kexec: new syscall kexec_file_load() declaration

This is the new syscall kexec_file_load() declaration/interface.  I have
reserved the syscall number only for x86_64 so far.  Other architectures
(including i386) can reserve syscall number when they enable the support
for this new syscall.
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Matthew Garrett <mjg59@srcf.ucam.org>
Cc: Greg Kroah-Hartman <greg@kroah.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: WANG Chao <chaowang@redhat.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/x86/syscalls/syscall_64.tbl

@@ -326,6 +326,7 @@
 317	common	seccomp			sys_seccomp
 318	common	getrandom		sys_getrandom
 319	common	memfd_create		sys_memfd_create
+320	common	kexec_file_load		sys_kexec_file_load
 
 #
 # x32-specific system call numbers start at 512 to avoid cache impact

include/linux/syscalls.h

@@ -317,6 +317,10 @@ asmlinkage long sys_restart_syscall(void);
 asmlinkage long sys_kexec_load(unsigned long entry, unsigned long nr_segments,
 				struct kexec_segment __user *segments,
 				unsigned long flags);
+asmlinkage long sys_kexec_file_load(int kernel_fd, int initrd_fd,
+				    unsigned long cmdline_len,
+				    const char __user *cmdline_ptr,
+				    unsigned long flags);
 
 asmlinkage long sys_exit(int error_code);
 asmlinkage long sys_exit_group(int error_code);

kernel/kexec.c

@@ -1058,6 +1058,13 @@ COMPAT_SYSCALL_DEFINE4(kexec_load, compat_ulong_t, entry,
 }
 #endif
 
+SYSCALL_DEFINE5(kexec_file_load, int, kernel_fd, int, initrd_fd,
+		unsigned long, cmdline_len, const char __user *, cmdline_ptr,
+		unsigned long, flags)
+{
+	return -ENOSYS;
+}
+
 void crash_kexec(struct pt_regs *regs)
 {
 	/* Take the kexec_mutex here to prevent sys_kexec_load

kernel/sys_ni.c

@@ -25,6 +25,7 @@ cond_syscall(sys_swapon);
 cond_syscall(sys_swapoff);
 cond_syscall(sys_kexec_load);
 cond_syscall(compat_sys_kexec_load);
+cond_syscall(sys_kexec_file_load);
 cond_syscall(sys_init_module);
 cond_syscall(sys_finit_module);
 cond_syscall(sys_delete_module);