linux-kernel - [PATCH 1/2] x86/fpu: Refactor xfeature bitmask update code for sigframe XSAVE

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Message-ID: <20250214010607.7067-2-chang.seok.bae@intel.com>
Date: Thu, 13 Feb 2025 17:06:06 -0800
From: "Chang S. Bae" <chang.seok.bae@...el.com>
To: linux-kernel@...r.kernel.org
Cc: x86@...nel.org,
	tglx@...utronix.de,
	mingo@...hat.com,
	bp@...en8.de,
	dave.hansen@...ux.intel.com,
	aruna.ramakrishna@...cle.com,
	TonyWWang-oc@...oxin.com,
	chang.seok.bae@...el.com
Subject: [PATCH 1/2] x86/fpu: Refactor xfeature bitmask update code for sigframe XSAVE

Currently, saving register states in the signal frame, the legacy feature
bits are always set in xregs_state->header->xfeatures. This code sequence
can be generalized for reuse in similar cases.

Refactor the logic to ensure a consistent approach across similar usages.

Signed-off-by: Chang S. Bae <chang.seok.bae@...el.com>
---
 arch/x86/kernel/fpu/signal.c | 11 +----------
 arch/x86/kernel/fpu/xstate.h | 12 ++++++++++++
 2 files changed, 13 insertions(+), 10 deletions(-)

diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c
index 8f62e0666dea..8abe60919e2f 100644
--- a/arch/x86/kernel/fpu/signal.c
+++ b/arch/x86/kernel/fpu/signal.c
@@ -119,7 +119,6 @@ static inline bool save_xstate_epilog(void __user *buf, int ia32_frame,
 {
 	struct xregs_state __user *x = buf;
 	struct _fpx_sw_bytes sw_bytes = {};
-	u32 xfeatures;
 	int err;
 
 	/* Setup the bytes not touched by the [f]xsave and reserved for SW. */
@@ -132,12 +131,6 @@ static inline bool save_xstate_epilog(void __user *buf, int ia32_frame,
 	err |= __put_user(FP_XSTATE_MAGIC2,
 			  (__u32 __user *)(buf + fpstate->user_size));
 
-	/*
-	 * Read the xfeatures which we copied (directly from the cpu or
-	 * from the state in task struct) to the user buffers.
-	 */
-	err |= __get_user(xfeatures, (__u32 __user *)&x->header.xfeatures);
-
 	/*
 	 * For legacy compatible, we always set FP/SSE bits in the bit
 	 * vector while saving the state to the user context. This will
@@ -149,9 +142,7 @@ static inline bool save_xstate_epilog(void __user *buf, int ia32_frame,
 	 * header as well as change any contents in the memory layout.
 	 * xrestore as part of sigreturn will capture all the changes.
 	 */
-	xfeatures |= XFEATURE_MASK_FPSSE;
-
-	err |= __put_user(xfeatures, (__u32 __user *)&x->header.xfeatures);
+	err |= set_xfeature_in_sigframe(x, XFEATURE_MASK_FPSSE);
 
 	return !err;
 }
diff --git a/arch/x86/kernel/fpu/xstate.h b/arch/x86/kernel/fpu/xstate.h
index aa16f1a1bbcf..27e20236bbbb 100644
--- a/arch/x86/kernel/fpu/xstate.h
+++ b/arch/x86/kernel/fpu/xstate.h
@@ -69,6 +69,18 @@ static inline u64 xfeatures_mask_independent(void)
 	return fpu_kernel_cfg.independent_features;
 }
 
+static inline int set_xfeature_in_sigframe(struct xregs_state __user *xbuf, u64 mask)
+{
+	u64 xfeatures;
+	int err;
+
+	/* Read the xfeatures value already saved in the user buffer */
+	err  = __get_user(xfeatures, &xbuf->header.xfeatures);
+	xfeatures |= mask;
+	err |= __put_user(xfeatures, &xbuf->header.xfeatures);
+	return err;
+}
+
 /*
  * Update the value of PKRU register that was already pushed onto the signal frame.
  */
-- 
2.45.2