[PATCH 1/3 v3] arm: init: save previous bootloader data

Dzmitry Sankouski dsankouski at gmail.com
Sun Feb 13 20:39:04 CET 2022


When u-boot is used as a chain-loaded bootloader (replacing OS kernel),
previous bootloader leaves data in RAM, that can be reused.

For example, on recent arm linux system, when chainloading u-boot,
there are initramfs and fdt in RAM prepared for OS booting. Initramfs
may be modified to store u-boot's payload, thus providing the ability to
use chainloaded u-boot to boot OS without any storage support.

Two config options added:
- SAVE_PREV_BL_INITRAMFS_START_ADDR
  saves initramfs start address to 'prevbl_initrd_start_addr' environment
  variable
- SAVE_PREV_BL_FDT_ADDR
  saves fdt address to 'prevbl_fdt_addr' environment variable

Signed-off-by: Dzmitry Sankouski <dsankouski at gmail.com>
Cc: Tom Rini <trini at konsulko.com>
---
Changes for v2:
- change signed off line
Changes for v3:
- use if (CONFIG_IS_ENABLED... instead of #if defined
- fix save_prev_bl_data.o in Makefile
- add save_prev_bl_data call to env initialization

 arch/arm/lib/Makefile            |  5 ++
 arch/arm/lib/save_prev_bl_data.c | 91 ++++++++++++++++++++++++++++++++
 boot/Kconfig                     | 79 +++++++++++++++++----------
 common/board_r.c                 |  5 ++
 include/init.h                   | 13 +++++
 5 files changed, 166 insertions(+), 27 deletions(-)
 create mode 100644 arch/arm/lib/save_prev_bl_data.c

diff --git a/arch/arm/lib/Makefile b/arch/arm/lib/Makefile
index c48e1f622d..f3c31c05e5 100644
--- a/arch/arm/lib/Makefile
+++ b/arch/arm/lib/Makefile
@@ -48,6 +48,11 @@ obj-$(CONFIG_$(SPL_TPL_)USE_ARCH_MEMCPY) += memcpy.o
 endif
 obj-$(CONFIG_SEMIHOSTING) += semihosting.o
 
+ifneq ($(filter y,$(CONFIG_SAVE_PREV_BL_INITRAMFS_START_ADDR) $(CONFIG_SAVE_PREV_BL_FDT_ADDR)),)
+obj-y += save_prev_bl_data.o
+endif
+
+# obj-$(CONFIG_SAVE_PREV_BL_INITRAMFS_START_ADDR) += save_prev_bl_data.o
 obj-y	+= bdinfo.o
 obj-y	+= sections.o
 CFLAGS_REMOVE_sections.o := $(LTO_CFLAGS)
diff --git a/arch/arm/lib/save_prev_bl_data.c b/arch/arm/lib/save_prev_bl_data.c
new file mode 100644
index 0000000000..f4ee86a89c
--- /dev/null
+++ b/arch/arm/lib/save_prev_bl_data.c
@@ -0,0 +1,91 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * save_prev_bl_data - saving previous bootloader data
+ * to environment variables.
+ *
+ * Copyright (c) 2022 Dzmitry Sankouski (dsankouski at gmail.com)
+ */
+#include <init.h>
+#include <env.h>
+#include <fdtdec.h>
+#include <fdt_support.h>
+#include <fdt.h>
+#include <common.h>
+#include <linux/errno.h>
+#include <asm/system.h>
+#include <asm/armv8/mmu.h>
+
+static ulong reg0 __section(".data");
+
+/**
+ * Save x0 register value, assuming previous bootloader set it to
+ * point on loaded fdt or (for older linux kernels)atags.
+ */
+void save_boot_params(ulong r0)
+{
+	reg0 = r0;
+	save_boot_params_ret();
+}
+
+bool is_addr_accessible(phys_addr_t addr)
+{
+	struct mm_region *mem = mem_map;
+	phys_addr_t bank_start;
+	phys_addr_t bank_end;
+
+	while (mem->size) {
+		bank_start = mem->phys;
+		bank_end = bank_start + mem->size;
+		debug("check if block %pap - %pap includes %pap\n", &bank_start, &bank_end, &addr);
+		if (addr > bank_start && addr < bank_end)
+			return true;
+		mem++;
+	}
+
+	return false;
+}
+
+int save_prev_bl_data(void)
+{
+	struct fdt_header *fdt_blob;
+	int node;
+	u64 initrd_start_prop;
+
+	if (!is_addr_accessible((phys_addr_t)reg0))
+		return -ENODATA;
+
+	fdt_blob = (struct fdt_header *)reg0;
+	if (!fdt_valid(&fdt_blob)) {
+		pr_warn("%s: address 0x%lx is not a valid fdt\n", __func__, reg0);
+		return -ENODATA;
+	}
+
+	if (CONFIG_IS_ENABLED(SAVE_PREV_BL_FDT_ADDR))
+		env_set_addr("prevbl_fdt_addr", (void *)reg0);
+	if (!CONFIG_IS_ENABLED(SAVE_PREV_BL_INITRAMFS_START_ADDR))
+		return 0;
+
+	node = fdt_path_offset(fdt_blob, "/chosen");
+	if (!node) {
+		pr_warn("%s: chosen node not found in device tree at addr: 0x%lx\n",
+					__func__, reg0);
+		return -ENODATA;
+	}
+	/*
+	 * linux,initrd-start property might be either 64 or 32 bit,
+	 * depending on primary bootloader implementation.
+	 */
+	initrd_start_prop = fdtdec_get_uint64(fdt_blob, node, "linux,initrd-start", 0);
+	if (!initrd_start_prop) {
+		debug("%s: attempt to get uint64 linux,initrd-start property failed, trying uint\n",
+				__func__);
+		initrd_start_prop = fdtdec_get_uint(fdt_blob, node, "linux,initrd-start", 0);
+		if (!initrd_start_prop) {
+			debug("%s: attempt to get uint failed, too\n", __func__);
+			return -ENODATA;
+		}
+	}
+	env_set_addr("prevbl_initrd_start_addr", (void *)initrd_start_prop);
+
+	return 0;
+}
diff --git a/boot/Kconfig b/boot/Kconfig
index c8d5906cd3..da2f0797e0 100644
--- a/boot/Kconfig
+++ b/boot/Kconfig
@@ -135,10 +135,10 @@ config FIT_IMAGE_POST_PROCESS
 	  processed before being added to the FIT image).
 
 config FIT_PRINT
-        bool "Support FIT printing"
-        default y
-        help
-          Support printing the content of the fitImage in a verbose manner.
+		bool "Support FIT printing"
+		default y
+		help
+		  Support printing the content of the fitImage in a verbose manner.
 
 if SPL
 
@@ -207,12 +207,12 @@ config SPL_LOAD_FIT
 	  This path has the following limitations:
 
 	  1. "loadables" images, other than FDTs, which do not have a "load"
-	     property will not be loaded. This limitation also applies to FPGA
-	     images with the correct "compatible" string.
+		 property will not be loaded. This limitation also applies to FPGA
+		 images with the correct "compatible" string.
 	  2. For FPGA images, only the "compatible" = "u-boot,fpga-legacy"
-	     loading method is supported.
+		 loading method is supported.
 	  3. FDTs are only loaded for images with an "os" property of "u-boot".
-	     "linux" images are also supported with Falcon boot mode.
+		 "linux" images are also supported with Falcon boot mode.
 
 config SPL_LOAD_FIT_ADDRESS
 	hex "load address of fit image"
@@ -345,8 +345,8 @@ config SYS_EXTRA_OPTIONS
 	  The old configuration infrastructure (= mkconfig + boards.cfg)
 	  provided the extra options field. If you have something like
 	  "HAS_BAR,BAZ=64", the optional options
-	    #define CONFIG_HAS
-	    #define CONFIG_BAZ	64
+		#define CONFIG_HAS
+		#define CONFIG_BAZ	64
 	  will be defined in include/config.h.
 	  This option was prepared for the smooth migration from the old
 	  configuration to Kconfig. Since this option will be removed sometime,
@@ -380,7 +380,7 @@ config SYS_CLK_FREQ
 	int "CPU clock frequency"
 	default 125000000 if ARCH_LS1012A
 	default 100000000 if ARCH_P2020 || ARCH_T1024 || ARCH_T1042 || \
-			     ARCH_LS1021A || FSL_LSCH2 || FSL_LSCH3
+				 ARCH_LS1021A || FSL_LSCH2 || FSL_LSCH3
 	default 66666666 if ARCH_P1010 || ARCH_P1020 || ARCH_T4240
 	default 66660000 if ARCH_T2080
 	default 33333333 if RCAR_GEN3
@@ -485,15 +485,15 @@ config BOOTSTAGE_REPORT
 	  boot process. The report looks something like this:
 
 		Timer summary in microseconds:
-		       Mark    Elapsed  Stage
-			  0          0  reset
+			   Mark	Elapsed  Stage
+			  0		  0  reset
 		  3,575,678  3,575,678  board_init_f start
-		  3,575,695         17  arch_cpu_init A9
-		  3,575,777         82  arch_cpu_init done
-		  3,659,598     83,821  board_init_r start
-		  3,910,375    250,777  main_loop
+		  3,575,695		 17  arch_cpu_init A9
+		  3,575,777		 82  arch_cpu_init done
+		  3,659,598	 83,821  board_init_r start
+		  3,910,375	250,777  main_loop
 		 29,916,167 26,005,792  bootm_start
-		 30,361,327    445,160  start_kernel
+		 30,361,327	445,160  start_kernel
 
 config BOOTSTAGE_RECORD_COUNT
 	int "Number of boot stage records to store"
@@ -580,24 +580,24 @@ config SHOW_BOOT_PROGRESS
 	  Legacy uImage format:
 
 	  Arg	Where			When
-	    1	common/cmd_bootm.c	before attempting to boot an image
+		1	common/cmd_bootm.c	before attempting to boot an image
 	   -1	common/cmd_bootm.c	Image header has bad	 magic number
-	    2	common/cmd_bootm.c	Image header has correct magic number
+		2	common/cmd_bootm.c	Image header has correct magic number
 	   -2	common/cmd_bootm.c	Image header has bad	 checksum
-	    3	common/cmd_bootm.c	Image header has correct checksum
+		3	common/cmd_bootm.c	Image header has correct checksum
 	   -3	common/cmd_bootm.c	Image data   has bad	 checksum
-	    4	common/cmd_bootm.c	Image data   has correct checksum
+		4	common/cmd_bootm.c	Image data   has correct checksum
 	   -4	common/cmd_bootm.c	Image is for unsupported architecture
-	    5	common/cmd_bootm.c	Architecture check OK
+		5	common/cmd_bootm.c	Architecture check OK
 	   -5	common/cmd_bootm.c	Wrong Image Type (not kernel, multi)
-	    6	common/cmd_bootm.c	Image Type check OK
+		6	common/cmd_bootm.c	Image Type check OK
 	   -6	common/cmd_bootm.c	gunzip uncompression error
 	   -7	common/cmd_bootm.c	Unimplemented compression type
-	    7	common/cmd_bootm.c	Uncompression OK
-	    8	common/cmd_bootm.c	No uncompress/copy overwrite error
+		7	common/cmd_bootm.c	Uncompression OK
+		8	common/cmd_bootm.c	No uncompress/copy overwrite error
 	   -9	common/cmd_bootm.c	Unsupported OS (not Linux, BSD, VxWorks, QNX)
 
-	    9	common/image.c		Start initial ramdisk verification
+		9	common/image.c		Start initial ramdisk verification
 	  -10	common/image.c		Ramdisk header has bad	   magic number
 	  -11	common/image.c		Ramdisk header has bad	   checksum
 	   10	common/image.c		Ramdisk header is OK
@@ -1067,4 +1067,29 @@ config DEFAULT_FDT_FILE
 	help
 	  This option is used to set the default fdt file to boot OS.
 
+config SAVE_PREV_BL_FDT_ADDR
+	depends on ARM
+	bool "Saves fdt address, passed by the previous bootloader, to env var"
+	default n
+	help
+	  When u-boot is used as a chain-loaded bootloader (replacing OS kernel),
+	  enable this option to save fdt address, passed by the
+	  previous bootloader for future use.
+	  Address is saved to `prevbl_fdt_addr` environment variable.
+
+	  If no fdt was provided by previous bootloader, no env variables
+	  will be created.
+
+config SAVE_PREV_BL_INITRAMFS_START_ADDR
+	depends on ARM
+	bool "Saves initramfs address, passed by the previous bootloader, to env var"
+	default n
+	help
+	  When u-boot is used as a chain-loaded bootloader(replacing OS kernel),
+	  enable this option to save initramfs address, passed by the
+	  previous bootloader for future use.
+	  Address is saved to `prevbl_initrd_start_addr` environment variable.
+
+	  If no initramfs was provided by previous bootloader, no env variables
+	  will be created.
 endmenu		# Booting
diff --git a/common/board_r.c b/common/board_r.c
index c24d9b4e22..5b717e2162 100644
--- a/common/board_r.c
+++ b/common/board_r.c
@@ -445,6 +445,11 @@ static int initr_env(void)
 		env_set_hex("fdtcontroladdr",
 			    (unsigned long)map_to_sysmem(gd->fdt_blob));
 
+	#if (CONFIG_IS_ENABLED(SAVE_PREV_BL_INITRAMFS_START_ADDR) || \
+						CONFIG_IS_ENABLED(SAVE_PREV_BL_FDT_ADDR))
+		save_prev_bl_data();
+	#endif
+
 	/* Initialize from environment */
 	image_load_addr = env_get_ulong("loadaddr", 16, image_load_addr);
 
diff --git a/include/init.h b/include/init.h
index 20c3976af0..1a55a0e2e4 100644
--- a/include/init.h
+++ b/include/init.h
@@ -166,6 +166,19 @@ int arch_setup_bdinfo(void);
  */
 int setup_bdinfo(void);
 
+#if defined(CONFIG_SAVE_PREV_BL_INITRAMFS_START_ADDR) || \
+defined(CONFIG_SAVE_PREV_BL_FDT_ADDR)
+/**
+ * save_prev_bl_data - Save prev bl data in env vars.
+ *
+ * When u-boot is chain-loaded, save previous bootloader data,
+ * like initramfs address to environment variables.
+ *
+ * Return: 0 if ok; -ENODATA on error
+ */
+int save_prev_bl_data(void);
+#endif
+
 /**
  * cpu_secondary_init_r() - CPU-specific secondary initialization
  *
-- 
2.20.1



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