/qemu/build/../softmmu/physmem.c:488 in
flatview_do_translate
or
SUMMARY: AddressSanitizer: stack-overflow
(/home/qiuhao/hack/qemu/build/qemu-system-i386+0x27ca049) in __asan_memcpy
Etc.
If we use the whole summary line as the token, we may be prevented from
further minimization. So in this patch, we only use the first three words
which indicate the type of crash:
SUMMARY: AddressSanitizer: stack-overflow
[1] https://bugs.launchpad.net/qemu/+bug/1910826
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: <SYCPR01MB350251DC04003450348FAF68FCAB0@SYCPR01MB3502.ausprd01.prod.outlook.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
The compiler encounters trace event format strings in generated code.
Format strings are error-prone and therefore clear compiler errors are
important.
Use the #line directive to show the trace-events filename and line
number in format string errors:
https://gcc.gnu.org/onlinedocs/gcc-10.2.0/cpp/Line-Control.html
For example, if the cpu_in trace event's %u is changed to %p the
following error is reported:
trace-events:29:18: error: format ‘%p’ expects argument of type ‘void *’, but argument 7 has type ‘unsigned int’ [-Werror=format=]
Line 29 in trace-events is where cpu_in is defined. This works for any
trace-events file in the QEMU source tree and the correct path is
displayed.
Unfortunately there does not seem to be a way to set the column, so "18"
is not the right character on that line.
Suggested-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Message-Id: <20200827142915.108730-5-stefanha@redhat.com>
The tracetool.py script writes to stdout. This means the output filename
is not available to the script. Add the output filename to the
command-line so that the script has access to the filename.
This also simplifies the tracetool.py invocation. It's no longer
necessary to use meson's custom_build(capture : true) to save output.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Message-Id: <20200827142915.108730-2-stefanha@redhat.com>
Benchmark for new preallocate filter.
Example usage:
./bench_prealloc.py ../../build/qemu-img \
ssd-ext4:/path/to/mount/point \
ssd-xfs:/path2 hdd-ext4:/path3 hdd-xfs:/path4
The benchmark shows performance improvement (or degradation) when use
new preallocate filter with qcow2 image.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20201021145859.11201-22-vsementsov@virtuozzo.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
