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74193ef0ec
__copy_from_user_inatomic() isn't NMI safe in that it can trigger the page fault handler which is another trap and its return path invokes IRET which will also close the NMI context. Therefore use a GUP based approach to copy the stack frames over. We tried an alternative solution as well: we used a forward ported version of Mathieu Desnoyers's "NMI safe INT3 and Page Fault" patch that modifies the exception return path to use an open-coded IRET with explicit stack unrolling and TF checking. This didnt work as it interacted with faulting user-space instructions, causing them not to restart properly, which corrupts user-space registers. Solving that would probably involve disassembling those instructions and backtracing the RIP. But even without that, the code was deemed rather complex to the already non-trivial x86 entry assembly code, so instead we went for this GUP based method that does a software-walk of the pagetables. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Nick Piggin <npiggin@suse.de> Cc: Pekka Enberg <penberg@cs.helsinki.fi> Cc: Vegard Nossum <vegard.nossum@gmail.com> Cc: Jeremy Fitzhardinge <jeremy@goop.org> Cc: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Paul Mackerras <paulus@samba.org> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu> |
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| crypto | ||
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| include/asm | ||
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| lguest | ||
| lib | ||
| math-emu | ||
| mm | ||
| oprofile | ||
| pci | ||
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| xen | ||
| Kbuild | ||
| Kconfig | ||
| Kconfig.cpu | ||
| Kconfig.debug | ||
| Makefile | ||
| Makefile_32.cpu | ||