linux-kernel - [patch V2 16/52] x86/fpu: Use copy_uabi_xstate_to_membuf() in fpregs

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Date:   Mon, 14 Jun 2021 17:44:24 +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 V2 16/52] x86/fpu: Use copy_uabi_xstate_to_membuf() in fpregs_get()

Use the new functionality of copy_uabi_xstate_to_membuf() to retrieve the
FX state when XSAVE* is in use. This avoids to overwrite the FPU state
buffer with fpstate_sanitize_xstate() which is error prone and duplicated
code.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
V2: New patch
---
 arch/x86/kernel/fpu/regset.c |   30 ++++++++++++++++++++----------
 1 file changed, 20 insertions(+), 10 deletions(-)

--- a/arch/x86/kernel/fpu/regset.c
+++ b/arch/x86/kernel/fpu/regset.c
@@ -211,10 +211,10 @@ static inline u32 twd_fxsr_to_i387(struc
  * FXSR floating point environment conversions.
  */
 
-void
-convert_from_fxsr(struct user_i387_ia32_struct *env, struct task_struct *tsk)
+static void __convert_from_fxsr(struct user_i387_ia32_struct *env,
+				struct task_struct *tsk,
+				struct fxregs_state *fxsave)
 {
-	struct fxregs_state *fxsave = &tsk->thread.fpu.state.fxsave;
 	struct _fpreg *to = (struct _fpreg *) &env->st_space[0];
 	struct _fpxreg *from = (struct _fpxreg *) &fxsave->st_space[0];
 	int i;
@@ -248,6 +248,12 @@ convert_from_fxsr(struct user_i387_ia32_
 		memcpy(&to[i], &from[i], sizeof(to[0]));
 }
 
+void
+convert_from_fxsr(struct user_i387_ia32_struct *env, struct task_struct *tsk)
+{
+	__convert_from_fxsr(env, tsk, &tsk->thread.fpu.state.fxsave);
+}
+
 void convert_to_fxsr(struct fxregs_state *fxsave,
 		     const struct user_i387_ia32_struct *env)
 
@@ -280,25 +286,29 @@ int fpregs_get(struct task_struct *targe
 {
 	struct fpu *fpu = &target->thread.fpu;
 	struct user_i387_ia32_struct env;
+	struct fxregs_state fxsave, *fx;
 
 	fpu__prepare_read(fpu);
 
-	if (!boot_cpu_has(X86_FEATURE_FPU))
+	if (!static_cpu_has(X86_FEATURE_FPU))
 		return fpregs_soft_get(target, regset, to);
 
-	if (!boot_cpu_has(X86_FEATURE_FXSR)) {
+	if (!static_cpu_has(X86_FEATURE_FXSR)) {
 		return membuf_write(&to, &fpu->state.fsave,
 				    sizeof(struct fregs_state));
 	}
 
-	fpstate_sanitize_xstate(fpu);
+	if (use_xsave()) {
+		struct membuf mb = { .p = &fxsave, .left = sizeof(fxsave) };
 
-	if (to.left == sizeof(env)) {
-		convert_from_fxsr(to.p, target);
-		return 0;
+		/* Handle init state optimized xstate correctly */
+		copy_uabi_xstate_to_membuf(mb, &fpu->state.xsave, XSTATE_COPY_FP);
+		fx = &fxsave;
+	} else {
+		fx = &fpu->state.fxsave;
 	}
 
-	convert_from_fxsr(&env, target);
+	__convert_from_fxsr(&env, target, fx);
 	return membuf_write(&to, &env, sizeof(env));
 }