On 2019/07/07 7:27, Steven Rostedt wrote:
>
> We also have to deal with reading vmalloc'd data as that can fault too.
> The perf ring buffer IIUC is vmalloc, so if perf records in one of
> these locations, then the reading of the vmalloc area has a potential
> to fault corrupting the CR2 register as well. Or have we changed
> vmalloc to no longer fault?
>
> -- Steve
>
It seems that perf ring buffer does not normally use vmalloc.
It depends on CONFIG_PERF_USE_VMALLOC introduced by the following commit:
commit 906010b2134e14a2e377decbadd357b3d0ab9c6a
Author: Peter Zijlstra <a.p.zijls...@chello.nl>
Date: Mon Sep 21 16:08:49 2009 +0200
perf_event: Provide vmalloc() based mmap() backing
Some architectures such as Sparc, ARM and MIPS (basically
everything with flush_dcache_page()) need to deal with dcache
aliases by carefully placing pages in both kernel and user maps.
These architectures typically have to use vmalloc_user() for this.
However, on other architectures, vmalloc() is not needed and has
the downsides of being more restricted and slower than regular
allocations.
Signed-off-by: Peter Zijlstra <a.p.zijls...@chello.nl>
Acked-by: David Miller <da...@davemloft.net>
Cc: Andrew Morton <a...@linux-foundation.org>
Cc: Jens Axboe <jens.ax...@oracle.com>
Cc: Paul Mackerras <pau...@samba.org>
LKML-Reference: <1254830228.21044.272.camel@laptop>
Signed-off-by: Ingo Molnar <mi...@elte.hu>
