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x86/fpu/xstate: Fix last_good_offset in setup_xstate_features() 

The function setup_xstate_features() uses CPUID to find each xfeature's
standard-format offset and size.  Since XSAVES always uses the compacted
format, supervisor xstates are *NEVER* in the standard-format and their
offsets are left as -1's.  However, they are still being tracked as
last_good_offset.

Fix it by tracking only user xstate offsets.

 [ bp: Use xfeature_is_supervisor() and save an indentation level. Drop
   now unused xfeature_is_user(). ]

Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://lkml.kernel.org/r/20200109211452.27369-2-yu-cheng.yu@intel.com
This commit is contained in:
Yu-cheng Yu 2020-01-09 13:14:50 -08:00 committed by Borislav Petkov
parent bb6d3fb354
commit c12e13dcd8
1 changed files with 15 additions and 16 deletions
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31
arch/x86/kernel/fpu/xstate.c
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@ -120,11 +120,6 @@ static bool xfeature_is_supervisor(int xfeature_nr)
return ecx & 1;
}
static bool xfeature_is_user(int xfeature_nr)
{
return !xfeature_is_supervisor(xfeature_nr);
}
/*
* When executing XSAVEOPT (or other optimized XSAVE instructions), if
* a processor implementation detects that an FPU state component is still
@ -265,21 +260,25 @@ static void __init setup_xstate_features(void)
cpuid_count(XSTATE_CPUID, i, &eax, &ebx, &ecx, &edx);
/*
* If an xfeature is supervisor state, the offset
* in EBX is invalid. We leave it to -1.
*/
if (xfeature_is_user(i))
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.
* If an xfeature is supervisor state, the offset in EBX is
* invalid, leave it to -1.
*/
if (xfeature_is_supervisor(i))
continue;
xstate_offsets[i] = ebx;
/*
* 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);
"x86/fpu: misordered xstate at %d\n", last_good_offset);
last_good_offset = xstate_offsets[i];
}
}