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From:   Yu-cheng Yu <yu-cheng.yu@intel.com>
To:     x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
        Thomas Gleixner <tglx@linutronix.de>,
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        Peter Zijlstra <peterz@infradead.org>,
        Randy Dunlap <rdunlap@infradead.org>,
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        Vedvyas Shanbhogue <vedvyas.shanbhogue@intel.com>,
        Dave Martin <Dave.Martin@arm.com>,
        Weijiang Yang <weijiang.yang@intel.com>,
        Pengfei Xu <pengfei.xu@intel.com>
Cc:     Yu-cheng Yu <yu-cheng.yu@intel.com>, Christoph Hellwig <hch@lst.de>
Subject: [PATCH v19 07/25] x86/mm: Remove _PAGE_DIRTY from kernel RO pages
Date:   Wed,  3 Feb 2021 14:55:29 -0800
Message-Id: <20210203225547.32221-8-yu-cheng.yu@intel.com>
In-Reply-To: <20210203225547.32221-1-yu-cheng.yu@intel.com>
References: <20210203225547.32221-1-yu-cheng.yu@intel.com>
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The x86 family of processors do not directly create read-only and Dirty
PTEs.  These PTEs are created by software.  One such case is that kernel
read-only pages are historically setup as Dirty.

New processors that support Shadow Stack regard read-only and Dirty PTEs as
shadow stack pages.  This results in ambiguity between shadow stack and
kernel read-only pages.  To resolve this, removed Dirty from kernel read-
only pages.

Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Peter Zijlstra <peterz@infradead.org>
---
 arch/x86/include/asm/pgtable_types.h | 6 +++---
 arch/x86/mm/pat/set_memory.c         | 2 +-
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/x86/include/asm/pgtable_types.h b/arch/x86/include/asm/pgtable_types.h
index 394757ee030a..b8b79d618bbc 100644
--- a/arch/x86/include/asm/pgtable_types.h
+++ b/arch/x86/include/asm/pgtable_types.h
@@ -194,10 +194,10 @@ enum page_cache_mode {
 #define _KERNPG_TABLE		 (__PP|__RW|   0|___A|   0|___D|   0|   0| _ENC)
 #define _PAGE_TABLE_NOENC	 (__PP|__RW|_USR|___A|   0|___D|   0|   0)
 #define _PAGE_TABLE		 (__PP|__RW|_USR|___A|   0|___D|   0|   0| _ENC)
-#define __PAGE_KERNEL_RO	 (__PP|   0|   0|___A|__NX|___D|   0|___G)
-#define __PAGE_KERNEL_ROX	 (__PP|   0|   0|___A|   0|___D|   0|___G)
+#define __PAGE_KERNEL_RO	 (__PP|   0|   0|___A|__NX|   0|   0|___G)
+#define __PAGE_KERNEL_ROX	 (__PP|   0|   0|___A|   0|   0|   0|___G)
 #define __PAGE_KERNEL_NOCACHE	 (__PP|__RW|   0|___A|__NX|___D|   0|___G| __NC)
-#define __PAGE_KERNEL_VVAR	 (__PP|   0|_USR|___A|__NX|___D|   0|___G)
+#define __PAGE_KERNEL_VVAR	 (__PP|   0|_USR|___A|__NX|   0|   0|___G)
 #define __PAGE_KERNEL_LARGE	 (__PP|__RW|   0|___A|__NX|___D|_PSE|___G)
 #define __PAGE_KERNEL_LARGE_EXEC (__PP|__RW|   0|___A|   0|___D|_PSE|___G)
 #define __PAGE_KERNEL_WP	 (__PP|__RW|   0|___A|__NX|___D|   0|___G| __WP)
diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c
index 16f878c26667..6bebb95a6988 100644
--- a/arch/x86/mm/pat/set_memory.c
+++ b/arch/x86/mm/pat/set_memory.c
@@ -1932,7 +1932,7 @@ int set_memory_nx(unsigned long addr, int numpages)
 
 int set_memory_ro(unsigned long addr, int numpages)
 {
-	return change_page_attr_clear(&addr, numpages, __pgprot(_PAGE_RW), 0);
+	return change_page_attr_clear(&addr, numpages, __pgprot(_PAGE_RW | _PAGE_DIRTY), 0);
 }
 
 int set_memory_rw(unsigned long addr, int numpages)
-- 
2.21.0