Support patching header in magiskboot

native/jni/magiskboot/bootimg.cpp

@@ -269,11 +269,35 @@ void boot_img::print_hdr() {
 	fprintf(stderr, "]\n");
 }
 
-int unpack(const char *image) {
+int unpack(const char *image, bool hdr) {
 	boot_img boot {};
 	int ret = boot.parse_file(image);
 	int fd;
 
+	if (hdr) {
+		FILE *fp = xfopen(HEADER_FILE, "w");
+		fprintf(fp, "pagesize=%u\n", boot.hdr.page_size());
+		fprintf(fp, "name=%s\n", boot.hdr.name());
+		fprintf(fp, "cmdline=%.512s%.1024s\n", boot.hdr.cmdline(), boot.hdr.extra_cmdline());
+		uint32_t ver = boot.hdr.os_version();
+		if (ver) {
+			int a, b, c, y, m = 0;
+			int version, patch_level;
+			version = ver >> 11;
+			patch_level = ver & 0x7ff;
+
+			a = (version >> 14) & 0x7f;
+			b = (version >> 7) & 0x7f;
+			c = version & 0x7f;
+			fprintf(fp, "os_version=%d.%d.%d\n", a, b, c);
+
+			y = (patch_level >> 4) + 2000;
+			m = patch_level & 0xf;
+			fprintf(fp, "patch_level=%d-%02d\n", y, m);
+		}
+		fclose(fp);
+	}
+
 	// Dump kernel
 	if (COMPRESSED(boot.k_fmt)) {
 		fd = creat(KERNEL_FILE, 0644);
@@ -338,6 +362,40 @@ void repack(const char* orig_image, const char* out_image) {
 		restore_buf(fd, boot.map_addr, ACCLAIM_PRE_HEADER_SZ);
 	}
 
+	// header
+	if (access(HEADER_FILE, R_OK) == 0) {
+		int os_version = 0;
+		parse_prop_file(HEADER_FILE, [&](string_view key, string_view value) -> bool {
+			if (key == "page_size") {
+				boot.hdr.page_size() = parse_int(value);
+			} else if (key == "name") {
+				memset(boot.hdr.name(), 0, 16);
+				memcpy(boot.hdr.name(), value.data(), value.length() + 1);
+			} else if (key == "cmdline") {
+				memset(boot.hdr.cmdline(), 0, 512);
+				memset(boot.hdr.extra_cmdline(), 0, 1024);
+				if (value.length() > 512) {
+					memcpy(boot.hdr.cmdline(), value.data(), 512);
+					memcpy(boot.hdr.extra_cmdline(), &value[512], value.length() - 511);
+				} else {
+					memcpy(boot.hdr.cmdline(), value.data(), value.length() + 1);
+				}
+			} else if (key == "os_version") {
+				int a, b, c;
+				sscanf(value.data(), "%d.%d.%d", &a, &b, &c);
+				os_version |= ((a << 14) | (b << 7) | c) << 11;
+			} else if (key == "patch_level") {
+				int y, m;
+				sscanf(value.data(), "%d-%d", &y, &m);
+				y -= 2000;
+				os_version |= (y << 4) | m;
+			}
+			return true;
+		});
+		if (os_version)
+			boot.hdr.os_version() = os_version;
+	}
+
 	// Skip a page for header
 	header_off = lseek(fd, 0, SEEK_CUR);
 	write_zero(fd, boot.hdr.page_size());

native/jni/magiskboot/magiskboot.h

@@ -2,6 +2,7 @@
 
 #include <sys/types.h>
 
+#define HEADER_FILE     "header"
 #define KERNEL_FILE     "kernel"
 #define RAMDISK_FILE    "ramdisk.cpio"
 #define SECOND_FILE     "second"
@@ -11,7 +12,7 @@
 #define NEW_BOOT        "new-boot.img"
 
 // Main entries
-int unpack(const char *image);
+int unpack(const char *image, bool hdr = false);
 void repack(const char* orig_image, const char* out_image);
 void hexpatch(const char *image, const char *from, const char *to);
 int cpio_commands(int argc, char *argv[]);

native/jni/magiskboot/main.cpp

@@ -18,9 +18,11 @@ static void usage(char *arg0) {
 		"Usage: %s <action> [args...]\n"
 		"\n"
 		"Supported actions:\n"
-		"  unpack <bootimg>\n"
+		"  unpack [-h] <bootimg>\n"
-		"    Unpack <bootimg> to, if available, kernel, ramdisk.cpio, \n"
+		"    Unpack <bootimg> to, if available, kernel, ramdisk.cpio,\n"
 		"    second, dtb, extra, and recovery_dtbo into current directory.\n"
+		"    If '-h' is provided, it will dump header info to 'header',\n"
+		"    which will be parsed when repacking.\n"
 		"    Return values:\n"
 		"    0:valid    1:error    2:chromeos    3:ELF32    4:ELF64\n"
 		"\n"
@@ -116,6 +118,7 @@ int main(int argc, char *argv[]) {
 
 	if (strcmp(argv[1], "cleanup") == 0) {
 		fprintf(stderr, "Cleaning up...\n");
+		unlink(HEADER_FILE);
 		unlink(KERNEL_FILE);
 		unlink(RAMDISK_FILE);
 		unlink(SECOND_FILE);
@@ -133,7 +136,13 @@ int main(int argc, char *argv[]) {
 		printf("\n");
 		munmap(buf, size);
 	} else if (argc > 2 && strcmp(argv[1], "unpack") == 0) {
-		return unpack(argv[2]);
+		if (strcmp(argv[2], "-h") == 0) {
+			if (argc == 3)
+				usage(argv[0]);
+			return unpack(argv[3], true);
+		} else {
+			return unpack(argv[2]);
+		}
 	} else if (argc > 2 && strcmp(argv[1], "repack") == 0) {
 		repack(argv[2], argv[3] ? argv[3] : NEW_BOOT);
 	} else if (argc > 2 && strcmp(argv[1], "decompress") == 0) {