mirror of
https://github.com/google/sandboxed-api.git
synced 2024-03-22 13:11:30 +08:00
88 lines
3.7 KiB
Markdown
88 lines
3.7 KiB
Markdown
# Sandboxing PFFFT library
|
||
|
||
Build System: CMake
|
||
OS: Linux
|
||
|
||
### Check out the PFFFT library & CMake set up
|
||
```
|
||
git submodule update --init --recursive
|
||
|
||
mkdir -p build && cd build
|
||
cmake .. -G Ninja -DPFFFT_ROOT_DIR=$PWD
|
||
ninjas
|
||
```
|
||
### For testing:
|
||
`cd build`, then `./pffft_sandboxed`
|
||
|
||
### For debug:
|
||
display custom info with
|
||
`./pffft_sandboxed --logtostderr`
|
||
|
||
## ***About the project***
|
||
*PFFFT library is concerned with 1D Fast-Fourier Transformations finding a
|
||
compromise between accuracy and speed. It deals with real and complex
|
||
vectors, both cases being illustrated in the testing part (`test_pffft.c`
|
||
for initially and original version, `main_pffft_sandboxed.cc` for our
|
||
currently implemented sandboxed version).
|
||
The original files can be found at: https://bitbucket.org/jpommier/pffft/src.*
|
||
|
||
*The purpose of sandboxing is to limit the permissions and capabilities of
|
||
library’s methods, in order to secure the usage of them.
|
||
After obtaining the sandbox, the functions will be called through an
|
||
Sandbox API (being called `api` in the current test) and so, the
|
||
operations, system calls or namspaces access may be controlled.
|
||
From both `pffft.h` and `fftpack.h` headers, useful methods are added to
|
||
sapi library builded with CMake. There is also a need to link math library
|
||
as the transformations made require mathematical operators.
|
||
Regarding the testing of the methods, one main is doing this job by
|
||
iterating through a set of values, that represents the accuracy of
|
||
transformations and print the speed for each value and type of
|
||
transformation. More specifically, the input length is the target for
|
||
accuracy (named as `n`) and it stands for the number of data points from
|
||
the series that calculate the result of transformation. It is also
|
||
important to mention that the `complex` variable stands for a boolean value
|
||
that tells the type of transformation (0 for REAL and 1 for COMPLEX) and
|
||
it is taken into account while testing.
|
||
In the end, the performance of PFFFT library it is outlined by the output.
|
||
There are two output formats available, from which you can choose through
|
||
`--output_format=` command-line flag.
|
||
Without using this type of argument when running, the output format is set
|
||
by default.*
|
||
|
||
#### CMake observations resume:
|
||
* linking pffft and fftpack (which contains necessary functions for pffft)
|
||
* set math library
|
||
|
||
#### Sandboxed main observations resume:
|
||
* containing two testing parts (fft / pffft benchmarks)
|
||
* showing the performance of the transformations implies
|
||
testing them through various FFT dimenstions.
|
||
Variable n, the input length, will take specific values
|
||
meaning the number of points to which it is set the calculus
|
||
(more details of mathematical purpose of n - https://en.wikipedia.org/wiki/Cooley%E2%80%93Tukey_FFT_algorithm).
|
||
* output shows speed depending on the input length
|
||
* use `--output_format=0` or `--output_format=1` arguments to choose between output formats.
|
||
`0` is for a detailed output, while `1` is only displaying each transformation process speed.
|
||
|
||
### Bugs history
|
||
1. [Solved] pffft benchmark bug: "Sandbox not active"
|
||
|
||
n = 64, status OK, `pffft_transform` generates error
|
||
n > 64, status not OK
|
||
Problem on initialising `sapi::StatusOr<PFFFT_Setup *> s;` the memory that stays
|
||
for s is not the same with the address passed in `pffft_transform` function.
|
||
(`sapi::v::GenericPtr` - to be changed)
|
||
|
||
Temporary solution: change the generated files to accept
|
||
`uintptr_t` instead of `PFFFT_Setup`
|
||
|
||
Solution: using `sapi::v::RemotePtr` instead of `sapi::v::GenericPtr`
|
||
to access the memory of object `s`
|
||
|
||
2. [Unresolved] compiling bug: "No space left on device"
|
||
|
||
The building process creates some `embed` files that use lots of
|
||
memory, trying to write them on `/tmp`.
|
||
|
||
Temporary solution: clean /tmp directory by `sudo rm -rf /tmp/*`
|