linux-kernel - [PATCH] ARM: add BUILD_BUG_ON to check if fixmap range spans multiple pmds

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Date:   Wed, 20 Oct 2021 13:49:42 +0800
From:   quanyang.wang@...driver.com
To:     Russell King <linux@...linux.org.uk>,
        Linus Walleij <linus.walleij@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ard Biesheuvel <ardb@...nel.org>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Quanyang Wang <quanyang.wang@...driver.com>
Subject: [PATCH] ARM: add BUILD_BUG_ON to check if fixmap range spans multiple pmds

From: Quanyang Wang <quanyang.wang@...driver.com>

Not only the early fixmap range, but also the fixmap range should be
checked if it spans multiple pmds. When enabling CONFIG_DEBUG_HIGHMEM,
some systems which contain up to 16 CPUs will crash.

Signed-off-by: Quanyang Wang <quanyang.wang@...driver.com>
---
 arch/arm/mm/mmu.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
index a4e0060051070..57eed92073a4a 100644
--- a/arch/arm/mm/mmu.c
+++ b/arch/arm/mm/mmu.c
@@ -369,6 +369,8 @@ void __init early_fixmap_init(void)
 	 */
 	BUILD_BUG_ON((__fix_to_virt(__end_of_early_ioremap_region) >> PMD_SHIFT)
 		     != FIXADDR_TOP >> PMD_SHIFT);
+	BUILD_BUG_ON((__fix_to_virt(__end_of_fixmap_region) >> PMD_SHIFT)
+		     != FIXADDR_TOP >> PMD_SHIFT);
 
 	pmd = fixmap_pmd(FIXADDR_TOP);
 	pmd_populate_kernel(&init_mm, pmd, bm_pte);
-- 
2.25.1