Messages in this thread | | | Subject | Re: [PATCH v2 1/3] arm64: compat: Split the sigreturn trampolines and kuser helpers (C sources) | From | Mark Salyzyn <> | Date | Wed, 6 Sep 2017 09:04:03 -0700 |
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On 08/16/2017 03:26 PM, Mark Salyzyn wrote: > From: Kevin Brodsky <kevin.brodsky@arm.com> > > AArch32 processes are currently installed a special [vectors] page that > contains the sigreturn trampolines and the kuser helpers, at the fixed > address mandated by the kuser helpers ABI. > > Having both functionalities in the same page has become problematic, > because: > > * It makes it impossible to disable the kuser helpers (the sigreturn > trampolines cannot be removed), which is possible on arm. > > * A future 32-bit vDSO would provide the sigreturn trampolines itself, > making those in [vectors] redundant. > > This patch addresses the problem by moving the sigreturn trampolines to > a separate [sigpage] page, mirroring [sigpage] on arm. > > Even though [vectors] has always been a misnomer on arm64/compat, as > there is no AArch32 vector there (and now only the kuser helpers), > its name has been left unchanged, for compatibility with arm (there > are reports of software relying on [vectors] being there as the last > mapping in /proc/maps). > > mm->context.vdso used to point to the [vectors] page, which is > unnecessary (as its address is fixed). It now points to the [sigpage] > page (whose address is randomized like a vDSO). > > Signed-off-by: Kevin Brodsky <kevin.brodsky@arm.com> > Signed-off-by: Mark Salyzyn <salyzyn@android.com> > > v2: > - reduce churniness (and defer later to vDSO patches) > - vctors_page and compat_vdso_spec as array of 2 > - free sigpage if vectors allocation failed > --- > arch/arm64/include/asm/processor.h | 4 +- > arch/arm64/include/asm/signal32.h | 2 - > arch/arm64/kernel/signal32.c | 5 +-- > arch/arm64/kernel/vdso.c | 82 ++++++++++++++++++++++++++------------ > 4 files changed, 60 insertions(+), 33 deletions(-) . . .
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