jingfei195887 opened a new pull request, #21770:
URL: https://github.com/apache/nuttx/pull/21770
## Summary
- **fs/shm: round the shm buffer up to a page for mmap().**
Without an MMU, `shmfs_mmap()` hands out the object buffer directly and
rejects a mapping longer than the object, because it would run into the
neighbouring heap memory. That also rejects the common POSIX sequence
`ftruncate(fd, size)` followed by `mmap()` of a whole page
(`sysconf(_SC_PAGESIZE)`) whenever `size` is not a page multiple:
`mmap()` fails with `EINVAL`. The buffer of a FLAT or PROTECTED build is
now allocated in whole pages, and a mapping up to the page-rounded size is
accepted.
- **fs/shm: fix nxstyle error.** A pre-existing missing blank line in
`shmfs_free_object()` that `checkpatch.sh` reports on the touched file.
## Impact
FLAT and PROTECTED builds with `CONFIG_FS_SHMFS`: an shm object costs up to
one page minus one byte of extra heap, and page-sized mappings of small
objects now succeed. A mapping beyond the rounded size is still rejected.
KERNEL builds already allocate whole pages and are unchanged.
## Testing
Host: Ubuntu x86_64, gcc (Ubuntu 13.1.0-8ubuntu1~22.04) 13.1.0, master
dc9481383e, `sim:nsh` with
`CONFIG_FS_SHMFS`. A test program creates a 100-byte shm object with
`shm_open()` + `ftruncate()` and maps it:
| step | master | this PR |
|---|---|---|
| `mmap(pagesize)` (pagesize = 256 on sim) | EINVAL | ok |
| `mmap(pagesize + 1)` | EINVAL | EINVAL |
- `./tools/checkpatch.sh -g master..HEAD`: all checks pass.
- Make and CMake builds pass with no new warnings; `ostest` exits with
status 0.
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