x86: livepatch: Treat R_X86_64_PLT32 as R_X86_64_PC32

Signed-off-by: chenzefeng <[email protected]>

On x86-64, for 32-bit PC-relacive branches, we can generate PLT32
relocation, instead of PC32 relocation. and R_X86_64_PLT32 can be
treated the same as R_X86_64_PC32 since linux kernel doesn't use PLT.

commit b21ebf2 ("x86: Treat R_X86_64_PLT32 as R_X86_64_PC32") been
fixed for the module loading, but not fixed for livepatch relocation,
which will fail to load livepatch with the error message as follow:
relocation failed for symbol <symbol name> at <symbol address>

This issue only effacted the kernel version from 4.0 to 4.6, becauce the
function klp_write_module_reloc is introduced by: commit b700e7f
("livepatch: kernel: add support for live patching") and deleted by:
commit 425595a ("livepatch: reuse module loader code to write
relocations")

Signed-off-by: chenzefeng <[email protected]>
Reviewed-by: Petr Mladek <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

arch/x86/kernel/livepatch.c

@@ -58,6 +58,7 @@ int klp_write_module_reloc(struct module *mod, unsigned long type,
 		val = (s32)value;
 		break;
 	case R_X86_64_PC32:
+	case R_X86_64_PLT32:
 		val = (u32)(value - loc);
 		break;
 	default: