On Thu, 27 Feb 2014, H. Peter Anvin wrote:
> On 02/27/2014 02:31 PM, Steven Rostedt wrote:
> >
> > Yeah, something is getting mesed up.
> >
>
> What it *looks* like to me is that we try to nest the cr2 save/restore,
> which doesn't nest because it is a percpu variable.
>
> ... except in the x86-64 case, we *ALSO* save/restore cr2 inside
> entry_64.S, which makes the stuff in do_nmi completely redundant and
> there for no good reason.
>
> I would actually suggest we do the equivalent on i386 as well.
>
> Vince, could you try this patch as an experiment?
OK with your patch applied it does not segfault.
The trace looks like you'd expect too:
perf_fuzzer-2910 [000] 255.355331: page_fault_kernel:
address=irq_stack_union ip=copy_user_handle_tail error_code=0x0
perf_fuzzer-2910 [000] 255.355331: function:
__do_page_fault
perf_fuzzer-2910 [000] 255.355331: function:
bad_area_nosemaphore
perf_fuzzer-2910 [000] 255.355331: function:
__bad_area_nosemaphore
perf_fuzzer-2910 [000] 255.355332: function:
no_context
perf_fuzzer-2910 [000] 255.355332: function:
fixup_exception
perf_fuzzer-2910 [000] 255.355332: function:
search_exception_tables
perf_fuzzer-2910 [000] 255.355332: function:
search_extable
perf_fuzzer-2910 [000] 255.355333: function:
perf_output_begin
perf_fuzzer-2910 [000] 255.355333: bprint:
perf_output_begin: VMW: event type 2 config 2a st: 2c3e7
perf_fuzzer-2910 [000] 255.355333: bprint:
perf_output_begin: VMW: before event->parent (nil)
perf_fuzzer-2910 [000] 255.355334: bprint:
perf_output_begin: VMW: before rcu_dereference (nil)
perf_fuzzer-2910 [000] 255.355334: function: __do_page_fault
perf_fuzzer-2910 [000] 255.355334: function:
down_read_trylock
perf_fuzzer-2910 [000] 255.355334: function:
_cond_resched
perf_fuzzer-2910 [000] 255.355335: function: find_vma
perf_fuzzer-2910 [000] 255.355335: function:
handle_mm_fault
perf_fuzzer-2910 [000] 255.355335: function:
__do_fault
perf_fuzzer-2910 [000] 255.355335: bputs:
perf_mmap_fault: VMW: perf_mmap_fault
perf_fuzzer-2910 [000] 255.355336: bprint:
perf_mmap_fault: VMW: perf_mmap_fault 0xffff8800cba6a980
perf_fuzzer-2910 [000] 255.355336: function:
perf_mmap_to_page
perf_fuzzer-2910 [000] 255.355336: function: _cond_resched
perf_fuzzer-2910 [000] 255.355336: function:
unlock_page
perf_fuzzer-2910 [000] 255.355336: function:
page_waitqueue
perf_fuzzer-2910 [000] 255.355337: function:
__wake_up_bit
perf_fuzzer-2910 [000] 255.355337: bputs:
perf_mmap_fault: VMW: perf_mmap_fault
perf_fuzzer-2910 [000] 255.355337: function: _cond_resched
perf_fuzzer-2910 [000] 255.355337: function:
_raw_spin_lock
perf_fuzzer-2910 [000] 255.355337: function:
page_add_file_rmap
perf_fuzzer-2910 [000] 255.355338: function:
__inc_zone_page_state
perf_fuzzer-2910 [000] 255.355338: function:
__inc_zone_state
perf_fuzzer-2910 [000] 255.355338: function:
set_page_dirty
perf_fuzzer-2910 [000] 255.355338: function:
page_mapping
perf_fuzzer-2910 [000] 255.355338: function:
anon_set_page_dirty
perf_fuzzer-2910 [000] 255.355339: function:
unlock_page
Vince
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