Commit a443bf6e authored Nov 14, 2017 by Kamalesh Babulal Committed by Michael Ellerman Dec 11, 2017

powerpc/modules: Add REL24 relocation support of livepatch symbols



Livepatch re-uses module loader function apply_relocate_add() to write
relocations, instead of managing them by arch-dependent
klp_write_module_reloc() function.

apply_relocate_add() doesn't understand livepatch symbols (marked with
SHN_LIVEPATCH symbol section index) and assumes them to be local
symbols by default for R_PPC64_REL24 relocation type. It fails with an
error, when trying to calculate offset with local_entry_offset():

  module_64: kpatch_meminfo: REL24 -1152921504897399800 out of range!

Whereas livepatch symbols are essentially SHN_UNDEF, should be called
via stub used for global calls. This issue can be fixed by teaching
apply_relocate_add() to handle both SHN_UNDEF/SHN_LIVEPATCH symbols
via the same stub. This patch extends SHN_UNDEF code to handle
livepatch symbols too.

Signed-off-by: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

parent 5138b314

arch/powerpc/kernel/module_64.c

+2 −1

Original line number	Original line	Diff line number	Diff line
	@@ -614,7 +614,8 @@ int apply_relocate_add(Elf64_Shdr *sechdrs,

	case R_PPC_REL24:		case R_PPC_REL24:
	/* FIXME: Handle weak symbols here --RR */		/* FIXME: Handle weak symbols here --RR */
	if (sym->st_shndx == SHN_UNDEF) {		if (sym->st_shndx == SHN_UNDEF \|\|
			sym->st_shndx == SHN_LIVEPATCH) {
	/* External: go via stub */		/* External: go via stub */
	value = stub_for_addr(sechdrs, value, me);		value = stub_for_addr(sechdrs, value, me);
	if (!value)		if (!value)