[PATCH v2 2/3] arm/mpu: Provide and populate MPU C data structures

[Ayan Kumar Halder <ayan.kumar.halder@xxxxxxx>]

Modify Arm32 assembly boot code to reset any unused MPU region, initialise
'max_mpu_regions' with the number of supported MPU regions and set/clear the
bitmap 'xen_mpumap_mask' used to track the enabled regions.

Use the macro definition for "dcache_line_size" from linux.

Signed-off-by: Ayan Kumar Halder <ayan.kumar.halder@xxxxxxx>
---
Changes from v1 :-

1. Introduce cache.S to hold arm32 cache initialization instructions.

2. Use dcache_line_size macro definition from linux.

3. Use mov_w instead of ldr.

4. Use a single stm instruction for 'store_pair' macro definition.

 xen/arch/arm/arm32/Makefile              |  1 +
 xen/arch/arm/arm32/asm-offsets.c         |  6 ++++
 xen/arch/arm/arm32/cache.S               | 41 ++++++++++++++++++++++++
 xen/arch/arm/arm32/mpu/head.S            | 25 +++++++++++++++
 xen/arch/arm/include/asm/mpu/regions.inc |  2 +-
 5 files changed, 74 insertions(+), 1 deletion(-)
 create mode 100644 xen/arch/arm/arm32/cache.S

diff --git a/xen/arch/arm/arm32/Makefile b/xen/arch/arm/arm32/Makefile
index 537969d753..531168f58a 100644
--- a/xen/arch/arm/arm32/Makefile
+++ b/xen/arch/arm/arm32/Makefile
@@ -2,6 +2,7 @@ obj-y += lib/
 obj-$(CONFIG_MMU) += mmu/
 obj-$(CONFIG_MPU) += mpu/
 
+obj-y += cache.o
 obj-$(CONFIG_EARLY_PRINTK) += debug.o
 obj-y += domctl.o
 obj-y += domain.o
diff --git a/xen/arch/arm/arm32/asm-offsets.c b/xen/arch/arm/arm32/asm-offsets.c
index 8bbb0f938e..c203ce269d 100644
--- a/xen/arch/arm/arm32/asm-offsets.c
+++ b/xen/arch/arm/arm32/asm-offsets.c
@@ -75,6 +75,12 @@ void __dummy__(void)
 
    OFFSET(INITINFO_stack, struct init_info, stack);
    BLANK();
+
+#ifdef CONFIG_MPU
+   DEFINE(XEN_MPUMAP_MASK_sizeof, sizeof(xen_mpumap_mask));
+   DEFINE(XEN_MPUMAP_sizeof, sizeof(xen_mpumap));
+   BLANK();
+#endif
 }
 
 /*
diff --git a/xen/arch/arm/arm32/cache.S b/xen/arch/arm/arm32/cache.S
new file mode 100644
index 0000000000..00ea390ce4
--- /dev/null
+++ b/xen/arch/arm/arm32/cache.S
@@ -0,0 +1,41 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/* Cache maintenance */
+
+#include <asm/arm32/sysregs.h>
+
+/* dcache_line_size - get the minimum D-cache line size from the CTR register 
*/
+    .macro  dcache_line_size, reg, tmp
+    mrc p15, 0, \tmp, c0, c0, 1     /* read ctr */
+    lsr \tmp, \tmp, #16
+    and \tmp, \tmp, #0xf            /* cache line size encoding */
+    mov \reg, #4                    /* bytes per word */
+    mov \reg, \reg, lsl \tmp        /* actual cache line size */
+    .endm
+
+/*
+ * __invalidate_dcache_area(addr, size)
+ *
+ * Ensure that the data held in the cache for the buffer is invalidated.
+ *
+ * - addr - start address of the buffer
+ * - size - size of the buffer
+ */
+FUNC(__invalidate_dcache_area)
+    dcache_line_size r2, r3
+    add   r1, r0, r1
+    sub   r3, r2, #1
+    bic   r0, r0, r3
+1:  mcr   CP32(r0, DCIMVAC)     /* invalidate D line / unified line */
+    add   r0, r0, r2
+    cmp   r0, r1
+    blo   1b
+    dsb   sy
+    ret
+END(__invalidate_dcache_area)
+
+/*
+ * Local variables:
+ * mode: ASM
+ * indent-tabs-mode: nil
+ * End:
+ */
diff --git a/xen/arch/arm/arm32/mpu/head.S b/xen/arch/arm/arm32/mpu/head.S
index b2c5245e51..435b140d09 100644
--- a/xen/arch/arm/arm32/mpu/head.S
+++ b/xen/arch/arm/arm32/mpu/head.S
@@ -49,6 +49,10 @@ FUNC(enable_boot_cpu_mm)
     mrc   CP32(r5, MPUIR_EL2)
     and   r5, r5, #NUM_MPU_REGIONS_MASK
 
+    mov_w   r0, max_mpu_regions
+    str   r5, [r0]
+    mcr   CP32(r0, DCIMVAC) /* Invalidate cache for max_mpu_regions addr */
+
     /* x0: region sel */
     mov   r0, #0
     /* Xen text section. */
@@ -83,6 +87,27 @@ FUNC(enable_boot_cpu_mm)
     prepare_xen_region r0, r1, r2, r3, r4, r5, attr_prbar=REGION_DEVICE_PRBAR, 
attr_prlar=REGION_DEVICE_PRLAR
 #endif
 
+zero_mpu:
+    /* Reset remaining MPU regions */
+    cmp   r0, r5
+    beq   out_zero_mpu
+    mov   r1, #0
+    mov   r2, #1
+    prepare_xen_region r0, r1, r2, r3, r4, r5, attr_prlar=REGION_DISABLED_PRLAR
+    b     zero_mpu
+
+out_zero_mpu:
+    /* Invalidate data cache for MPU data structures */
+    mov r4, lr
+    mov_w r0, xen_mpumap_mask
+    mov r1, #XEN_MPUMAP_MASK_sizeof
+    bl __invalidate_dcache_area
+
+    ldr r0, =xen_mpumap
+    mov r1, #XEN_MPUMAP_sizeof
+    bl __invalidate_dcache_area
+    mov lr, r4
+
     b    enable_mpu
 END(enable_boot_cpu_mm)
 
diff --git a/xen/arch/arm/include/asm/mpu/regions.inc 
b/xen/arch/arm/include/asm/mpu/regions.inc
index 6b8c233e6c..631b0b2b86 100644
--- a/xen/arch/arm/include/asm/mpu/regions.inc
+++ b/xen/arch/arm/include/asm/mpu/regions.inc
@@ -24,7 +24,7 @@
 #define XEN_MPUMAP_ENTRY_SHIFT  0x3     /* 8 byte structure */
 
 .macro store_pair reg1, reg2, dst
-    .word 0xe7f000f0                    /* unimplemented */
+    stm \dst, {\reg1, \reg2}  /* reg2 should be a higher register than reg1 */
 .endm
 
 #endif
-- 
2.25.1