# Re: \[PATCH v3 3/5\] arch: Register fchmodat4, usually as syscall 451

- From: Arnd Bergmann \<arnd@arndb.de\>
- Date: 2023-07-11 11:32:12 
- List: linux-api
- Page: https://ratatoskr.run/linux-api/2023/07/255188
- Thread: https://ratatoskr.run/linux-api/2020/06/181723/t.md

```text
On Tue, Jul 11, 2023, at 13:25, Alexey Gladkov wrote:
> From: Palmer Dabbelt <redacted>
>
> This registers the new fchmodat4 syscall in most places as nuber 451,
> with alpha being the exception where it's 561.  I found all these sites
> by grepping for fspick, which I assume has found me everything.
>
> Signed-off-by: Palmer Dabbelt <redacted>
> Signed-off-by: Alexey Gladkov <legion@kernel.org>

In linux-6.5-rc1, number 451 is used for __NR_cachestat, the
next free one at the moment is 452.

>  arch/arm/tools/syscall.tbl                  | 1 +
>  arch/arm64/include/asm/unistd32.h           | 2 ++

Unfortunately, you still also need to change __NR_compat_syscalls
in arch/arm64/include/asm/unistd.h. Aside from these two issues,
your patch is the correct way to hook up a new syscall.

   Arnd
```