linux-hardening - [RFC PATCH 10/12] mm: add default definition of p4d

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Date:   Wed, 26 Jan 2022 18:30:09 +0100
From:   Ard Biesheuvel <ardb@...nel.org>
To:     linux-arm-kernel@...ts.infradead.org
Cc:     kvmarm@...ts.cs.columbia.edu, linux-hardening@...r.kernel.org,
        Ard Biesheuvel <ardb@...nel.org>,
        Will Deacon <will@...nel.org>, Marc Zyngier <maz@...nel.org>,
        Fuad Tabba <tabba@...gle.com>,
        Quentin Perret <qperret@...gle.com>,
        Mark Rutland <mark.rutland@....com>,
        James Morse <james.morse@....com>,
        Catalin Marinas <catalin.marinas@....com>
Subject: [RFC PATCH 10/12] mm: add default definition of p4d_index()

Implement a default version of p4d_index() similar to how pud/pmd_index
are defined.

Signed-off-by: Ard Biesheuvel <ardb@...nel.org>
---
 include/linux/pgtable.h | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
index bc8713a76e03..e8aacf6ea207 100644
--- a/include/linux/pgtable.h
+++ b/include/linux/pgtable.h
@@ -79,6 +79,14 @@ static inline unsigned long pud_index(unsigned long address)
 #define pud_index pud_index
 #endif
 
+#ifndef p4d_index
+static inline unsigned long p4d_index(unsigned long address)
+{
+	return (address >> P4D_SHIFT) & (PTRS_PER_P4D - 1);
+}
+#define p4d_index p4d_index
+#endif
+
 #ifndef pgd_index
 /* Must be a compile-time constant, so implement it as a macro */
 #define pgd_index(a)  (((a) >> PGDIR_SHIFT) & (PTRS_PER_PGD - 1))
-- 
2.30.2