Messages in this thread | | | Date | Thu, 20 Dec 2012 10:23:39 -0800 | Subject | Re: [PATCH 6/6] Add 32 bit VDSO support for 32 and 64 bit kernels | From | "H.J. Lu" <> |
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On Thu, Dec 20, 2012 at 10:21 AM, H. Peter Anvin <hpa@zytor.com> wrote: > On 12/20/2012 09:53 AM, Stefani Seibold wrote: >> >> In a 32 bit kernel a VDSO can mapped on an fix address VDSO_HIGH_BASE >> (kernel parameter vdso32=2 or CONFIG_COMPAT_VDSO), which is 0xffffe000. >> There is no available page BEFORE nor AFTER the page, so it is not >> possible to have VVAR or HPET as a part of that list!!!! >> > > [Cc: Roland, Linus, H.J.] > > The pages before it are safe to use, because they are kernel internal > and hence not ABI (and in fact depend on the kernel configuration > parameters.) So pushing down the start of the fixmap region is not a > problem. This means that to retain this compatibility the existing > entry points need to be at the end, which is more painful than we'd > like, but nevertheless there. > > Do we know what actually used these fixed address, if anything, ever? >
Glibc gets VDSO address from AT_* vector. I think glibc is safe.
-- H.J.
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