riscv/vdso: Refactor asm/vdso.h

The asm/vdso.h will be included in vdso.lds.S in the next patch, the
following cleanup is needed to avoid syntax error:

 1.the declaration of sys_riscv_flush_icache() is moved into asm/syscall.h.
 2.the definition of struct vdso_data is moved into kernel/vdso.c.
 2.the definition of VDSO_SYMBOL is placed under "#ifndef __ASSEMBLY__".

Also remove the redundant linux/types.h include.
Signed-off-by: Tong Tiangen <tongtiangen@huawei.com>
Reviewed-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

arch/riscv/include/asm/syscall.h

@@ -82,4 +82,5 @@ static inline int syscall_get_arch(struct task_struct *task)
 #endif
 }
 
+asmlinkage long sys_riscv_flush_icache(uintptr_t, uintptr_t, uintptr_t);
 #endif	/* _ASM_RISCV_SYSCALL_H */

arch/riscv/include/asm/vdso.h

@@ -16,18 +16,22 @@
 #ifdef CONFIG_MMU
 
 #include <linux/types.h>
-#include <generated/vdso-offsets.h>
+/*
+ * All systems with an MMU have a VDSO, but systems without an MMU don't
+ * support shared libraries and therefor don't have one.
+ */
+#ifdef CONFIG_MMU
 
-#ifndef CONFIG_GENERIC_TIME_VSYSCALL
-struct vdso_data {
-};
-#endif
+#ifndef __ASSEMBLY__
+#include <generated/vdso-offsets.h>
 
 #define VDSO_SYMBOL(base, name)							\
 	(void __user *)((unsigned long)(base) + __vdso_##name##_offset)
 
 #endif /* CONFIG_MMU */
 
-asmlinkage long sys_riscv_flush_icache(uintptr_t, uintptr_t, uintptr_t);
+#endif /* !__ASSEMBLY__ */
+
+#endif /* CONFIG_MMU */
 
 #endif /* _ASM_RISCV_VDSO_H */

arch/riscv/kernel/syscall_table.c

@@ -7,7 +7,6 @@
 #include <linux/linkage.h>
 #include <linux/syscalls.h>
 #include <asm-generic/syscalls.h>
-#include <asm/vdso.h>
 #include <asm/syscall.h>
 
 #undef __SYSCALL

arch/riscv/kernel/vdso.c

@@ -12,10 +12,13 @@
 #include <linux/binfmts.h>
 #include <linux/err.h>
 #include <asm/page.h>
+#include <asm/vdso.h>
+
 #ifdef CONFIG_GENERIC_TIME_VSYSCALL
 #include <vdso/datapage.h>
 #else
-#include <asm/vdso.h>
+struct vdso_data {
+};
 #endif
 
 extern char vdso_start[], vdso_end[];