[PATCH v2 2/2] arm64/mm: make tramp_pg_dir read-only

[Jun Yao]

Make tramp_pg_dir read-only.

Signed-off-by: Jun Yao <yaojun8558...@gmail.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