4e501eb7cc
Long ago, perhaps only on i386, kernel text was mapped read-only and it was necessary to change the mapping to read-write to set breakpoints in kernel text. Other writes by ddb to kernel text were also allowed. This write protection is harder to implement with 4MB pages, and was lost even for 4K pages when 4MB pages were implemented. So changing the mapping became useless. It was actually worse than useless since it followed followed various null and otherwise garbage pointers to not change random memory instead of the mapping. (On i386s, the pointers became good in pmap_bootstrap(), and on amd64 the pointers became bad in pmap_bootstrap() if not before.) Another bug broke detection of following of null pointers on i386, except early in boot where not detecting this was a feature. When I fixed the bug, I accidentally broke the feature and soon got traps in db_write_bytes(). Setting breakpoints early in ddb was broken. kib pointed out that a clean way to do the adjustment would be to use a special [sub]map giving a small window on the bytes to be written. The trap handler didn't know how to fix up errors for pagefaults accessing the map itself. Such errors rarely need fixups, since most traps for the map are for the first access which is a read. Reviewed by: kib |
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| bin | ||
| cddl | ||
| contrib | ||
| crypto | ||
| etc | ||
| gnu | ||
| include | ||
| kerberos5 | ||
| lib | ||
| libexec | ||
| release | ||
| rescue | ||
| sbin | ||
| secure | ||
| share | ||
| sys | ||
| targets | ||
| tests | ||
| tools | ||
| usr.bin | ||
| usr.sbin | ||
| .arcconfig | ||
| .arclint | ||
| COPYRIGHT | ||
| LOCKS | ||
| MAINTAINERS | ||
| Makefile | ||
| Makefile.inc1 | ||
| Makefile.libcompat | ||
| ObsoleteFiles.inc | ||
| README | ||
| README.md | ||
| UPDATING | ||
FreeBSD Source:
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. See build(7) and http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/makeworld.html for more information, including setting make(1) variables.
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. See build(7), config(8), and http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/kernelconfig.html for more information.
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 kernel configuration files reside in the sys/<arch>/conf
sub-directory. GENERIC is the default configuration used in release builds.
NOTES contains entries and documentation for all possible
devices, not just those commonly used.
Source Roadmap:
bin System/user commands.
cddl Various commands and libraries under the Common Development
and Distribution License.
contrib Packages contributed by 3rd parties.
crypto Cryptography stuff (see crypto/README).
etc Template files for /etc.
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.
rescue Build system for statically linked /rescue utilities.
sbin System commands.
secure Cryptographic libraries and commands.
share Shared resources.
sys Kernel sources.
tests Regression tests which can be run by Kyua. See tests/README
for additional information.
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usr.bin User commands.
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http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/synching.html