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[PULL 20/31] fuzz: Add instructions for using generic-fuzz
From: |
Thomas Huth |
Subject: |
[PULL 20/31] fuzz: Add instructions for using generic-fuzz |
Date: |
Mon, 26 Oct 2020 11:06:21 +0100 |
From: Alexander Bulekov <alxndr@bu.edu>
Reviewed-by: Darren Kenny <darren.kenny@oracle.com>
Signed-off-by: Alexander Bulekov <alxndr@bu.edu>
Message-Id: <20201023150746.107063-13-alxndr@bu.edu>
Signed-off-by: Thomas Huth <thuth@redhat.com>
---
docs/devel/fuzzing.txt | 39 +++++++++++++++++++++++++++++++++++++++
1 file changed, 39 insertions(+)
diff --git a/docs/devel/fuzzing.txt b/docs/devel/fuzzing.txt
index 96d71c94d7..03585c1a9b 100644
--- a/docs/devel/fuzzing.txt
+++ b/docs/devel/fuzzing.txt
@@ -125,6 +125,45 @@ provided by libfuzzer. Libfuzzer passes a byte array and
length. Commonly the
fuzzer loops over the byte-array interpreting it as a list of qtest commands,
addresses, or values.
+== The Generic Fuzzer ==
+Writing a fuzz target can be a lot of effort (especially if a device driver has
+not be built-out within libqos). Many devices can be fuzzed to some degree,
+without any device-specific code, using the generic-fuzz target.
+
+The generic-fuzz target is capable of fuzzing devices over their PIO, MMIO,
+and DMA input-spaces. To apply the generic-fuzz to a device, we need to define
+two env-variables, at minimum:
+
+QEMU_FUZZ_ARGS= is the set of QEMU arguments used to configure a machine, with
+the device attached. For example, if we want to fuzz the virtio-net device
+attached to a pc-i440fx machine, we can specify:
+QEMU_FUZZ_ARGS="-M pc -nodefaults -netdev user,id=user0 \
+ -device virtio-net,netdev=user0"
+
+QEMU_FUZZ_OBJECTS= is a set of space-delimited strings used to identify the
+MemoryRegions that will be fuzzed. These strings are compared against
+MemoryRegion names and MemoryRegion owner names, to decide whether each
+MemoryRegion should be fuzzed. These strings support globbing. For the
+virtio-net example, we could use QEMU_FUZZ_OBJECTS=
+ * 'virtio-net'
+ * 'virtio*'
+ * 'virtio* pcspk' (Fuzz the virtio devices and the PC speaker...)
+ * '*' (Fuzz the whole machine)
+
+The "info mtree" and "info qom-tree" monitor commands can be especially useful
+for identifying the MemoryRegion and Object names used for matching.
+
+As a generic rule-of-thumb, the more MemoryRegions/Devices we match, the
greater
+the input-space, and the smaller the probability of finding crashing inputs for
+individual devices. As such, it is usually a good idea to limit the fuzzer to
+only a few MemoryRegions.
+
+To ensure that these env variables have been configured correctly, we can use:
+
+./qemu-fuzz-i386 --fuzz-target=generic-fuzz -runs=0
+
+The output should contain a complete list of matched MemoryRegions.
+
= Implementation Details =
== The Fuzzer's Lifecycle ==
--
2.18.2
- [PULL 07/31] libqtest: fix the order of buffered events, (continued)
- [PULL 07/31] libqtest: fix the order of buffered events, Thomas Huth, 2020/10/26
- [PULL 08/31] libqtest: fix memory leak in the qtest_qmp_event_ref, Thomas Huth, 2020/10/26
- [PULL 09/31] memory: Add FlatView foreach function, Thomas Huth, 2020/10/26
- [PULL 10/31] fuzz: Add generic virtual-device fuzzer, Thomas Huth, 2020/10/26
- [PULL 11/31] fuzz: Add PCI features to the generic fuzzer, Thomas Huth, 2020/10/26
- [PULL 12/31] fuzz: Add DMA support to the generic-fuzzer, Thomas Huth, 2020/10/26
- [PULL 15/31] fuzz: Add support for custom crossover functions, Thomas Huth, 2020/10/26
- [PULL 14/31] fuzz: Add fuzzer callbacks to DMA-read functions, Thomas Huth, 2020/10/26
- [PULL 19/31] scripts/oss-fuzz: Add crash trace minimization script, Thomas Huth, 2020/10/26
- [PULL 16/31] fuzz: add a DISABLE_PCI op to generic-fuzzer, Thomas Huth, 2020/10/26
- [PULL 20/31] fuzz: Add instructions for using generic-fuzz,
Thomas Huth <=
- [PULL 21/31] fuzz: add an "opaque" to the FuzzTarget struct, Thomas Huth, 2020/10/26
- [PULL 17/31] fuzz: add a crossover function to generic-fuzzer, Thomas Huth, 2020/10/26
- [PULL 18/31] scripts/oss-fuzz: Add script to reorder a generic-fuzzer trace, Thomas Huth, 2020/10/26
- [PULL 22/31] fuzz: add generic-fuzz configs for oss-fuzz, Thomas Huth, 2020/10/26
- [PULL 24/31] scripts/oss-fuzz: use hardlinks instead of copying, Thomas Huth, 2020/10/26
- [PULL 13/31] fuzz: Declare DMA Read callback function, Thomas Huth, 2020/10/26
- [PULL 23/31] fuzz: register predefined generic-fuzz configs, Thomas Huth, 2020/10/26
- [PULL 25/31] scripts/oss-fuzz: ignore the generic-fuzz target, Thomas Huth, 2020/10/26
- [PULL 27/31] test/acceptance: Remove the CONTINUOUS_INTEGRATION tags, Thomas Huth, 2020/10/26
- [PULL 26/31] tests/acceptance/ppc_prep_40p: Fix the URL to the NetBSD-4.0 archive, Thomas Huth, 2020/10/26