[PATCH v2 3/8] ARM: mmu: use reserve mem entries to modify maps

[Rouven Czerwinski]

Use the information from the reserved memory entries to modify the
mapping of memory regions to mark them as uncachable and not-executable.
This also prevents the processor from speculating into these regions,
preventing hard to debug scenarios where boots fail for unknown reasons.

Signed-off-by: Rouven Czerwinski <r.czerwinski at pengutronix.de>
---
 arch/arm/cpu/mmu.c | 34 ++++++++++++++++++++++++++++++++--
 1 file changed, 32 insertions(+), 2 deletions(-)

diff --git a/arch/arm/cpu/mmu.c b/arch/arm/cpu/mmu.c
index 6388e1bf14..73f4cf5b36 100644
--- a/arch/arm/cpu/mmu.c
+++ b/arch/arm/cpu/mmu.c
@@ -17,6 +17,7 @@
 #include <memory.h>
 #include <asm/system_info.h>
 #include <asm/sections.h>
+#include <of.h>
 
 #include "mmu.h"
 
@@ -407,6 +408,36 @@ static void vectors_init(void)
 	create_vector_table(ARM_LOW_VECTORS);
 }
 
+static void create_sections_with_intersect(struct memory_bank *bank)
+{
+	struct of_reserve_map *res_map;
+	unsigned long j_end;
+	unsigned long end;
+	unsigned long j;
+	u32 pmd_flags;
+	int i;
+
+	res_map = of_get_reserve_map();
+	if (!res_map)
+		return;
+
+	end = bank->start + bank->size - 1;
+
+	for (j = bank->start; j < end; j += PGDIR_SIZE) {
+		pmd_flags = PMD_SECT_DEF_CACHED;
+		j_end = j + PGDIR_SIZE - 1;
+
+		for (i = 0; i < res_map->num_entries; i++) {
+			if ((BIT(i) & res_map->xn) &&
+			    j_end >= res_map->start[i] &&
+			    j_end <= res_map->end[i])
+				pmd_flags = PMD_SECT_DEF_UNCACHED | PMD_SECT_XN;
+		}
+
+		create_sections(ttb, j, j_end, pmd_flags);
+	}
+}
+
 /*
  * Prepare MMU for usage enable it.
  */
@@ -468,8 +499,7 @@ void __mmu_init(bool mmu_on)
 	vectors_init();
 
 	for_each_memory_bank(bank) {
-		create_sections(ttb, bank->start, bank->start + bank->size - 1,
-				PMD_SECT_DEF_CACHED);
+		create_sections_with_intersect(bank);
 		__mmu_cache_flush();
 	}
 
-- 
2.32.0