Re: x86/kprobes: kretprobe fails to triggered if kprobe at function entry is not optimized (trigger by int3 breakpoint)

[Masami Hiramatsu]

On Wed, 26 Aug 2020 07:07:09 +0000
"Eddy_Wu@xxxxxxxxxxxxxx" <Eddy_Wu@xxxxxxxxxxxxxx> wrote:

> 
> > -----Original Message-----
> > From: peterz@xxxxxxxxxxxxx <peterz@xxxxxxxxxxxxx>
> > Sent: Tuesday, August 25, 2020 8:09 PM
> > To: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
> > Cc: Eddy Wu (RD-TW) <Eddy_Wu@xxxxxxxxxxxxxx>; linux-kernel@xxxxxxxxxxxxxxx; x86@xxxxxxxxxx; David S. Miller
> > <davem@xxxxxxxxxxxxx>
> > Subject: Re: x86/kprobes: kretprobe fails to triggered if kprobe at function entry is not optimized (trigger by int3 breakpoint)
> >
> > Surely we can do a lockless list for this. We have llist_add() and
> > llist_del_first() to make a lockless LIFO/stack.
> >
> 
> llist operations require atomic cmpxchg, for some arch doesn't have CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG, in_nmi() check might still needed.
> (HAVE_KRETPROBES && !CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG): arc, arm, csky, mips

Good catch. In those cases, we can add in_nmi() check at arch dependent code.

Thank you,

-- 
Masami Hiramatsu <mhiramat@xxxxxxxxxx>