From: Benjamin Gray <bgray@linux.ibm.com>
To: linuxppc-dev@lists.ozlabs.org
Cc: christophe.leroy@c-s.fr, ajd@linux.ibm.com, peterz@infradead.org,
Benjamin Gray <bgray@linux.ibm.com>,
npiggin@gmail.com, ardb@kernel.org, jbaron@akamai.com,
rostedt@goodmis.org, jpoimboe@kernel.org
Subject: [PATCH v2 3/6] powerpc/module: Optimise nearby branches in ELF V2 ABI stub
Date: Mon, 26 Sep 2022 16:43:13 +1000 [thread overview]
Message-ID: <20220926064316.765967-4-bgray@linux.ibm.com> (raw)
In-Reply-To: <20220926064316.765967-1-bgray@linux.ibm.com>
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))
+ return 0;
+
/* Stub uses address relative to r2. */
reladdr = (unsigned long)entry - my_r2(sechdrs, me);
if (reladdr > 0x7FFFFFFF || reladdr < -(0x80000000L)) {
--
2.37.3
next prev parent reply other threads:[~2022-09-26 6:46 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-26 6:43 [PATCH v2 0/6] Out-of-line static calls for powerpc64 ELF V2 Benjamin Gray
2022-09-26 6:43 ` [PATCH v2 1/6] powerpc/code-patching: Implement generic text patching function Benjamin Gray
2022-09-26 8:56 ` kernel test robot
2022-09-26 13:28 ` kernel test robot
2022-09-26 14:33 ` Christophe Leroy
2022-09-27 2:57 ` Benjamin Gray
2022-09-27 5:54 ` Christophe Leroy
2022-09-27 6:40 ` Christophe Leroy
2022-09-28 1:30 ` Benjamin Gray
2022-09-28 10:52 ` Christophe Leroy
2022-09-27 7:30 ` Christophe Leroy
2022-09-26 6:43 ` [PATCH v2 2/6] powerpc/module: Handle caller-saved TOC in module linker Benjamin Gray
2022-09-26 6:43 ` Benjamin Gray [this message]
2022-09-26 14:49 ` [PATCH v2 3/6] powerpc/module: Optimise nearby branches in ELF V2 ABI stub Christophe Leroy
2022-09-27 3:12 ` Benjamin Gray
2022-09-26 6:43 ` [PATCH v2 4/6] static_call: Move static call selftest to static_call_selftest.c Benjamin Gray
2022-09-26 14:50 ` Christophe Leroy
2022-09-26 6:43 ` [PATCH v2 5/6] powerpc/64: Add support for out-of-line static calls Benjamin Gray
2022-09-26 13:16 ` Christophe Leroy
2022-09-27 5:18 ` Benjamin Gray
2022-09-27 6:07 ` Christophe Leroy
2022-09-26 14:54 ` Christophe Leroy
2022-09-27 3:21 ` Benjamin Gray
2022-09-27 6:01 ` Christophe Leroy
2022-09-26 6:43 ` [PATCH v2 6/6] powerpc/64: Add tests " Benjamin Gray
2022-09-26 14:55 ` Christophe Leroy
2022-09-27 3:31 ` Benjamin Gray
2022-09-27 6:05 ` Christophe Leroy
2022-09-26 14:19 ` [PATCH v2 0/6] Out-of-line static calls for powerpc64 ELF V2 Christophe Leroy
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