[RFC PATCH 7/7] arm: cache: cp15: don't map the reserved region with no-map property

[Patrick Delaunay]

No more map the reserved region with "no-map" property by marking
the corresponding TLB entries with invalid entry (=0) to avoid
speculative access.

This patch fixes an issue on STM32MP15x where predictive read access
on secure DDR area are caught by OP-TEE.

Signed-off-by: Patrick Delaunay <patrick.delaunay at st.com>
---

 arch/arm/include/asm/system.h |  3 +++
 arch/arm/lib/cache-cp15.c     | 17 +++++++++++++++--
 2 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/arch/arm/include/asm/system.h b/arch/arm/include/asm/system.h
index ce552944b7..932f12af1c 100644
--- a/arch/arm/include/asm/system.h
+++ b/arch/arm/include/asm/system.h
@@ -458,6 +458,7 @@ static inline void set_dacr(unsigned int val)
 
 /* options available for data cache on each page */
 enum dcache_option {
+	INVALID_ENTRY = 0,
 	DCACHE_OFF = TTB_SECT | TTB_SECT_MAIR(0) | TTB_SECT_XN_MASK,
 	DCACHE_WRITETHROUGH = TTB_SECT | TTB_SECT_MAIR(1),
 	DCACHE_WRITEBACK = TTB_SECT | TTB_SECT_MAIR(2),
@@ -488,6 +489,7 @@ enum dcache_option {
  *   1    1  1   Outer/Inner Write-Back, Read-Allocate Write-Allocate
  */
 enum dcache_option {
+	INVALID_ENTRY = 0,
 	DCACHE_OFF = TTB_SECT_DOMAIN(0) | TTB_SECT_XN_MASK | TTB_SECT,
 	DCACHE_WRITETHROUGH = DCACHE_OFF | TTB_SECT_C_MASK,
 	DCACHE_WRITEBACK = DCACHE_WRITETHROUGH | TTB_SECT_B_MASK,
@@ -497,6 +499,7 @@ enum dcache_option {
 #define TTB_SECT_AP		(3 << 10)
 /* options available for data cache on each page */
 enum dcache_option {
+	INVALID_ENTRY = 0,
 	DCACHE_OFF = 0x12,
 	DCACHE_WRITETHROUGH = 0x1a,
 	DCACHE_WRITEBACK = 0x1e,
diff --git a/arch/arm/lib/cache-cp15.c b/arch/arm/lib/cache-cp15.c
index abd81d21c7..b3ec8d2513 100644
--- a/arch/arm/lib/cache-cp15.c
+++ b/arch/arm/lib/cache-cp15.c
@@ -6,6 +6,7 @@
 
 #include <common.h>
 #include <cpu_func.h>
+#include <lmb.h>
 #include <log.h>
 #include <asm/system.h>
 #include <asm/cache.h>
@@ -105,18 +106,30 @@ void mmu_set_region_dcache_behaviour(phys_addr_t start, size_t size,
 __weak void dram_bank_mmu_setup(int bank)
 {
 	struct bd_info *bd = gd->bd;
+	struct lmb lmb;
 	int	i;
 
 	/* bd->bi_dram is available only after relocation */
 	if ((gd->flags & GD_FLG_RELOC) == 0)
 		return;
 
+	/*
+	 * don't allow cache on reserved memory tagged 'no-map' in DT
+	 * => avoid speculative access to "secure" data
+	 */
+	lmb_init_and_reserve(&lmb, bd, (void *)gd->fdt_blob);
+
 	debug("%s: bank: %d\n", __func__, bank);
 	for (i = bd->bi_dram[bank].start >> MMU_SECTION_SHIFT;
 	     i < (bd->bi_dram[bank].start >> MMU_SECTION_SHIFT) +
 		 (bd->bi_dram[bank].size >> MMU_SECTION_SHIFT);
-	     i++)
-		set_section_dcache(i, DCACHE_DEFAULT_OPTION);
+	     i++) {
+		if (lmb_is_reserved_flags(&lmb, i << MMU_SECTION_SHIFT,
+					  LMB_NOMAP))
+			set_section_dcache(i, INVALID_ENTRY);
+		else
+			set_section_dcache(i, DCACHE_DEFAULT_OPTION);
+	}
 }
 
 /* to activate the MMU we need to set up virtual memory: use 1M areas */
-- 
2.17.1