From mboxrd@z Thu Jan 1 00:00:00 1970 From: Josh Poimboeuf Subject: Re: [PATCH] x86/crypto: Add missing RETs Date: Tue, 26 Jun 2018 07:31:54 -0500 Message-ID: <20180626123154.unjji5glpokedwal@treble> References: <1529242717.4472.3.camel@gmx.de> <1529244178.4674.1.camel@gmx.de> <20180617194747.GA21160@zn.tnic> <1529289279.31745.3.camel@gmx.de> <20180623103622.GA2760@zn.tnic> <20180624071105.GA29407@gmail.com> <20180624104449.GA20159@avx2> <20180625072438.GA19063@gmail.com> <20180625131932.sge43esxdb5ejoxg@treble> <20180626064930.GB25879@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Cc: Alexey Dobriyan , Borislav Petkov , linux-crypto@vger.kernel.org, Mike Galbraith , torvalds@linux-foundation.org, tglx@linutronix.de, luto@kernel.org, peterz@infradead.org, brgerst@gmail.com, hpa@zytor.com, linux-kernel@vger.kernel.org, dvlasenk@redhat.com, h.peter.anvin@intel.com, linux-tip-commits , Herbert Xu , Peter Zijlstra To: Ingo Molnar Return-path: Content-Disposition: inline In-Reply-To: <20180626064930.GB25879@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-crypto.vger.kernel.org On Tue, Jun 26, 2018 at 08:49:30AM +0200, Ingo Molnar wrote: > > * Josh Poimboeuf wrote: > > > On Mon, Jun 25, 2018 at 09:24:38AM +0200, Ingo Molnar wrote: > > > > > > * Alexey Dobriyan wrote: > > > > > > > On Sun, Jun 24, 2018 at 09:11:05AM +0200, Ingo Molnar wrote: > > > > > > Add explicit RETs to the tail calls of AEGIS and MORUS crypto algorithms > > > > > > otherwise they run into INT3 padding due to > > > > > > > > > > > > 51bad67ffbce ("x86/asm: Pad assembly functions with INT3 instructions") > > > > > > > > > > > > leading to spurious debug exceptions. > > > > > > > > > > > > Mike Galbraith took care of all the remaining callsites. > > > > > > > > > > Note that 51bad67ffbce has been zapped because it caused too many problems like > > > > > this, but the explicit RETs make sense nevertheless. > > > > > > > > So commit which found real bug(s) was zapped. > > > > > > > > OK > > > > > > No, what happened is that the commit was first moved into WIP.x86/debug showing > > > its work-in-progress status, because it was incomplete and caused bugs: > > > > > > https://lore.kernel.org/lkml/20180518073644.GA8593@gmail.com/T/#u > > > > > > ... and finally, after weeks of inaction I zapped it because I didn't see progress > > > and you didn't answer my question. > > > > > > If a fixed patch with updated tooling to detect these crashes before they occur on > > > live systems is submitted we'll reconsider - it didn't get NAK-ed, it's just > > > incomplete in the current form. > > > > Hm, what happened to the objtool patch to detect these at build time? > > Did it not work? > > > > https://lore.kernel.org/lkml/20180517134934.eog2fgoby5azq5a7@treble > > So that's still incomplete in that doesn't analyze the 32-bit build yet, right? We could do INT3s on 64-bit and NOPs on 32-bit. Or, possibly even better, we could just keep NOPs everywhere and instead make objtool smart enough to detect function fallthroughs. That should be pretty easy, actually. It already does it for C files. Something like the below should work, though it's still got a few issues: a) objtool is currently disabled for crypto code because it doesn't yet understand crypto stack re-alignments (which really needs fixing anyway); and b) it complains about the blank xen hypercalls falling through. Those aren't actual functions anyway, so we should probably annotate those somehow so that objtool ignores them anyway. I'm a bit swamped at the moment but I can fix those once I get a little more bandwidth. I at least verified that this patch caught the crypto missing RETs. diff --git a/arch/x86/crypto/Makefile b/arch/x86/crypto/Makefile index a450ad573dcb..a2c52eec2863 100644 --- a/arch/x86/crypto/Makefile +++ b/arch/x86/crypto/Makefile @@ -3,8 +3,6 @@ # Arch-specific CryptoAPI modules. # -OBJECT_FILES_NON_STANDARD := y - avx_supported := $(call as-instr,vpxor %xmm0$(comma)%xmm0$(comma)%xmm0,yes,no) avx2_supported := $(call as-instr,vpgatherdd %ymm0$(comma)(%eax$(comma)%ymm1\ $(comma)4)$(comma)%ymm2,yes,no) diff --git a/tools/objtool/check.c b/tools/objtool/check.c index 2928939b98ec..f740fd828cba 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -1798,13 +1798,14 @@ static int validate_branch(struct objtool_file *file, struct instruction *first, while (1) { next_insn = next_insn_same_sec(file, insn); - if (file->c_file && func && insn->func && func != insn->func->pfunc) { + if (func && insn->func && func != insn->func->pfunc) { WARN("%s() falls through to next function %s()", func->name, insn->func->name); return 1; } - func = insn->func ? insn->func->pfunc : NULL; + if (insn->type != INSN_NOP) + func = insn->func ? insn->func->pfunc : NULL; if (func && insn->ignore) { WARN_FUNC("BUG: why am I validating an ignored function?",