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powerpc/modules: Add REL24 relocation support of livepatch symbols

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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>
This commit is contained in:
Kamalesh Babulal 2017-11-14 04:29:08 -05:00 committed by Michael Ellerman
parent 5138b31422
commit a443bf6e8a
1 changed files with 2 additions and 1 deletions
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3
arch/powerpc/kernel/module_64.c
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@ -614,7 +614,8 @@ int apply_relocate_add(Elf64_Shdr *sechdrs,
case R_PPC_REL24:
/* 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 */
value = stub_for_addr(sechdrs, value, me);
if (!value)