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Jan Beulich
8a184632a1
This is to accompany sanitize_input(). Just like for initial state we want to have state between two emulated insns sane, at least as far as assumptions in the main emulator go. Do minimal checking after segment register, CR, and MSR writes, and roll back to the old value in case of failure (raising #GP(0) at the same time). In the particular case observed, a CR0 write clearing CR0.PE was followed by a VEX-encoded insn, which the decoder accepts based on guest address size, restricting things just outside of the 64-bit case (real and virtual modes don't allow VEX-encoded insns). Subsequently _get_fpu() would then assert that CR0.PE must be set (and EFLAGS.VM clear) when trying to invoke YMM, ZMM, or OPMASK state. Signed-off-by: Jan Beulich <jbeulich@suse.com> Reviewed-by: George Dunlap <george.dunlap@citrix.com>
# OVERVIEW This directory provides fuzzing targets to be run inside Google oss-fuzz infrastructure. See also https://github.com/google/oss-fuzz. # HOW IT WORKS We need to provide the source code and the rune to produce objects or archives (artefacts) from source code. These items ideally should live inside xen.git so that they can be kept up to date. The artefacts contain all the code we wish to fuzz and a function called LLVMFuzzerTestOneInput. LLVMFuzzerTestOneInput is the entry point to the code we wish to fuzz. Note that we don't produce executable programs because we don't have libFuzzEngine locally. libFuzzEngine is maintained by oss-fuzz. We also provide build script to oss-fuzz. The build script will inherit the correct compiler settings and be run in a pre-setup environment, which has libFuzzEngine installed. The build script is responsible for calling the correct Xen build rune to produce the artefacts, then link them against libFuzzEngine to produce executables, which will run in oss-fuzz infrastructure. Please refer to official oss-fuzz documents for the most up-to-date descriptions for all moving parts. # HOW TO IMPROVE THE FUZZING TARGETS Feel free to modify each fuzzing targets at will. Make sure they build by invoking make as you would build tools. To actually test the new code, you would need to run the target in standalone mode, please refer to oss-fuzz documents on how to do that. It is highly recommended that you run the new target for a while to weed out error in plumbing code to avoid false positives.