Messages in this thread | | | From | Joerg Roedel <> | Subject | [PATCH 0/3] PTI for x86-32 Fixes and Updates | Date | Fri, 20 Jul 2018 18:22:21 +0200 |
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Hi,
here are 3 patches which update the PTI-x86-32 patches recently merged into the tip-tree. The patches are ordered by importance:
Patch 1: Very important, it fixes a vmalloc-fault in NMI context when PTI is enabled. This is pretty unlikely to hit when starting perf on an idle machine, which is why I didn't find it earlier in my testing. I always started 'perf top' first :/ But when I start 'perf top' last when the kernel-compile already runs, it hits almost immediatly.
Patch 2: Fix the 'from-kernel-check' in SWITCH_TO_KERNEL_STACK to also take VM86 into account. This is not strictly necessary because the slow-path also works for VM86 mode but it is not how the code was intended to work. And it breaks when Patch 3 is applied on-top.
Patch 3: Implement the reduced copying in the paranoid entry/exit path as suggested by Andy Lutomirski while reviewing version 7 of the original patches.
I have the x86/tip branch with these patches on-top running my test for 6h now, with no issues so far. So for now it looks like there are no scheduling points or irq-enabled sections reached from the paranoid entry/exit paths and we always return to the entry-stack we came from.
I keep the test running over the weekend at least.
Please review.
[ If Patch 1 looks good to the maintainers I suggest applying it soon, before too many linux-next testers run into this issue. It is actually the reason why I send out the patches _now_ and didn't wait until next week when the other two patches got more testing from my side. ]
Thanks,
Joerg
Joerg Roedel (3): perf/core: Make sure the ring-buffer is mapped in all page-tables x86/entry/32: Check for VM86 mode in slow-path check x86/entry/32: Copy only ptregs on paranoid entry/exit path
arch/x86/entry/entry_32.S | 82 ++++++++++++++++++++++++++------------------- kernel/events/ring_buffer.c | 10 ++++++ 2 files changed, 58 insertions(+), 34 deletions(-)
-- 2.7.4
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