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From:   Joerg Roedel <joro@8bytes.org>
To:     Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@kernel.org>,
        "H . Peter Anvin" <hpa@zytor.com>
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        Linus Torvalds <torvalds@linux-foundation.org>,
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Subject: [PATCH 27/37] x86/mm/pti: Keep permissions when cloning kernel text in pti_clone_kernel_text()
Date:   Mon, 23 Apr 2018 17:47:30 +0200
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From: Joerg Roedel <jroedel@suse.de>

Mapping the kernel text area to user-space makes only sense
if it has the same permissions as in the kernel page-table.
If permissions are different this will cause a TLB reload
when using the kernel page-table, which is as good as not
mapping it at all.

On 64-bit kernels this patch makes no difference, as the
whole range cloned by pti_clone_kernel_text() is mapped RO
anyway. On 32 bit there are writeable mappings in the range,
so just keep the permissions as they are.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
---
 arch/x86/mm/pti.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/mm/pti.c b/arch/x86/mm/pti.c
index 9cceae3..e3059bb0 100644
--- a/arch/x86/mm/pti.c
+++ b/arch/x86/mm/pti.c
@@ -460,7 +460,7 @@ void pti_clone_kernel_text(void)
 	if (!pti_kernel_image_global_ok())
 		return;
 
-	pti_clone_pmds(start, end, _PAGE_RW);
+	pti_clone_pmds(start, end, 0);
 }
 
 /*
-- 
2.7.4