可执行有效载荷作为独立的覆盖包生成。

下面是一个示例“package_overlay.py”脚本，用于从“bin”文件生成覆盖包。

#!/usr/bin/env python3
import struct
import sys
from pathlib import Path

# Must match BootApp_OverlayPkgHeader / boot_app side checks
BOOTAPP_OVERLAY_MAGIC = 0x4F56524C  # 'OVRL'

# Header layout (32 bytes)
#   uint32_t magic;
#   uint32_t totalSize;
#   uint32_t codeSize;
#   uint32_t entryOffset;
#   uint32_t flags;
#   uint32_t reserved[3];
HEADER_FMT = "<8I"
HEADER_SIZE = struct.calcsize(HEADER_FMT)

def make_pkg(bin_path: Path,
             out_path: Path,
             entry_offset: int = 0,
             flags: int = 0,
             prepad: int = 0) -> None:
    code = bin_path.read_bytes()

    if len(code) == 0:
        raise ValueError(f"Empty binary: {bin_path}")
    if entry_offset < 0:
        raise ValueError(f"entry_offset must be >= 0: {entry_offset}")
    if prepad < 0:
        raise ValueError(f"prepad must be >= 0: {prepad}")

    # For XIP packages, TI objcopy emits the binary without preserving the
    # absolute load address. If the linker aligns .text from header_end
    # 0x...20 to 0x...40, the raw binary still starts at file offset 0.
    # Add explicit padding after the OVRL header so the first binary byte is
    # physically placed at the same address used by the linker.
    payload = (b"\x00" * prepad) + code
    code_size = len(payload)
    total_size = HEADER_SIZE + code_size

    header = struct.pack(
        HEADER_FMT,
        BOOTAPP_OVERLAY_MAGIC,  # magic
        total_size,             # totalSize
        code_size,              # codeSize, including any XIP prepad
        entry_offset,           # entryOffset from first byte after header
        flags,                  # flags
        0, 0, 0                 # reserved[3]
    )

    out_path.write_bytes(header + payload)

    print(f"Created {out_path}")
    print(f"  totalSize   : {total_size}")
    print(f"  codeSize    : {code_size}")
    print(f"  entryOffset : {entry_offset}")
    print(f"  flags       : {flags}")
    print(f"  prepad      : {prepad}")

def main() -> int:
    if len(sys.argv) not in (3, 4, 5, 6):
        print("Usage: package_overlay.py <input.bin> <output.pkg> [entry_offset] [flags] [prepad]")
        return 1

    in_path = Path(sys.argv[1])
    out_path = Path(sys.argv[2])

    entry_offset = int(sys.argv[3], 0) if len(sys.argv) >= 4 else 0
    flags = int(sys.argv[4], 0) if len(sys.argv) >= 5 else 0
    prepad = int(sys.argv[5], 0) if len(sys.argv) >= 6 else 0

    make_pkg(in_path, out_path, entry_offset, flags, prepad)
    return 0

if __name__ == "__main__":
    raise SystemExit(main())

下面是一个示例 shell 脚本“build_payloads.sh”，用于生成有效载荷 payloadA.pkg、payloadB.pkg 和 payloadC.pkg。

#!/usr/bin/env bash
set -e

SCRIPT_DIR=$(cd "$(dirname "$0")" && pwd)
OUT_DIR=${OUT_DIR:-$SCRIPT_DIR/out}
TIARMCLANG=${TIARMCLANG:-tiarmclang}
TIARMLNK=${TIARMLNK:-tiarmlnk}
TIARMOBJCOPY=${TIARMOBJCOPY:-tiarmobjcopy}
SLOT_ADDR=${SLOT_ADDR:-0x41C70000}

mkdir -p "$OUT_DIR"

prepare_linker_cmd() {
    local addr=$1
    local out_cmd=$2
    sed "s/0x41C70000/${addr}/g" "$SCRIPT_DIR/emmc_overlay_payload.cmd" > "$out_cmd"
}

build_one() {
    local tag=$1
    local src=$2
    local obj="$OUT_DIR/${tag}.o"
    local elf="$OUT_DIR/${tag}.elf"
    local bin="$OUT_DIR/${tag}.bin"
    local pkg="$OUT_DIR/payload${tag^^}.pkg"
    local lnk="$OUT_DIR/${tag}.cmd"

    echo "[build] ${tag^^}: slot=${SLOT_ADDR} src=${src}"
    prepare_linker_cmd "$SLOT_ADDR" "$lnk"

    $TIARMCLANG -mcpu=cortex-r5 -mthumb -Oz -ffreestanding -fno-builtin -nostdlib \
        -c -I"$SCRIPT_DIR/../include" "$SCRIPT_DIR/$src" -o "$obj"
    $TIARMLNK -o "$elf" "$obj" -c "$lnk" --cinit_compression=off
    $TIARMOBJCOPY -O binary "$elf" "$bin"
    python3 "$SCRIPT_DIR/package_overlay.py" "$bin" "$pkg" 0x0 0x0 0x0
}

build_one a emmc_overlay_payload_a.c
build_one b emmc_overlay_payload_b.c
build_one c emmc_overlay_payload_c.c

cat <<MSG

Done. Copy these files to the FAT partition root used by boot_app:
  $OUT_DIR/payloadA.pkg -> 0:/payloadA.pkg
  $OUT_DIR/payloadB.pkg -> 0:/payloadB.pkg
  $OUT_DIR/payloadC.pkg -> 0:/payloadC.pkg
MSG

每个包均包含

• 覆盖包标头

• 可执行代码段

• 运行时入口点信息

使用以下命令可生成有效载荷包

SLOT_ADDR=0x41C70000 ./build_payloads.sh

生成的包文件随后被复制到 eMMC FATFS 分区。

图 5-1 覆盖有效载荷包生成流程.

图 5-2 覆盖包格式.