s390: enable HAVE_FUNCTION_ERROR_INJECTION

This kernel feature is required for enabling BPF_KPROBE_OVERRIDE.

Define override_function_with_return() and regs_set_return_value()
functions, and fix compile errors in syscall_wrapper.h.
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

arch/s390/Kconfig

@@ -145,6 +145,7 @@ config S390
 	select HAVE_EFFICIENT_UNALIGNED_ACCESS
 	select HAVE_FENTRY
 	select HAVE_FTRACE_MCOUNT_RECORD
+	select HAVE_FUNCTION_ERROR_INJECTION
 	select HAVE_FUNCTION_GRAPH_TRACER
 	select HAVE_FUNCTION_TRACER
 	select HAVE_FUTEX_CMPXCHG if FUTEX

arch/s390/include/asm/ptrace.h

@@ -184,5 +184,10 @@ static inline unsigned long kernel_stack_pointer(struct pt_regs *regs)
 	return regs->gprs[15];
 }
 
+static inline void regs_set_return_value(struct pt_regs *regs, unsigned long rc)
+{
+	regs->gprs[2] = rc;
+}
+
 #endif /* __ASSEMBLY__ */
 #endif /* _S390_PTRACE_H */

arch/s390/include/asm/syscall_wrapper.h

@@ -30,7 +30,7 @@
 })
 
 #define __S390_SYS_STUBx(x, name, ...)					\
-	asmlinkage long __s390_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__))\
+	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__))\
 	{								\
@@ -46,7 +46,7 @@
 #define COMPAT_SYSCALL_DEFINE0(sname)					\
 	SYSCALL_METADATA(_##sname, 0);					\
 	asmlinkage long __s390_compat_sys_##sname(void);		\
-	ALLOW_ERROR_INJECTION(__s390_compat__sys_##sname, ERRNO);	\
+	ALLOW_ERROR_INJECTION(__s390_compat_sys_##sname, ERRNO);	\
 	asmlinkage long __s390_compat_sys_##sname(void)
 
 #define SYSCALL_DEFINE0(sname)						\
@@ -72,7 +72,7 @@
 	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);				\
+	ALLOW_ERROR_INJECTION(__s390_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__))	\

arch/s390/lib/Makefile

@@ -14,3 +14,5 @@ KASAN_SANITIZE_uaccess.o := n
 
 obj-$(CONFIG_S390_UNWIND_SELFTEST) += test_unwind.o
 CFLAGS_test_unwind.o += -fno-optimize-sibling-calls
+
+lib-$(CONFIG_FUNCTION_ERROR_INJECTION) += error-inject.o

arch/s390/lib/error-inject.c

+// SPDX-License-Identifier: GPL-2.0+
+#include <asm/ptrace.h>
+#include <linux/error-injection.h>
+#include <linux/kprobes.h>
+
+void override_function_with_return(struct pt_regs *regs)
+{
+	/*
+	 * Emulate 'br 14'. 'regs' is captured by kprobes on entry to some
+	 * kernel function.
+	 */
+	regs->psw.addr = regs->gprs[14];
+}
+NOKPROBE_SYMBOL(override_function_with_return);