FreeBSD src
ca125f9c17
When interrupting a kernel context, we don't need to switch stacks (memory nor register). As such, we were also not restoring the register stack pointer (ar.bspstore). This, however, fails to be valid in 1 situation: when we interrupt a register stack switch as is being done in restorectx(). The problem is that restorectx() needs to have ar.bsp == ar.bspstore before it can assign the new value to ar.bspstore. This is achieved by doing a loadrs prior to assigning to ar.bspstore. If we take an interrupt in between the loadrs and the assignment and we don't make sure we restore the ar.bspstore prior to returning from the interrupt, we switch stacks with possibly non-zero dirty registers, which means that the new frame pointer (ar.bsp) will be invalid. So, instead of jumping over the restoration of the register frame pointer and related registers, we conditionalize it based on whether we return to kernel context or user context. A future performance tweak is possible by only restoring ar.bspstore when returning to kernel mode *and* when the RSE is in enforced lazy mode. One cannot assume ar.bsp == ar.bspstore if the RSE is not in enforced lazy mode anyway. While here (well, not quite) don't unconditionally assign to ar.bspstore in exception_save. Only do that when we actually switch stacks. It can only harm us to do it unconditionally. Approved by: re@ (blanket) |
||
|---|---|---|
| bin | ||
| contrib | ||
| crypto | ||
| etc | ||
| games | ||
| gnu | ||
| include | ||
| kerberos5 | ||
| lib | ||
| libexec | ||
| release | ||
| sbin | ||
| secure | ||
| share | ||
| sys | ||
| tools | ||
| usr.bin | ||
| usr.sbin | ||
| COPYRIGHT | ||
| MAINTAINERS | ||
| Makefile | ||
| Makefile.inc1 | ||
| README | ||
| UPDATING | ||
This is the top level of the FreeBSD source directory. This file was last revised on: $FreeBSD$ 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, the kernel-modules and the contents of /etc. The ``buildkernel'' and ``installkernel'' targets build and install the kernel and the modules (see below). 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 is a somewhat more involved process, documentation for which can be found at: http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/kernelconfig.html And in the config(8) man page. Note: If you want to build and install the kernel with the ``buildkernel'' and ``installkernel'' targets, you might need to build world before. More information is available in the handbook. The sample kernel configuration files reside in the sys/<arch>/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 NOTES contains entries and documentation for all possible devices, not just those commonly used. It is the successor of the ancient LINT file, but in contrast to LINT, it is not buildable as a kernel but a pure reference and documentation file. Source Roadmap: --------------- bin System/user commands. contrib Packages contributed by 3rd parties. crypto Cryptography 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. kerberos5 Kerberos5 (Heimdal) package. lib System libraries. libexec System daemons. release Release building Makefile & associated tools. sbin System commands. secure Cryptographic libraries and commands. 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/doc/en_US.ISO8859-1/books/handbook/synching.html