freebsd kernel with SKQ
79d49a061b
reporting since this past summer. (I think Daniel O'Conner was the first.) The problem appears to have been something like this: - cdda2wav by default passes in a buffer that is close to the 128K MAXPHYS limit. - many times, the buffer is not page aligned - vmapbuf() truncates the address, so that it is page aligned - that causes the total size of the buffer to be greater than MAXPHYS, which of course is a bad thing. Here's a quote from the PR (kern/9067): ================== In particular, note bp->b_bufsize = 0x0001f950 and bp->b_data = 0xf2219960 (which does not start on a page boundary). vunmapbuf() loops through all the pages without any difficulty until addr reaches 0xf2239000, and then the panic occurs. This seems to indicate that we are exceeding MAXPHYS since we actually started from the middle of a page (the data is being transfered to a non page aligned location). To complete the description, note that the system call originates from ReadCddaMMC12() (in scsi_cmds.c of cdda2wav) with a request to read 55 audio sectors of 2352 bytes (which is calculated to fall under MAXPHYS). This in turn ends up calling scsi_send() (in scsi-bsd.c) which calls cam_fill_csio() and cam_send_ccb(). This results in a CAMIOCOMMAND ioctl with a ccb function code of XPT_SCSI_IO. ================== The fix is to change the size check in cam_periph_mapmem() so that it is like the one in minphys(). In particular, it is something like: if ((buffer_length + (buf_ptr & PAGE_MASK)) > MAXPHYS) buffer is too big My fix is based on the one in the PR, but I cleaned up a fair number of things in cam_periph_mapmem(). The checks for each buffer to be mapped are now in a separate loop from the actual mapping operation. With the new arrangement, we don't have to bother with unmapping any previously mapped buffers if one of the checks fails. Many thanks to James Liu for tracking this down. I'd appreciate it if some vm-savvy folks would look this over. I believe this fix is correct, but I could be wrong. PR: kern/9067 (also, kern/8112) Reviewed by: gibbs Submitted by: "James T. Liu" <jtliu@phlebas.rockefeller.edu> |
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| kerberos5 | ||
| kerberosIV | ||
| lib | ||
| libexec | ||
| lkm | ||
| release | ||
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| secure | ||
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| sys | ||
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| Makefile | ||
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| README | ||
| UPDATING | ||
This is the top level of the FreeBSD source directory. This file was last revised on: $Id: README,v 1.12 1998/06/30 08:08:05 jkh Exp $ For copyright information, please see the file COPYRIGHT in this directory (additional copyright information also exists for some sources in this tree - please see the specific source directories for more information). The Makefile in this directory supports a number of targets for building components (or all) of the FreeBSD source tree, the most commonly used one being ``world'', which rebuilds and installs everything in the FreeBSD system from the source tree except the kernel and the contents of /etc. Please see the top of the Makefile in this directory for more information on the standard build targets and compile-time flags. Building a kernel with config(8) is a somewhat more involved process, documentation for which can be found at: http://www.freebsd.org/handbook/kernelconfig.html And in the config(8) man page. The sample kernel configuration files reside in the sys/i386/conf sub-directory (assuming that you've installed the kernel sources), the file named GENERIC being the one used to build your initial installation kernel. The file LINT contains entries for all possible devices, not just those commonly used, and is meant more as a general reference than an actual kernel configuration file (a kernel built from it wouldn't even run). Source Roadmap: --------------- bin System/User commands. contrib Packages contributed by 3rd parties. crypto Export controlled stuff (see crypto/README). etc Template files for /etc games Amusements. gnu Various commands and libraries under the GNU Public License. Please see gnu/COPYING* for more information. include System include files. kerberosIV Kerberos package. lib System libraries. libexec System daemons. lkm Loadable Kernel Modules. release Release building Makefile & associated tools. sbin System commands. secure DES and DES-related utilities - NOT FOR EXPORT! share Shared resources. sys Kernel sources. tools Utilities for regression testing and miscellaneous tasks. usr.bin User commands. usr.sbin System administration commands. For information on synchronizing your source tree with one or more of the FreeBSD Project's development branches, please see: http://www.freebsd.org/handbook/synching.html