This is a note to let you know that I've just added the patch titled
riscv: ftrace: Remove wasted nops for !RISCV_ISA_C
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
riscv-ftrace-remove-wasted-nops-for-riscv_isa_c.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 409c8fb20c66df7150e592747412438c04aeb11f Mon Sep 17 00:00:00 2001
From: Guo Ren <guoren@xxxxxxxxxxxxxxxxx>
Date: Thu, 12 Jan 2023 04:05:58 -0500
Subject: riscv: ftrace: Remove wasted nops for !RISCV_ISA_C
From: Guo Ren <guoren@xxxxxxxxxxxxxxxxx>
commit 409c8fb20c66df7150e592747412438c04aeb11f upstream.
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@xxxxxxxxxxxxxxxxx>
Signed-off-by: Guo Ren <guoren@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20230112090603.1295340-3-guoren@xxxxxxxxxx
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Palmer Dabbelt <palmer@xxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/riscv/Makefile | 4 ++++
1 file changed, 4 insertions(+)
--- a/arch/riscv/Makefile
+++ b/arch/riscv/Makefile
@@ -13,7 +13,11 @@ 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)
Patches currently in stable-queue which might be from guoren@xxxxxxxxxxxxxxxxx are
queue-5.15/riscv-ftrace-remove-wasted-nops-for-riscv_isa_c.patch
queue-5.15/riscv-ftrace-reduce-the-detour-code-size-to-half.patch
