Messages in this thread Patch in this message | | | From | Yu-cheng Yu <> | Subject | [PATCH] x86/fpu/xstate: Fix xcomp_bv in XSAVES header | Date | Mon, 23 Jan 2017 14:54:44 -0800 |
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The compacted-format XSAVES area is determined at boot time and never changed after. The field xsave.header.xcomp_bv indicates which components are in the fixed XSAVES format.
In fpstate_init() we did not set xcomp_bv to reflect the XSAVES format since at the time there is no valid data.
However, after we do copy_init_fpstate_to_fpregs() in fpu__clear(), as in commit: b22cbe404a9cc3c7949e380fa1861e31934c8978, and when __fpu_restore_sig() does fpu__restore() for a COMPAT-mode app, a #GP occurs. This can be easily triggered by doing valgrind on a COMPAT-mode "Hello World," as reported by Joakim Tjernlund and others:
https://bugzilla.kernel.org/show_bug.cgi?id=190061
Fix it by setting xcomp_bv correctly.
Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com> Reported-by: Joakim Tjernlund <Joakim.Tjernlund@infinera.com> --- arch/x86/kernel/fpu/core.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c index c289e2f..e540dc1 100644 --- a/arch/x86/kernel/fpu/core.c +++ b/arch/x86/kernel/fpu/core.c @@ -9,6 +9,7 @@ #include <asm/fpu/regset.h> #include <asm/fpu/signal.h> #include <asm/fpu/types.h> +#include <asm/fpu/xstate.h> #include <asm/traps.h> #include <linux/hardirq.h> @@ -235,7 +236,8 @@ void fpstate_init(union fpregs_state *state) * it will #GP. Make sure it is replaced after the memset(). */ if (static_cpu_has(X86_FEATURE_XSAVES)) - state->xsave.header.xcomp_bv = XCOMP_BV_COMPACTED_FORMAT; + state->xsave.header.xcomp_bv = XCOMP_BV_COMPACTED_FORMAT | + xfeatures_mask; if (static_cpu_has(X86_FEATURE_FXSR)) fpstate_init_fxstate(&state->fxsave); -- 1.9.1
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