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>

1 files changed, 135 insertions, 0 deletions

diff --git a/arch/s390/include/asm/syscall_wrapper.h b/arch/s390/include/asm/syscall_wrapper.h
new file mode 100644
index 000000000000..5596c5c625d2
--- /dev/null
+++ b/arch/s390/include/asm/syscall_wrapper.h
@@ -0,0 +1,135 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * syscall_wrapper.h - s390 specific wrappers to syscall definitions
+ *
+ */
+
+#ifndef _ASM_S390_SYSCALL_WRAPPER_H
+#define _ASM_S390_SYSCALL_WRAPPER_H
+
+#ifdef CONFIG_COMPAT
+#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) &&		\
+		     !__TYPE_IS_LL(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;					\
+	if (__TYPE_IS_LL(t))						\
+		return -ENOSYS;						\
+	(t)__ReS;							\
+})
+
+#define __S390_SYS_STUBx(x, name, ...)					\
+	asmlinkage long __s390_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__))\
+	ALLOW_ERROR_INJECTION(__s390_sys##name, ERRNO);			\
+	asmlinkage long __s390_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__))\
+	{								\
+		long ret = __s390x_sys##name(__MAP(x,__SC_COMPAT_CAST,__VA_ARGS__));\
+		__MAP(x,__SC_TEST,__VA_ARGS__);				\
+		return ret;						\
+	}
+
+/*
+ * To keep the naming coherent, re-define SYSCALL_DEFINE0 to create an alias
+ * named __s390x_sys_*()
+ */
+#define COMPAT_SYSCALL_DEFINE0(sname)					\
+	SYSCALL_METADATA(_##sname, 0);					\
+	asmlinkage long __s390_compat_sys_##sname(void);		\
+	ALLOW_ERROR_INJECTION(__s390_compat__sys_##sname, ERRNO);	\
+	asmlinkage long __s390_compat_sys_##sname(void)
+
+#define SYSCALL_DEFINE0(sname)						\
+	SYSCALL_METADATA(_##sname, 0);					\
+	asmlinkage long __s390x_sys_##sname(void);			\
+	ALLOW_ERROR_INJECTION(__s390x_sys_##sname, ERRNO);		\
+	asmlinkage long __s390_sys_##sname(void)			\
+		__attribute__((alias(__stringify(__s390x_sys_##sname)))); \
+	asmlinkage long __s390x_sys_##sname(void)
+
+#define COND_SYSCALL(name)						\
+	cond_syscall(__s390x_sys_##name);				\
+	cond_syscall(__s390_sys_##name)
+
+#define SYS_NI(name)							\
+	SYSCALL_ALIAS(__s390x_sys_##name, sys_ni_posix_timers);		\
+	SYSCALL_ALIAS(__s390_sys_##name, sys_ni_posix_timers)
+
+#define COMPAT_SYSCALL_DEFINEx(x, name, ...)					\
+	__diag_push();								\
+	__diag_ignore(GCC, 8, "-Wattribute-alias",				\
+		      "Type aliasing is used to sanitize syscall arguments");\
+	asmlinkage long __s390_compat_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__));	\
+	asmlinkage long __s390_compat_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__))	\
+		__attribute__((alias(__stringify(__se_compat_sys##name))));	\
+	ALLOW_ERROR_INJECTION(compat_sys##name, ERRNO);				\
+	static inline long __do_compat_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__));\
+	asmlinkage long __se_compat_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__));	\
+	asmlinkage long __se_compat_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__))	\
+	{									\
+		long ret = __do_compat_sys##name(__MAP(x,__SC_DELOUSE,__VA_ARGS__));\
+		__MAP(x,__SC_TEST,__VA_ARGS__);					\
+		return ret;							\
+	}									\
+	__diag_pop();								\
+	static inline long __do_compat_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__))
+
+/*
+ * As some compat syscalls may not be implemented, we need to expand
+ * COND_SYSCALL_COMPAT in kernel/sys_ni.c and COMPAT_SYS_NI in
+ * kernel/time/posix-stubs.c to cover this case as well.
+ */
+#define COND_SYSCALL_COMPAT(name)					\
+	cond_syscall(__s390_compat_sys_##name)
+
+#define COMPAT_SYS_NI(name)						\
+	SYSCALL_ALIAS(__s390_compat_sys_##name, sys_ni_posix_timers)
+
+#else /* CONFIG_COMPAT */
+
+#define __S390_SYS_STUBx(x, fullname, name, ...)
+
+#define SYSCALL_DEFINE0(sname)						\
+	SYSCALL_METADATA(_##sname, 0);					\
+	asmlinkage long __s390x_sys_##sname(void);			\
+	ALLOW_ERROR_INJECTION(__s390x_sys_##sname, ERRNO);		\
+	asmlinkage long __s390x_sys_##sname(void)
+
+#define COND_SYSCALL(name)						\
+	cond_syscall(__s390x_sys_##name)
+
+#define SYS_NI(name)							\
+	SYSCALL_ALIAS(__s390x_sys_##name, sys_ni_posix_timers);
+
+#endif /* CONFIG_COMPAT */
+
+#define __SYSCALL_DEFINEx(x, name, ...)						\
+	__diag_push();								\
+	__diag_ignore(GCC, 8, "-Wattribute-alias",				\
+		      "Type aliasing is used to sanitize syscall arguments");\
+	asmlinkage long __s390x_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__))	\
+		__attribute__((alias(__stringify(__se_sys##name))));		\
+	ALLOW_ERROR_INJECTION(__s390x_sys##name, ERRNO);				\
+	static long __se_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__));		\
+	static inline long __do_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__));	\
+	__S390_SYS_STUBx(x, name, __VA_ARGS__)					\
+	asmlinkage long __se_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__))		\
+	{									\
+		long ret = __do_sys##name(__MAP(x,__SC_CAST,__VA_ARGS__));	\
+		__MAP(x,__SC_TEST,__VA_ARGS__);					\
+		return ret;							\
+	}									\
+	__diag_pop();								\
+	static inline long __do_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__))
+
+#endif /* _ASM_X86_SYSCALL_WRAPPER_H */