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From 64e54461ab6e8524a8de4e63b7d1a3e4481b5cf3 Mon Sep 17 00:00:00 2001
From: "Chang S. Bae" <chang.seok.bae@intel.com>
Date: Tue, 15 Apr 2025 19:16:57 -0700
Subject: x86/fpu: Refactor xfeature bitmask update code for sigframe XSAVE
From: Chang S. Bae <chang.seok.bae@intel.com>
commit 64e54461ab6e8524a8de4e63b7d1a3e4481b5cf3 upstream.
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@intel.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Link: https://lore.kernel.org/r/20250416021720.12305-8-chang.seok.bae@intel.com
Cc: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/x86/kernel/fpu/signal.c | 11 +----------
arch/x86/kernel/fpu/xstate.h | 13 +++++++++++++
2 files changed, 14 insertions(+), 10 deletions(-)
--- a/arch/x86/kernel/fpu/signal.c
+++ b/arch/x86/kernel/fpu/signal.c
@@ -119,7 +119,6 @@ static inline bool save_xstate_epilog(vo
{
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. */
@@ -133,12 +132,6 @@ static inline bool save_xstate_epilog(vo
(__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
* enable us capturing any changes(during sigreturn) to
@@ -149,9 +142,7 @@ static inline bool save_xstate_epilog(vo
* 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;
}
--- a/arch/x86/kernel/fpu/xstate.h
+++ b/arch/x86/kernel/fpu/xstate.h
@@ -69,6 +69,19 @@ static inline u64 xfeatures_mask_indepen
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.
*/
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