s390/kexec_file: move kernel image size check

In preparation of adding support for command lines with variable
sizes on s390, the check whether the new kernel image is at least HEAD_END
bytes long isn't correct. Move the check to kexec_file_add_components()
so we can get the size of the parm area and check the size there.

The '.org HEAD_END' directive can now also be removed from head.S. This
was used in the past to reserve space for the early sccb buffer, but with
commit 9a5131b87cac1 ("s390/boot: move sclp early buffer from fixed address
in asm to C") this is no longer required.

Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

arch/s390/boot/head.S

@@ -400,5 +400,3 @@ SYM_DATA_START(parmarea)
 	.byte	0
 	.org	PARMAREA+__PARMAREA_SIZE
 SYM_DATA_END(parmarea)
-
-	.org	HEAD_END

arch/s390/include/asm/setup.h

@@ -11,7 +11,6 @@
 #include <linux/build_bug.h>
 
 #define PARMAREA		0x10400
-#define HEAD_END		0x11000
 
 /*
  * Machine features detected in early.c

arch/s390/kernel/machine_kexec_file.c

@@ -227,7 +227,8 @@ void *kexec_file_add_components(struct kimage *image,
 	if (ret)
 		goto out;
 
-	if (image->cmdline_buf_len >= ARCH_COMMAND_LINE_SIZE) {
+	if (image->kernel_buf_len < PARMAREA + sizeof(struct parmarea) ||
+	    image->cmdline_buf_len >= ARCH_COMMAND_LINE_SIZE) {
 		ret = -EINVAL;
 		goto out;
 	}
@@ -307,17 +308,3 @@ int arch_kexec_apply_relocations_add(struct purgatory_info *pi,
 	}
 	return 0;
 }
-
-int arch_kexec_kernel_image_probe(struct kimage *image, void *buf,
-				  unsigned long buf_len)
-{
-	/* A kernel must be at least large enough to contain head.S. During
-	 * load memory in head.S will be accessed, e.g. to register the next
-	 * command line. If the next kernel were smaller the current kernel
-	 * will panic at load.
-	 */
-	if (buf_len < HEAD_END)
-		return -ENOEXEC;
-
-	return kexec_image_probe_default(image, buf, buf_len);
-}