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authorPalmer Dabbelt <palmerdabbelt@google.com>2020-08-24 17:21:22 -0700
committerPalmer Dabbelt <palmerdabbelt@google.com>2020-09-11 12:15:21 -0700
commit66d18dbda8469a944dfec6c49d26d5946efba218 (patch)
tree85f71e6b0e4ee323d508fb1ba1bb19a74e8c47a9
parentd012a7190fc1fd72ed48911e77ca97ba4521bccd (diff)
RISC-V: Take text_mutex in ftrace_init_nop()
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@google.com> Acked-by: Guo Ren <guoren@kernel.org> Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>
-rw-r--r--arch/riscv/include/asm/ftrace.h7
-rw-r--r--arch/riscv/kernel/ftrace.c19
2 files changed, 26 insertions, 0 deletions
diff --git a/arch/riscv/include/asm/ftrace.h b/arch/riscv/include/asm/ftrace.h
index ace8a6e2d11d..845002cc2e57 100644
--- a/arch/riscv/include/asm/ftrace.h
+++ b/arch/riscv/include/asm/ftrace.h
@@ -66,6 +66,13 @@ 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
#endif /* _ASM_RISCV_FTRACE_H */
diff --git a/arch/riscv/kernel/ftrace.c b/arch/riscv/kernel/ftrace.c
index 2ff63d0cbb50..99e12faa5498 100644
--- a/arch/riscv/kernel/ftrace.c
+++ b/arch/riscv/kernel/ftrace.c
@@ -97,6 +97,25 @@ 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,