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RISC-V: Take text_mutex in ftrace_init_nop()

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[ 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@google.com>
Acked-by: Guo Ren <guoren@kernel.org>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Palmer Dabbelt 2020-08-24 17:21:22 -07:00 committed by Greg Kroah-Hartman
parent 487e3a1bc9
commit 66d987b80d
2 changed files with 26 additions and 0 deletions
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7
arch/riscv/include/asm/ftrace.h
View File

@ -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

19
arch/riscv/kernel/ftrace.c
View File

@ -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,