Messages in this thread | | | From | Song Shuai <> | Date | Tue, 22 Nov 2022 09:51:11 +0000 | Subject | Re: [PATCH] riscv/ftrace: fix ftrace_modify_call bug |
| |
Guo Ren <guoren@kernel.org> 于2022年11月22日周二 09:29写道: > > > > On Tue, Nov 22, 2022 at 5:11 PM Song Shuai <suagrfillet@gmail.com> wrote: >> >> Guo Ren <guoren@kernel.org> 于2022年11月22日周二 08:57写道: >> > >> > 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? >> > >> Yes, you're right. >> >> Here's my simple test case for your convenience. >> ``` >> echo kernel_read > set_ftrace_filter >> echo function > current_tracer >> echo 'p:myp kernel_read' > kprobe_events >> echo 1 > events/kprobes/myp/enable # ftrace bug > > > Thx, I would fold the patch into (riscv: ftrace: Reduce the detour code size to half). And add Co-developed-by: Song Shuai <suagrfillet@gmail.com> tag on that. > > I would send the v3 series involving your patches. > That's an honor for me.
Thanks, Song >> >> ``` >> > > >> > > 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 >> Thanks, >> Song > > > > -- > Best Regards > Guo Ren
| |