Commit ef78f2a4 authored by Dave Hansen's avatar Dave Hansen Committed by Ingo Molnar
Browse files

x86/fpu: Check CPU-provided sizes against struct declarations 



We now have C structures defined for each of the XSAVE state
components that we support.  This patch adds checks during our
verification pass to ensure that the CPU-provided data
enumerated in CPUID leaves matches our C structures.

If not, we warn and dump all the XSAVE CPUID leaves.

Note: this *actually* found an inconsistency with the MPX
'bndcsr' state.  The hardware pads it out differently from
our C structures.  This patch caught it and warned.

Signed-off-by: default avatarDave Hansen <dave.hansen@linux.intel.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: dave@sr71.net
Cc: linux-kernel@vger.kernel.org
Link: http://lkml.kernel.org/r/20150902233131.A8DB36DA@viggo.jf.intel.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent e6e888f9

arch/x86/kernel/fpu/xstate.c

+45 −0
Original line number Original line Diff line number Diff line
@@ -432,6 +432,49 @@ static void __xstate_dump_leaves(void) 
	}									\

	}									\

} while (0)

} while (0)





#define XCHECK_SZ(sz, nr, nr_macro, __struct) do {			\

	if ((nr == nr_macro) &&						\

	    WARN_ONCE(sz != sizeof(__struct),				\

		"%s: struct is %zu bytes, cpu state %d bytes\n",	\

		__stringify(nr_macro), sizeof(__struct), sz)) {		\

		__xstate_dump_leaves();					\

	}								\

} while (0)



/*

 * We have a C struct for each 'xstate'.  We need to ensure

 * that our software representation matches what the CPU

 * tells us about the state's size.

 */

static void check_xstate_against_struct(int nr)

{

	/*

	 * Ask the CPU for the size of the state.

	 */

	int sz = xfeature_size(nr);

	/*

	 * Match each CPU state with the corresponding software

	 * structure.

	 */

	XCHECK_SZ(sz, nr, XFEATURE_YMM,       struct ymmh_struct);

	XCHECK_SZ(sz, nr, XFEATURE_BNDREGS,   struct mpx_bndreg_state);

	XCHECK_SZ(sz, nr, XFEATURE_BNDCSR,    struct mpx_bndcsr_state);

	XCHECK_SZ(sz, nr, XFEATURE_OPMASK,    struct avx_512_opmask_state);

	XCHECK_SZ(sz, nr, XFEATURE_ZMM_Hi256, struct avx_512_zmm_uppers_state);

	XCHECK_SZ(sz, nr, XFEATURE_Hi16_ZMM,  struct avx_512_hi16_state);



	/*

	 * Make *SURE* to add any feature numbers in below if

	 * there are "holes" in the xsave state component

	 * numbers.

	 */

	if ((nr < XFEATURE_YMM) ||

	    (nr >= XFEATURE_MAX)) {

		WARN_ONCE(1, "no structure for xstate: %d\n", nr);

		XSTATE_WARN_ON(1);

	}

}



/*

/*

 * This essentially double-checks what the cpu told us about

 * This essentially double-checks what the cpu told us about

 * how large the XSAVE buffer needs to be.  We are recalculating

 * how large the XSAVE buffer needs to be.  We are recalculating
@@ -445,6 +488,8 @@ static void do_extra_xstate_size_checks(void) 
	for (i = FIRST_EXTENDED_XFEATURE; i < XFEATURE_MAX; i++) {

	for (i = FIRST_EXTENDED_XFEATURE; i < XFEATURE_MAX; i++) {

		if (!xfeature_enabled(i))

		if (!xfeature_enabled(i))

			continue;

			continue;



		check_xstate_against_struct(i);

		/*

		/*

		 * Supervisor state components can be managed only by

		 * Supervisor state components can be managed only by

		 * XSAVES, which is compacted-format only.

		 * XSAVES, which is compacted-format only.

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