From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 48) id 203B43858D28; Thu, 28 Mar 2024 19:17:01 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 203B43858D28 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org; s=default; t=1711653421; bh=VF3dLjBzAHX3SDNoSDEgE5ecpLEjju+JF+nud23QTFs=; h=From:To:Subject:Date:In-Reply-To:References:From; b=upewS/V93WzXYe54NuX1iWRaRXJkrUPjaZfI7ZohLSUkYjRWxNRnE3eH+o9EWCI0d nfrWofD1Jzuhev6A7ZQyPOHsM0F9Bmyw1iKCEaEfQJZ0+S9ArGE+KAWHKo+BdzCM9P o5nFGEDuHA5nBNTHczqcXV2gVR5gh2jizginuPo4= From: "jemarch at gcc dot gnu.org" To: gcc-bugs@gcc.gnu.org Subject: [Bug target/114523] bpf: ssa-phiopt optimization generates unverifiable code. Date: Thu, 28 Mar 2024 19:17:00 +0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: gcc X-Bugzilla-Component: target X-Bugzilla-Version: unknown X-Bugzilla-Keywords: X-Bugzilla-Severity: normal X-Bugzilla-Who: jemarch at gcc dot gnu.org X-Bugzilla-Status: NEW X-Bugzilla-Resolution: X-Bugzilla-Priority: P3 X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org X-Bugzilla-Target-Milestone: --- X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: everconfirmed bug_status resolution cc cf_reconfirmed_on Message-ID: In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/ Auto-Submitted: auto-generated MIME-Version: 1.0 List-Id: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D114523 Jose E. Marchesi changed: What |Removed |Added ---------------------------------------------------------------------------- Ever confirmed|0 |1 Status|RESOLVED |NEW Resolution|INVALID |--- CC| |jemarch at gcc dot gnu.org Last reconfirmed| |2024-03-28 --- Comment #9 from Jose E. Marchesi --- Please do not close this bug. We are well aware this is a limitation in the kernel verifier, but we need to keep track of this. In general, like in this case, many of the problems related to unverifiable generated code can be reduced to "this is a kernel verifier bug, make it smarter", but that doesn't mean we can't put workarounds in the back-end so= we can actually compile actually-existing BPF programs (such as that systemd utility) in actually-existing current kernels. That includes disabling cer= tain optimizations. I don't like it any more than you do, trust me on that. Note that the development of the BPF backends, in both clang and GCC, are by necessity very much in lock-step with the kernel BPF support. So this is n= ot something we will forget to "undo" as soon as the verifier can handle these instructions. Very likely we will be doing the kernel patch as well.=