[RFC PATCH v0 2/6] Add DTB processing

[ardb@kernel.org]

From: Ard Biesheuvel <ardb@google.com>

Add handling of the QEMU provided DTB, which we will need to consult to
find the DRAM layout and the fwcfg device. Initially, just dump the
/chosen/bootargs only, if one is provided.
---
 Cargo.lock  |  7 +++++++
 Cargo.toml  |  1 +
 src/main.rs | 10 ++++++++++
 3 files changed, 18 insertions(+)

diff --git a/Cargo.lock b/Cargo.lock
index 617acc9c6086..2750d4a3937c 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -12,12 +12,19 @@ checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd"
 name = "efilite"
 version = "0.1.0"
 dependencies = [
+ "fdt",
  "linked_list_allocator",
  "log",
  "mmio",
  "rlibc",
 ]
 
+[[package]]
+name = "fdt"
+version = "0.1.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b643857cf70949306b81d7e92cb9d47add673868edac9863c4a49c42feaf3f1e"
+
 [[package]]
 name = "linked_list_allocator"
 version = "0.9.1"
diff --git a/Cargo.toml b/Cargo.toml
index 9bc2b39f6e9b..b073376d9e16 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -10,6 +10,7 @@ rlibc = "1.0.0"
 linked_list_allocator = "0.9.1"
 log = "0.4.14"
 mmio = "2.1.0"
+fdt = "0.1.3"
 
 [profile.dev]
 panic = "abort"
diff --git a/src/main.rs b/src/main.rs
index 698e9c5724bf..6d880732b469 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -13,6 +13,10 @@ use log::{error, info};
 #[global_allocator]
 pub static ALLOCATOR: LockedHeap = LockedHeap::empty();
 
+extern "C" {
+    static _dtb: u8;
+}
+
 #[no_mangle]
 extern "C" fn efilite_main(base: usize, mapped: usize, used: usize) {
     #[cfg(debug_assertions)]
@@ -28,6 +32,12 @@ extern "C" fn efilite_main(base: usize, mapped: usize, used: usize) {
     unsafe {
         ALLOCATOR.lock().init(base + used, mapped - used);
     }
+
+    let fdt = unsafe { fdt::Fdt::from_ptr(&_dtb).expect("Failed to parse device tree") };
+
+    fdt.chosen()
+        .bootargs()
+        .map(|args| info!("/chosen/bootargs: {:?}\n", args));
 }
 
 #[no_mangle]
-- 
2.30.2