Inserts a direct branch to the stub target when possible, replacing the
mtctr/btctr sequence.
The load into r12 could potentially be skipped too, but that change
would need to refactor the arguments to indicate that the address
does not have a separate local entry point.
This helps the static call implementation, where modules calling their
own trampolines are called through this stub and the trampoline is
easily within range of a direct branch.
Signed-off-by: Benjamin Gray <bg...@linux.ibm.com>
---
arch/powerpc/kernel/module_64.c | 13 +++++++++++--
1 file changed, 11 insertions(+), 2 deletions(-)
diff --git a/arch/powerpc/kernel/module_64.c b/arch/powerpc/kernel/module_64.c
index 3656476097c2..03ab28d86008 100644
--- a/arch/powerpc/kernel/module_64.c
+++ b/arch/powerpc/kernel/module_64.c
@@ -432,8 +432,17 @@ static inline int create_stub(const Elf64_Shdr *sechdrs,
return create_ftrace_stub(entry, addr, me);
for (i = 0; i < ARRAY_SIZE(ppc64_stub_insns); i++) {
- if (patch_instruction(&entry->jump[i],
- ppc_inst(ppc64_stub_insns[i])))
+ ppc_inst_t inst = ppc_inst(ppc64_stub_insns[i]);
+
+ // Replace the indirect branch with a direct branch where
possible
+ if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V2) && i == 4) {
+ ppc_inst_t direct;
+ if (create_branch(&direct, (void*) entry + (i * 4),
addr, 0) == 0) {
+ inst = direct;
+ }
+ }
+
+ if (patch_instruction(&entry->jump[i], inst))
return 0;
}
--
2.37.3
