[tip:x86/fpu] x86/fpu: Factor out memset(xstate, 0) in fpu_finit( ) paths

[tip-bot for Oleg Nesterov]

Commit-ID:  1d23c4518b1f3a03c278f23333149245c178d2a6
Gitweb:     http://git.kernel.org/tip/1d23c4518b1f3a03c278f23333149245c178d2a6
Author:     Oleg Nesterov <oleg@xxxxxxxxxx>
AuthorDate: Tue, 10 Mar 2015 07:06:25 +0100
Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Tue, 10 Mar 2015 07:14:31 +0100

x86/fpu: Factor out memset(xstate, 0) in fpu_finit() paths

fx_finit() has two users but only fpu_finit() needs to clear
xstate, alloc_bootmem_align() in setup_init_fpu_buf() returns
zero-filled memory.

And note that both memset()'s look confusing. Yes, offsetof() is
0 for ->fxsave or ->fsave, but it would be cleaner to turn
them into a single memset() which zeroes fpu->state.

Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Acked-by: Rik van Riel <riel@xxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Tavis Ormandy <taviso@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/1425967585-4725-2-git-send-email-bp@xxxxxxxxx
Link: http://lkml.kernel.org/r/20150302183257.GC23085@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 arch/x86/include/asm/fpu-internal.h | 1 -
 arch/x86/kernel/i387.c              | 3 ++-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/fpu-internal.h b/arch/x86/include/asm/fpu-internal.h
index 61609b9..5fa1be2 100644
--- a/arch/x86/include/asm/fpu-internal.h
+++ b/arch/x86/include/asm/fpu-internal.h
@@ -135,7 +135,6 @@ static __always_inline __pure bool use_fxsr(void)
 
 static inline void fx_finit(struct i387_fxsave_struct *fx)
 {
-	memset(fx, 0, xstate_size);
 	fx->cwd = 0x37f;
 	fx->mxcsr = MXCSR_DEFAULT;
 }
diff --git a/arch/x86/kernel/i387.c b/arch/x86/kernel/i387.c
index 03cc0ad..0f3de66 100644
--- a/arch/x86/kernel/i387.c
+++ b/arch/x86/kernel/i387.c
@@ -224,11 +224,12 @@ void fpu_finit(struct fpu *fpu)
 		return;
 	}
 
+	memset(fpu->state, 0, xstate_size);
+
 	if (cpu_has_fxsr) {
 		fx_finit(&fpu->state->fxsave);
 	} else {
 		struct i387_fsave_struct *fp = &fpu->state->fsave;
-		memset(fp, 0, xstate_size);
 		fp->cwd = 0xffff037fu;
 		fp->swd = 0xffff0000u;
 		fp->twd = 0xffffffffu;
--
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