[RFCv2 05/10] x86/mm: Provide untagged_addr() helper

Kirill A. Shutemov
2022-05-11T02:30:20Z

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@linux.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