Messages in this thread | | | Date | Fri, 29 Apr 2016 15:30:50 -0700 | From | Yu-cheng Yu <> | Subject | Re: [PATCH v4 07/10] x86/xsaves: Fix PTRACE frames for XSAVES |
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On Fri, Apr 29, 2016 at 01:25:34PM -0700, Dave Hansen wrote: > On 03/04/2016 10:12 AM, Yu-cheng Yu wrote: > > + for (i = 0; i < XFEATURE_MAX; i++) { > > + /* > > + * Copy only in-use xstates. > > + */ > > + if (((header.xfeatures >> i) & 1) && xfeature_enabled(i)) { > > + void *src = get_xsave_addr_no_check(xsave, i); > > How could a bit in header.xfeatures get set if it is not set in > xfeature_enabled() aka xfeatures_mask aka XCR0?
Do you mean, we should test xfeature_enabled(i) first, like,
if (xfeature_enabled(i) && ((header.xfeatures >> i) & 1)) ?
The result will be the same, like you said, if XCR0[i] is not set, hader.xfeatures[i] cannot be set. But if XCR0[i] is set, header.xfeatures[i] can be cleared.
> > If a caller tries to pass a non-enabled xfeature in, we appear to just > silently drop it and return success. Is that really what we want to do > or do we want to error out?
Let it fail. I will chage it.
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