linux-kernel - Re: [PATCH RFCv2 08/18] uprobes/x86: Add uprobe syscall to speed up uprobe

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAADnVQKNeWKFkZxb_-Fuenvmfy47-t6Z7KLY_j3UUOrj5pFP-g@mail.gmail.com>
Date: Tue, 25 Feb 2025 10:06:19 -0800
From: Alexei Starovoitov <alexei.starovoitov@...il.com>
To: Jiri Olsa <olsajiri@...il.com>
Cc: Oleg Nesterov <oleg@...hat.com>, Peter Zijlstra <peterz@...radead.org>, 
	Andrii Nakryiko <andrii@...nel.org>, bpf <bpf@...r.kernel.org>, 
	LKML <linux-kernel@...r.kernel.org>, 
	linux-trace-kernel <linux-trace-kernel@...r.kernel.org>, X86 ML <x86@...nel.org>, 
	Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>, 
	John Fastabend <john.fastabend@...il.com>, Hao Luo <haoluo@...gle.com>, 
	Steven Rostedt <rostedt@...dmis.org>, Masami Hiramatsu <mhiramat@...nel.org>, 
	Alan Maguire <alan.maguire@...cle.com>, David Laight <David.Laight@...lab.com>, 
	Thomas Weißschuh <thomas@...ch.de>
Subject: Re: [PATCH RFCv2 08/18] uprobes/x86: Add uprobe syscall to speed up uprobe

On Tue, Feb 25, 2025 at 5:35 AM Jiri Olsa <olsajiri@...il.com> wrote:
>
> > In later patches I see nop5 is replaced with a call to
> > uprobe_trampoline_entry, but which part saves
> > rdi and other regs?
> > Compiler doesn't automatically spill/fill around USDT's nop/nop5.
> > Selftest is doing:
> > +__naked noinline void uprobe_test(void)
> > so just lucky ?
>
> if you mean registers that would carry usdt arguments, ebpf programs
> access those based on assembler operand string stored in usdt record:

No. I'm talking about all normal registers that trap-style uprobe
preserves, but this nop5->call will scratch.
Instead of void uprobe_test(void)
add some arguments to it, and read them before and after nop5 uprobe.
They must remain the same.