linux-kernel - [patch V3 60/66] x86/fpu/signal: Remove the legacy alignment check

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Message-Id: <20210618143451.217774510@linutronix.de>
Date:   Fri, 18 Jun 2021 16:19:23 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Tony Luck <tony.luck@...el.com>,
        Yu-cheng Yu <yu-cheng.yu@...el.com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Borislav Petkov <bp@...e.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Kan Liang <kan.liang@...ux.intel.com>
Subject: [patch V3 60/66] x86/fpu/signal: Remove the legacy alignment check

Checking for the XSTATE buffer being 64 byte aligned and if not deciding
just to restore the FXSR state is daft.

If user space provides an unaligned math frame and has the extended state
magic set in the FX software reserved bytes, then it really can keep the
pieces.

If the frame is unaligned and the FX software magic is not set, then
fx_only is already set and the restore will use fxrstor.

Remove it.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
 arch/x86/kernel/fpu/signal.c |    3 ---
 1 file changed, 3 deletions(-)

--- a/arch/x86/kernel/fpu/signal.c
+++ b/arch/x86/kernel/fpu/signal.c
@@ -306,9 +306,6 @@ static int __fpu_restore_sig(void __user
 		}
 	}
 
-	if ((unsigned long)buf_fx % 64)
-		fx_only = 1;
-
 	if (!ia32_fxstate) {
 		/*
 		 * Attempt to restore the FPU registers directly from user