Re: [PATCH] Implement leftpad syscall

Frederic Weisbecker
2016-04-01T01:33:40Z

On Fri, Apr 01, 2016 at 12:33:32AM +0200, Richard Weinberger wrote:
> From: David Gstir <david@sigma-star.at>
>
> Implement the leftpad() system call such that userspace,
> especially node.js applications, can in the near future directly
> use it and no longer depend on fragile npm packages.
>
> Signed-off-by: David Gstir <david@sigma-star.at>
> Signed-off-by: Richard Weinberger <richard@nod.at>
> ---
> arch/x86/entry/syscalls/syscall_64.tbl | 1 +
> include/linux/syscalls.h | 1 +
> kernel/sys.c | 35 ++++++++++++++++++++++++++++++++++
> kernel/sys_ni.c | 1 +
> 4 files changed, 38 insertions(+)
>
> diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl
> index cac6d17..f287712 100644
> --- a/arch/x86/entry/syscalls/syscall_64.tbl
> +++ b/arch/x86/entry/syscalls/syscall_64.tbl
> @@ -335,6 +335,7 @@
> 326 common copy_file_range sys_copy_file_range
> 327 64 preadv2 sys_preadv2
> 328 64 pwritev2 sys_pwritev2
> +329 common leftpad sys_leftpad
>
> #
> # x32-specific system call numbers start at 512 to avoid cache impact
> diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
> index d795472..a0850bb 100644
> --- a/include/linux/syscalls.h
> +++ b/include/linux/syscalls.h
> @@ -898,4 +898,5 @@ asmlinkage long sys_copy_file_range(int fd_in, loff_t __user *off_in,
>
> asmlinkage long sys_mlock2(unsigned long start, size_t len, int flags);
>
> +asmlinkage long sys_leftpad(char *str, char pad, char *dst, size_t dst_len);
> #endif
> diff --git a/kernel/sys.c b/kernel/sys.c
> index cf8ba54..e42d972 100644
> --- a/kernel/sys.c
> +++ b/kernel/sys.c
> @@ -2432,3 +2432,38 @@ COMPAT_SYSCALL_DEFINE1(sysinfo, struct compat_sysinfo __user *, info)
> return 0;
> }
> #endif /* CONFIG_COMPAT */
> +
> +
> +SYSCALL_DEFINE4(leftpad, char *, src, char, pad, char *, dst, size_t, dst_len)

Have you considered /dev/leftpad instead?