Refactor dtb in rust

.gitmodules

@@ -4,9 +4,6 @@
 [submodule "busybox"]
 	path = native/src/external/busybox
 	url = https://github.com/topjohnwu/ndk-busybox.git
-[submodule "dtc"]
-	path = native/src/external/dtc
-	url = https://github.com/dgibson/dtc.git
 [submodule "lz4"]
 	path = native/src/external/lz4
 	url = https://github.com/lz4/lz4.git

native/src/Android.mk

@@ -99,7 +99,6 @@ LOCAL_STATIC_LIBRARIES := \
     liblzma \
     liblz4 \
     libbz2 \
-    libfdt \
     libz \
     libzopfli \
     libboot-rs
@@ -109,7 +108,6 @@ LOCAL_SRC_FILES := \
     boot/bootimg.cpp \
     boot/compress.cpp \
     boot/format.cpp \
-    boot/dtb.cpp \
     boot/boot-rs.cpp
 
 include $(BUILD_EXECUTABLE)

native/src/Cargo.toml

@@ -22,6 +22,7 @@ rsa = "0.9"
 x509-cert = "0.2"
 der = "0.7"
 bytemuck = "1.14"
+fdt = "0.1"
 
 [workspace.dependencies.argh]
 git = "https://github.com/topjohnwu/argh.git"

native/src/boot/Cargo.toml

@@ -26,3 +26,4 @@ p384 = { workspace = true }
 rsa = { workspace = true, features = ["sha2"] }
 x509-cert = { workspace = true }
 der = { workspace = true, features = ["derive"] }
+fdt = { workspace = true }

native/src/boot/bootimg.cpp

@@ -1,7 +1,7 @@
+#include <bit>
 #include <functional>
 #include <memory>
 
-#include <libfdt.h>
 #include <base.hpp>
 
 #include "boot-rs.hpp"
@@ -183,29 +183,70 @@ boot_img::~boot_img() {
     delete hdr;
 }
 
+struct [[gnu::packed]] fdt_header {
+    struct fdt32_t {
+        uint32_t byte0: 8;
+        uint32_t byte1: 8;
+        uint32_t byte2: 8;
+        uint32_t byte3: 8;
+
+        constexpr operator uint32_t() const {
+            return bit_cast<uint32_t>(fdt32_t {
+                .byte0 = byte3,
+                .byte1 = byte2,
+                .byte2 = byte1,
+                .byte3 = byte0
+            });
+        }
+    };
+
+    struct node_header {
+        fdt32_t tag;
+        char name[0];
+    };
+
+    fdt32_t magic;			 /* magic word FDT_MAGIC */
+    fdt32_t totalsize;		 /* total size of DT block */
+    fdt32_t off_dt_struct;		 /* offset to structure */
+    fdt32_t off_dt_strings;		 /* offset to strings */
+    fdt32_t off_mem_rsvmap;		 /* offset to memory reserve map */
+    fdt32_t version;		 /* format version */
+    fdt32_t last_comp_version;	 /* last compatible version */
+
+    /* version 2 fields below */
+    fdt32_t boot_cpuid_phys;	 /* Which physical CPU id we're
+					    booting on */
+    /* version 3 fields below */
+    fdt32_t size_dt_strings;	 /* size of the strings block */
+
+    /* version 17 fields below */
+    fdt32_t size_dt_struct;		 /* size of the structure block */
+};
+
+
 static int find_dtb_offset(const uint8_t *buf, unsigned sz) {
     const uint8_t * const end = buf + sz;
 
     for (auto curr = buf; curr < end; curr += sizeof(fdt_header)) {
-        curr = static_cast<uint8_t*>(memmem(curr, end - curr, DTB_MAGIC, sizeof(fdt32_t)));
+        curr = static_cast<uint8_t*>(memmem(curr, end - curr, DTB_MAGIC, sizeof(fdt_header::fdt32_t)));
         if (curr == nullptr)
             return -1;
 
         auto fdt_hdr = reinterpret_cast<const fdt_header *>(curr);
 
         // Check that fdt_header.totalsize does not overflow kernel image size
-        uint32_t totalsize = fdt32_to_cpu(fdt_hdr->totalsize);
+        uint32_t totalsize = fdt_hdr->totalsize;
         if (totalsize > end - curr)
             continue;
 
         // Check that fdt_header.off_dt_struct does not overflow kernel image size
-        uint32_t off_dt_struct = fdt32_to_cpu(fdt_hdr->off_dt_struct);
+        uint32_t off_dt_struct = fdt_hdr->off_dt_struct;
         if (off_dt_struct > end - curr)
             continue;
 
         // Check that fdt_node_header.tag of first node is FDT_BEGIN_NODE
-        auto fdt_node_hdr = reinterpret_cast<const fdt_node_header *>(curr + off_dt_struct);
-        if (fdt32_to_cpu(fdt_node_hdr->tag) != FDT_BEGIN_NODE)
+        auto fdt_node_hdr = reinterpret_cast<const fdt_header::node_header *>(curr + off_dt_struct);
+        if (fdt_node_hdr->tag != 0x1u)
             continue;
 
         return curr - buf;