Messages in this thread | | | From | Guo Ren <> | Date | Tue, 22 Nov 2022 16:57:07 +0800 | Subject | Re: [PATCH] riscv/ftrace: fix ftrace_modify_call bug |
| |
On Tue, Nov 22, 2022 at 3:54 PM Song Shuai <suagrfillet@gmail.com> wrote: > > With this commit (riscv: ftrace: Reduce the detour code size to half) > patched, ftrace bug occurred When hosting kprobe and function tracer > at the same function. > > Obviously, the variable caller in ftrace_modify_call was assigned by > rec->ip with 4 offset failing the code replacing at function entry. > And the caller should be assigned by rec->ip directly to indicate > the function entry. Thank you, it's my fault, but I think the problem is:
Before (riscv: ftrace: Reduce the detour code size to half) 0: REG_S ra, -SZREG(sp) 4: auipc ra, ? <- We need "rec->ip + 4" here 8: jalr ?(ra) 12: REG_L ra, -SZREG(sp)
After (riscv: ftrace: Reduce the detour code size to half) 0: auipc t0, ? <- We needn't "rec->ip + 4" anymore 4: jalr t0, ?(t0)
I copied rec->ip + 4 blindly, then caused the bug. Right?
> > The following is the ftrace bug log. > > ``` > [ 419.632855] 00000000f8776803: expected (ffe00297 1a4282e7) but got (1a8282e7 f0227179) > [ 419.633390] ------------[ ftrace bug ]------------ > [ 419.633553] ftrace failed to modify > [ 419.633569] [<ffffffff802091cc>] kernel_read+0x0/0x52 > [ 419.633863] actual: 97:02:e0:ff:e7:82:82:1a > [ 419.634087] Updating ftrace call site to call a different ftrace function > [ 419.634279] ftrace record flags: e0000002 > [ 419.634487] (2) R > [ 419.634487] expected tramp: ffffffff800093cc > [ 419.634935] ------------[ cut here ]------------ > ``` > > Signed-off-by: Song Shuai <suagrfillet@gmail.com> > --- > arch/riscv/kernel/ftrace.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/riscv/kernel/ftrace.c b/arch/riscv/kernel/ftrace.c > index 8c77f236fc71..61b24d767e2e 100644 > --- a/arch/riscv/kernel/ftrace.c > +++ b/arch/riscv/kernel/ftrace.c > @@ -132,7 +132,7 @@ int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr, > unsigned long addr) > { > unsigned int call[2]; > - unsigned long caller = rec->ip + 4; > + unsigned long caller = rec->ip; > int ret; > > make_call_t0(caller, old_addr, call); > -- > 2.20.1 >
-- Best Regards Guo Ren
| |