add vsyscall

- getcpu() is not implemented. It will cause SIGILL.
- gettimeofday() and time() are implemented with syscall.

kernel/config/attached-mic.lds

@@ -20,6 +20,19 @@ SECTIONS
 	.rodata : {
 	      *(.rodata .rodata.*)
 	} :data
+
+	.vsyscall : ALIGN(0x1000) {
+		vsyscall_page = .;
+
+		. = vsyscall_page + 0x000;
+		*(.vsyscall.gettimeofday)
+
+		. = vsyscall_page + 0x400;
+		*(.vsyscall.time)
+
+		. = ALIGN(4096);
+	} : data = 0xf4
+
     .bss : {
           *(.bss .bss.*)
     }

kernel/config/builtin-mic.lds

@@ -20,6 +20,19 @@ SECTIONS
 	.rodata : {
 	      *(.rodata .rodata.*)
 	} :data
+
+	.vsyscall : ALIGN(0x1000) {
+		vsyscall_page = .;
+
+		. = vsyscall_page + 0x000;
+		*(.vsyscall.gettimeofday)
+
+		. = vsyscall_page + 0x400;
+		*(.vsyscall.time)
+
+		. = ALIGN(4096);
+	} : data = 0xf4
+
     .bss : {
           *(.bss .bss.*)
     }

kernel/config/builtin-x86.lds

@@ -20,6 +20,19 @@ SECTIONS
 	.rodata : {
 	      *(.rodata .rodata.*)
 	} :data
+
+	.vsyscall : ALIGN(0x1000) {
+		vsyscall_page = .;
+
+		. = vsyscall_page + 0x000;
+		*(.vsyscall.gettimeofday)
+
+		. = vsyscall_page + 0x400;
+		*(.vsyscall.time)
+
+		. = ALIGN(4096);
+	} : data = 0xf4
+
     .bss : {
           *(.bss .bss.*)
     }

kernel/include/syscall.h

@@ -13,6 +13,7 @@
 #ifndef __HEADER_SYSCALL_H
 #define __HEADER_SYSCALL_H
 
+#include <ihk/context.h>
 #include <ihk/memconst.h>
 
 #define NUM_SYSCALLS 255