s390: autogenerate compat syscall wrappers

Any system call that takes a pointer argument on s390 requires
a wrapper function to do a 31-to-64 zero-extension, these are
currently generated in arch/s390/kernel/compat_wrapper.c.

On arm64 and x86, we already generate similar wrappers for all
system calls in the place of their definition, just for a different
purpose (they load the arguments from pt_regs).

We can do the same thing here, by adding an asm/syscall_wrapper.h
file with a copy of all the relevant macros to override the generic
version. Besides the addition of the compat entry point, these also
rename the entry points with a __s390_ or __s390x_ prefix, similar
to what we do on arm64 and x86. This in turn requires renaming
a few things, and adding a proper ni_syscall() entry point.

In order to still compile system call definitions that pass an
loff_t argument, the __SC_COMPAT_CAST() macro checks for that
and forces an -ENOSYS error, which was the best I could come up
with. Those functions must obviously not get called from user
space, but instead require hand-written compat_sys_*() handlers,
which fortunately already exist.

Link: https://lore.kernel.org/lkml/20190116131527.2071570-5-arnd@arndb.de
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
[heiko.carstens@de.ibm.com: compile fix for !CONFIG_COMPAT]
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

3 files changed, 11 insertions, 21 deletions

diff --git a/arch/s390/kernel/compat_wrapper.c b/arch/s390/kernel/compat_wrapper.c
index f54b7b73f316..9d07cd553fc7 100644
--- a/arch/s390/kernel/compat_wrapper.c
+++ b/arch/s390/kernel/compat_wrapper.c
@@ -25,21 +25,6 @@
 #define __SC_COMPAT_TYPE(t, a) \
 	__typeof(__builtin_choose_expr(sizeof(t) > 4, 0L, (t)0)) a
 
-#define __SC_COMPAT_CAST(t, a)						\
-({									\
-	long __ReS = a;							\
-									\
-	BUILD_BUG_ON((sizeof(t) > 4) && !__TYPE_IS_L(t) &&		\
-		     !__TYPE_IS_UL(t) && !__TYPE_IS_PTR(t));		\
-	if (__TYPE_IS_L(t))						\
-		__ReS = (s32)a;						\
-	if (__TYPE_IS_UL(t))						\
-		__ReS = (u32)a;						\
-	if (__TYPE_IS_PTR(t))						\
-		__ReS = a & 0x7fffffff;					\
-	(t)__ReS;							\
-})
-
 /*
  * The COMPAT_SYSCALL_WRAP macro generates system call wrappers to be used by
  * compat tasks. These wrappers will only be used for system calls where only
@@ -53,11 +38,11 @@
  * the regular system call wrappers.
  */
 #define COMPAT_SYSCALL_WRAPx(x, name, ...)					\
-asmlinkage long sys##name(__MAP(x,__SC_DECL,__VA_ARGS__));			\
-asmlinkage long notrace compat_sys##name(__MAP(x,__SC_COMPAT_TYPE,__VA_ARGS__));\
-asmlinkage long notrace compat_sys##name(__MAP(x,__SC_COMPAT_TYPE,__VA_ARGS__))	\
+asmlinkage long __s390_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__));		\
+asmlinkage long notrace __s390_compat_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__));\
+asmlinkage long notrace __s390_compat_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__))	\
 {										\
-	return sys##name(__MAP(x,__SC_COMPAT_CAST,__VA_ARGS__));		\
+	return __s390_sys##name(__MAP(x,__SC_ARGS,__VA_ARGS__));		\
 }
 
 COMPAT_SYSCALL_WRAP2(creat, const char __user *, pathname, umode_t, mode);
diff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.S
index 39191a0feed1..583d65ef5007 100644
--- a/arch/s390/kernel/entry.S
+++ b/arch/s390/kernel/entry.S
@@ -1512,7 +1512,7 @@ cleanup_critical:
 	.quad   .Lsie_skip - .Lsie_entry
 #endif
 	.section .rodata, "a"
-#define SYSCALL(esame,emu)	.long esame
+#define SYSCALL(esame,emu)	.long __s390x_ ## esame
 	.globl	sys_call_table
 sys_call_table:
 #include "asm/syscall_table.h"
@@ -1520,7 +1520,7 @@ sys_call_table:
 
 #ifdef CONFIG_COMPAT
 
-#define SYSCALL(esame,emu)	.long emu
+#define SYSCALL(esame,emu)	.long __s390_ ## emu
 	.globl	sys_call_table_emu
 sys_call_table_emu:
 #include "asm/syscall_table.h"
diff --git a/arch/s390/kernel/sys_s390.c b/arch/s390/kernel/sys_s390.c
index fd0cbbed4d9f..202fa73ac167 100644
--- a/arch/s390/kernel/sys_s390.c
+++ b/arch/s390/kernel/sys_s390.c
@@ -95,3 +95,8 @@ SYSCALL_DEFINE1(s390_personality, unsigned int, personality)
 
 	return ret;
 }
+
+SYSCALL_DEFINE0(ni_syscall)
+{
+	return -ENOSYS;
+}