Messages in this thread | | | From | "Yu, Fenghua" <> | Subject | RE: [PATCH Bugfix v2 2/4] x86/xsaves: Define and use user_xstate_size for xstate size in signal context | Date | Wed, 22 Apr 2015 19:05:21 +0000 |
| |
> From: Hansen, Dave > Sent: Wednesday, April 22, 2015 11:45 AM > To: Yu, Fenghua; H. Peter Anvin; Ingo Molnar; Thomas Gleixner; Mallick, Asit > K; Williamson, Glenn P > Cc: linux-kernel; x86 > Subject: Re: [PATCH Bugfix v2 2/4] x86/xsaves: Define and use > user_xstate_size for xstate size in signal context > > On 04/21/2015 09:51 PM, Fenghua Yu wrote: > > + /* > > + * Copy rest of xstates in compact format to user. > > + */ > > + for (i = 2; i < xstate_features; i++) { > > + if (test_bit(i, (unsigned long *)&pcntxt_mask)) { > > + int user_offset, kernel_offset; > > + int size; > > + > > + user_offset = xstate_offsets[i]; > > + kernel_offset = xstate_comp_offsets[i]; > > + size = xstate_sizes[i]; > > + > > + if (__copy_to_user(buf_fx + user_offset, > > + xsave + kernel_offset, size)) > > + return -1; > > + } > > + } > > Is this checking the right bitmap? > > The 'xsaves' documentation says: "If RFBM[i] = 1, XSTATE_BV[i] is set to the > value of XINUSE[i]". Where "XINUSE denotes the state-component bitmap > corresponding to the init optimization". > > So shouldn't this be checking xsave->xsave_hdr.xstate_bv instead of > pcntxt_mask? The will be equal unless the "init optimization" is in play.
Xsave->xsave_hdr.xstate_bv is equal to pcntxt_mask (see setup_init_fpu_buf()).
And here XINUSE and RFBM are irrelevant because they are used in init or modified optimization during xsave*/xrstore*. We only copy out the xstates from kernel to user and XINUSE and RFBM are not in scope here.
So I would think pcntxt_mask is good to be used here.
Thanks.
-Fenghua
| |