[PATCHv3] kexec-tools:arm: support zImage with appended device tree

[Hoeun Ryu]

Arm linux supports zImage with appended dtb (CONFIG_ARM_APPENDED_DTB) and
the concatenated image is generated like `cat zImage dtb > zImage_w_dtb`.

This patch is to support the concatednated zImage. This changes the
priority of sources for dtb.

 1. --dtb dtb_file
 2. zImage_with_dtb	<= newly added
 3. /sys/firmware/fdt
 4. /proc/device-tree

The dtb content in the concatenated zImage has priority over the other fdt
sources like /sys/firmware/fdt or /proc/device-tree. It's because the same
reason that --dtb command line option has the most priority for fdt source.
Users have some cases when they'd like to use different dtb from running
system.

Users don't need to specify dtb file separately in the command line (--dtb)
and don't have to have /sys/firmware/fdt or /proc/device-tree if dtb is
available in zImage.

We can do
  - `kexec --load-panic zImage_with_different_dtb_from_running_system`
rather than
  - `kexec --load-panic zImage --dtb different_dtb_from_running_system`

Signed-off-by: Hoeun Ryu <hoeun.ryu at gmail.com>
---

 v3: fix bug in fdt header & file size checking.
 v2: make checking for fdt header & file size robust.
     amend commit log.

 kexec/arch/arm/kexec-arm.h        |  1 +
 kexec/arch/arm/kexec-zImage-arm.c | 54 +++++++++++++++++++++++++++++++--------
 2 files changed, 44 insertions(+), 11 deletions(-)

diff --git a/kexec/arch/arm/kexec-arm.h b/kexec/arch/arm/kexec-arm.h
index a74cce2..94695b7 100644
--- a/kexec/arch/arm/kexec-arm.h
+++ b/kexec/arch/arm/kexec-arm.h
@@ -4,6 +4,7 @@
 #include <sys/types.h>
 
 #define SYSFS_FDT "/sys/firmware/fdt"
+#define APPENDED_FDT ((char *)-1) /* it doesn't mean to be opened. */
 #define BOOT_BLOCK_VERSION 17
 #define BOOT_BLOCK_LAST_COMP_VERSION 16
 
diff --git a/kexec/arch/arm/kexec-zImage-arm.c b/kexec/arch/arm/kexec-zImage-arm.c
index 7f02b93..12c3b2c 100644
--- a/kexec/arch/arm/kexec-zImage-arm.c
+++ b/kexec/arch/arm/kexec-zImage-arm.c
@@ -390,6 +390,7 @@ int zImage_arm_load(int argc, char **argv, const char *buf, off_t len,
 	initrd_size = 0;
 	use_atags = 0;
 	dtb_file = NULL;
+	dtb_buf = NULL;
 	while((opt = getopt_long(argc, argv, short_options, options, 0)) != -1) {
 		switch(opt) {
 		default:
@@ -424,14 +425,6 @@ int zImage_arm_load(int argc, char **argv, const char *buf, off_t len,
 		return -1;
 	}
 
-	if (!use_atags && !dtb_file) {
-		int f;
-
-		f = have_sysfs_fdt();
-		if (f)
-			dtb_file = SYSFS_FDT;
-	}
-
 	if (command_line) {
 		command_line_len = strlen(command_line) + 1;
 		if (command_line_len > COMMAND_LINE_SIZE)
@@ -440,9 +433,6 @@ int zImage_arm_load(int argc, char **argv, const char *buf, off_t len,
 	if (ramdisk)
 		ramdisk_buf = slurp_file(ramdisk, &initrd_size);
 
-	if (dtb_file)
-		dtb_buf = slurp_file(dtb_file, &dtb_length);
-
 	if (len > 0x34) {
 		const struct zimage_header *hdr;
 		off_t size;
@@ -466,6 +456,32 @@ int zImage_arm_load(int argc, char **argv, const char *buf, off_t len,
 					(unsigned long long)size);
 				return -1;
 			}
+
+			/* check if zImage has an appended dtb */
+			if (!dtb_file && \
+			    ((size + sizeof(struct fdt_header)) <= len) && \
+			    (fdt_check_header(buf + size) == 0)) {
+				/* check dtb size */
+				dtb_length = fdt_totalsize(buf + size);
+				if (size + dtb_length > len) {
+					fprintf(stderr,
+						"dtb is truncated - file "
+						"0x%llx vs header 0x%llx\n",
+						(unsigned long long)len - size,
+						(unsigned long long)dtb_length);
+				}
+				/*
+				 * dtb_file won't be opened.
+				 * It's set just to pass NULL checking.
+				 */
+				dtb_file = APPENDED_FDT;
+				dtb_buf = xmalloc(dtb_length);
+				memcpy(dtb_buf, buf + size, dtb_length);
+
+				dbgprintf("found appended dtb, size 0x%llx\n",
+					  (unsigned long long)dtb_length);
+			}
+
 			if (size < len)
 				len = size;
 		}
@@ -575,6 +591,22 @@ int zImage_arm_load(int argc, char **argv, const char *buf, off_t len,
 		initrd_base = kernel_base + _ALIGN(len * 5, getpagesize());
 	}
 
+	if (!use_atags && !dtb_file) {
+		int f;
+
+		f = have_sysfs_fdt();
+		if (f)
+			dtb_file = SYSFS_FDT;
+	}
+
+	/*
+	 * dtb_buf can be allocated when checking zImage_with_dtb.
+	 * dtb_buf won't be allocated in the logic if dtb_file is handed over
+	 * in argv[].
+	 */
+	if (dtb_file && !dtb_buf)
+		dtb_buf = slurp_file(dtb_file, &dtb_length);
+
 	if (use_atags) {
 		/*
 		 * use ATAGs from /proc/atags
-- 
2.7.4