linux-kernel - [RFCv2 05/10] x86/mm: Provide untagged

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Date:   Wed, 11 May 2022 05:27:46 +0300
From:   "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:     Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>
Cc:     x86@...nel.org, Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        "H . J . Lu" <hjl.tools@...il.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Rick Edgecombe <rick.p.edgecombe@...el.com>,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: [RFCv2 05/10] x86/mm: Provide untagged_addr() helper

The helper used by the core-mm to strip tag bits and get the address to
the canonical shape. In only handles userspace addresses.

For LAM, the address gets sanitized according to the thread features.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
---
 arch/x86/include/asm/page_32.h |  3 +++
 arch/x86/include/asm/page_64.h | 20 ++++++++++++++++++++
 2 files changed, 23 insertions(+)

diff --git a/arch/x86/include/asm/page_32.h b/arch/x86/include/asm/page_32.h
index df42f8aa99e4..2d35059b90c1 100644
--- a/arch/x86/include/asm/page_32.h
+++ b/arch/x86/include/asm/page_32.h
@@ -15,6 +15,9 @@ extern unsigned long __phys_addr(unsigned long);
 #define __phys_addr_symbol(x)	__phys_addr(x)
 #define __phys_reloc_hide(x)	RELOC_HIDE((x), 0)
 
+#define untagged_addr(addr)	(addr)
+#define untagged_ptr(ptr)	(ptr)
+
 #ifdef CONFIG_FLATMEM
 #define pfn_valid(pfn)		((pfn) < max_mapnr)
 #endif /* CONFIG_FLATMEM */
diff --git a/arch/x86/include/asm/page_64.h b/arch/x86/include/asm/page_64.h
index e9c86299b835..3a40c958b24a 100644
--- a/arch/x86/include/asm/page_64.h
+++ b/arch/x86/include/asm/page_64.h
@@ -7,6 +7,7 @@
 #ifndef __ASSEMBLY__
 #include <asm/cpufeatures.h>
 #include <asm/alternative.h>
+#include <uapi/asm/prctl.h>
 
 /* duplicated to the one in bootmem.h */
 extern unsigned long max_pfn;
@@ -90,6 +91,25 @@ static __always_inline unsigned long task_size_max(void)
 }
 #endif	/* CONFIG_X86_5LEVEL */
 
+#define __untagged_addr(addr, n)	\
+	((__force __typeof__(addr))sign_extend64((__force u64)(addr), n))
+
+#define untagged_addr(addr)	({					\
+	u64 __addr = (__force u64)(addr);				\
+	if (__addr >> 63 == 0) {					\
+		if (current->thread.features & X86_THREAD_LAM_U57)	\
+			__addr &= __untagged_addr(__addr, 56);		\
+		else if (current->thread.features & X86_THREAD_LAM_U48)	\
+			__addr &= __untagged_addr(__addr, 47);		\
+	}								\
+	(__force __typeof__(addr))__addr;				\
+})
+
+#define untagged_ptr(ptr)	({					\
+	u64 __ptrval = (__force u64)(ptr);				\
+	__ptrval = untagged_addr(__ptrval);				\
+	(__force __typeof__(*(ptr)) *)__ptrval;				\
+})
 #endif	/* !__ASSEMBLY__ */
 
 #ifdef CONFIG_X86_VSYSCALL_EMULATION
-- 
2.35.1