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@@ -19,11 +19,6 @@ responsibility to ensure that state is reset between fuzzing-runs.
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Building the fuzzers
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Building the fuzzers
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--------------------
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--------------------
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-*NOTE*: If possible, build a 32-bit binary. When forking, the 32-bit fuzzer is
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-much faster, since the page-map has a smaller size. This is due to the fact that
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-AddressSanitizer maps ~20TB of memory, as part of its detection. This results
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-in a large page-map, and a much slower ``fork()``.
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-
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To build the fuzzers, install a recent version of clang:
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To build the fuzzers, install a recent version of clang:
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Configure with (substitute the clang binaries with the version you installed).
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Configure with (substitute the clang binaries with the version you installed).
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Here, enable-sanitizers, is optional but it allows us to reliably detect bugs
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Here, enable-sanitizers, is optional but it allows us to reliably detect bugs
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@@ -296,10 +291,9 @@ input. It is also responsible for manually calling ``main_loop_wait`` to ensure
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that bottom halves are executed and any cleanup required before the next input.
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that bottom halves are executed and any cleanup required before the next input.
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Since the same process is reused for many fuzzing runs, QEMU state needs to
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Since the same process is reused for many fuzzing runs, QEMU state needs to
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-be reset at the end of each run. There are currently two implemented
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-options for resetting state:
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+be reset at the end of each run. For example, this can be done by rebooting the
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+VM, after each run.
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-- Reboot the guest between runs.
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- *Pros*: Straightforward and fast for simple fuzz targets.
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- *Pros*: Straightforward and fast for simple fuzz targets.
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- *Cons*: Depending on the device, does not reset all device state. If the
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- *Cons*: Depending on the device, does not reset all device state. If the
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@@ -308,15 +302,3 @@ options for resetting state:
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reboot.
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reboot.
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- *Example target*: ``i440fx-qtest-reboot-fuzz``
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- *Example target*: ``i440fx-qtest-reboot-fuzz``
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-
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-- Run each test case in a separate forked process and copy the coverage
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- information back to the parent. This is fairly similar to AFL's "deferred"
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- fork-server mode [3]
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-
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- - *Pros*: Relatively fast. Devices only need to be initialized once. No need to
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- do slow reboots or vmloads.
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-
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- - *Cons*: Not officially supported by libfuzzer. Does not work well for
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- devices that rely on dedicated threads.
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-
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- - *Example target*: ``virtio-net-fork-fuzz``
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Alexander Bulekov