linux-kernel - [PATCH V10 04/44] x86/fpu: Refactor arch_set_user_pkey

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Date:   Tue, 19 Apr 2022 10:06:09 -0700
From:   ira.weiny@...el.com
To:     Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Dan Williams <dan.j.williams@...el.com>
Cc:     Ira Weiny <ira.weiny@...el.com>, Fenghua Yu <fenghua.yu@...el.com>,
        Rick Edgecombe <rick.p.edgecombe@...el.com>,
        "Shankar, Ravi V" <ravi.v.shankar@...el.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH V10 04/44] x86/fpu: Refactor arch_set_user_pkey_access()

From: Ira Weiny <ira.weiny@...el.com>

Both PKU and PKS update their register values in the same way.  They can
therefore share the update code.

Define a helper, pkey_update_pkval(), which will be used to support both
Protection Key User (PKU) and the new Protection Key for Supervisor
(PKS) in subsequent patches.

pkey_update_pkval() contributed by Thomas

Acked-by: Dave Hansen <dave.hansen@...ux.intel.com>
Co-developed-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Ira Weiny <ira.weiny@...el.com>

---
Update for V8:
	From Rick Edgecombe
		Change pkey type to u8
	Replace the code Peter provided in update_pkey_reg() for
	Thomas' pkey_update_pkval()
		-- https://lore.kernel.org/lkml/20200717085442.GX10769@hirez.programming.kicks-ass.net/
---
 arch/x86/include/asm/pkeys.h |  2 ++
 arch/x86/kernel/fpu/xstate.c | 22 ++++------------------
 arch/x86/mm/pkeys.c          | 16 ++++++++++++++++
 3 files changed, 22 insertions(+), 18 deletions(-)

diff --git a/arch/x86/include/asm/pkeys.h b/arch/x86/include/asm/pkeys.h
index 1d5f14aff5f6..26616cbe19e2 100644
--- a/arch/x86/include/asm/pkeys.h
+++ b/arch/x86/include/asm/pkeys.h
@@ -131,4 +131,6 @@ static inline int vma_pkey(struct vm_area_struct *vma)
 	return (vma->vm_flags & vma_pkey_mask) >> VM_PKEY_SHIFT;
 }
 
+u32 pkey_update_pkval(u32 pkval, u8 pkey, u32 accessbits);
+
 #endif /*_ASM_X86_PKEYS_H */
diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index e525bfee7e07..ea9207b12863 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -984,8 +984,7 @@ void *get_xsave_addr(struct xregs_state *xsave, int xfeature_nr)
 int arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
 			      unsigned long init_val)
 {
-	u32 old_pkru, new_pkru_bits = 0;
-	int pkey_shift;
+	u32 pkru;
 
 	/*
 	 * This check implies XSAVE support.  OSPKE only gets
@@ -1002,22 +1001,9 @@ int arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
 	if (WARN_ON_ONCE(pkey >= arch_max_pkey()))
 		return -EINVAL;
 
-	/* Set the bits needed in PKRU:  */
-	if (init_val & PKEY_DISABLE_ACCESS)
-		new_pkru_bits |= PKR_AD_BIT;
-	if (init_val & PKEY_DISABLE_WRITE)
-		new_pkru_bits |= PKR_WD_BIT;
-
-	/* Shift the bits in to the correct place in PKRU for pkey: */
-	pkey_shift = pkey * PKR_BITS_PER_PKEY;
-	new_pkru_bits <<= pkey_shift;
-
-	/* Get old PKRU and mask off any old bits in place: */
-	old_pkru = read_pkru();
-	old_pkru &= ~((PKR_AD_BIT|PKR_WD_BIT) << pkey_shift);
-
-	/* Write old part along with new part: */
-	write_pkru(old_pkru | new_pkru_bits);
+	pkru = read_pkru();
+	pkru = pkey_update_pkval(pkru, pkey, init_val);
+	write_pkru(pkru);
 
 	return 0;
 }
diff --git a/arch/x86/mm/pkeys.c b/arch/x86/mm/pkeys.c
index e1527b4619e1..7c90b2188c5f 100644
--- a/arch/x86/mm/pkeys.c
+++ b/arch/x86/mm/pkeys.c
@@ -193,3 +193,19 @@ static __init int setup_init_pkru(char *opt)
 	return 1;
 }
 __setup("init_pkru=", setup_init_pkru);
+
+/*
+ * Kernel users use the same flags as user space:
+ *     PKEY_DISABLE_ACCESS
+ *     PKEY_DISABLE_WRITE
+ */
+u32 pkey_update_pkval(u32 pkval, u8 pkey, u32 accessbits)
+{
+	int shift = pkey * PKR_BITS_PER_PKEY;
+
+	if (WARN_ON_ONCE(accessbits & ~PKEY_ACCESS_MASK))
+		accessbits &= PKEY_ACCESS_MASK;
+
+	pkval &= ~(PKEY_ACCESS_MASK << shift);
+	return pkval | accessbits << shift;
+}
-- 
2.35.1