Message ID | 20220916062330.430468-4-bgray@linux.ibm.com (mailing list archive) |
---|---|
State | Superseded |
Headers | show |
Series | Out-of-line static calls for powerpc64 ELF V2 | expand |
Le 16/09/2022 à 08:23, Benjamin Gray a écrit : > 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 <bgray@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; Add blank line here. > + if (create_branch(&direct, (void*) entry + (i * 4), addr, 0) == 0) { No braces for single lines if statement. > + inst = direct; > + } > + } > + > + if (patch_instruction(&entry->jump[i], inst)) > return 0; > } >
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; }
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 <bgray@linux.ibm.com> --- arch/powerpc/kernel/module_64.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-)