Date: Mon, 24 Oct 2011 00:55:33 GMT From: Charles Davis <cdavis@mymail.mines.edu> To: freebsd-gnats-submit@FreeBSD.org Subject: amd64/161949: [kern] 64-bit structures are used even with 32-bit code Message-ID: <201110240055.p9O0tXex092211@red.freebsd.org> Resent-Message-ID: <201110240100.p9O102cE072182@freefall.freebsd.org>
next in thread | raw e-mail | index | archive | help
>Number: 161949 >Category: amd64 >Synopsis: [kern] 64-bit structures are used even with 32-bit code >Confidential: no >Severity: serious >Priority: low >Responsible: freebsd-amd64 >State: open >Quarter: >Keywords: >Date-Required: >Class: sw-bug >Submitter-Id: current-users >Arrival-Date: Mon Oct 24 01:00:02 UTC 2011 >Closed-Date: >Last-Modified: >Originator: Charles Davis >Release: 8.2-RELEASE >Organization: Colorado School of Mines >Environment: FreeBSD <hostname> 8.2-RELEASE-p3 FreeBSD 8.2-RELEASE-p3 #0: Tue Sep 27 18:45:57 UTC 2011 root@amd64-builder.daemonology.net:/usr/obj/usr/src/sys/GENERIC amd64 >Description: When a process transfers data to or from the kernel, and those data are organized into structures whose size depends on whether or not the size of a pointer is 4 or 8 bytes, an LP64 kernel always uses 64-bit structures, even with 32-bit processes. I know this is true of structures returned from sysctl(3), but I also think it is true of structures used with ioctl(2) and fcntl(2). Because 32-bit processes expect 32-bit structures, attempts to use the 64-bit structures fail at best and cause massive data corruption at worst. This is already affecting real-world code. A patch of mine that was recently committed to Wine (http://www.winehq.org) exposed this issue with the xtcpcb and xinpcb structs returned by the sysctl(3)s "net.inet.tcp.pcblist" and "net.inet.udp.pcblist" (cf. Wine bug 28857: http://bugs.winehq.org/show_bug.cgi?id=28857). >How-To-Repeat: Run any 32-bit program under a 64-bit kernel that calls sysctl(3), ioctl(2), or fcntl(2) and uses a data structure with those calls whose size depends on the pointer size. >Fix: FreeBSD should detect if a process is a 32-bit one, and if so, it should use 32-bit structures instead of 64-bit ones. I don't know how the former can be done; a cursory look through the <sys/proc.h> header reveals nothing. The latter is easy, but tedious: definitions for the 32-bit structs must be added to the kernel headers. Another way to solve this problem (at the cost of binary compatibility for 32-bit programs) is to simply make the 32-bit and 64-bit structures the same. >Release-Note: >Audit-Trail: >Unformatted:
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?201110240055.p9O0tXex092211>