FreeBSD src
bd20334ca0
This is not very easy to do, since ddb didn't know when traps are for single-stepping. It more or less assumed that traps are either breakpoints or single-step, but even for x86 this became inadequate with the release of the i386 in ~1986, and FreeBSD passes it other trap types for NMIs and panics. On x86, teach ddb when a trap is for single stepping using the %dr6 register. Unknown traps are now treated almost the same as breakpoints instead of as the same as single-steps. Previously, the classification of breakpoints was almost correct and everything else was unknown so had to be treated as a single-step. Now the classification of single- steps is precise, the classification of breakpoints is almost correct (as before) and everything else is unknown and treated like a breakpoint. This fixes: - breakpoints not set by ddb, including the main one in kdb_enter(), were treated as single-steps and not stopped on when stepping (except for the usual, simple case of a step with residual count 1). As special cases, kdb_enter() didn't stop for fatal traps or panics - similarly for "hardware breakpoints". Use a new MD macro IS_SSTEP_TRAP(type, code) to code to classify single-steps. This is excessively complicated for bug-for-bug and backwards compatibilty. Design errors apparently started in Mach in ~1990 or perhaps in the FreeBSD interface in ~1993. Common trap types like single steps should have a unique MI code (like the TRAP* codes for user SIGTRAP) so that debuggers don't need macros like IS_SSTEP_TRAP() to decode them. But 'type' is actually an ambiguous MD trap number, and code was always 0 (now it is (int)%dr6 on x86). So it was impossible to determine the trap type from the args. Global variables had to be used. There is already a classification macro db_pc_is_single_step(), but this just gets in the way. It is only used to recover from bugs in IS_BREAKPOINT_TRAP(). On some arches, IS_BREAKPOINT_TRAP() just duplicates the ambiguity in 'type' and misclassifies single-steps as breakpoints. It defaults to 'false', which is the opposite of what is needed for bug-for-bug compatibility. When this is cleaned up, MI classification bits should be passed in 'code'. This could be done now for positive-logic bits, since 'code' was always 0, but some negative logic is needed for compatibility so a simple MI classificition is not usable yet. After reading %dr6, clear the single-step bit in it so that the type of the next debugger trap can be decoded. This is a little ddb-specific. ddb doesn't understand the need to clear this bit and doing it before calling kdb is easiest. gdb would need to reverse this to support hardware breakpoints, but it just doesn't support them now since gdbstub doesn't support %dr*. Fix a bug involving %dr6: when emulating a single-step trap for vm86, set the bit for it in %dr6. Userland debuggers need this. ddb now needs this for vm86 bios calls. The bit gets copied to 'code' then cleared again. Fix related style bugs: - when clearing bits for hardware breakpoints in %dr6, spell the mask as ~0xf on both amd64 and i386 to get the correct number of bits using sign extension and not need a comment about using the wrong mask on amd64 (amd64 traps for invalid results but clearing the reserved top bits didn't trap since they are 0). - rewrite my old wrong comments about using %dr6 for ddb watchpoints. |
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| 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 | ||
| 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. 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. 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