[PATCH v2 1/5] x86: use the correct function type in SYSCALL_DEFINE0

[Sami Tolvanen]

Although a syscall defined using SYSCALL_DEFINE0 doesn't accept
parameters, use the correct function type to avoid type mismatches
with Control-Flow Integrity (CFI) checking.

Signed-off-by: Sami Tolvanen <samitolva...@google.com>
Acked-by: Andy Lutomirski <l...@kernel.org>
---
 arch/x86/include/asm/syscall_wrapper.h | 23 ++++++++++++-----------
 1 file changed, 12 insertions(+), 11 deletions(-)

diff --git a/arch/x86/include/asm/syscall_wrapper.h 
b/arch/x86/include/asm/syscall_wrapper.h
index e046a405743d..90eb70df0b18 100644
--- a/arch/x86/include/asm/syscall_wrapper.h
+++ b/arch/x86/include/asm/syscall_wrapper.h
@@ -48,12 +48,13 @@
  * To keep the naming coherent, re-define SYSCALL_DEFINE0 to create an alias
  * named __ia32_sys_*()
  */
-#define SYSCALL_DEFINE0(sname)                                 \
-       SYSCALL_METADATA(_##sname, 0);                          \
-       asmlinkage long __x64_sys_##sname(void);                \
-       ALLOW_ERROR_INJECTION(__x64_sys_##sname, ERRNO);        \
-       SYSCALL_ALIAS(__ia32_sys_##sname, __x64_sys_##sname);   \
-       asmlinkage long __x64_sys_##sname(void)
+
+#define SYSCALL_DEFINE0(sname)                                         \
+       SYSCALL_METADATA(_##sname, 0);                                  \
+       asmlinkage long __x64_sys_##sname(const struct pt_regs *__unused);\
+       ALLOW_ERROR_INJECTION(__x64_sys_##sname, ERRNO);                \
+       SYSCALL_ALIAS(__ia32_sys_##sname, __x64_sys_##sname);           \
+       asmlinkage long __x64_sys_##sname(const struct pt_regs *__unused)
 
 #define COND_SYSCALL(name)                                             \
        cond_syscall(__x64_sys_##name);                                 \
@@ -181,11 +182,11 @@
  * macros to work correctly.
  */
 #ifndef SYSCALL_DEFINE0
-#define SYSCALL_DEFINE0(sname)                                 \
-       SYSCALL_METADATA(_##sname, 0);                          \
-       asmlinkage long __x64_sys_##sname(void);                \
-       ALLOW_ERROR_INJECTION(__x64_sys_##sname, ERRNO);        \
-       asmlinkage long __x64_sys_##sname(void)
+#define SYSCALL_DEFINE0(sname)                                         \
+       SYSCALL_METADATA(_##sname, 0);                                  \
+       asmlinkage long __x64_sys_##sname(const struct pt_regs *__unused);\
+       ALLOW_ERROR_INJECTION(__x64_sys_##sname, ERRNO);                \
+       asmlinkage long __x64_sys_##sname(const struct pt_regs *__unused)
 #endif
 
 #ifndef COND_SYSCALL
-- 
2.23.0.351.gc4317032e6-goog