Re: [PATCH] riscv: ftrace: only use pre-function NOPs with call ops

Commit c217157bcd1d ("riscv: Implement
HAVE_DYNAMIC_FTRACE_WITH_CALL_OPS") changed CC_FLAGS_FTRACE to use
-fpatchable-function-entry=8,4 or -fpatchable-function-entry=4,2
for all dynamic ftrace builds. That layout makes the compiler place an
8-byte area before the function entry, which is used as the per-callsite
ftrace_ops literal when CONFIG_DYNAMIC_FTRACE_WITH_CALL_OPS is enabled.

RISC-V can still build with CONFIG_DYNAMIC_FTRACE=y and
CONFIG_DYNAMIC_FTRACE_WITH_CALL_OPS=n, for example when
CONFIG_CFI_CLANG is enabled because HAVE_DYNAMIC_FTRACE_WITH_CALL_OPS
is selected only when !CFI_CLANG. In that configuration
ftrace_call_adjust() does not skip the pre-function literal area and
only returns addr + MCOUNT_AUIPC_SIZE. With the pre-function layout,
that points into the pre-entry padding instead of the callsite jalr, so
dynamic ftrace records the wrong patch address.

Use the pre-function literal layout only when call ops are enabled.
Otherwise keep the previous patchable-function-entry counts so the
recorded address matches ftrace_call_adjust() non-call-ops path.

Fixes: c217157bcd1d ("riscv: Implement HAVE_DYNAMIC_FTRACE_WITH_CALL_OPS")
Cc: stable@vger.kernel.org
Signed-off-by: Rui Qi <redacted>
---
 arch/riscv/Makefile | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/arch/riscv/Makefile b/arch/riscv/Makefile
index 3070c3874305..235730a243aa 100644
--- a/arch/riscv/Makefile
+++ b/arch/riscv/Makefile

@@ -14,11 +14,19 @@ endif
 ifeq ($(CONFIG_DYNAMIC_FTRACE),y)
 	LDFLAGS_vmlinux += --no-relax
 	KBUILD_CPPFLAGS += -DCC_USING_PATCHABLE_FUNCTION_ENTRY
+ifeq ($(CONFIG_DYNAMIC_FTRACE_WITH_CALL_OPS),y)
 ifeq ($(CONFIG_RISCV_ISA_C),y)
 	CC_FLAGS_FTRACE := -fpatchable-function-entry=8,4
 else
 	CC_FLAGS_FTRACE := -fpatchable-function-entry=4,2
 endif
+else
+ifeq ($(CONFIG_RISCV_ISA_C),y)
+	CC_FLAGS_FTRACE := -fpatchable-function-entry=4
+else
+	CC_FLAGS_FTRACE := -fpatchable-function-entry=2
+endif
+endif
 endif
 
 ifeq ($(CONFIG_CMODEL_MEDLOW),y)