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[PATCH v5 12/16] fuzz: Add instructions for using general-fuzz
From: |
Alexander Bulekov |
Subject: |
[PATCH v5 12/16] fuzz: Add instructions for using general-fuzz |
Date: |
Tue, 20 Oct 2020 21:07:48 -0400 |
Reviewed-by: Darren Kenny <darren.kenny@oracle.com>
Signed-off-by: Alexander Bulekov <alxndr@bu.edu>
---
docs/devel/fuzzing.txt | 39 +++++++++++++++++++++++++++++++++++++++
1 file changed, 39 insertions(+)
diff --git a/docs/devel/fuzzing.txt b/docs/devel/fuzzing.txt
index 96d71c94d7..c40278fe0a 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 General 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 general-fuzz target.
+
+The general-fuzz target is capable of fuzzing devices over their PIO, MMIO,
+and DMA input-spaces. To apply the general-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 general 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=general-fuzz -runs=0
+
+The output should contain a complete list of matched MemoryRegions.
+
= Implementation Details =
== The Fuzzer's Lifecycle ==
--
2.28.0
- Re: [PATCH v5 02/16] fuzz: Add general virtual-device fuzzer, (continued)
- [PATCH v5 03/16] fuzz: Add PCI features to the general fuzzer, Alexander Bulekov, 2020/10/20
- [PATCH v5 04/16] fuzz: Add DMA support to the generic-fuzzer, Alexander Bulekov, 2020/10/20
- [PATCH v5 05/16] fuzz: Declare DMA Read callback function, Alexander Bulekov, 2020/10/20
- [PATCH v5 06/16] fuzz: Add fuzzer callbacks to DMA-read functions, Alexander Bulekov, 2020/10/20
- [PATCH v5 07/16] fuzz: Add support for custom crossover functions, Alexander Bulekov, 2020/10/20
- [PATCH v5 08/16] fuzz: add a DISABLE_PCI op to general-fuzzer, Alexander Bulekov, 2020/10/20
- [PATCH v5 09/16] fuzz: add a crossover function to generic-fuzzer, Alexander Bulekov, 2020/10/20
- [PATCH v5 10/16] scripts/oss-fuzz: Add script to reorder a general-fuzzer trace, Alexander Bulekov, 2020/10/20
- [PATCH v5 11/16] scripts/oss-fuzz: Add crash trace minimization script, Alexander Bulekov, 2020/10/20
- [PATCH v5 12/16] fuzz: Add instructions for using general-fuzz,
Alexander Bulekov <=
- [PATCH v5 13/16] fuzz: add an "opaque" to the FuzzTarget struct, Alexander Bulekov, 2020/10/20
- [PATCH v5 14/16] fuzz: add general-fuzz configs for oss-fuzz, Alexander Bulekov, 2020/10/20
- [PATCH v5 15/16] fuzz: register predefined general-fuzz configs, Alexander Bulekov, 2020/10/20
- [PATCH v5 16/16] scripts/oss-fuzz: remove the general-fuzz target, Alexander Bulekov, 2020/10/20
- Re: [PATCH v5 00/16] Add a Generic Virtual Device Fuzzer, Thomas Huth, 2020/10/21