s390/kaslr: add support for R_390_JMP_SLOT relocation type

With certain kernel configurations, the R_390_JMP_SLOT relocation type
might be generated, which is not expected by the KASLR relocation code,
and the kernel stops with the message "Unknown relocation type".

This was found with a zfcpdump kernel config, where CONFIG_MODULES=n
and CONFIG_VFIO=n. In that case, symbol_get() is used on undefined
__weak symbols in virt/kvm/vfio.c, which results in the generation
of R_390_JMP_SLOT relocation types.

Fix this by handling R_390_JMP_SLOT similar to R_390_GLOB_DAT.

Fixes: 805bc0bc ("s390/kernel: build a relocatable kernel")
Cc: <stable@vger.kernel.org> # v5.2+
Signed-off-by: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Reviewed-by: Philipp Rudo <prudo@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

arch/s390/kernel/machine_kexec_reloc.c

@@ -28,6 +28,7 @@ int arch_kexec_do_relocs(int r_type, void *loc, unsigned long val,
 		break;
 	case R_390_64:		/* Direct 64 bit.  */
 	case R_390_GLOB_DAT:
+	case R_390_JMP_SLOT:
 		*(u64 *)loc = val;
 		break;
 	case R_390_PC16:	/* PC relative 16 bit.	*/