This is a note to let you know that I've just added the patch titled
RISC-V: Take text_mutex in ftrace_init_nop()
to the 4.19-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:
risc-v-take-text_mutex-in-ftrace_init_nop.patch
and it can be found in the queue-4.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 8457d9c578f3431d2508a57759130b7feb4bb365
Author: Palmer Dabbelt <palmerdabbelt@xxxxxxxxxx>
Date: Mon Aug 24 17:21:22 2020 -0700
RISC-V: Take text_mutex in ftrace_init_nop()
[ Upstream commit 66d18dbda8469a944dfec6c49d26d5946efba218 ]
Without this we get lockdep failures. They're spurious failures as SMP isn't
up when ftrace_init_nop() is called. As far as I can tell the easiest fix is
to just take the lock, which also seems like the safest fix.
Signed-off-by: Palmer Dabbelt <palmerdabbelt@xxxxxxxxxx>
Acked-by: Guo Ren <guoren@xxxxxxxxxx>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/arch/riscv/include/asm/ftrace.h b/arch/riscv/include/asm/ftrace.h
index c6dcc5291f972..02fbc175142e2 100644
--- a/arch/riscv/include/asm/ftrace.h
+++ b/arch/riscv/include/asm/ftrace.h
@@ -63,4 +63,11 @@ do { \
* Let auipc+jalr be the basic *mcount unit*, so we make it 8 bytes here.
*/
#define MCOUNT_INSN_SIZE 8
+
+#ifndef __ASSEMBLY__
+struct dyn_ftrace;
+int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec);
+#define ftrace_init_nop ftrace_init_nop
+#endif
+
#endif
diff --git a/arch/riscv/kernel/ftrace.c b/arch/riscv/kernel/ftrace.c
index 6d39f64e4dce4..fa8530f05ed4f 100644
--- a/arch/riscv/kernel/ftrace.c
+++ b/arch/riscv/kernel/ftrace.c
@@ -88,6 +88,25 @@ int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
return __ftrace_modify_call(rec->ip, addr, false);
}
+
+/*
+ * This is called early on, and isn't wrapped by
+ * ftrace_arch_code_modify_{prepare,post_process}() and therefor doesn't hold
+ * text_mutex, which triggers a lockdep failure. SMP isn't running so we could
+ * just directly poke the text, but it's simpler to just take the lock
+ * ourselves.
+ */
+int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec)
+{
+ int out;
+
+ ftrace_arch_code_modify_prepare();
+ out = ftrace_make_nop(mod, rec, MCOUNT_ADDR);
+ ftrace_arch_code_modify_post_process();
+
+ return out;
+}
+
int ftrace_update_ftrace_func(ftrace_func_t func)
{
int ret = __ftrace_modify_call((unsigned long)&ftrace_call,
