Build vsock payload as ELF OBJ format and linux GCC calling convention …

…#26

By specifying build target to rust-vsock-payload/target.json, payload can
be built as ELF format and linux GCC x86-64 calling convention.

'Cargo elfbuild..' can be use directly, the usage has been document to
rust-vsock-payload/readme.md

Signed-off-by: Jiaqi Gao <jiaqi.gao@intel.com>

.cargo/config.toml

@@ -1,3 +1,4 @@
 
 [alias]
 mbuild = "build --target x86_64-unknown-uefi -Zbuild-std=core,alloc -Zbuild-std-features=compiler-builtins-mem"
+elfbuild = "xbuild --target rust-vsock-payload/target.json"

rust-vsock-payload/readme.md

@@ -11,12 +11,27 @@ export RESET_VECTOR_BIN=$BASE_DIR/target/x86_64-unknown-uefi/release/ResetVector
 export RUST_IPL_BIN=$BASE_DIR/target/x86_64-unknown-uefi/release/rust_ipl.efi
 export RUST_PAYLOAD_BIN=$BASE_DIR/target/x86_64-unknown-uefi/release/rust-vsock-payload.efi
 export RUST_FIRMWARE_BIN=$BASE_DIR/target/x86_64-unknown-uefi/release/final_vsock.bin
+```
+
+To build default PE format OBJ and link with a static C library:
 
+```bash
 cargo mbuild -p rust-vsock-payload --release
-cargo run -p rust-firmware-tool -- $RESET_VECTOR_BIN $RUST_IPL_BIN $RUST_PAYLOAD_BIN $RUST_FIRMWARE_BIN
+```
+
+To build ELF format OBJ and link with a static C library:
 
+```bash
+cargo elfbuild -p rust-vsock-payload --release
 ```
 
+Then:
+
+```bash
+cargo run -p rust-firmware-tool -- $RESET_VECTOR_BIN $RUST_IPL_BIN $RUST_PAYLOAD_BIN $RUST_FIRMWARE_BIN
+```
+
+
 ## How to Run
 
 Qemu version is *QEMU emulator version 5.2.0*

rust-vsock-payload/target.json

@@ -0,0 +1,16 @@
+{
+  "llvm-target": "x86_64-unknown-none",
+  "data-layout": "e-m:e-i64:64-f80:128-n8:16:32:64-S128",
+  "arch": "x86_64",
+  "target-endian": "little",
+  "target-pointer-width": "64",
+  "target-c-int-width": "32",
+  "os": "none",
+  "executables": true,
+  "linker": "rust-lld",
+  "linker-flavor": "ld.lld",
+  "panic-strategy": "abort",
+  "disable-redzone": true,
+  "features": "-mmx,-sse,+soft-float",
+  "position-independent-executables": true
+}