Copyright (c) 2021 Peter A. Dinda Please see LICENSE file. This is a tool for floating point trap and emulate processing on x64. This is a work in progress

To Configure:

make menuconfig

To build:

make

To test:

make test

To build kernel support:

cd kernel
./kmod_build.sh

To insert kernel support:

cd kernel
./kmod_setup.sh

To run FPVM against a binary, you must first source the environment file to update your path:

source ./ENV

Then, you can use the fpvm tool to run your program:

fpvm run ./a.out

This will, most likely, take quite a while on the first run. This is due to the need to patch non-virtualizable parts of the binary. Subsequent runs of the same (hash-identical) binary will be much faster, as the results are stored in ~/.cache/fpvm/.

If you wish to run the patched binary directly, you can get the exact hash identifier using the following command:

# Ask FPVM to patch lu
$ fpvm patch nas/lu
--- snip ---
/~.cache/fpvm/b63c5a2f481baaf3bed306a32edb1d6df8b43a24-patch-lu/lu.magic
# ^ output of patching (potentially already cached)

This will patch the binary, then print the cache location of the resultant binary. You can then run that binary directly using:

fpvm run --nopatch ~/.cache/fpvm/b63c5a2f481baaf3bed306a32edb1d6df8b43a24-patch-lu/lu.magic

NOTE: It's important that you always run FPVM through the above tool. Using FPVM.so directly will likely result in incorrect output due to wrapped functions and whatnot.

The following environment variables configure FPVM:

FPVM_AGGRESSIVE=y|n
    Aggressive interposition (you almost always want this)

FPVM_KERNEL=y|n
    Use kernel support if it is available (FPVM kernel module)

FPVM_DISABLE_PTHREADS=y|n
    Turn off pthread support (do not attempt to interpose on pthreads)
    You will want to set this if there is a link failure involving pthreads
    
FPVM_EXCEPT_LIST=inv;den;div;over;under;prec
    Exceptions that will invoke FPVM
    You almost certainly do not want to set this variable so that
    it can configure given the defaults

FPVM_FORCE_ROUNDING=pos|neg|zer|nea;daz;ftz
    Force rounding mode and subnormal handling on the hardware
    You almost certainly do not want to set this variable

To compile SSE only:

gcc ..... -mno-avx -mno-avx2 -mno-avx512f -mno-avx512pf -mno-avx512er -mno-avx512cd

To force libc to use SSE only:

export GLIBC_TUNABLES=glibc.cpu.hwcaps=-AVX2_Usable,-AVX_Usable,-AVX512_Usable

If you want to add your own alternative math implementation, foo, edit Kconfig to add your alternative math to the choice option, calling it ALT_MATH_FOO in this example. Then add your implementation to src/alt/foo.cpp. Wrap all your code except for #include <fpvm/config.h> in #if CONFIG_ALT_MATH_FOO, so the compiler doesn't compile your implementation unless you want it to.