Messages in this thread | | | Date | Wed, 22 Apr 2015 12:40:47 +0200 | From | Borislav Petkov <> | Subject | Re: [PATCH 01/16] x86, fpu: wrap get_xsave_addr() to make it safer |
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On Tue, Mar 31, 2015 at 05:46:24PM -0700, Dave Hansen wrote: > +/* > + * This wraps up the common operations that need to occur when retrieving > + * data from an xsave struct. It first ensures that the task was actually > + * using the FPU and retrieves the data in to a buffer. It then calculates > + * the offset of the requested field in the buffer. > + * > + * This function is safe to call whether the FPU is in use or not. > + * > + * Inputs: > + * @tsk: the task from which we are fetching xsave state > + * @xsave_field: state which is defined in xsave.h (e.g. XSTATE_FP, > + * XSTATE_SSE, etc...) > + * Output: > + * address of the state in the xsave area. > + */ > +void *tsk_get_xsave_field(struct task_struct *tsk, int xsave_field) > +{ > + union thread_xstate *xstate; > + > + if (!used_math()) > + return NULL;
Shouldn't this be
if (!tsk_used_math(tsk))
?
Because used_math() is looking at current, maybe even in preemption-enabled paths - I'm eyeing task_get_bounds_dir() - and that current might get changed from under us and it might happen that current != tsk. Yes, no?
> + /* > + * unlazy_fpu() is poorly named and will actually > + * save the xstate off in to the memory buffer. > + */ > + unlazy_fpu(tsk); > + xstate = tsk->thread.fpu.state; > + > + return get_xsave_addr(&xstate->xsave, xsave_field);
And I understand this as "give me the xsave address of @tsk".
Right?
Thanks.
-- Regards/Gruss, Boris.
ECO tip #101: Trim your mails when you reply. --
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