From: Jiri Olsa <olsajiri@gmail.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>,
Masami Hiramatsu <mhiramat@kernel.org>,
Oleg Nesterov <oleg@redhat.com>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org,
linux-api@vger.kernel.org, linux-man@vger.kernel.org,
x86@kernel.org, bpf@vger.kernel.org,
Song Liu <songliubraving@fb.com>, Yonghong Song <yhs@fb.com>,
John Fastabend <john.fastabend@gmail.com>,
Thomas Gleixner <tglx@linutronix.de>,
"Borislav Petkov (AMD)" <bp@alien8.de>,
Ingo Molnar <mingo@redhat.com>, Andy Lutomirski <luto@kernel.org>,
rick.p.edgecombe@intel.com
Subject: Re: [PATCHv4 bpf-next 2/7] uprobe: Add uretprobe syscall to speed up return probe
Date: Fri, 3 May 2024 15:04:25 +0200 [thread overview]
Message-ID: <ZjTg2cunShA6VbpY@krava> (raw)
In-Reply-To: <20240503113453.GK40213@noisy.programming.kicks-ass.net>
On Fri, May 03, 2024 at 01:34:53PM +0200, Peter Zijlstra wrote:
> On Thu, May 02, 2024 at 02:23:08PM +0200, Jiri Olsa wrote:
> > Adding uretprobe syscall instead of trap to speed up return probe.
> >
> > At the moment the uretprobe setup/path is:
> >
> > - install entry uprobe
> >
> > - when the uprobe is hit, it overwrites probed function's return address
> > on stack with address of the trampoline that contains breakpoint
> > instruction
> >
> > - the breakpoint trap code handles the uretprobe consumers execution and
> > jumps back to original return address
> >
> > This patch replaces the above trampoline's breakpoint instruction with new
> > ureprobe syscall call. This syscall does exactly the same job as the trap
> > with some more extra work:
> >
> > - syscall trampoline must save original value for rax/r11/rcx registers
> > on stack - rax is set to syscall number and r11/rcx are changed and
> > used by syscall instruction
> >
> > - the syscall code reads the original values of those registers and
> > restore those values in task's pt_regs area
> >
> > - only caller from trampoline exposed in '[uprobes]' is allowed,
> > the process will receive SIGILL signal otherwise
> >
>
> Did you consider shadow stacks? IIRC we currently have userspace shadow
> stack support available, and that will utterly break all of this.
nope.. I guess it's the extra ret instruction in the trampoline that would
make it crash?
>
> It would be really nice if the new scheme would consider shadow stacks.
I seem to have the hw with support for user_shstk, let me test that
thanks,
jirka
next prev parent reply other threads:[~2024-05-03 13:04 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-05-02 12:23 [PATCHv4 bpf-next 0/7] uprobe: uretprobe speed up Jiri Olsa
2024-05-02 12:23 ` [PATCHv4 bpf-next 1/7] uprobe: Wire up uretprobe system call Jiri Olsa
2024-05-02 12:23 ` [PATCHv4 bpf-next 2/7] uprobe: Add uretprobe syscall to speed up return probe Jiri Olsa
2024-05-03 11:34 ` Peter Zijlstra
2024-05-03 13:04 ` Jiri Olsa [this message]
2024-05-03 15:53 ` Edgecombe, Rick P
2024-05-03 19:18 ` Jiri Olsa
2024-05-03 19:38 ` Edgecombe, Rick P
2024-05-03 20:17 ` Jiri Olsa
2024-05-03 20:35 ` Edgecombe, Rick P
2024-05-06 10:56 ` Jiri Olsa
2024-05-03 23:01 ` Deepak Gupta
2024-05-02 12:23 ` [PATCHv4 bpf-next 3/7] selftests/bpf: Add uretprobe syscall test for regs integrity Jiri Olsa
2024-05-02 12:23 ` [PATCHv4 bpf-next 4/7] selftests/bpf: Add uretprobe syscall test for regs changes Jiri Olsa
2024-05-02 12:23 ` [PATCHv4 bpf-next 5/7] selftests/bpf: Add uretprobe syscall call from user space test Jiri Olsa
2024-05-02 16:33 ` Andrii Nakryiko
2024-05-02 12:23 ` [PATCHv4 bpf-next 6/7] selftests/bpf: Add uretprobe compat test Jiri Olsa
2024-05-02 16:35 ` Andrii Nakryiko
2024-05-02 12:23 ` [PATCHv4 7/7] man2: Add uretprobe syscall page Jiri Olsa
2024-05-02 13:43 ` Alejandro Colomar
2024-05-02 20:13 ` Jiri Olsa
2024-05-02 22:06 ` Alejandro Colomar
2024-05-02 16:43 ` [PATCHv4 bpf-next 0/7] uprobe: uretprobe speed up Andrii Nakryiko
2024-05-02 20:04 ` Jiri Olsa
2024-05-03 18:03 ` Andrii Nakryiko
2024-05-03 20:39 ` Jiri Olsa
2024-05-07 7:47 ` Jiri Olsa
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