From owner-freebsd-arm@freebsd.org Fri Oct 25 14:26:25 2019 Return-Path: Delivered-To: freebsd-arm@mailman.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.nyi.freebsd.org (Postfix) with ESMTP id 768CF1721C3 for ; Fri, 25 Oct 2019 14:26:25 +0000 (UTC) (envelope-from ian@freebsd.org) Received: from outbound2m.ore.mailhop.org (outbound2m.ore.mailhop.org [54.149.155.156]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) server-signature RSA-PSS (4096 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 4705yT0Zdxz4Z4x for ; Fri, 25 Oct 2019 14:26:24 +0000 (UTC) (envelope-from ian@freebsd.org) ARC-Seal: i=1; a=rsa-sha256; t=1572013583; cv=none; d=outbound.mailhop.org; s=arc-outbound20181012; b=qnt70hV47fM6U70hF1UYvxqLmeMQmDVHNe1djcvm+tnz2C0C0/DyfGagz9weVEFhtC7fua0nBQfLQ S+qXRIojvWMDqfp0vvvSoV5kCtYYpvUkWRazZhgJVX4Y6rR2v0UswKBoQnjQdrGRup1y4X78zd3LXK CRQ2iQtf5sUUDFtxcqQLTxImrDdkLzEpC/KXuotHlro1643tCdLSPoXGTA3nrxxxzIXiUBTx9kHUkZ bz1/byM61JdF92B63eRfyib0MS+B2hHhpG/rkqXlC6TYtsakFguD0HC9i5unrGyvm1osFkhyPdUYGI v9J1seFTZuP81zNoaxEQ2e6IExZd79g== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=outbound.mailhop.org; s=arc-outbound20181012; h=content-transfer-encoding:mime-version:content-type:references:in-reply-to: date:cc:to:from:subject:message-id:dkim-signature:from; bh=/K83OZzVJNz2iz9yeIFaPK8vfN3At1RkYbqa4Oum2LU=; b=U4iVbqJagBW2WuUDJu3B745jM2mS0vonJXJJyVJQPT125KnFZRKTNpY570dl9HZ1H65HFUCWcV/YJ z+1s1Ks/a35pEW24cmqcww7azaP24pKn+XJSOuAdwbnsDYY6JKeL2dfpkX13xzMMF4FGljt95Q7PVH rlHRRVTq5SkiPxWVmC3TfYjB3hl1EztvKFPrYD9IomNGj5OOjLE2koeoXPlhnCBeKGLRXqozGdqun0 8KX2wOL8vkElWzKSVjHNK4HWN43dj0PhEQ33LYIChqlHNVyMyv1/l8IrjTywgmX3r3SVkJ6pAXmh6g 4DYF6PoS7bZHzJjVFCrpGjQf8x9xn0Q== ARC-Authentication-Results: i=1; outbound4.ore.mailhop.org; spf=softfail smtp.mailfrom=freebsd.org smtp.remote-ip=67.177.211.60; dmarc=none header.from=freebsd.org; arc=none header.oldest-pass=0; DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=outbound.mailhop.org; s=dkim-high; h=content-transfer-encoding:mime-version:content-type:references:in-reply-to: date:cc:to:from:subject:message-id:from; bh=/K83OZzVJNz2iz9yeIFaPK8vfN3At1RkYbqa4Oum2LU=; b=ssRCciPdZN8e+O/eHZuoXeS7DEWSwx/2Te7Ap61cTmjA8hLm3rw23Gkv5th+PBZH/wQMg6iXpyVuk U/e1BJX57IGTk59ximyc5EtennOWUZOM7IdH7tY/g4dlBvYkBDR3zw/fzjSxXfXEPzTG9DQmaNZnfM ONJozvAgHkmZfSebuti7l1+2OysVAuXScHEdF36l5VAlcb4lhlV8Pj0qYMX9L02Bkkh7GeVO7hGYMl gV92degEDRN1SmnbeAWTCu263PP0vnI0z5qsuTrD5yNL4Nm6bhOfn1Mw6K6JwGEarR9DUVOF0FjWuL zmN9MrDm5h9aUipK3Q71MRWFd0Asf5A== X-MHO-RoutePath: aGlwcGll X-MHO-User: 69d311b4-f733-11e9-829e-79a40d15cccd X-Report-Abuse-To: https://support.duocircle.com/support/solutions/articles/5000540958-duocircle-standard-smtp-abuse-information X-Originating-IP: 67.177.211.60 X-Mail-Handler: DuoCircle Outbound SMTP Received: from ilsoft.org (unknown [67.177.211.60]) by outbound4.ore.mailhop.org (Halon) with ESMTPSA id 69d311b4-f733-11e9-829e-79a40d15cccd; Fri, 25 Oct 2019 14:26:22 +0000 (UTC) Received: from rev (rev [172.22.42.240]) by ilsoft.org (8.15.2/8.15.2) with ESMTP id x9PEQJaF049419; Fri, 25 Oct 2019 08:26:19 -0600 (MDT) (envelope-from ian@freebsd.org) Message-ID: <78c9868cf23643dfa2f88694542e86251bde13e7.camel@freebsd.org> Subject: Re: ucontext From: Ian Lepore To: Konstantin Belousov , Nick Kostirya Cc: freebsd-arm@freebsd.org Date: Fri, 25 Oct 2019 08:26:19 -0600 In-Reply-To: <20191025083803.GD73312@kib.kiev.ua> References: <20191024141133.04fb0693@i11.co> <20191024145436.GX73312@kib.kiev.ua> <20191025104421.012c1e5e@i11.co> <20191025083803.GD73312@kib.kiev.ua> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.28.5 FreeBSD GNOME Team Mime-Version: 1.0 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 4705yT0Zdxz4Z4x X-Spamd-Bar: - Authentication-Results: mx1.freebsd.org; none X-Spamd-Result: default: False [-1.89 / 15.00]; local_wl_from(0.00)[freebsd.org]; NEURAL_HAM_MEDIUM(-0.89)[-0.893,0]; ASN(0.00)[asn:16509, ipnet:54.148.0.0/15, country:US]; NEURAL_HAM_LONG(-1.00)[-1.000,0] X-BeenThere: freebsd-arm@freebsd.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: "Porting FreeBSD to ARM processors." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 25 Oct 2019 14:26:25 -0000 On Fri, 2019-10-25 at 11:38 +0300, Konstantin Belousov wrote: > On Fri, Oct 25, 2019 at 10:44:21AM +0300, Nick Kostirya wrote: > > On Thu, 24 Oct 2019 17:54:36 +0300 > > Konstantin Belousov wrote: > > > > > > > > I believe you want > > > uc_context.__gregs[_REG_PC] > > > on arm (32bit) and > > > uc_context.mc_gpregs.gp_elr > > > on arm64 for aarch64. > > > > > > Sometimes the thumb bit (lowest bit in PC) leaks there, then you should > > > mask it. > > > > Thanks! > > > > Although I did not understand your last phrase. > > There is leak of what? > > Leak of the thumb bit. ARM ARM specifies that in non-thumb mode, pc must > be word-aligned, in thumb it is half-word aligned. A way to enter thumb > mode is to execute BX or BLX instruction with the lowest bit of the target > PC set to 1. > > Sometimes you might get pc with the bit 0 set, which should > be masked out then. This is a bigger issue for unwinders than for simple > profilers. > > > Where can I read about it? > > ARM ARM (ARM architecture reference manual), available from arm.com. > Or Google for it. > The kernel has some support for running thumb binaries, but I've never heard of anybody actually doing so on freebsd. Nobody has ever reported a bug related to running a thumb binary, and it would be astounding to me if we accidentally got everything in the kernel thumb support right on the first try without ever testing it. -- Ian