[PATCH v5] ARM: boot: Obtain start of physical memory from DTB
From: Geert Uytterhoeven
Date: Wed Apr 15 2020 - 11:34:27 EST
Currently, the start address of physical memory is obtained by masking
the program counter with a fixed mask of 0xf8000000. This mask value
was chosen as a balance between the requirements of different platforms.
However, this does require that the start address of physical memory is
a multiple of 128 MiB, precluding booting Linux on platforms where this
requirement is not fulfilled.
Fix this limitation by obtaining the start address from the DTB instead,
if available (either explicitly passed, or appended to the kernel).
Fall back to the traditional method when needed.
This allows to boot Linux on r7s9210/rza2mevb using the 64 MiB of SDRAM
on the RZA2MEVB sub board, which is located at 0x0C000000 (CS3 space),
i.e. not at a multiple of 128 MiB.
Suggested-by: Nicolas Pitre <nico@xxxxxxxxxxx>
Signed-off-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
Reviewed-by: Nicolas Pitre <nico@xxxxxxxxxxx>
Reviewed-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
Tested-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
Tested-by: Dmitry Osipenko <digetx@xxxxxxxxx>
---
v5:
- Add Tested-by, Reviewed-by,
- Round up start of memory to satisfy 16 MiB alignment rule,
v4:
- Fix stack location after commit 184bf653a7a452c1 ("ARM:
decompressor: factor out routine to obtain the inflated image
size"),
v3:
- Add Reviewed-by,
- Fix ATAGs with appended DTB,
- Add Tested-by,
v2:
- Use "cmp r0, #-1", instead of "cmn r0, #1",
- Add missing stack setup,
- Support appended DTB.
---
arch/arm/boot/compressed/Makefile | 6 ++-
arch/arm/boot/compressed/fdt_get_mem_start.c | 57 ++++++++++++++++++++
arch/arm/boot/compressed/head.S | 54 ++++++++++++++++++-
3 files changed, 115 insertions(+), 2 deletions(-)
create mode 100644 arch/arm/boot/compressed/fdt_get_mem_start.c
diff --git a/arch/arm/boot/compressed/Makefile b/arch/arm/boot/compressed/Makefile
index 9c11e7490292f0e0..82e4cee97cb5d905 100644
--- a/arch/arm/boot/compressed/Makefile
+++ b/arch/arm/boot/compressed/Makefile
@@ -86,12 +86,15 @@ libfdt_objs := $(addsuffix .o, $(basename $(libfdt)))
$(addprefix $(obj)/,$(libfdt) $(libfdt_hdrs)): $(obj)/%: $(srctree)/scripts/dtc/libfdt/%
$(call cmd,shipped)
-$(addprefix $(obj)/,$(libfdt_objs) atags_to_fdt.o): \
+$(addprefix $(obj)/,$(libfdt_objs) atags_to_fdt.o fdt_get_mem_start.o): \
$(addprefix $(obj)/,$(libfdt_hdrs))
ifeq ($(CONFIG_ARM_ATAG_DTB_COMPAT),y)
OBJS += $(libfdt_objs) atags_to_fdt.o
endif
+ifeq ($(CONFIG_USE_OF),y)
+OBJS += $(libfdt_objs) fdt_get_mem_start.o
+endif
targets := vmlinux vmlinux.lds piggy_data piggy.o \
lib1funcs.o ashldi3.o bswapsdi2.o \
@@ -115,6 +118,7 @@ CFLAGS_fdt.o := $(nossp-flags-y)
CFLAGS_fdt_ro.o := $(nossp-flags-y)
CFLAGS_fdt_rw.o := $(nossp-flags-y)
CFLAGS_fdt_wip.o := $(nossp-flags-y)
+CFLAGS_fdt_get_mem_start.o := $(nossp-flags-y)
ccflags-y := -fpic $(call cc-option,-mno-single-pic-base,) -fno-builtin \
-I$(obj) $(DISABLE_ARM_SSP_PER_TASK_PLUGIN)
diff --git a/arch/arm/boot/compressed/fdt_get_mem_start.c b/arch/arm/boot/compressed/fdt_get_mem_start.c
new file mode 100644
index 0000000000000000..e29caa4cbfecb36a
--- /dev/null
+++ b/arch/arm/boot/compressed/fdt_get_mem_start.c
@@ -0,0 +1,57 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include <linux/kernel.h>
+#include <linux/sizes.h>
+
+#include <libfdt.h>
+
+static const void *getprop(const void *fdt, const char *node_path,
+ const char *property)
+{
+ int offset = fdt_path_offset(fdt, node_path);
+
+ if (offset == -FDT_ERR_NOTFOUND)
+ return NULL;
+
+ return fdt_getprop(fdt, offset, property, NULL);
+}
+
+static uint32_t get_addr_size(const void *fdt)
+{
+ const __be32 *addr_len = getprop(fdt, "/", "#address-cells");
+
+ if (!addr_len) {
+ /* default */
+ return 1;
+ }
+
+ return fdt32_to_cpu(*addr_len);
+}
+
+/*
+ * Get the start of physical memory
+ */
+
+unsigned long fdt_get_mem_start(const void *fdt)
+{
+ uint32_t addr_size, mem_start;
+ const __be32 *memory;
+
+ if (!fdt)
+ return -1;
+
+ if (*(__be32 *)fdt != cpu_to_fdt32(FDT_MAGIC))
+ return -1;
+
+ /* Find the first memory node */
+ memory = getprop(fdt, "/memory", "reg");
+ if (!memory)
+ return -1;
+
+ /* There may be multiple cells on LPAE platforms */
+ addr_size = get_addr_size(fdt);
+
+ mem_start = fdt32_to_cpu(memory[addr_size - 1]);
+ /* Must be a multiple of 16 MiB for phys/virt patching */
+ return round_up(mem_start, SZ_16M);
+}
diff --git a/arch/arm/boot/compressed/head.S b/arch/arm/boot/compressed/head.S
index cabdd8f4a2482e2b..2d2a42865b3974da 100644
--- a/arch/arm/boot/compressed/head.S
+++ b/arch/arm/boot/compressed/head.S
@@ -254,8 +254,58 @@ not_angel:
.text
#ifdef CONFIG_AUTO_ZRELADDR
+#ifdef CONFIG_USE_OF
/*
- * Find the start of physical memory. As we are executing
+ * Find the start of physical memory.
+ * Try the DTB first, if available.
+ */
+ adr r0, LC0
+ ldr r1, [r0] @ get absolute LC0
+ ldr sp, [r0, #24] @ get stack location
+ sub r1, r0, r1 @ compute relocation offset
+ add sp, sp, r1 @ apply relocation
+
+#ifdef CONFIG_ARM_APPENDED_DTB
+ /*
+ * Look for an appended DTB. If found, use it and
+ * move stack away from it.
+ */
+ ldr r6, [r0, #12] @ get &_edata
+ add r6, r6, r1 @ relocate it
+ ldmia r6, {r0, r5} @ get DTB signature and size
+#ifndef __ARMEB__
+ ldr r1, =0xedfe0dd0 @ sig is 0xd00dfeed big endian
+ /* convert DTB size to little endian */
+ eor r2, r5, r5, ror #16
+ bic r2, r2, #0x00ff0000
+ mov r5, r5, ror #8
+ eor r5, r5, r2, lsr #8
+#else
+ ldr r1, =0xd00dfeed
+#endif
+ cmp r0, r1 @ do we have a DTB there?
+ bne 1f
+
+ /* preserve 64-bit alignment */
+ add r5, r5, #7
+ bic r5, r5, #7
+ add sp, sp, r5 @ if so, move stack above DTB
+ mov r0, r6 @ and extract memory start from DTB
+ b 2f
+
+1:
+#endif /* CONFIG_ARM_APPENDED_DTB */
+
+ mov r0, r8
+2:
+ bl fdt_get_mem_start
+ mov r4, r0
+ cmp r0, #-1
+ bne 1f
+#endif /* CONFIG_USE_OF */
+
+ /*
+ * Fall back to the traditional method. As we are executing
* without the MMU on, we are in the physical address space.
* We just need to get rid of any offset by aligning the
* address.
@@ -273,6 +323,8 @@ not_angel:
*/
mov r4, pc
and r4, r4, #0xf8000000
+
+1:
/* Determine final kernel image address. */
add r4, r4, #TEXT_OFFSET
#else
--
2.17.1