linux-kernel - [PATCH v2 2/2] arm64/mm: make tramp_pg

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Date:   Thu, 31 May 2018 18:31:22 +0800
From:   Jun Yao <yaojun8558363@...il.com>
To:     linux-arm-kernel@...ts.infradead.org
Cc:     catalin.marinas@....com, will.deacon@....com,
        ard.biesheuvel@...aro.org, linux-kernel@...r.kernel.org,
        kernel-hardening@...ts.openwall.com
Subject: [PATCH v2 2/2] arm64/mm: make tramp_pg_dir read-only

Make tramp_pg_dir read-only.

Signed-off-by: Jun Yao <yaojun8558363@...il.com>
---
 arch/arm64/mm/mmu.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index a675fb88914e..2c6e6433090c 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -542,6 +542,7 @@ static int __init map_entry_trampoline(void)
 {
 	pgprot_t prot = rodata_enabled ? PAGE_KERNEL_ROX : PAGE_KERNEL_EXEC;
 	phys_addr_t pa_start = __pa_symbol(__entry_tramp_text_start);
+	int segment_size;
 
 	/* The trampoline is always mapped and can therefore be global */
 	pgprot_val(prot) &= ~PTE_NG;
@@ -551,6 +552,11 @@ static int __init map_entry_trampoline(void)
 	__create_pgd_mapping(tramp_pg_dir, pa_start, TRAMP_VALIAS, PAGE_SIZE,
 			     prot, pgd_pgtable_alloc, 0);
 
+	segment_size = __tramp_pgdir_segment_end - __tramp_pgdir_segment_start;
+	update_mapping_prot(__pa_symbol(__tramp_pgdir_segment_start),
+				(unsigned long)__tramp_pgdir_segment_start,
+				segment_size, PAGE_KERNEL_RO);
+
 	/* Map both the text and data into the kernel page table */
 	__set_fixmap(FIX_ENTRY_TRAMP_TEXT, pa_start, prot);
 	if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) {
-- 
2.17.0