Messages in this thread | | | Subject | Re: [PATCH 6/6] Add 32 bit VDSO support for 32 and 64 bit kernels | From | Stefani Seibold <> | Date | Tue, 18 Dec 2012 21:32:39 +0100 |
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Am Dienstag, den 18.12.2012, 10:44 -0800 schrieb H. Peter Anvin: > On 12/18/2012 08:52 AM, Stefani Seibold wrote: > > > > Pardon, i never disregarded nor i have agreed that this is going to be a > > part of the VDSO. I currently have also no idea how to do this and i see > > no need at the moment to do this revamp. The 64 bit VDSO lives since > > more than 6 years with this kind of implementation. > > > > It was part of this discussion thread, about how to best manage the > address space. Fixed addresses are a major problem, and introducing new > ones are extremely undesirable. >
There is no introduce of new fix address. There are still there for x86_64. If this will currently not a major problem on this architecture than it will not for x86_32 too.
> Hence I wrote: > > > IMO it seems this is making it way more complicated than it is. Just > > make sure you have a section in the vdso where you can map in a data > > page with the symbols in the right offsets. Extra points for doing > > magic so that it is at the beginning or end, but I think that might > > be harder than necessary. > > Basically, make the vvar and hpet pages part of the vdso page list. > Optionally they can be mapped without the MAYWRITE option -- in fact, we > could easily split the vdso into an executable area which gets MAYWRITE > to be able to set breakpoints and a data area which doesn't -- but that > is a minor tweak IMO. >
I see the benefits, but it will not work under all circumstance. The VDSO compat mode for x86_32 requires a fix address and there is no room behind this. So since this must preserved, i see no real gain for this.
> > You asked me to do the VDSO 32 bit stuff for the IA32_EMULATION, before > > it is ready for inclusion into the kernel. Thats exactly what i did. I > > spend the whole weekend of my spare time to do this implementation. Now > > we have them all. > > > > The patch works perfectly, all issues are solved: > > > > - Calling conventions > > - ABI transformations > > - System call gateway for X86 32 bit > > - Mapping of the FIXMAP and HPET into the lower 32 bit address space for > > IA32_EMULATION > > - Support for 32 bit programs in 32 kernel and 64 bit kernel > > - One VDSO source for all > > > > If you prefer an other solutions, its okay. There are many ways to code > > things. But for now i think it is a good step ahead. That is what i > > currently can provide. > > This is good. We have some time anyway to get this ready for the 3.9 > merge window. >
What does this mean? Do you accept my patch or drop it? I see no real technical issue to drop it. It makes things better not worse. Maybe there is a better solution, but this is the next step.
I advocate to apply this patch, because i spend a lot time to write it and it is a good base to continue the work.
- Stefani
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