From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 48) id 4A821384AB63; Wed, 10 Apr 2024 21:25:17 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 4A821384AB63 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org; s=default; t=1712784317; bh=Mf1aXu1hZmdL5TrOopNXekhIylo1O/iSNrgl4dsh+rs=; h=From:To:Subject:Date:In-Reply-To:References:From; b=VEK8NoSYeMduwz+LTihG6LbObthf59+yT4qjscZBeQh9NveNGlTiT6IxzcKNzUCe8 fyAmIuh+B4qFpB4HvgRG0TMsZNkPBJjh19jw1LRDSD+CWgmOXXdNC6A7x/y40T7eeu EYn+dWC+2fhOykI5xgwfX0KFVjX6ojB3MNU7oSm0= From: "wcohen at redhat dot com" To: systemtap@sourceware.org Subject: [Bug runtime/24935] Reading userland static data always leads to read faults on Fedora 29 x86_64 Date: Wed, 10 Apr 2024 21:25:15 +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: RESOLVED X-Bugzilla-Resolution: NOTABUG X-Bugzilla-Priority: P2 X-Bugzilla-Assigned-To: systemtap at sourceware dot org X-Bugzilla-Target-Milestone: --- X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: bug_status cc resolution 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=3D24935 William Cohen changed: What |Removed |Added ---------------------------------------------------------------------------- Status|UNCONFIRMED |RESOLVED CC| |wcohen at redhat dot com Resolution|--- |NOTABUG --- Comment #1 from William Cohen --- One could have the probe fire after the static string has been accessed by test.c, for example in the process("function").return for a function that accesses s. However, in this test.c example for this PR nothing is going to ever going to cause a page fault to pull in that static page that s points = at. Systemtap can only access pages that are already mapped in. SystemTap can't trigger a pagefault to map in a page that is not currently mapped in. A sim= ilar situation was observed on a number of the testsuite/systemtap.syscall tests where a string was stored on a page that was not mapped in on syscall entry= and the syscall would page fault the string in. The work around in the syscall tests was to use mlockall(MCL_CURRENT) to ensure that the string in .rodata section was mapped in. One example fix of this is git commit e67e4b19fd73953fbc8a23c91ae22f9d35a7c817: Author: William Cohen 2023-11-15 17:01:14 Committer: William Cohen 2023-11-15 17:01:14 Parent: 114de05acfdab36295c9c6beee9715e986810d11 (PR29076: Additional sysca= ll test fixes for .rodata on x86_64) Child: 130af146398ca5788be92d258eabe1cee662037f (Tweak testsuite/semok/target_addr.stp to work with linux 5.14 and newer.) Branches: master, remotes/origin/master, remotes/origin/mcermak-pr30321, wcohen/nfs Follows: release-5.0a Precedes:=20 PR29076: syscall test fixes for .rodata on x86_64 for pwritev.c and sys= fs.c --=20 You are receiving this mail because: You are the assignee for the bug.=