[RFC PATCH 0/3] fuzz: add generic fuzzer

[Alexander Bulekov]

These patches add a generic fuzzer for virtual devices. This should
allow us to fuzz devices that accept inputs over MMIO, PIO and DMA
without any device-specific code.

Example:
QEMU_FUZZ_ARGS="-device virtio-net" \
FUZZ_REGION_WHITELIST="virtio pci-" \
./i386-softmmu/qemu-fuzz-i386 --fuzz-target=general-pci-enum-fuzz

The above command will add a virtio-net device to the QEMU arguments and
restrict the fuzzer to only interact with MMIO and PIO regions with
names that contain "virtio" or "pci-". I find these names using the info
mtree monitor command. 

Basically, the fuzzer splits the input into a series of commands, such
as mmio_write, pio_write, etc. Additionally, these patches add "hooks"
to functions that are typically used by virtual-devices to read from RAM
(DMA). These hooks attempt to populate these DMA regions with fuzzed
data, just in time.  There are some differences from my reference code
that seem to result in performance issues that I am still trying to iron
out. I also need to figure out how to add the DMA "hooks" in a neat way.
Maybe I can use -Wl,--wrap for this. I appreciate any feedback.

Alexander Bulekov (3):
  fuzz: add a general fuzzer for any qemu arguments
  fuzz: add support for fuzzing DMA regions
  fuzz: Add callbacks for dma-access functions

 exec.c                                |  17 +-
 include/exec/memory.h                 |   8 +
 include/exec/memory_ldst_cached.inc.h |   9 +
 include/sysemu/dma.h                  |   5 +-
 memory_ldst.inc.c                     |  12 +
 tests/qtest/fuzz/Makefile.include     |   1 +
 tests/qtest/fuzz/general_fuzz.c       | 556 ++++++++++++++++++++++++++
 7 files changed, 606 insertions(+), 2 deletions(-)
 create mode 100644 tests/qtest/fuzz/general_fuzz.c

-- 
2.26.2