[PATCH 12/18] kernel: add ksys_personality()

[Mark Rutland]

Using this helper allows us to avoid the in-kernel call to the
sys_personality() syscall. The ksys_ prefix denotes that this function
is meant as a drop-in replacement for the syscall. In particular, it
uses the same calling convention as sys_personality().

This is necessary to enable conversion of arm64's syscall handling to
use pt_regs wrappers.

Signed-off-by: Mark Rutland <mark.rutland@xxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Dominik Brodowski <linux@xxxxxxxxxxxxxxxxxxxx>
---
 include/linux/syscalls.h | 1 +
 kernel/exec_domain.c     | 7 ++++++-
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index 70fcda1a9049..6723ea51ec99 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -1148,6 +1148,7 @@ unsigned long ksys_mmap_pgoff(unsigned long addr, unsigned long len,
 			      unsigned long prot, unsigned long flags,
 			      unsigned long fd, unsigned long pgoff);
 ssize_t ksys_readahead(int fd, loff_t offset, size_t count);
+unsigned int ksys_personality(unsigned int personality);
 
 /*
  * The following kernel syscall equivalents are just wrappers to fs-internal
diff --git a/kernel/exec_domain.c b/kernel/exec_domain.c
index a5697119290e..4ba2b404cba2 100644
--- a/kernel/exec_domain.c
+++ b/kernel/exec_domain.c
@@ -47,7 +47,7 @@ static int __init proc_execdomains_init(void)
 module_init(proc_execdomains_init);
 #endif
 
-SYSCALL_DEFINE1(personality, unsigned int, personality)
+unsigned int ksys_personality(unsigned int personality)
 {
 	unsigned int old = current->personality;
 
@@ -56,3 +56,8 @@ SYSCALL_DEFINE1(personality, unsigned int, personality)
 
 	return old;
 }
+
+SYSCALL_DEFINE1(personality, unsigned int, personality)
+{
+	return ksys_personality(personality);
+}
-- 
2.11.0