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Aether Kernel and the Init Program Contract

Data provided by the kernel and initial stack

Upon process entry, the kernel provides the following resources mapped into the init address space:

  • The boot_info structure.
  • The initrd (tarball archive).
  • A single page-sized (4096 bytes) bootstrap stack.

Memory Layout Convention

All kernel-provided data shall reside at the high end of the userspace virtual address range (the "Top of the Lower Half").

  1. Growth Direction: Data blocks are placed contiguously, starting from the highest available canonical address (e.g., 0x00007FFFFFFFF000) and growing downwards.
  2. Bootstrap Stack: The one-page initial stack is placed as the final (lowest address) item in this kernel-provided data block.
  3. Allocation Boundary: The lowest address of the bootstrap stack serves as the Stack Limit. The init program can rely on this address as the hard upper bound for its own self-allocated "real" stack.

Execution State at Entry

  • RSP/SP: Shall point to the top of the bootstrap stack.
  • RDI/X0: Shall contain the virtual address of the boot_info structure.
  • Alignment: The initial stack pointer must be 16-byte aligned to satisfy the SysV ABI before the first function call.