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The switch is reached through four register functions and the SFR_DATA registers, so a flat register file behind them is enough to run the table code on the host. A few addresses are live: writing TBL_CTRL with EXECUTE performs the VLAN or L2 operation at once and clears the bit, STAT_GET fetches a counter, L2_TBL_FLUSH_CTRL drops entries. Nothing ever reports busy, so a polling loop runs once and the tests say nothing about what happens when hardware stalls; that question was settled elsewhere. The header states the VLAN and L2 entry layouts on its own, so a test can hold what rtl837x_port.c writes against a second reading of the same bits rather than against itself. The first suite does that for the VLAN entry, the PVID register two ports share, the static multicast and management entries, the per-port flush and the trunk registers. Two stub headers stand in for the ones a firmware build generates, so the harness needs no SDCC build first.
61 lines
3.4 KiB
Markdown
61 lines
3.4 KiB
Markdown
# Host unit-test harness
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Compile and test individual firmware translation units on the build host with
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**gcc + AddressSanitizer + UBSan** — no SDCC, no flashing, no hardware. This is
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the fast inner loop for the logic-level bugs in `../../NOTES/08-findings.md`
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(parser, line editor, HTTP header, DHCP): edit → `make` → see red/green in
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seconds instead of a minutes-long flash-and-reboot cycle.
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## Run
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```
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cd test
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make # build + run all tests (ASan/UBSan on)
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make clean
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```
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Exit status is non-zero if any check fails, a sanitizer trips, or the watchdog
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fires — so it drops straight into CI.
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## How it works
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- **`sdcc_shim.h`** (force-included) erases SDCC 8051 keywords (`__xdata`,
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`__code`, `__banked`, …) so firmware sources compile under host gcc. It changes
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no logic — the code under test is byte-for-byte the firmware source.
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- **`hw_mock.c` / `hw_mock.h`** simulate the ASIC edge: a flat register file
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behind `reg_read`/`reg_write` and the `SFR_DATA_*` registers, with a table
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engine that performs a VLAN or L2 operation the moment `TBL_CTRL` is written,
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fetches a MIB counter on `STAT_GET` and drops entries on `L2_TBL_FLUSH_CTRL`.
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Nothing ever reports busy, so a polling loop runs once. The header states the
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VLAN and L2 entry layouts independently of the firmware, so a test can hold
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what `rtl837x_port.c` writes against an independent statement of the layout.
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- **`env_tables.c`** carries the globals and leaf calls those two modules link
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against; **`stub/`** stands in for the two headers only a firmware build
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generates, so the harness needs no SDCC build first.
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- **`support.c` / `support.h`** mock the hardware edges: the 16-byte serial ring
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(`sbuf`), the command/history buffers, and the character-output sink
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(`write_char` etc.). Buffers are sized **exactly** as on target, so ASan
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redzones catch the same off-by-one overflows the 8051 hits.
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- Builds define **`RTLP_HOST_TEST`**, which hides the firmware's libc-named
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prototypes (`memset`/`strlen`/…) in `rtl837x_common.h` so they don't clash with
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glibc. Argument order matches libc, so on-host callers transparently use the C
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library. This guard is compiled out of normal firmware builds — zero on-target
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effect.
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- A **SIGALRM watchdog** (`watchdog_arm`) turns an infinite-loop bug into a fast
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test failure instead of a hung runner.
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## Current coverage
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| Test binary | TU under test | Findings exercised |
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|-------------|---------------|--------------------|
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| `test_cmd_editor` | `cmd_editor.c` | **C4** — full-line hang + `cmd_buffer` 1-byte overflow; basic entry & backspace regressions |
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| `test_port_tables` | `rtl837x_port.c` | VLAN entry layout and round trip, PVID register sharing, static multicast and management entries, per-port flush, trunk membership and hash seed |
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## Adding a test for another module
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1. Write `test_<module>.c` with `main()` driving the module's entry points and
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`CHECK(cond, msg)` assertions.
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2. Add any missing mocked symbols to `support.c` (only what the linker asks for).
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3. Add a target in the `Makefile` listing `test_<module>.c support.c ../<module>.c`.
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4. If the module calls a firmware libc-name (`memcpy`/`strcpy`/…), it will use the
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C library on host (compatible arg order); provide a `fw_*`-style mock only if
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the semantics differ in a way the test cares about.
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Good next targets (pure logic, high finding density): `cmd_parser.c` (C6/C8),
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the HTTP header parser in `httpd/httpd.c` (S1), `dhcp.c` (S5).
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