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Message-Id: <20230107133549.4192639-3-guoren@kernel.org>
Date: Sat, 7 Jan 2023 08:35:44 -0500
From: guoren@...nel.org
To: anup@...infault.org, paul.walmsley@...ive.com, palmer@...belt.com,
conor.dooley@...rochip.com, heiko@...ech.de, rostedt@...dmis.org,
mhiramat@...nel.org, jolsa@...hat.com, bp@...e.de,
jpoimboe@...nel.org, suagrfillet@...il.com, andy.chiu@...ive.com,
e.shatokhin@...ro.com, guoren@...nel.org
Cc: linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
Guo Ren <guoren@...ux.alibaba.com>
Subject: [PATCH -next V6 2/7] riscv: ftrace: Remove wasted nops for !RISCV_ISA_C
From: Guo Ren <guoren@...ux.alibaba.com>
When CONFIG_RISCV_ISA_C=n, -fpatchable-function-entry=8 would generate
more nops than we expect. Because it treat nop opcode as 0x00000013
instead of 0x0001.
Dump of assembler code for function dw_pcie_free_msi:
0xffffffff806fce94 <+0>: sd ra,-8(sp)
0xffffffff806fce98 <+4>: auipc ra,0xff90f
0xffffffff806fce9c <+8>: jalr -684(ra) # 0xffffffff8000bbec
<ftrace_caller>
0xffffffff806fcea0 <+12>: ld ra,-8(sp)
0xffffffff806fcea4 <+16>: nop /* wasted */
0xffffffff806fcea8 <+20>: nop /* wasted */
0xffffffff806fceac <+24>: nop /* wasted */
0xffffffff806fceb0 <+28>: nop /* wasted */
0xffffffff806fceb4 <+0>: addi sp,sp,-48
0xffffffff806fceb8 <+4>: sd s0,32(sp)
0xffffffff806fcebc <+8>: sd s1,24(sp)
0xffffffff806fcec0 <+12>: sd s2,16(sp)
0xffffffff806fcec4 <+16>: sd s3,8(sp)
0xffffffff806fcec8 <+20>: sd ra,40(sp)
0xffffffff806fcecc <+24>: addi s0,sp,48
Signed-off-by: Guo Ren <guoren@...ux.alibaba.com>
Signed-off-by: Guo Ren <guoren@...nel.org>
---
arch/riscv/Makefile | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/arch/riscv/Makefile b/arch/riscv/Makefile
index 12d91b0a73d8..ea5a91da6897 100644
--- a/arch/riscv/Makefile
+++ b/arch/riscv/Makefile
@@ -11,7 +11,11 @@ LDFLAGS_vmlinux :=
ifeq ($(CONFIG_DYNAMIC_FTRACE),y)
LDFLAGS_vmlinux := --no-relax
KBUILD_CPPFLAGS += -DCC_USING_PATCHABLE_FUNCTION_ENTRY
+ifeq ($(CONFIG_RISCV_ISA_C),y)
CC_FLAGS_FTRACE := -fpatchable-function-entry=8
+else
+ CC_FLAGS_FTRACE := -fpatchable-function-entry=4
+endif
endif
ifeq ($(CONFIG_CMODEL_MEDLOW),y)
--
2.36.1
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