* Lorenzo Stoakes <[email protected]> [250226 00:26]: > On Tue, Feb 25, 2025 at 02:26:50PM -0800, Jeff Xu wrote: > > On Mon, Feb 24, 2025 at 10:20 PM Lorenzo Stoakes > > <[email protected]> wrote: > > > > > > On Mon, Feb 24, 2025 at 10:52:43PM +0000, [email protected] wrote: > > > > From: Jeff Xu <[email protected]> > > > > > > > > Provide support for CONFIG_MSEAL_SYSTEM_MAPPINGS on arm64, covering > > > > the vdso, vvar, and compat-mode vectors and sigpage mappings. > > > > > > > > Production release testing passes on Android and Chrome OS. > > > > > > This is pretty limited (yes yes I know android is massive etc. but we must > > > account for all the weird and wonderful arm64 devices out there in > > > context of > > > upstream :) > > > > > > Have you looking through all arm64-code relating to vdso, vvar, > > > compat-mode > > > vectors, sigpage mapping and ensured nothing kernel-side relies upon > > > relocation? > > > Some arches actually seem to want to do this. Pretty sure PPC does... so > > > a bit > > > nervous of that. > > > > > Can you please point out where PPC munmap/mremap the vdso ? > > > > Previously, when you mentioned that, I thought you meant user space in > > PPC, I didn't realize that you meant that kernel code in PPC. I > > tried, but didn't find anything, hence asking. > > Jeff, please stick to replying to review. 'Have you looking through all > arm64-code'. > > I ended up doing this myself yesterday and found no issues, as with x86-64. > > I said I'm _pretty sure_ PPC does this. Liam mentioned something about > it. We can discuss it, and I can find specifics if + when you try to add > this to PPC. >
PPC allows the vma to be munmapped then detects and falls back to the slower method, iirc. They were against the removal of the fallback; other archs also have this infrastructure. Really, if we fixed the fallback to work for all platforms then it would probably also remove the possibility of a remap over the VDSO being a problem (if it is today, which still isn't clear?). Thanks, Liam
