On Wed, Feb 26, 2025 at 9:12 AM Liam R. Howlett <liam.howl...@oracle.com> wrote: > > * Lorenzo Stoakes <lorenzo.stoa...@oracle.com> [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 > > > <lorenzo.stoa...@oracle.com> wrote: > > > > > > > > On Mon, Feb 24, 2025 at 10:52:43PM +0000, jef...@chromium.org wrote: > > > > > From: Jeff Xu <jef...@chromium.org> > > > > > > > > > > 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. > Is this code in the kernel or userspace?
If PPC doesn't want to create vdso for all its userspace apps, we could instead "don't create" vdso during the execve call. > 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?). > Any past thread/communication about this that I can read ? Thanks -Jeff > Thanks, > Liam
