maxikrie opened a new pull request, #21023:
URL: https://github.com/apache/nuttx/pull/21023
## Summary
`struct tcbinfo_s` is packed, so `g_tcbinfo` (const, placed in `.text`
on Cortex-M boards) can end up at an odd address, depending on what
else is linked. GDB reports such an address with bit 0 cleared, as if
it were Thumb code, and passes that to the J-Link GDB server when the
RTOS plugin asks for the symbol. `tools/jlink-nuttx.c` then reads every
offset one byte off.
nrf52840-dk, master b9d1d6a834, `nsh` + `DEBUG_SYMBOLS`, `FS_PROCFS`
with tcbinfo, `EXAMPLES_HELLO` (CMake):
```
$ readelf -s nuttx | grep g_tcbinfo
2309: 0001987b 24 OBJECT GLOBAL DEFAULT 1 g_tcbinfo
(gdb) p &g_tcbinfo
$1 = (const struct tcbinfo_s *) 0x1987a <g_tcbinfo>
(gdb) x/8hx 0x1987a <- what GDB and the plugin read
0x1987a: 0x3000 0x4000 0x3400 0x0000 0x7000 0x6800 0xb000 0x1100
(gdb) x/8hx 0x1987b <- the real g_tcbinfo
0x1987b: 0x0030 0x0040 0x0034 0x0000 0x0070 0x0068 0x00b0 0x0011
```
J-Link GDB server log: `Received symbol: g_tcbinfo (0x0001987A)`.
`info threads` shows the idle task with state 0 and priority 165, and
no `nsh_main` thread.
The fix aligns the type (`aligned_data(8)`, the way `bl602_dma.h` does
for a packed struct). All members are naturally aligned, so the layout
is unchanged (`ptype/o struct tcbinfo_s`: 24 bytes, same offsets),
and the J-Link plugin and the Python tools need no change.
This is likely what apache/nuttx#18109 is about: the plugin works or
not depending on where the linker puts `g_tcbinfo` (at an even
0x0802e940 in the stm32f429i-disco build used to try to reproduce it).
## Impact
Debuggers reading `g_tcbinfo` through GDB (J-Link RTOS plugin, nxgdb)
on Thumb targets. Up to 7 bytes of padding before `g_tcbinfo`; no
change to the structure's contents.
## Testing
nRF52840-DK, J-Link V9.82 GDB server with `tools/jlink-nuttx`,
gdb-multiarch 13.1:
| | master (g_tcbinfo at 0x1987b) | this PR (at 0x19880) |
|---|---|---|
| attach, `info threads` | Idle `[PRI:165]`, no nsh_main | Idle `[PRI:000]`,
nsh_main `[PRI:100]` |
| `thread 3`, `bt` | — | nsh_main in `nxsem_wait_slow()` on the console |
| break in `hello_main`, run `hello`, break in `up_idle` after it exits | —
| hello thread listed and selected at its breakpoint; after it exits GDB goes
on with the remaining threads |
`tools/checkpatch.sh -f include/nuttx/sched.h` passes; `sim:nsh` builds.
Fixes #18109 (probably; the reporter's board not tested).
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