From: Oleg Nesterov <oleg@redhat.com>
To: David Laight <David.Laight@ACULAB.COM>
Cc: 'Jiri Olsa' <jolsa@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Andrii Nakryiko <andrii@kernel.org>,
"bpf@vger.kernel.org" <bpf@vger.kernel.org>,
Song Liu <songliubraving@fb.com>, Yonghong Song <yhs@fb.com>,
John Fastabend <john.fastabend@gmail.com>,
Hao Luo <haoluo@google.com>, Steven Rostedt <rostedt@goodmis.org>,
Masami Hiramatsu <mhiramat@kernel.org>,
Alan Maguire <alan.maguire@oracle.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-trace-kernel@vger.kernel.org"
<linux-trace-kernel@vger.kernel.org>
Subject: Re: [PATCH bpf-next 08/13] uprobes/x86: Add support to optimize uprobes
Date: Sun, 15 Dec 2024 15:14:13 +0100 [thread overview]
Message-ID: <20241215141412.GA13580@redhat.com> (raw)
In-Reply-To: <1521ff93bc0649b0aade9cfc444929ca@AcuMS.aculab.com>
On 12/15, David Laight wrote:
>
> From: Jiri Olsa
> > The optimized uprobe path
> >
> > - checks the original instruction is 5-byte nop (plus other checks)
> > - adds (or uses existing) user space trampoline and overwrites original
> > instruction (5-byte nop) with call to user space trampoline
> > - the user space trampoline executes uprobe syscall that calls related uprobe
> > consumers
> > - trampoline returns back to next instruction
> ...
>
> How on earth can you safely overwrite a randomly aligned 5 byte instruction
> that might be being prefetched and executed by another thread of the
> same process.
uprobe_write_opcode() doesn't overwrite the instruction in place.
It creates the new page with the same content, overwrites the probed insn in
that page, then calls __replace_page().
Oleg.
next prev parent reply other threads:[~2024-12-15 14:14 UTC|newest]
Thread overview: 63+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-12-11 13:33 [PATCH bpf-next 00/13] uprobes: Add support to optimize usdt probes on x86_64 Jiri Olsa
2024-12-11 13:33 ` [PATCH bpf-next 01/13] uprobes: Rename arch_uretprobe_trampoline function Jiri Olsa
2024-12-13 0:42 ` Andrii Nakryiko
2024-12-11 13:33 ` [PATCH bpf-next 02/13] uprobes: Make copy_from_page global Jiri Olsa
2024-12-13 0:43 ` Andrii Nakryiko
2024-12-11 13:33 ` [PATCH bpf-next 03/13] uprobes: Add nbytes argument to uprobe_write_opcode Jiri Olsa
2024-12-13 0:45 ` Andrii Nakryiko
2024-12-11 13:33 ` [PATCH bpf-next 04/13] uprobes: Add arch_uprobe_verify_opcode function Jiri Olsa
2024-12-13 0:48 ` Andrii Nakryiko
2024-12-13 13:21 ` Jiri Olsa
2024-12-13 21:11 ` Andrii Nakryiko
2024-12-13 21:52 ` Jiri Olsa
2024-12-11 13:33 ` [PATCH bpf-next 05/13] uprobes: Add mapping for optimized uprobe trampolines Jiri Olsa
2024-12-13 1:01 ` Andrii Nakryiko
2024-12-13 13:42 ` Jiri Olsa
2024-12-13 21:58 ` Andrii Nakryiko
2024-12-11 13:33 ` [PATCH bpf-next 06/13] uprobes/x86: Add uprobe syscall to speed up uprobe Jiri Olsa
2024-12-13 13:48 ` Thomas Weißschuh
2024-12-13 14:51 ` Jiri Olsa
2024-12-13 15:12 ` Thomas Weißschuh
2024-12-13 21:52 ` Jiri Olsa
2024-12-14 13:21 ` Thomas Weißschuh
2024-12-16 8:03 ` Jiri Olsa
2024-12-11 13:33 ` [PATCH bpf-next 07/13] uprobes/x86: Add support to emulate nop5 instruction Jiri Olsa
2024-12-13 10:45 ` Peter Zijlstra
2024-12-13 13:02 ` Jiri Olsa
2024-12-11 13:33 ` [PATCH bpf-next 08/13] uprobes/x86: Add support to optimize uprobes Jiri Olsa
2024-12-13 10:49 ` Peter Zijlstra
2024-12-13 13:06 ` Jiri Olsa
2024-12-13 21:58 ` Andrii Nakryiko
2024-12-15 12:06 ` David Laight
2024-12-15 14:14 ` Oleg Nesterov [this message]
2024-12-16 8:08 ` Jiri Olsa
2024-12-16 9:18 ` David Laight
2024-12-16 10:12 ` Oleg Nesterov
2024-12-16 11:10 ` David Laight
2024-12-16 12:22 ` Oleg Nesterov
2024-12-16 12:50 ` Jiri Olsa
2024-12-16 15:08 ` David Laight
2024-12-16 16:06 ` Jiri Olsa
2024-12-11 13:33 ` [PATCH bpf-next 09/13] selftests/bpf: Use 5-byte nop for x86 usdt probes Jiri Olsa
2024-12-13 21:58 ` Andrii Nakryiko
2024-12-16 8:32 ` Jiri Olsa
2024-12-16 23:06 ` Andrii Nakryiko
2024-12-11 13:33 ` [PATCH bpf-next 10/13] selftests/bpf: Add uprobe/usdt optimized test Jiri Olsa
2024-12-13 21:58 ` Andrii Nakryiko
2024-12-16 7:58 ` Jiri Olsa
2024-12-11 13:34 ` [PATCH bpf-next 11/13] selftests/bpf: Add hit/attach/detach race optimized uprobe test Jiri Olsa
2024-12-13 21:58 ` Andrii Nakryiko
2024-12-16 7:59 ` Jiri Olsa
2024-12-11 13:34 ` [PATCH bpf-next 12/13] selftests/bpf: Add uprobe syscall sigill signal test Jiri Olsa
2024-12-11 13:34 ` [PATCH bpf-next 13/13] selftests/bpf: Add 5-byte nop uprobe trigger bench Jiri Olsa
2024-12-13 21:57 ` Andrii Nakryiko
2024-12-16 7:56 ` Jiri Olsa
2024-12-13 0:43 ` [PATCH bpf-next 00/13] uprobes: Add support to optimize usdt probes on x86_64 Andrii Nakryiko
2024-12-13 9:46 ` Jiri Olsa
2024-12-13 10:51 ` Peter Zijlstra
2024-12-13 13:07 ` Jiri Olsa
2024-12-13 13:54 ` Peter Zijlstra
2024-12-13 14:05 ` Jiri Olsa
2024-12-13 18:39 ` Peter Zijlstra
2024-12-13 21:52 ` Jiri Olsa
2024-12-13 21:59 ` Andrii Nakryiko
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