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[85.193.35.41]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-43bad347823sm17046455e9.0.2025.02.28.15.00.46 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 28 Feb 2025 15:00:47 -0800 (PST) From: Jiri Olsa X-Google-Original-From: Jiri Olsa Date: Sat, 1 Mar 2025 00:00:44 +0100 To: Oleg Nesterov , Peter Zijlstra , Andrii Nakryiko Cc: bpf@vger.kernel.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, x86@kernel.org, Song Liu , Yonghong Song , John Fastabend , Hao Luo , Steven Rostedt , Masami Hiramatsu , Alan Maguire , David Laight , Thomas =?iso-8859-1?Q?Wei=DFschuh?= Subject: Re: [PATCH RFCv2 12/18] uprobes/x86: Add support to optimize uprobes Message-ID: References: <20250224140151.667679-1-jolsa@kernel.org> <20250224140151.667679-13-jolsa@kernel.org> Precedence: bulk X-Mailing-List: bpf@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: <20250224140151.667679-13-jolsa@kernel.org> On Mon, Feb 24, 2025 at 03:01:44PM +0100, Jiri Olsa wrote: SNIP > @@ -1523,15 +1698,23 @@ arch_uretprobe_hijack_return_addr(unsigned long trampoline_vaddr, struct pt_regs > { > int rasize = sizeof_long(regs), nleft; > unsigned long orig_ret_vaddr = 0; /* clear high bits for 32-bit apps */ > + unsigned long off = 0; > + > + /* > + * Optimized uprobe goes through uprobe trampoline which adds 4 8-byte > + * values on stack, check uprobe_trampoline_entry for details. > + */ > + if (!swbp) > + off = 4*8; ok, now when I started to add the missing register modifications in uprobe syscall, I realized we will modify the regs->sp appropriately already in the uprobe syscall (before the code above is hit) so we don't need this code and we can get rid of the swbp flag and patch#7 completely jirka > > - if (copy_from_user(&orig_ret_vaddr, (void __user *)regs->sp, rasize)) > + if (copy_from_user(&orig_ret_vaddr, (void __user *)regs->sp + off, rasize)) > return -1; > > /* check whether address has been already hijacked */ > if (orig_ret_vaddr == trampoline_vaddr) > return orig_ret_vaddr; > > - nleft = copy_to_user((void __user *)regs->sp, &trampoline_vaddr, rasize); > + nleft = copy_to_user((void __user *)regs->sp + off, &trampoline_vaddr, rasize); > if (likely(!nleft)) { > if (shstk_update_last_frame(trampoline_vaddr)) { > force_sig(SIGSEGV); SNIP