bastion: initial implementation

ready project skeleton
dual-arch build system with Linux-config style configuration
UEFI EFI stub loader (PE32+) for x86_64 and AArch64
ELF64 kernel parser
Temporary framebuffer console
freestanding string and c++ abi stubs

For now, kernel boots, prints banner, memory map and go halt

1 files changed, 32 insertions, 0 deletions

diff --git a/doc/boot/image_format.md b/doc/boot/image_format.md
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+# Final Image format
+
+The main binary is bastion.elf (in some cases it calls kernel.elf).
+It has format of ELF64
+
+## Why ELF64?
+ELF is the basic executable format for unix-like, and this format is very easy for understandable.
+Also elf is what Clang/GCC emit by default when targeting Linux or bare-metal. 
+And GDB/LLDB has great understanding of ELF format.
+
+## What format is Linux image
+Linux has its own format for each architecture.
+For example for x86:
+bzImage layout:
+┌──────────────────────┐
+│ Real-mode boot header│  "Boot protocol" setup header
+│ (struct boot_params) │  at offset 0x1F1
+├──────────────────────┤
+│ PE/COFF header       │  Grafted on if CONFIG_EFI_STUB=y
+│ (optional)           │  so UEFI can load it directly
+├──────────────────────┤
+│ Compressed kernel    │  The actual vmlinux (ELF), compressed
+│ (gzip/lz4/zstd)      │  with a small decompressor stub
+├──────────────────────┤
+│ Decompressor code    │  Runs in protected/long mode,
+│                      │  decompresses → real vmlinux
+└──────────────────────┘
+
+for aarch64, kernel Image is a flat binary with 64-byte header defined by the ARM64 boot protocol (with efi_stub config it also can have PE header).
+
+
+