[FFmpeg-devel] [PATCH 1/2] libavutil/libavfilter: add opencl wrapper to ffmpeg

[Michael Niedermayer]

On Mon, Mar 25, 2013 at 10:17:20AM +0800, Wei Gao wrote:
> 2013/3/25 Michael Niedermayer <michaelni at gmx.at>
> 
> > On Sun, Mar 24, 2013 at 08:00:46PM +0100, Michael Niedermayer wrote:
> > > On Sun, Mar 24, 2013 at 06:40:27PM +0100, Stefano Sabatini wrote:
> > > > On date Sunday 2013-03-24 19:55:00 +0800, Wei Gao encoded:
> > > > >
> > > >
> > > > > From ab91c74fa166f557eadb39ab399d7ba667b91340 Mon Sep 17 00:00:00
> > 2001
> > > > > From: highgod0401 <highgod0401 at gmail.com>
> > > > > Date: Sun, 24 Mar 2013 19:20:16 +0800
> > > > > Subject: [PATCH 1/2] add opencl wrapper to ffmpeg
> > > [...]
> > >
> > > > > +static int access_binaries(cl_device_id *device_ids, int
> > numdevices, const char *cl_file_name, FILE **fhandle,
> > > > > +                                size_t *binarysizes, char
> > **binaries, int write)
> > > > > +{
> > > > > +    FILE *fd = NULL;
> > > > > +    int status;
> > > > > +    char filename[1024] = {0};
> > > > > +    char cl_name[1024] = {0};
> > > > > +    char devicename[1024] = {0};
> > > > > +    int i;
> > > > > +    for (i = 0; i < numdevices; i++) {
> > > > > +        if (device_ids[i] != 0) {
> > > > > +            status = clGetDeviceInfo(device_ids[i],
> > > > > +                                     CL_DEVICE_NAME,
> > > > > +                                     sizeof(devicename),
> > > > > +                                     devicename,
> > > > > +                                     NULL);
> > > > > +            if (status == CL_SUCCESS) {
> > > > > +                av_strlcpy(cl_name,cl_file_name,sizeof(cl_name));
> > > > > +                snprintf(filename, sizeof(filename),"./%s-%s.bin",
> > cl_name, devicename);
> > >
> > > [...]
> > >
> > > > > +                    if (binarysizes[i] != 0) {
> > > > > +                        output = fopen(filename, "wb");
> > >
> > > [...]
> > >
> > > > > +                        }
> > > > > +                        fwrite(binaries[i], sizeof(char),
> > binarysizes[i], output);
> > >
> > > theres no gurantee that you have write permission in the current
> > > directory or in any directory.
> > > Also its not nice from a library to drop files in the current
> > > directory unrequested
> >
> > also, while i didnt read the whole file read/write code it appears
> > to me that files are read and executed from the current directory
> > this is not safe, someone could have placed a mallicious file there
> >
> The file is use to save compile informations of OpenCL kernels in ffmpeg.
> Because OpenCL kernels is compiled in the runtime, and the compile time
> will be longer if there are more OpenCL kernels.If ffmpeg compile kernel
> every time, it will cost a long time in compiling every time.So we record
> the compile information the first time. And ffmpeg will load the file and
> run kernel without compile. It can save much time.

This is not a compile cache vs. security argumentation.
security is a requirement.
If we can implement a secure compile cache that would be ideal.
But if its not secure then a insecure cache is not an alternative.

Also for such a cache you need a directory where to place the files
the current directory is not ok. The directory path needs to be
configureable at build time, if no path is configured the code should
not read or write any excutables.
The path also needs to support $HOME or something like that.
And accessing the cache needs to work correctly if, 2 or more ffmpeg
processes access the cache at the same time.
also the cache must work when newer code has become available, that
is a user might have updated his ffmpeg to one with newer opencl code.
or updated opencl itself

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

He who knows, does not speak. He who speaks, does not know. -- Lao Tsu
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 198 bytes
Desc: Digital signature
URL: <http://ffmpeg.org/pipermail/ffmpeg-devel/attachments/20130325/225b9bd5/attachment.asc>