Patch "riscv: ftrace: Remove wasted nops for !RISCV_ISA_C" has been added to the 5.15-stable tree

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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



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