[PATCH v2 0/3] Add additional plugin API functions to read and write memory and registers

[Rowan Hart]

This patch set follows a previous patch which added the
qemu_plugin_read_memory_vaddr function and adds a set of similar
functions to read and write registers, virtual memory, and
physical memory.

The use case I have in mind is for use of QEMU for program analysis and
testing. For example, a fuzzer which uses QEMU for emulation might wish to
inject test data into a program at runtime using qemu_plugin_write_memory_vaddr
(and likewise if testing an operating system or bare metal application using
qemu_plugin_write_memory_hwaddr). It may also wish to read the initial contents
of memory using qemu_plugin_read_memory_vaddr/hwaddr.

Similarly, a testing framework may wish to fake register values, perhaps to
simulate a device failure, perhaps by using qemu_plugin_write_register to set a
register value to an error code.

I think all this functionality works together to make QEMU
plugins more powerful and versatile, hopefully removing barriers
to using upstream QEMU for these tasks which have historically
required maintaining a QEMU fork downstream (like QEMUAFL
https://github.com/AFLplusplus/qemuafl), which is tedious, error
prone, and results in users missing out on enhancements to QEMU.

A test is provided, compile:

gcc -o tests/tcg/x86_64/inject-target tests/tcg/x86_64/inject-target.c

And run:

./build/qemu-x86_64 -d plugin --plugin build/tests/tcg/plugins/libinject.so 
tests/tcg/x86_64/inject-target

Hopefully after a number of tries, the inject plugin will inject the right
value into the target program, leading to a victory message. This plugin
handles simple "hypercalls", only one of which is implemented and injects
data into guest memory.

novafacing (3):
  Expose gdb_write_register function to consumers of gdbstub
  Add plugin API functions for register R/W, hwaddr R/W, vaddr W
  Add inject plugin and x86_64 target for the inject plugin

 gdbstub/gdbstub.c                |   2 +-
 include/exec/gdbstub.h           |  14 +++
 include/qemu/qemu-plugin.h       | 116 +++++++++++++++--
 plugins/api.c                    |  66 +++++++++-
 tests/tcg/plugins/inject.c       | 206 +++++++++++++++++++++++++++++++
 tests/tcg/plugins/meson.build    |   2 +-
 tests/tcg/x86_64/Makefile.target |   1 +
 tests/tcg/x86_64/inject-target.c |  27 ++++
 8 files changed, 418 insertions(+), 16 deletions(-)
 create mode 100644 tests/tcg/plugins/inject.c
 create mode 100644 tests/tcg/x86_64/inject-target.c

-- 
2.46.1