From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id ED4B480BF8 for ; Tue, 19 Mar 2024 06:33:57 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1710830039; cv=none; b=vDtuGekb+XnZO/1AlQ+tkM6R/R+nwjJLhkB4531nuemBqnpv93FgxpGzYAJ34rUfURgEXSR9RXCasHbYfl4EVUBXIEHrz8vIXBfU+xYWv365LDSnS0YVB4wXMnn4gpiyfCfYuaLMqrT+C7aQtJoROsDKOUmkANcFGsY72UqyhkM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1710830039; c=relaxed/simple; bh=k8Eo5FPdblqYucHgqojDjWLSno2Jgx1u5TwQpy+l2Z8=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=nWZZCMeBxbGBbjL8pMM0KtW/bAAnKc1bd4w2Xb9whCAqfephiZZPb1IXw4wzW/MbB8WBZToNe//EMpIjXmY0pOveV+w4xi70adeeSpfBTkHfyD7b41g1NAMB9mOayZmi5uZo3R/ysOGckBvWiV5ybXrOr5seAPo9oMLQoKv/n4M= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=PFnT1vKy; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="PFnT1vKy" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1710830036; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=Vc3xMzUk8gywc/kCGXwO98d0jqY0WWJGV4cGc3rbc7g=; b=PFnT1vKyNwEXf2iKx4fYarjyfzHerp7ZO8PTlS8UpwJRoAAhu2CKaFVJ4u4O1iykM/o28r /x2hg6ltPTJH9qefxuBXh7OoURqFMq+4LANcW7d0x5Hy2jUCEF8at2dpCrO2PvTm6GlZNS piO6fVTbnGLWQb4r+a2BzQQ3+RKTagA= Received: from mimecast-mx02.redhat.com (mx-ext.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-614-2u0CM-IdN_6v5npsIWOjCg-1; Tue, 19 Mar 2024 02:33:50 -0400 X-MC-Unique: 2u0CM-IdN_6v5npsIWOjCg-1 Received: from smtp.corp.redhat.com (int-mx10.intmail.prod.int.rdu2.redhat.com [10.11.54.10]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 935643C02B87; Tue, 19 Mar 2024 06:33:49 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.45.224.50]) by smtp.corp.redhat.com (Postfix) with SMTP id C86C7492BDA; Tue, 19 Mar 2024 06:33:46 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Tue, 19 Mar 2024 07:32:27 +0100 (CET) Date: Tue, 19 Mar 2024 07:32:19 +0100 From: Oleg Nesterov To: Andrii Nakryiko Cc: Jiri Olsa , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , bpf@vger.kernel.org, Song Liu , Yonghong Song , John Fastabend , Peter Zijlstra , Thomas Gleixner , "Borislav Petkov (AMD)" , x86@kernel.org Subject: Re: [PATCH RFC bpf-next 1/3] uprobe: Add uretprobe syscall to speed up return probe Message-ID: <20240319063219.GB20287@redhat.com> References: <20240318093139.293497-1-jolsa@kernel.org> <20240318093139.293497-2-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: User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.10 On 03/18, Andrii Nakryiko wrote: > > > + "syscall\n" > > oh, btw, do we need to save flags register as well or it's handled > somehow? I think according to manual syscall instruction does > something to rflags register. So do we need pushfq before syscall? The comment above entry_SYSCALL_64() says 64-bit SYSCALL saves rip to rcx, clears rflags.RF, then saves rflags to r11 then entry_SYSCALL_64 does pushq %r11 /* pt_regs->flags */ which should be restored on return to userspace. So I think that only X86_EFLAGS_RF can be lost, we probably do not care. Oleg.