From: will.deacon@arm.com (Will Deacon)
To: linux-arm-kernel@lists.infradead.org
Subject: [BUG] arm64/hw_breakpoint: trigger breakpoint exception infinitely
Date: Tue, 26 Apr 2016 13:22:13 +0100 [thread overview]
Message-ID: <20160426122212.GN27312@arm.com> (raw)
In-Reply-To: <571F2577.2080203@huawei.com>
On Tue, Apr 26, 2016 at 04:23:19PM +0800, Li Bin wrote:
> This bug can be reproduced by compiling the hw_breakpoint sample
> module that is in the kernel tree, when loading it with parameter
> ksym=nfsdstats, and running nfsstat:
>
> $ insmod data_breakpoint.ko ksym=nfsdstats
> $ nfsstat
>
> It will trigger breakpoint exception infinitely:
>
> nfsdstats value is changed
> ...
> Call trace:
> ...
> Dump stack from sample_hbp_handler
> nfsdstats value is changed
> ...
> Call trace:
> ...
> Dump stack from sample_hbp_handler
> ......
> ......
>
> This is because that the overflow_handler is set to the callback
> in the module, and in watchpoint_handler, it will not disable the
> breakpoint (and set single step that reenable it), so when exception
> return, it will trigger the breakpoint exception again immediately...
As I explained before, GDB/ptrace *relies* on this behaviour. If you
register an breakpoint overflow handler on arm64, then you need to handle
the step.
Will
next prev parent reply other threads:[~2016-04-26 12:22 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-26 8:23 [BUG] arm64/hw_breakpoint: trigger breakpoint exception infinitely Li Bin
2016-04-26 12:22 ` Will Deacon [this message]
2016-04-27 2:35 ` Li Bin
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