| Message ID | 20220926064316.765967-4-bgray@linux.ibm.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | Out-of-line static calls for powerpc64 ELF V2 | expand |
Le 26/09/2022 à 08:43, 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, 13 insertions(+) > > diff --git a/arch/powerpc/kernel/module_64.c b/arch/powerpc/kernel/module_64.c > index 4d816f7785b4..745ce9097dcf 100644 > --- a/arch/powerpc/kernel/module_64.c > +++ b/arch/powerpc/kernel/module_64.c > @@ -141,6 +141,12 @@ static u32 ppc64_stub_insns[] = { > PPC_RAW_BCTR(), > }; > > +#ifdef CONFIG_PPC64_ELF_ABI_V1 > +#define PPC64_STUB_MTCTR_OFFSET 5 > +#else > +#define PPC64_STUB_MTCTR_OFFSET 4 > +#endif > + > /* Count how many different 24-bit relocations (different symbol, > different addend) */ > static unsigned int count_relocs(const Elf64_Rela *rela, unsigned int num) > @@ -429,6 +435,8 @@ static inline int create_stub(const Elf64_Shdr *sechdrs, > long reladdr; > func_desc_t desc; > int i; > + u32 *jump_seq_addr = &entry->jump[PPC64_STUB_MTCTR_OFFSET]; > + ppc_inst_t direct; > > if (is_mprofile_ftrace_call(name)) > return create_ftrace_stub(entry, addr, me); > @@ -439,6 +447,11 @@ static inline int create_stub(const Elf64_Shdr *sechdrs, > return 0; > } > > + /* Replace indirect branch sequence with direct branch where possible */ > + if (!create_branch(&direct, jump_seq_addr, addr, 0)) > + if (patch_instruction(jump_seq_addr, direct)) Why not use patch_branch() ? > + return 0; > + > /* Stub uses address relative to r2. */ > reladdr = (unsigned long)entry - my_r2(sechdrs, me); > if (reladdr > 0x7FFFFFFF || reladdr < -(0x80000000L)) {
On Mon, 2022-09-26 at 14:49 +0000, Christophe Leroy wrote: > > + /* Replace indirect branch sequence with direct branch > > where possible */ > > + if (!create_branch(&direct, jump_seq_addr, addr, 0)) > > + if (patch_instruction(jump_seq_addr, direct)) > > Why not use patch_branch() ? I didn't think of it at the time. To get the same abort-if-patch-failed semantics then the following should work int err; ... /* Replace indirect branch sequence with direct branch where * possible */ err = patch_branch(&entry->jump[PPC64_STUB_MTCTR_OFFSET], addr, 0); if (err && err != -ERANGE) return 0; >
diff --git a/arch/powerpc/kernel/module_64.c b/arch/powerpc/kernel/module_64.c index 4d816f7785b4..745ce9097dcf 100644 --- a/arch/powerpc/kernel/module_64.c +++ b/arch/powerpc/kernel/module_64.c @@ -141,6 +141,12 @@ static u32 ppc64_stub_insns[] = { PPC_RAW_BCTR(), }; +#ifdef CONFIG_PPC64_ELF_ABI_V1 +#define PPC64_STUB_MTCTR_OFFSET 5 +#else +#define PPC64_STUB_MTCTR_OFFSET 4 +#endif + /* Count how many different 24-bit relocations (different symbol, different addend) */ static unsigned int count_relocs(const Elf64_Rela *rela, unsigned int num) @@ -429,6 +435,8 @@ static inline int create_stub(const Elf64_Shdr *sechdrs, long reladdr; func_desc_t desc; int i; + u32 *jump_seq_addr = &entry->jump[PPC64_STUB_MTCTR_OFFSET]; + ppc_inst_t direct; if (is_mprofile_ftrace_call(name)) return create_ftrace_stub(entry, addr, me); @@ -439,6 +447,11 @@ static inline int create_stub(const Elf64_Shdr *sechdrs, return 0; } + /* Replace indirect branch sequence with direct branch where possible */ + if (!create_branch(&direct, jump_seq_addr, addr, 0)) + if (patch_instruction(jump_seq_addr, direct)) + return 0; + /* Stub uses address relative to r2. */ reladdr = (unsigned long)entry - my_r2(sechdrs, me); if (reladdr > 0x7FFFFFFF || reladdr < -(0x80000000L)) {
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, 13 insertions(+)