[PATCH] x86: livepatch: Treat R_X86_64_PLT32 as R_X86_64_PC32

["chenzefeng (A)" <chenzefeng2@huawei.com>]

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 b21ebf2fb4cd ("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 b700e7f03df5 ("livepatch: kernel: add support for live patching") and deleted by: commit 425595a7fc20
("livepatch: reuse module loader code to write relocations")

Signed-off-by: chenzefeng <chenzefeng2@huawei.com>
---
 arch/x86/kernel/livepatch.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/kernel/livepatch.c b/arch/x86/kernel/livepatch.c index d1d35cc..579f8f8 100644
--- a/arch/x86/kernel/livepatch.c
+++ b/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:
--
1.8.5.6