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([2601:646:c200:1ef2:4138:7cfc:eb31:bf4a]) by smtp.gmail.com with ESMTPSA id j67sm38422pfc.72.2019.05.02.13.25.57 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 02 May 2019 13:25:57 -0700 (PDT) Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (1.0) Subject: Re: [RFC][PATCH 1/2] x86: Allow breakpoints to emulate call functions From: Andy Lutomirski X-Mailer: iPhone Mail (16E227) In-Reply-To: Date: Thu, 2 May 2019 13:25:56 -0700 Cc: Linus Torvalds , Peter Zijlstra , Steven Rostedt , Linux List Kernel Mailing , Ingo Molnar , Andrew Morton , Andy Lutomirski , Nicolai Stange , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , the arch/x86 maintainers , Josh Poimboeuf , Miroslav Benes , Petr Mladek , Joe Lawrence , Shuah Khan , Konrad Rzeszutek Wilk , Tim Chen , Sebastian Andrzej Siewior , Mimi Zohar , Juergen Gross , Nick Desaulniers , Nayna Jain , Masahiro Yamada , Joerg Roedel , "open list:KERNEL SELFTEST FRAMEWORK" , stable Content-Transfer-Encoding: quoted-printable Message-Id: References: <20190501202830.347656894@goodmis.org> <20190501203152.397154664@goodmis.org> <20190501232412.1196ef18@oasis.local.home> <20190502162133.GX2623@hirez.programming.kicks-ass.net> <20190502181811.GY2623@hirez.programming.kicks-ass.net> To: Jiri Kosina Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > On May 2, 2019, at 12:28 PM, Jiri Kosina wrote: >=20 >> On Thu, 2 May 2019, Linus Torvalds wrote: >>=20 >> I forget: is #BP _only_ for the "int3" instruction?=20 >=20 > Hmm, according to 17.3.2 in vol 3 of SDM (and table 6-1 there), that=20 > indeed seems to be the case, so we should be fine. I=E2=80=99m reasonably confident that the absurd MOV SS; INT3 sequence resul= ts in #BP from user mode and then #DB inside that (as opposed to vice versa)= , so this should be okay.