[PATCH v2] sys_personality: Add a optional arch hook arch_check_personality()

[Wang ShaoBo]

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

Signed-off-by: Wang ShaoBo <bobo.shaobowang@xxxxxxxxxx>
---
 arch/arm64/kernel/sys.c |  6 +++---
 kernel/exec_domain.c    | 11 +++++++++++
 2 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/kernel/sys.c b/arch/arm64/kernel/sys.c
index d5ffaaab31a7..751fbd57eb1e 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);
@@ -46,7 +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 *);
diff --git a/kernel/exec_domain.c b/kernel/exec_domain.c
index f7a0512ddc23..d1d5d14441e2 100644
--- a/kernel/exec_domain.c
+++ b/kernel/exec_domain.c
@@ -35,7 +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)
 {
+	int check;
+
+	check = arch_check_personality(personality);
+	if (check)
+		return check;
+
 	return ksys_personality(personality);
 }
-- 
2.20.1