Messages in this thread | | | Date | Wed, 3 Apr 2019 18:30:57 +0200 (CEST) | From | Thomas Gleixner <> | Subject | Re: [patch 00/14] x86/exceptions: Add guard patches to IST stacks |
| |
On Sun, 31 Mar 2019, Andy Lutomirski wrote: > On Sun, Mar 31, 2019 at 3:10 PM Thomas Gleixner <tglx@linutronix.de> wrote: > > While looking for something different I stumbled over the comment in struct > > cpu_entry_area: > > > > * Exception stacks used for IST entries. > > * > > * In the future, this should have a separate slot for each stack > > * with guard pages between them. > > > > As usual with such comments they are added in good faith and then > > forgotten. Looking what it takes to fix that let me stumble over some other > > leftovers like orig_ist[], now unused macros, useless defines and a bunch > > of assumptions about the exception stacks being a big lump. Aside of that I > > found a too broad check of the exception stack in the x86/64 stack overflow > > detector. > > > > The following series cleans that up and gradually prepares for guard pages > > between the IST stacks. > > Thanks! I'll review this over the next couple days. > > Meanwhile, if you're inspired, I have a WIP series to do the same > thing to the IRQ stacks here: > > https://git.kernel.org/pub/scm/linux/kernel/git/luto/linux.git/log/?h=x86/guard_pages > > Want to take a look or pick it up if you want to keep working on this?
I grabbed the lot and addressed the todo's there. Not completely done though, but it builds and boots :)
With all stacks having guard pages now, the stack_overflow_check() in irq_64.c is kind of pointless. When the kernel overflows any of the stacks independent of what we do with DB (we at least split it into 2 different valid stacks) then it hits a guard page and dies. Mission accomplished....
Thanks,
tglx
| |