linux-user, x86_64: add syscall table generation support

Copy syscall_64.tbl and syscallhdr.sh from linux/arch/x86/kernel/syscalls v5.5
Update syscallhdr.sh to generate QEMU syscall_nr.h

Signed-off-by: Laurent Vivier <laurent@vivier.eu>
Reviewed-by: Taylor Simpson <tsimpson@quicinc.com>
Message-Id: <20200310103403.3284090-16-laurent@vivier.eu>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>

configure

@@ -1890,7 +1890,7 @@ rm -f */config-devices.mak.d
 # Remove syscall_nr.h to be sure they will be regenerated in the build
 # directory, not in the source directory
 for arch in alpha hppa m68k xtensa sh4 microblaze arm ppc s390x sparc sparc64 \
-    i386 ; do
+    i386 x86_64 ; do
     # remove the file if it has been generated in the source directory
     rm -f "${source_path}/linux-user/${arch}/syscall_nr.h"
     # remove the dependency files
@@ -7792,6 +7792,7 @@ case "$target_name" in
   ;;
   x86_64)
     TARGET_BASE_ARCH=i386
+    TARGET_SYSTBL_ABI=common,64
     mttcg="yes"
 	gdb_xml_files="i386-64bit.xml"
   ;;

linux-user/Makefile.objs

@@ -19,4 +19,5 @@ obj-$(TARGET_S390X) += s390x/
 obj-$(TARGET_SH4) += sh4/
 obj-$(TARGET_SPARC) += sparc/
 obj-$(TARGET_SPARC64) += $(TARGET_ABI_DIR)/
+obj-$(TARGET_X86_64) += x86_64/
 obj-$(TARGET_XTENSA) += xtensa/

linux-user/x86_64/Makefile.objs

@@ -0,0 +1,5 @@
+generated-files-y += linux-user/x86_64/syscall_nr.h
+
+syshdr := $(SRC_PATH)/linux-user/x86_64/syscallhdr.sh
+%/syscall_nr.h: $(SRC_PATH)/linux-user/x86_64/syscall_64.tbl $(syshdr)
+	$(call quiet-command, sh $(syshdr) $< $@ $(TARGET_SYSTBL_ABI),"GEN","$@")