Messages in this thread | | | Date | Sun, 21 Oct 2012 21:40:58 +0200 | From | Oleg Nesterov <> | Subject | Re: [PATCH 3/9] uprobes: allow ignoring of probe hits |
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On 10/21, Rabin Vincent wrote: > > On Wed, Oct 17, 2012 at 07:35:10PM +0200, Oleg Nesterov wrote: > > > > And, to clarify, I am not arguing. Just curious. > > > > So, is this like cmov on x86? And this patch allows to not report if > > the condition is not true? Or there are other issues on arm? > > Yes, I guess this is like CMOV on x86. In the ARM instruction set most > instructions can be conditionally executed. > > In order to set the probe on a conditional instruction, we use an > undefined instruction with the same condition as the instruction we > replace. However, it is implementation defined whether an undefined > instruction with a failing condition code will trigger an undefined > instruction exception or just be executed as a NOP. So for those > processor implementations where we do get the undefined instruction > exception even for a failing condition code, we have to ignore it in > order to provide consistent behaviour.
OK, I see, thanks for your explanation.
Oleg.
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