From: Dave Hansen <dave@sr71.net>
To: dave@sr71.net
Cc: dave.hansen@linux.intel.com, mingo@redhat.com, x86@kernel.org,
bp@alien8.de, fenghua.yu@intel.com, tim.c.chen@linux.intel.com,
linux-kernel@vger.kernel.org
Subject: [PATCH 14/15] x86, fpu: check to ensure increasing-offset xstate offsets
Date: Wed, 02 Sep 2015 16:31:30 -0700 [thread overview]
Message-ID: <20150902233130.0843AB15@viggo.jf.intel.com> (raw)
In-Reply-To: <20150902233123.3A7E5FB0@viggo.jf.intel.com>
From: Dave Hansen <dave.hansen@linux.intel.com>
The xstate CPUID leaves enumerate where each state component is
inside the XSAVE buffer, along with the size of the entire
buffer. Our new XSAVE sanity-checking code extrapolates an
expected _total_ buffer size by looking at the last component
that it encounters.
That method requires that the highest-numbered component also
be the one with the highest offset. This is a pretty safe
assumption, but let's add some code to ensure it stays true.
To make this check work correctly, we also need to ensure we
only consider the offsets from enabled features because the
offset register (ebx) will return 0 on unsupported features.
This also means that we will preserve the -1's that we
initialized xstate_offsets/sizes[] with. That will help
find bugs.
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: x86@kernel.org
Cc: Borislav Petkov <bp@alien8.de>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: linux-kernel@vger.kernel.org
---
b/arch/x86/kernel/fpu/xstate.c | 35 ++++++++++++++++++++++++-----------
1 file changed, 24 insertions(+), 11 deletions(-)
diff -puN arch/x86/kernel/fpu/xstate.c~x86-fpu-increasing-offset-assumption arch/x86/kernel/fpu/xstate.c
--- a/arch/x86/kernel/fpu/xstate.c~x86-fpu-increasing-offset-assumption 2015-09-02 16:23:52.556530877 -0700
+++ b/arch/x86/kernel/fpu/xstate.c 2015-09-02 16:23:52.560531059 -0700
@@ -185,18 +185,41 @@ void fpu__init_cpu_xstate(void)
}
/*
+ * Note that in the future we will likely need a pair of
+ * functions here: one for user xstates and the other for
+ * system xstates. For now, they are the same.
+ */
+static int xfeature_enabled(enum xfeature xfeature)
+{
+ return !!(xfeatures_mask & (1UL << xfeature));
+}
+
+/*
* Record the offsets and sizes of various xstates contained
* in the XSAVE state memory layout.
*/
static void __init setup_xstate_features(void)
{
u32 eax, ebx, ecx, edx, i;
+ /* start at the beginnning of the "extended state" */
+ unsigned int last_good_offset = offsetof(struct xregs_state,
+ extended_state_area);
for (i = FIRST_EXTENDED_XFEATURE; i < XFEATURE_MAX; i++) {
- cpuid_count(XSTATE_CPUID, i, &eax, &ebx, &ecx, &edx);
+ if (!xfeature_enabled(i))
+ continue;
+ cpuid_count(XSTATE_CPUID, i, &eax, &ebx, &ecx, &edx);
xstate_offsets[i] = ebx;
xstate_sizes[i] = eax;
+ /*
+ * In our xstate size checks, we assume that the
+ * highest-numbered xstate feature has the
+ * highest offset in the buffer. Ensure it does.
+ */
+ WARN_ONCE(last_good_offset > xstate_offsets[i],
+ "x86/fpu: misordered xstate at %d\n", last_good_offset);
+ last_good_offset = xstate_offsets[i];
printk(KERN_INFO "x86/fpu: xstate_offset[%d]: %4d, xstate_sizes[%d]: %4d\n", i, ebx, i, eax);
}
@@ -226,16 +249,6 @@ static void __init print_xstate_features
}
/*
- * Note that in the future we will likely need a pair of
- * functions here: one for user xstates and the other for
- * system xstates. For now, they are the same.
- */
-static int xfeature_enabled(enum xfeature xfeature)
-{
- return !!(xfeatures_mask & (1UL << xfeature));
-}
-
-/*
* This function sets up offsets and sizes of all extended states in
* xsave area. This supports both standard format and compacted format
* of the xsave aread.
_
next prev parent reply other threads:[~2015-09-02 23:32 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-09-02 23:31 [PATCH 00/15] [v4] x86, fpu: XSAVE cleanups and sanity checks Dave Hansen
2015-09-02 23:31 ` [PATCH 01/15] x86, fpu: print xfeature buffer size in decimal Dave Hansen
2015-09-14 12:19 ` [tip:x86/fpu] x86/fpu: Print " tip-bot for Dave Hansen
2015-09-02 23:31 ` [PATCH 02/15] x86, fpu: move XSAVE-disabling code to a helper Dave Hansen
2015-09-14 12:19 ` [tip:x86/fpu] x86/fpu: Move " tip-bot for Dave Hansen
2015-09-02 23:31 ` [PATCH 03/15] x86, fpu: remove XSTATE_RESERVE Dave Hansen
2015-09-14 12:20 ` [tip:x86/fpu] x86/fpu: Remove XSTATE_RESERVE tip-bot for Dave Hansen
2015-09-02 23:31 ` [PATCH 04/15] x86, fpu: kill LWP support Dave Hansen
2015-09-14 12:20 ` [tip:x86/fpu] x86/fpu: Remove partial LWP support definitions tip-bot for Dave Hansen
2015-09-02 23:31 ` [PATCH 05/15] x86, fpu: XSAVE macro renames Dave Hansen
2015-09-14 12:21 ` [tip:x86/fpu] x86/fpu: Rename XSAVE macros tip-bot for Dave Hansen
2015-09-23 10:49 ` Borislav Petkov
2015-09-24 7:24 ` [tip:x86/fpu] x86/fpu: Fixup uninitialized feature_name warning tip-bot for Borislav Petkov
2015-09-02 23:31 ` [PATCH 06/15] x86, fpu: rename XFEATURES_NR_MAX Dave Hansen
2015-09-14 12:21 ` [tip:x86/fpu] x86/fpu: Rename XFEATURES_NR_MAX tip-bot for Dave Hansen
2015-09-02 23:31 ` [PATCH 08/15] x86, fpu: remove xfeature_nr Dave Hansen
2015-09-14 12:22 ` [tip:x86/fpu] x86/fpu: Remove 'xfeature_nr' tip-bot for Dave Hansen
2015-09-02 23:31 ` [PATCH 07/15] x86, fpu: rework XSTATE_* macros to remove magic '2' Dave Hansen
2015-09-14 12:21 ` [tip:x86/fpu] x86/fpu: Rework " tip-bot for Dave Hansen
2015-09-02 23:31 ` [PATCH 12/15] x86, fpu: add C structures for AVX-512 state components Dave Hansen
2015-09-14 12:23 ` [tip:x86/fpu] x86/fpu: Add " tip-bot for Dave Hansen
2015-09-02 23:31 ` [PATCH 09/15] x86, fpu: add helper xfeature_enabled() instead of test_bit() Dave Hansen
2015-09-14 12:22 ` [tip:x86/fpu] x86/fpu: Add xfeature_enabled() helper " tip-bot for Dave Hansen
2015-09-02 23:31 ` [PATCH 10/15] x86, fpu: rework MPX 'xstate' types Dave Hansen
2015-09-14 12:22 ` [tip:x86/fpu] x86/fpu/mpx: Rework " tip-bot for Dave Hansen
2015-09-02 23:31 ` [PATCH 11/15] x86, fpu: rework YMM definition Dave Hansen
2015-09-14 12:23 ` [tip:x86/fpu] x86/fpu: Rework " tip-bot for Dave Hansen
2015-09-02 23:31 ` Dave Hansen [this message]
2015-09-14 12:24 ` [tip:x86/fpu] x86/fpu: Check to ensure increasing-offset xstate offsets tip-bot for Dave Hansen
2015-09-02 23:31 ` [PATCH 13/15] x86, fpu: correct and check XSAVE xstate size calculations Dave Hansen
2015-09-14 12:23 ` [tip:x86/fpu] x86/fpu: Correct " tip-bot for Dave Hansen
2015-09-02 23:31 ` [PATCH 15/15] x86, fpu: check CPU-provided sizes against struct declarations Dave Hansen
2015-09-14 12:24 ` [tip:x86/fpu] x86/fpu: Check " tip-bot for Dave Hansen
2015-09-14 10:07 ` [PATCH 00/15] [v4] x86, fpu: XSAVE cleanups and sanity checks Ingo Molnar
-- strict thread matches above, loose matches on Subject: below --
2015-08-31 22:20 [PATCH 00/15] [v3] " Dave Hansen
2015-08-31 22:20 ` [PATCH 14/15] x86, fpu: check to ensure increasing-offset xstate offsets Dave Hansen
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