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From:   "Eddy_Wu@trendmicro.com" <Eddy_Wu@trendmicro.com>
To:     "peterz@infradead.org" <peterz@infradead.org>
CC:     Masami Hiramatsu <mhiramat@kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "x86@kernel.org" <x86@kernel.org>
Subject: RE: x86/kprobes: kretprobe fails to triggered if kprobe at function
 entry is not optimized (trigger by int3 breakpoint)
Thread-Topic: x86/kprobes: kretprobe fails to triggered if kprobe at function
 entry is not optimized (trigger by int3 breakpoint)
Thread-Index: AdZ5/y9ucVi7Kf0NSwa8vnc6Q/ol0wAL6hEAAAENaQAAHQZRAAAMWPyAACXNoJA=
Date:   Wed, 26 Aug 2020 07:07:09 +0000
Message-ID: <d3027772a6834f89a1ddc07c0fefaa0a@trendmicro.com>
References: <8816bdbbc55c4d2397e0b02aad2825d3@trendmicro.com>
 <20200825005426.f592075d13be740cb3c9aa77@kernel.org>
 <7396e7b2079644a6aafd9670a111232b@trendmicro.com>
 <20200825151538.f856d701a34f4e0561a64932@kernel.org>
 <20200825120911.GX1362448@hirez.programming.kicks-ass.net>
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> -----Original Message-----
> From: peterz@infradead.org <peterz@infradead.org>
> Sent: Tuesday, August 25, 2020 8:09 PM
> To: Masami Hiramatsu <mhiramat@kernel.org>
> Cc: Eddy Wu (RD-TW) <Eddy_Wu@trendmicro.com>; linux-kernel@vger.kernel.or=
g; x86@kernel.org; David S. Miller
> <davem@davemloft.net>
> Subject: Re: x86/kprobes: kretprobe fails to triggered if kprobe at funct=
ion 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, mi=
ps

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