linux-kernel - [PATCH] riscv: Define TASK_SIZE_MAX for __access

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Message-ID: <20240313180010.295747-1-samuel.holland@sifive.com>
Date: Wed, 13 Mar 2024 10:59:43 -0700
From: Samuel Holland <samuel.holland@...ive.com>
To: Palmer Dabbelt <palmer@...belt.com>,
	linux-riscv@...ts.infradead.org
Cc: Samuel Holland <samuel.holland@...ive.com>,
	Albert Ou <aou@...s.berkeley.edu>,
	Alexandre Ghiti <alexghiti@...osinc.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Charlie Jenkins <charlie@...osinc.com>,
	Guo Ren <guoren@...nel.org>,
	Jisheng Zhang <jszhang@...nel.org>,
	Kemeng Shi <shikemeng@...weicloud.com>,
	"Matthew Wilcox (Oracle)" <willy@...radead.org>,
	"Mike Rapoport (IBM)" <rppt@...nel.org>,
	Paul Walmsley <paul.walmsley@...ive.com>,
	Xiao Wang <xiao.w.wang@...el.com>,
	Yangyu Chen <cyy@...self.name>,
	linux-kernel@...r.kernel.org
Subject: [PATCH] riscv: Define TASK_SIZE_MAX for __access_ok()

TASK_SIZE_MAX should be set to the largest userspace address under any
runtime configuration. This optimizes the check in __access_ok(), which
no longer needs to compute the current value of TASK_SIZE. It is still
safe because addresses between TASK_SIZE and TASK_SIZE_MAX are invalid
at the hardware level.

This removes about half of the references to pgtable_l[45]_enabled.

Signed-off-by: Samuel Holland <samuel.holland@...ive.com>
---

 arch/riscv/include/asm/pgtable-64.h | 1 +
 arch/riscv/include/asm/pgtable.h    | 1 +
 2 files changed, 2 insertions(+)

diff --git a/arch/riscv/include/asm/pgtable-64.h b/arch/riscv/include/asm/pgtable-64.h
index b99bd66107a6..a677ef3c0fe2 100644
--- a/arch/riscv/include/asm/pgtable-64.h
+++ b/arch/riscv/include/asm/pgtable-64.h
@@ -17,6 +17,7 @@ extern bool pgtable_l5_enabled;
 #define PGDIR_SHIFT_L4  39
 #define PGDIR_SHIFT_L5  48
 #define PGDIR_SIZE_L3   (_AC(1, UL) << PGDIR_SHIFT_L3)
+#define PGDIR_SIZE_L5   (_AC(1, UL) << PGDIR_SHIFT_L5)
 
 #define PGDIR_SHIFT     (pgtable_l5_enabled ? PGDIR_SHIFT_L5 : \
 		(pgtable_l4_enabled ? PGDIR_SHIFT_L4 : PGDIR_SHIFT_L3))
diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
index 6066822e7396..2032f8ac5fc5 100644
--- a/arch/riscv/include/asm/pgtable.h
+++ b/arch/riscv/include/asm/pgtable.h
@@ -867,6 +867,7 @@ static inline pte_t pte_swp_clear_exclusive(pte_t pte)
 #ifdef CONFIG_64BIT
 #define TASK_SIZE_64	(PGDIR_SIZE * PTRS_PER_PGD / 2)
 #define TASK_SIZE_MIN	(PGDIR_SIZE_L3 * PTRS_PER_PGD / 2)
+#define TASK_SIZE_MAX	(PGDIR_SIZE_L5 * PTRS_PER_PGD / 2)
 
 #ifdef CONFIG_COMPAT
 #define TASK_SIZE_32	(_AC(0x80000000, UL))
-- 
2.43.1