From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 48) id C341A3858D35; Thu, 17 Aug 2023 15:48:11 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org C341A3858D35 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org; s=default; t=1692287291; bh=4fkGQ4P0RbsXotziRbOG7Rw0WykegNtZqcR6pMV1oYE=; h=From:To:Subject:Date:In-Reply-To:References:From; b=EAFc7248s7PTk8K+ssLTiaHuLJ+ca76fvwzKTiwxd6ONTbJis0iBx3e3iIoBntHgS ssnroAKkF8YB3MyhJAuna0G9cyRjEiZI7UuT0mgb6vuDI8bilHixxa5EPvpqU8pI62 7eF0C3O9IxW53m61ynvARlxYxS6LENRlvT9psAjo= From: "wcohen at redhat dot com" To: systemtap@sourceware.org Subject: [Bug runtime/30777] Systemtap modules unable to run on systemtap supporting Intel CET IBT Date: Thu, 17 Aug 2023 15:48:11 +0000 X-Bugzilla-Reason: AssignedTo X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: systemtap X-Bugzilla-Component: runtime X-Bugzilla-Version: unspecified X-Bugzilla-Keywords: X-Bugzilla-Severity: normal X-Bugzilla-Who: wcohen at redhat dot com X-Bugzilla-Status: NEW X-Bugzilla-Resolution: X-Bugzilla-Priority: P2 X-Bugzilla-Assigned-To: systemtap at sourceware dot org X-Bugzilla-Target-Milestone: --- X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: Message-ID: In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Bugzilla-URL: http://sourceware.org/bugzilla/ Auto-Submitted: auto-generated MIME-Version: 1.0 List-Id: https://sourceware.org/bugzilla/show_bug.cgi?id=3D30777 --- Comment #1 from William Cohen --- When comparing the output of objdump of the /usr/lib/debug/lib/modules/6.4.10-200.fc38.x86_64/vmlinux and the dmesg "Co= de :" it appears that the ENDBR64 and the=20 call to __fentry__ get overwrite with a multibyte nop: from the objdump -d /usr/lib/debug/lib/modules/6.4.10-200.fc38.x86_64/vmlin= ux ffffffff81206980 : kallsyms_lookup_name(): /usr/src/debug/kernel-6.4.10/linux-6.4.10-200.fc38.x86_64/kernel/kallsyms.c= :271 ffffffff81206980: f3 0f 1e fa endbr64 ffffffff81206984: e8 27 dc e7 ff call ffffffff810845b0 <__fentry__> ffffffff81206989: 53 push %rbx ffffffff8120698a: 48 83 ec 10 sub $0x10,%rsp >From the dmesg output: Code: 79 0a 48 f7 d0 48 03 05 d6 41 5b 01 c3 cc cc cc cc 66 0f 1f 84 00 00 = 00 00 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 <66> 0f 1f 00 0f 1f 4= 4 00 00 53 48 83 ec 10 65 48 8b 04 25 28 00 00 Working through to match up objdump and dmesg output: <66> 0f 1f 00 0f 1f 44 00 00 nopw 0x0(%rax,%rax,1) # *doesn't match original code* 53 push %rbx=20=20 48 83 ec 10 sub %0x10,$rsp 65 48 8b 04 25 28 00 mov %gs:0x28,%rax Something has changed the entry for kallsyms_lookup_name. Internal kernel calls to the function still work because those are not using indirect calls (call *%reg). --=20 You are receiving this mail because: You are the assignee for the bug.=