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Tue, 14 Jan 2025 06:19:17 -0800 (PST) Received: from krava ([213.175.46.84]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-5d99046e048sm6077873a12.71.2025.01.14.06.19.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 14 Jan 2025 06:19:17 -0800 (PST) From: Jiri Olsa X-Google-Original-From: Jiri Olsa Date: Tue, 14 Jan 2025 15:19:14 +0100 To: Oleg Nesterov Cc: Jiri Olsa , Aleksa Sarai , Eyal Birger , mhiramat@kernel.org, linux-kernel , linux-trace-kernel@vger.kernel.org, BPF-dev-list , Song Liu , Yonghong Song , John Fastabend , peterz@infradead.org, tglx@linutronix.de, bp@alien8.de, x86@kernel.org, linux-api@vger.kernel.org, Andrii Nakryiko , Daniel Borkmann , Alexei Starovoitov , Andrii Nakryiko , "rostedt@goodmis.org" , rafi@rbk.io, Shmulik Ladkani Subject: Re: Crash when attaching uretprobes to processes running in Docker Message-ID: References: <20250110.152323-sassy.torch.lavish.rent-vKX3ul5B3qyi@cyphar.com> <20250114105802.GA19816@redhat.com> Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250114105802.GA19816@redhat.com> On Tue, Jan 14, 2025 at 11:58:03AM +0100, Oleg Nesterov wrote: > On 01/14, Jiri Olsa wrote: > > > > --- a/arch/x86/kernel/uprobes.c > > +++ b/arch/x86/kernel/uprobes.c > > @@ -315,14 +315,25 @@ asm ( > > ".global uretprobe_trampoline_entry\n" > > "uretprobe_trampoline_entry:\n" > > "pushq %rax\n" > > + "pushq %rbx\n" > > "pushq %rcx\n" > > "pushq %r11\n" > > + "movq $1, %rbx\n" > > "movq $" __stringify(__NR_uretprobe) ", %rax\n" > > "syscall\n" > > ".global uretprobe_syscall_check\n" > > "uretprobe_syscall_check:\n" > > + "or %rbx,%rbx\n" > > + "jz uretprobe_syscall_return\n" > > "popq %r11\n" > > "popq %rcx\n" > > + "popq %rbx\n" > > + "popq %rax\n" > > + "int3\n" > > + "uretprobe_syscall_return:\n" > > + "popq %r11\n" > > + "popq %rcx\n" > > + "popq %rbx\n" > > But why do we need to abuse %rbx? Can't uretprobe_trampoline_entry do > > syscall > > // int3_section, in case sys_uretprobe() doesn't work > popq %r11 > popq %rcx > popq %rax > int3 > > uretprobe_syscall_return: > popq %r11 > popq %rcx > popq %rbx > retq > > and change sys_uretprobe() to do > > - regs->ip = ip; > + regs->ip = ip + sizeof(int3_section); nice idea, I wonder we get the trampoline size under one xol slot with that thanks, jirka