Em Fri, Nov 20, 2015 at 01:18:55PM -0800, Brian Robbins escreveu: > > > On Fri, 20 Nov 2015, Peter Zijlstra wrote: > > > On Thu, Nov 19, 2015 at 11:45:45PM +0000, Brian Robbins wrote: > > > > > Thank you for the feedback. The file format is similar to PE, but is > > > not identical. So, we would be implementing something very scoped, > > > which doesn't feel right to me. > > > > *groan* you just had to go and invent yet another executable format, > > right? :-) > Nah, it just has some extra stuff in it that makes this less desirable - > it's technically PE, but anyway. > > > > > I am interested in the new JIT support, however my understanding from > > > the information that I've read is that it requires kernel support in > > > 4.x, though I can't seem to find where I read that. I want to make > > > sure that this works on older kernels (3.x) as well. > > > > As I think Stephane explained, this is only required if you need to > > match up kernel and userspace timestamps, which is important for dynamic > > code generation, less so for static code in a weird format. > > Yes, agreed. > > > > > So what the new JIT stuff does is online write 'fake' ELF files with > > symbol sections and (optionally?) dwarf debug info for line numbers. > > > > Since you don't dynamically generate code, you can offline generate > > these ELF files and redirect the symbol parser bits to that (we already > > look for debug ELF files in various locations), or... > > > > > The reason I went with this approach is because it is simple for > > > runtimes to implement and has no requirement that perf understand the > > > file format. I am open to feedback if there is a preferred solution > > > that would still work for older kernels as well. > > > > Since, someone somewhere needs to go parse this funny new file format > > anyhow to either generate /tmp files or fake ELF files or whatever, you > > might as well put that decoder in perf? > > > > Or just ship these fake ELF files in /usr/lib/debug/ or whatever the > > 'right' location for the distro at hand is. > > This seems like a reasonable approach. > > Stephane, are your changes available for public consumption? Last I > recall, the patches were still in review.
Its in my queue, AFAIK there were not objections expressed, I'll try to get this reviewed/merged soon. - Arnaldo -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
