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Date: Wed, 02 Sep 2015 16:31:31 -0700
From: Dave Hansen <dave@...1.net>
To: dave@...1.net
Cc: dave.hansen@...ux.intel.com, mingo@...hat.com, x86@...nel.org,
bp@...en8.de, fenghua.yu@...el.com, tim.c.chen@...ux.intel.com,
linux-kernel@...r.kernel.org
Subject: [PATCH 15/15] x86, fpu: check CPU-provided sizes against struct declarations
From: Dave Hansen <dave.hansen@...ux.intel.com>
Changes from v2:
* remove XSTATE_RESERVED check, since it is gone now
--
From: Dave Hansen <dave.hansen@...ux.intel.com>
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: Dave Hansen <dave.hansen@...ux.intel.com>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: x86@...nel.org
Cc: Borislav Petkov <bp@...en8.de>
Cc: Fenghua Yu <fenghua.yu@...el.com>
Cc: Tim Chen <tim.c.chen@...ux.intel.com>
Cc: linux-kernel@...r.kernel.org
---
b/arch/x86/kernel/fpu/xstate.c | 45 +++++++++++++++++++++++++++++++++++++++++
1 file changed, 45 insertions(+)
diff -puN arch/x86/kernel/fpu/xstate.c~x86-fpu-check-against-struct-declarations arch/x86/kernel/fpu/xstate.c
--- a/arch/x86/kernel/fpu/xstate.c~x86-fpu-check-against-struct-declarations 2015-09-02 16:26:46.232419598 -0700
+++ b/arch/x86/kernel/fpu/xstate.c 2015-09-02 16:26:46.236419780 -0700
@@ -432,6 +432,49 @@ static void __xstate_dump_leaves(void)
} \
} 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
* how large the XSAVE buffer needs to be. We are recalculating
@@ -445,6 +488,8 @@ static void do_extra_xstate_size_checks(
for (i = FIRST_EXTENDED_XFEATURE; i < XFEATURE_MAX; i++) {
if (!xfeature_enabled(i))
continue;
+
+ check_xstate_against_struct(i);
/*
* Supervisor state components can be managed only by
* XSAVES, which is compacted-format only.
_
--
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