From mboxrd@z Thu Jan  1 00:00:00 1970
From: torvalds@linux-foundation.org (Linus Torvalds)
Date: Sat, 4 May 2019 13:36:11 -0700
Subject: [RFC][PATCH 1/2] x86: Allow breakpoints to emulate call functions
In-Reply-To: <2BF1AE4B-8105-49F0-8B6A-AA3B11FD66FD@amacapital.net>
References: <20190501202830.347656894@goodmis.org>
 <20190501203152.397154664@goodmis.org>
 <20190501232412.1196ef18@oasis.local.home>
 <20190502162133.GX2623@hirez.programming.kicks-ass.net>
 <CAHk-=wijZ-MD4g3zMJ9W2r=h8LUWneiu29OWuxZEoSfAF=0bhQ@mail.gmail.com>
 <20190502181811.GY2623@hirez.programming.kicks-ass.net>
 <CAHk-=wi6A9tgw=kkPh5Ywqt687VvsVEjYXVkAnq0jpt0u0tk6g@mail.gmail.com>
 <20190502202146.GZ2623@hirez.programming.kicks-ass.net>
 <CAHk-=wh8bi5c_GkyjPtDAiaXaZRqtmhWs30usUvs4qK_F+c9tg@mail.gmail.com>
 <20190503152405.2d741af8@gandalf.local.home>
 <CAHk-=wiA-WbrFrDs-kOfJZMXy4zMo9-SZfk=7B-GfmBJ866naw@mail.gmail.com>
 <20190503184919.2b7ef242@gandalf.local.home>
 <CAHk-=wh2vPLvsGBi6JtmEYeqHxB5UpTzHDjY5JsWG=YR0Lypzw@mail.gmail.com>
 <20190504001756.17fad840@oasis.local.home>
 <CAHk-=wiuSFbv_rELND-BLWcP0GSZ0yF=xOAEcf61GE3bU9d=yg@mail.gmail.com>
 <CAHk-=wjGNx8xcwg=7nE_0-nLQ_d4UALHvJ8O+TurbA25n8MyNg@mail.gmail.com>
 <2BF1AE4B-8105-49F0-8B6A-AA3B11FD66FD@amacapital.net>
Message-ID:
 <CAHk-=wgEDAFUKRR=iELwUCk1kpoACk4eOfyyQhnYb78H9AEaSw@mail.gmail.com>
Content-Type: text/plain; charset="UTF-8"
Message-ID: <20190504203611.vK1nkl_l5kyMgw0fpWBeZJ-ivNJYQTOkfytulxi5Ojc@z>

On Sat, May 4, 2019@1:12 PM Andy Lutomirski <luto@amacapital.net> wrote:
>
> As an aside, is it even *possible* to get #BP from v8086 mode?  On a quick SDM read, the INT3 instruction causes #GP if VM=1 and IOPL<3.  And, if we allow vm86() to have IOPL=3, we should just remove that ability. It’s nuts.

Oh, and I think you mis-read the SDM.

Yes, iopl matters for "int X" (cd xx) instruction in vm86 mode.

But no, iopl does *not* matter for the special "int3/into/int1"
(cc/ce/f1) instructions, I think.

              Linus