When an FPU instruction with a memory destination fails during the
memory write, it should not affect FPU register state. Due to the way
we emulate FPU (and SIMD) instructions, we can only guarantee this by
- backing out changes to the FPU register state in such a case or
- doing a descriptor read and/or page walk up front, perhaps with the
stubs accessing the actual memory location then.
The latter would require a significant change in how the emulator does
its guest memory accessing, so for now the former variant is being
chosen.
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Paul Durrant <paul.durrant@citrix.com> [hvm/emulate.c]
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
AFL has an alternative llvm-base instrumentation mode, which has much lower
overhead than the traditional afl-gcc.
One extra ability is to chose exactly where the master process gets
initialised to, before being forked for testing. This point is chosen after
the call to LLVMFuzzerInitialize(), so the stack isn't being remapped
executable for every test.
Another extra ability is to feed multiple inputs into a single test process,
to reduce the number of fork() calls required overall. Two caveats are that if
stdin is used for data, it must be unbuffered, and if input is passed via a
command line parameter, the underlying file must be opened and closed on each
iteration.
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Wei Liu <wei.liu2@citrix.com>
libfuzz can perform one-time initialisation by calling LLVMFuzzerInitialize().
Move emul_test_init() into this, to avoid repeating it on every
LLVMFuzzerTestOneInput() call.
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Wei Liu <wei.liu2@citrix.com>
This is rather faster for afl-fuzz to arrange than using an explicit file
parameter. Also update the README to recommend using a tmpfs for findings_dir
which reduces disk load and is more performant.
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Wei Liu <wei.liu2@citrix.com>
Several `ln -sf` can race with each other and cause error like:
14:43:56 00:07:06 O: ln: cannot remove 'asm': No such file or directory
Provide dedicated targets for soft-linking directories.
Reported-by: Andrew Cooper <andrew.cooper3@citrix.com>
Signed-off-by: Wei Liu <wei.liu2@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
The "reg" variable in fuzz_read_msr stores the real MSR index, not an
index within the fuzzer.
The rest of that function already handles things correctly. We just need
to remove the bogus check.
Spotted by Coverity.
Signed-off-by: Wei Liu <wei.liu2@citrix.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
... so that users can know how big the initial input should be.
Signed-off-by: Wei Liu <wei.liu2@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Change the names used in code according to numeric values. Remove the
now unused macros in x86_emualte.c and fix indentation. This in turns
requires including msr-index.h and removing duplicates in userspace
x86_emulate.c in userspace harness program.
No functional change.
Signed-off-by: Wei Liu <wei.liu2@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Basically this patch does 's/EFLG_/X86_EFLAGS_/g' and with indentation
fixed up. And remove the duplicates in x86_emualte.c. This in turn
requires userspace test harness to include x86-defns.h. Also remove a
few duplicates in userspace harness program.
No functional change.
Signed-off-by: Wei Liu <wei.liu2@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Now the function can return nonzero value. Use that value as exit code
for the stub program. AFL might be able to use such information to
optimise fuzzing process.
Signed-off-by: Wei Liu <wei.liu2@citrix.com>
This is a basic program to call into the unified fuzzing function.
Hook it up into build system so that we can always build test it.
Signed-off-by: Wei Liu <wei.liu2@citrix.com>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>
Invocation of `make' in top-level directory would end up invoking the
install target.
Adjust fuzzing target makefiles a bit so that they are always build in
that situation.
Signed-off-by: Wei Liu <wei.liu2@citrix.com>
This will make all fuzzing targets get build every time tools directory
is built. This serves as basic regression test.
Signed-off-by: Wei Liu <wei.liu2@citrix.com>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>
Instruction emulator fuzzing code is from code previous written by
Andrew and George. Adapt it to llvm fuzzer and hook up the build system.
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Signed-off-by: George Dunlap <george.dunlap@citrix.com>
Signed-off-by: Wei Liu <wei.liu2@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Source code and Makefile to fuzz libelf in Google's oss-fuzz
infrastructure.
Introduce FUZZ_NO_LIBXC in libelf-private.h. That macro will be set when
compiling libelf fuzzer target because libxc is not required in libelf
fuzzing.
Signed-off-by: Wei Liu <wei.liu2@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Jan Beulich
Andrew Cooper
Wei Liu