Messages in this thread | | | Subject | Re: [PATCH v4 07/10] x86/xsaves: Fix PTRACE frames for XSAVES | From | Dave Hansen <> | Date | Fri, 29 Apr 2016 15:36:12 -0700 |
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On 04/29/2016 03:30 PM, Yu-cheng Yu wrote: > 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.
I think the xfeature_enabled(i) is probably redundant. Does it serve any actual purpose?
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