[PATCH] sys_personality: Add a optional arch hook arch_check_personality() for common sys_personality()

[Wang ShaoBo <bobo.shaobowang@huawei.com>]

currently arm64 use __arm64_sys_arm64_personality() as its default
syscall. But using a normal hook arch_check_personality() can reject
personality settings for special case of different archs.

Signed-off-by: Wang ShaoBo <bobo.shaobowang@huawei.com>
---
 arch/arm64/kernel/sys.c |  7 +++----
 kernel/exec_domain.c    | 14 ++++++++++----
 2 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/arch/arm64/kernel/sys.c b/arch/arm64/kernel/sys.c
index d5ffaaab31a7..5c01816d7a77 100644
--- a/arch/arm64/kernel/sys.c
+++ b/arch/arm64/kernel/sys.c
@@ -28,12 +28,13 @@ SYSCALL_DEFINE6(mmap, unsigned long, addr, unsigned long, len,
 	return ksys_mmap_pgoff(addr, len, prot, flags, fd, off >> PAGE_SHIFT);
 }
 
-SYSCALL_DEFINE1(arm64_personality, unsigned int, personality)
+int arch_check_personality(unsigned int personality)
 {
 	if (personality(personality) == PER_LINUX32 &&
 		!system_supports_32bit_el0())
 		return -EINVAL;
-	return ksys_personality(personality);
+
+	return 0;
 }
 
 asmlinkage long sys_ni_syscall(void);
@@ -46,8 +47,6 @@ asmlinkage long __arm64_sys_ni_syscall(const struct pt_regs *__unused)
 /*
  * Wrappers to pass the pt_regs argument.
  */
-#define __arm64_sys_personality		__arm64_sys_arm64_personality
-
 #undef __SYSCALL
 #define __SYSCALL(nr, sym)	asmlinkage long __arm64_##sym(const struct pt_regs *);
 #include <asm/unistd.h>
diff --git a/kernel/exec_domain.c b/kernel/exec_domain.c
index 33f07c5f2515..d1d5d14441e2 100644
--- a/kernel/exec_domain.c
+++ b/kernel/exec_domain.c
@@ -35,12 +35,18 @@ static int __init proc_execdomains_init(void)
 module_init(proc_execdomains_init);
 #endif
 
+int __weak arch_check_personality(unsigned int personality)
+{
+	return 0;
+}
+
 SYSCALL_DEFINE1(personality, unsigned int, personality)
 {
-	unsigned int old = current->personality;
+	int check;
 
-	if (personality != 0xffffffff)
-		set_personality(personality);
+	check = arch_check_personality(personality);
+	if (check)
+		return check;
 
-	return old;
+	return ksys_personality(personality);
 }
-- 
2.20.1