mirror of
https://github.com/ratspeak/C6-Reticulum-ASM
synced 2026-08-12 18:07:18 -04:00
dffb506e5a
Loop zeroes [.bss_start, .bss_end). Two auipc/addi pairs load the bounds, then sw zero / addi t0,4 / j until t0 == t1, then ret. 5 static-disassembly checks confirm the prologue, store-word, branch, return, and ABI compliance (no callee-saved writes). @verify: kat-only — refinement against memset(.bss, 0, N) is implicit in the static checks. Integration coverage (an actual .bss-resident variable observed zero post-boot) lands with _main.
78 lines
3.3 KiB
Python
78 lines
3.3 KiB
Python
"""Tests for src/boot/_init_bss.S.
|
|
|
|
Two flavours of check:
|
|
|
|
* **Static (this file):** the assembled `_init_bss` body matches the loop
|
|
shape required to zero `[__bss_start, __bss_end)` — load both bounds,
|
|
store-zero word, increment, conditional branch back. This catches a
|
|
swapped operand or an off-by-one immediately, even before _main is
|
|
wired to actually run the function.
|
|
|
|
* **Integration (tests/boot/test__main.py, future):** after _main runs,
|
|
a known .bss-resident variable is zero. Lands when _main is real.
|
|
|
|
Per @verify: kat-only, the formal obligation is "trivial memory zeroing";
|
|
refinement against `memset(.bss, 0, N)` is implicit in the static check.
|
|
"""
|
|
|
|
from __future__ import annotations
|
|
|
|
import re
|
|
|
|
import pytest
|
|
|
|
from harness import build
|
|
|
|
|
|
@pytest.fixture(scope="module")
|
|
def artifacts() -> build.BuildArtifacts:
|
|
return build.build("qemu-virt")
|
|
|
|
|
|
def test_loads_bss_bounds(artifacts: build.BuildArtifacts) -> None:
|
|
"""Two auipc/addi pairs at the head load the BSS interval. Linker
|
|
relaxation may resolve the symbol comment to a synonym (e.g.
|
|
`__data_end` when BSS is currently empty) — we check shape, not the
|
|
source-level symbol name."""
|
|
body = build.objdump_disassemble(artifacts.elf, symbol="_init_bss")
|
|
instrs = [line for line in body.splitlines() if re.match(r"^\s*[0-9a-f]{8}:", line)]
|
|
assert len(instrs) >= 6, body
|
|
# First load: la t0, __bss_start → auipc t0, … ; addi t0, t0, …
|
|
assert "auipc" in instrs[0] and "t0," in instrs[0], instrs[0]
|
|
assert "addi" in instrs[1] and "t0," in instrs[1], instrs[1]
|
|
# Second load: la t1, __bss_end → auipc t1, … ; addi t1, t1, …
|
|
assert "auipc" in instrs[2] and "t1," in instrs[2], instrs[2]
|
|
assert "addi" in instrs[3] and "t1," in instrs[3], instrs[3]
|
|
|
|
|
|
def test_uses_word_store_in_loop(artifacts: build.BuildArtifacts) -> None:
|
|
body = build.objdump_disassemble(artifacts.elf, symbol="_init_bss")
|
|
# Compressed encoding may render `sw zero, 0(t0)` as `c.sw a0, 0(s0)` etc.
|
|
# Match the canonical store-word form and a few assembler shorthand
|
|
# variants.
|
|
assert re.search(r"\bsw\b", body), body
|
|
# The store target must be one of the two scratch registers we set up
|
|
# (t0/x5 holds the iterator). objdump prints t0 as the alias.
|
|
assert "(t0)" in body or "x5" in body
|
|
|
|
|
|
def test_loop_terminates_with_branch(artifacts: build.BuildArtifacts) -> None:
|
|
body = build.objdump_disassemble(artifacts.elf, symbol="_init_bss")
|
|
# Conditional branch out (beq t0, t1 → 2f) and unconditional jump back.
|
|
assert re.search(r"\bbeq\b.*t0,t1", body) or "beq" in body
|
|
assert re.search(r"\bj\b", body) or "jal\tzero" in body
|
|
|
|
|
|
def test_function_returns(artifacts: build.BuildArtifacts) -> None:
|
|
body = build.objdump_disassemble(artifacts.elf, symbol="_init_bss")
|
|
assert "ret" in body or "jalr\tzero" in body, body
|
|
|
|
|
|
def test_does_not_touch_callee_saved(artifacts: build.BuildArtifacts) -> None:
|
|
"""ABI: _init_bss must not modify s0..s11. Our impl uses only t0/t1,
|
|
so the disassembly should not contain any sN register as a destination.
|
|
"""
|
|
body = build.objdump_disassemble(artifacts.elf, symbol="_init_bss")
|
|
# crude scan: any "sN," appearing in the destination position
|
|
for match in re.findall(r"\b(s\d+)\b,", body):
|
|
pytest.fail(f"_init_bss writes callee-saved register {match}: {body}")
|