linux-kernel - [PATCH] arm64: mm: support setting page attributes for debug situation

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Date:   Fri, 10 Jan 2020 15:47:41 +0800
From:   yeyunfeng <yeyunfeng@...wei.com>
To:     <catalin.marinas@....com>, <will@...nel.org>,
        <anshuman.khandual@....com>, <akpm@...ux-foundation.org>,
        <willy@...radead.org>, <yeyunfeng@...wei.com>,
        <ard.biesheuvel@....com>, <tglx@...utronix.de>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
CC:     <hushiyuan@...wei.com>, <linfeilong@...wei.com>
Subject: [PATCH] arm64: mm: support setting page attributes for debug
 situation

When rodata_full is set or pagealloc debug is enabled, block mappings or
contiguou hints are no longer used for linear address area. Therefore,
support setting page attributes in this case is useful for debugging
memory corruption problems.

Signed-off-by: Yunfeng Ye <yeyunfeng@...wei.com>
---
 arch/arm64/mm/pageattr.c | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c
index 9ce7bd9d4d9c..823143534a93 100644
--- a/arch/arm64/mm/pageattr.c
+++ b/arch/arm64/mm/pageattr.c
@@ -65,6 +65,9 @@ static int change_memory_common(unsigned long addr, int numpages,
 		WARN_ON_ONCE(1);
 	}

+	if (!numpages)
+		return 0;
+
 	/*
 	 * Kernel VA mappings are always live, and splitting live section
 	 * mappings into page mappings may cause TLB conflicts. This means
@@ -81,11 +84,18 @@ static int change_memory_common(unsigned long addr, int numpages,
 	area = find_vm_area((void *)addr);
 	if (!area ||
 	    end > (unsigned long)area->addr + area->size ||
-	    !(area->flags & VM_ALLOC))
+	    !(area->flags & VM_ALLOC)) {
+
+		/*
+		 * When rodata_full is set, or pagealloc debug is enabled,
+		 * the linear address is mapped with NO_BLOCK_MAPPINGS or
+		 * NO_CONT_MAPPINGS flags, so splitting is never needed.
+		 */
+		if (rodata_full || debug_pagealloc_enabled())
+			return __change_memory_common(start, size, set_mask,
+							clear_mask);
 		return -EINVAL;
-
-	if (!numpages)
-		return 0;
+	}

 	/*
 	 * If we are manipulating read-only permissions, apply the same
-- 
2.7.4