Messages in this thread | | | Date | Wed, 17 Aug 2022 22:28:36 -0400 | From | Steven Rostedt <> | Subject | Re: [PATCH] x86/unwind/orc: unwind ftrace trampolines with correct orc |
| |
On Thu, 18 Aug 2022 09:55:25 +0800 Chen Zhongjin <chenzhongjin@huawei.com> wrote:
> arch/x86/kernel/unwind_orc.c | 13 ++++++++----- > 1 file changed, 8 insertions(+), 5 deletions(-) > > diff --git a/arch/x86/kernel/unwind_orc.c b/arch/x86/kernel/unwind_orc.c > index 38185aedf7d1..a938c5d0ed6f 100644 > --- a/arch/x86/kernel/unwind_orc.c > +++ b/arch/x86/kernel/unwind_orc.c > @@ -93,22 +93,25 @@ static struct orc_entry *orc_find(unsigned long ip); > static struct orc_entry *orc_ftrace_find(unsigned long ip) > { > struct ftrace_ops *ops; > - unsigned long caller; > + unsigned long tramp_addr, offset; > > ops = ftrace_ops_trampoline(ip); > if (!ops) > return NULL; >
Now if this is that unlikely recursion mentioned below then ops->trampoline will be NULL, and if we do that offset addition, it will be incorrect.
Perhaps we should add here:
if (!ops->trampoline) return NULL;
Let's add some comments.
/* Set tramp_addr to the start of the code copied by the trampoline */
> if (ops->flags & FTRACE_OPS_FL_SAVE_REGS) > - caller = (unsigned long)ftrace_regs_call; > + tramp_addr = (unsigned long)ftrace_regs_caller; > else > - caller = (unsigned long)ftrace_call; > + tramp_addr = (unsigned long)ftrace_caller; > +
/* Now place tramp_addr to the location within the trampoline ip is at */
> + offset = ip - ops->trampoline; > + tramp_addr += offset; > > /* Prevent unlikely recursion */ > - if (ip == caller) > + if (ip == tramp_addr) > return NULL; > > - return orc_find(caller); > + return orc_find(tramp_addr); > } > #else > static struct orc_entry *orc_ftrace_find(unsigned long ip)
| |