Re: [PATCH] Implement leftpad syscall

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)