From: Zhen Lei <thunder.leizhen@xxxxxxxxxx>
Use page-level mappings for crashkernel region so that we can use
set_memory_valid() to do access protection for it.
Signed-off-by: Zhen Lei <thunder.leizhen@xxxxxxxxxx>
---
arch/arm64/mm/mmu.c | 21 +++++++++++++++++++++
1 file changed, 21 insertions(+)
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 95d360805f8aeb3..e0a197ebe14837d 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -594,6 +594,11 @@ static void __init map_mem(pgd_t *pgdp)
*/
memblock_mark_nomap(kernel_start, kernel_end - kernel_start);
+#ifdef CONFIG_KEXEC_CORE
+ if (crashk_res.end)
+ memblock_mark_nomap(crashk_res.start, resource_size(&crashk_res));
+#endif
+
/* map all the memory banks */
for_each_mem_range(i, &start, &end) {
if (start >= end)
@@ -621,6 +626,22 @@ static void __init map_mem(pgd_t *pgdp)
PAGE_KERNEL, NO_CONT_MAPPINGS);
memblock_clear_nomap(kernel_start, kernel_end - kernel_start);
arm64_kfence_map_pool(early_kfence_pool, pgdp);
+
+ /*
+ * Use page-level mappings here so that we can shrink the region
+ * in page granularity and put back unused memory to buddy system
+ * through /sys/kernel/kexec_crash_size interface.
+ */
+#ifdef CONFIG_KEXEC_CORE
+ if (crashk_res.end) {
+ __map_memblock(pgdp, crashk_res.start,
+ crashk_res.end + 1,
+ PAGE_KERNEL,
+ NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS);
+ memblock_clear_nomap(crashk_res.start,
+ resource_size(&crashk_res));
+ }
+#endif
}
void mark_rodata_ro(void)
--
2.25.1
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