Commit Graph

387 Commits

Author SHA1 Message Date
Mateusz Guzik
879e0604ee Add KERNEL_PANICKED macro for use in place of direct panicstr tests 2020-01-12 06:07:54 +00:00
Conrad Meyer
fea73412a0 sleep(9), sleepqueue(9): const'ify wchan pointers
_sleep(9), wakeup(9), sleepqueue(9), et al do not dereference or modify the
channel pointers provided in any way; they are merely used as intptrs into a
dictionary structure to match waiters with wakers.  Correctly annotate this
such that _sleep() and wakeup() may be used on const pointers without
invoking ugly patterns like __DECONST().  Plumb const through all of the
underlying sleepqueue bits.

No functional change.

Reviewed by:	rlibby
Discussed with:	kib, markj
Differential Revision:	https://reviews.freebsd.org/D22914
2019-12-24 16:19:33 +00:00
Conrad Meyer
25b3370cfd ddb(4): Add some support for lexing IPv6 addresses
Allow commands to specify that (hex) numbers may start with A-F, by adding
the DRT_HEX flag for db_read_token_flags().  As before, numbers containing
invalid digits for the current radix are rejected.

Also, lex ':' and '::' tokens as tCOLON and tCOLONCOLON respectively.

There is a mild conflict here with lexed "identifiers" (tIDENT): ddb
identifiers may contain arbitrary colons, and the ddb lexer is greedy.  So
the identifier lex will swallow any colons it finds inside identifiers, and
consumers are still unable to expect the token sequence 'tIDENT tCOLON'.
That limitation does not matter for IPv6 addresses, because the lexer always
attempts to lex numbers before identifiers.

Reviewed by:	markj
Differential Revision:	https://reviews.freebsd.org/D21509
2019-09-09 16:32:23 +00:00
Conrad Meyer
e0c5dd431b ddb(4): Enhance lexer functionality for specialized commands
Add a db_read_token_flags() variant of db_read_token() with configurable
parameters.

Allow specifying an explicit radix for tNUMBER lexing.  It overrides the
default inference and db_radix setting.

Also provide the option of yielding any lexed whitespace (tWSPACE) (instead
of ignoring it).  This is useful for whitespace-sensitive CS_OWN commands.

Reviewed by:	markj
Differential Revision:	https://reviews.freebsd.org/D21459
2019-09-09 16:31:14 +00:00
Conrad Meyer
3c40d3fc54 ddb(4): Move an extern variable declaration to a header
Trivial cleanup, no functional change.
2019-09-09 01:33:45 +00:00
Mateusz Guzik
88cc62e5a5 proc: eliminate the zombproc list
It is not needed by anything in the kernel and it slightly drives up contention
on both proctree and allproc locks.

Reviewed by:	kib
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D21447
2019-08-28 16:18:23 +00:00
Jeff Roberson
0b26119b21 Cache kernel stacks in UMA. This gives us NUMA support, better concurrency,
and more statistics.

Reviewed by:	kib, markj
Tested by:	pho
Sponsored by:	Netflix
Differential Revision:	https://reviews.freebsd.org/D20931
2019-08-06 23:15:34 +00:00
Ryan Libby
a6d2a24c3e ddb show proc typo 2019-06-22 05:35:23 +00:00
Conrad Meyer
e2e050c8ef Extract eventfilter declarations to sys/_eventfilter.h
This allows replacing "sys/eventfilter.h" includes with "sys/_eventfilter.h"
in other header files (e.g., sys/{bus,conf,cpu}.h) and reduces header
pollution substantially.

EVENTHANDLER_DECLARE and EVENTHANDLER_LIST_DECLAREs were moved out of .c
files into appropriate headers (e.g., sys/proc.h, powernv/opal.h).

As a side effect of reduced header pollution, many .c files and headers no
longer contain needed definitions.  The remainder of the patch addresses
adding appropriate includes to fix those files.

LOCK_DEBUG and LOCK_FILE_LINE_ARG are moved to sys/_lock.h, as required by
sys/mutex.h since r326106 (but silently protected by header pollution prior
to this change).

No functional change (intended).  Of course, any out of tree modules that
relied on header pollution for sys/eventhandler.h, sys/lock.h, or
sys/mutex.h inclusion need to be fixed.  __FreeBSD_version has been bumped.
2019-05-20 00:38:23 +00:00
Ryan Libby
64e0efab39 db show thread: avoid overflow in tick conversion
The previous calculations for displaying the time since last switch
easily overflowed, after less than 36 min for hz=1000.  Now overflow
takes 2000 times longer (as long as ticks takes to wrap).

Reviewed by:	cem, markj
Sponsored by:	Dell EMC Isilon
Differential revision:	https://reviews.freebsd.org/D20273
2019-05-16 05:29:54 +00:00
Justin Hibbits
517ba0d3f1 ddb: Print the thread's pcb in 'show thread'
This can aid with debugging when a thread is running and has no backtrace.
State can be estimated based on the pcb, and refined from there, for
example, to get a rough idea of the stack pointer.
2019-02-09 21:08:19 +00:00
Conrad Meyer
e41793db2c ddb: Enable 'thread <address>'
Currently, the 'thread' command (to switch the debugger to another thread)
only accepts decimal-encoded tids.  Use the same parsing logic as 'show
thread <arg>' to accept hex-encoded thread pointers in addition to
decimal-encoded tids.

Document the 'thread' command in ddb.4 and expand the 'show thread'
documentation to cover the tid usage.

Reported by:	bwidawsk
Reviewed by:	bwidawsk (earlier version), kib (earlier version), markj
Sponsored by:	Dell EMC Isilon
Differential Revision:	https://reviews.freebsd.org/D16962
2018-10-20 20:45:49 +00:00
Andriy Gapon
27cfcd9599 add an option for ddb ps command to print process arguments
We use ps to collect the information of all processes in textdump. But
it doesn't contain process arguments which however sometimes are very
useful for debugging.  The new 'a' modifier adds that capability.

While here, remove 'm' modifier from ddb.4.  It was in the manual page
from its very first revision, but I could not find any evidence of the
code ever supporting it.

Submitted by:	Terry Hu <thu@panzura.com>
Reviewed by:	kib
MFC after:	1 week
Sponsored by:	Panzura
Differential Revision: https://reviews.freebsd.org/D16603
2018-08-09 11:21:31 +00:00
Bjoern A. Zeeb
e76bd38065 Extend show proc with reaper, sigparent, and vmspace information
I have regularly needed the last couple of months.

Sponsored by:	iXsystems, Inc.
2018-05-25 13:59:48 +00:00
Justin Hibbits
b4a0a59871 Fix PPC symbol resolution
Summary:
There were 2 issues that were preventing correct symbol resolution
on PowerPC/pseries:

1- memory corruption at chrp_attach() - this caused the inital
   part of the symbol table to become zeroed, which would cause
   the kernel linker to fail to parse it.
   (this was probably zeroing out other memory parts as well)

2- DDB symbol resolution wasn't working because symtab contained
   not relocated addresses but it was given relocated offsets.
   Although relocating the symbol table fixed this, it broke the
   linker, that already handled this case.
   Thus, the fix for this consists in adding a new DDB macro:
   DB_STOFFS(offs) that converts a (potentially) relocated offset
   into one that can be compared with symbol table values.

PR:		227093
Submitted by:	Leandro Lupori <leandro.lupori_gmail.com>
Differential Revision: https://reviews.freebsd.org/D15372
2018-05-10 03:59:48 +00:00
Warner Losh
3531bbb5ea Restore db_radix on parse error, otherwise we'll silently change it to
10 on a botched trace command.
2018-04-17 15:44:05 +00:00
Warner Losh
9d89a9f326 No need to force md code to define a macro that's the same as
_BYTE_ORDER. Use that instead.
2018-04-16 13:52:23 +00:00
Andriy Gapon
3761bead4a db_script_exec: use a saved script name when reporting commands executed
Before executing a command in a ddb script ddb prints an information
line of the form:
  db:1:my-script> command
where 1 is the script's depth level, "my-script" is the scipt's name,
and "command" is the current command in the script.
db_script_exec() uses its 'scriptname' parameter to produce that string.
In the case when db_script_exec() is called from db_run_cmd() the
argument points to db_tok_string that is a global variable used for
command parsing.  So, its value changes with every command executed.

This commit changes the code to use the script's name stored in
ds_scriptname to print the line.

MFC after:	2 weeks
2018-03-04 13:27:21 +00:00
Jeff Roberson
3f289c3fcf Implement 'domainset', a cpuset based NUMA policy mechanism. This allows
userspace to control NUMA policy administratively and programmatically.

Implement domainset based iterators in the page layer.

Remove the now legacy numa_* syscalls.

Cleanup some header polution created by having seq.h in proc.h.

Reviewed by:	markj, kib
Discussed with:	alc
Tested by:	pho
Sponsored by:	Netflix, Dell/EMC Isilon
Differential Revision:	https://reviews.freebsd.org/D13403
2018-01-12 22:48:23 +00:00
Mark Johnston
78f57a9cde Generalize the gzio API.
We currently use a set of subroutines in kern_gzio.c to perform
compression of user and kernel core dumps. In the interest of adding
support for other compression algorithms (zstd) in this role without
complicating the API consumers, add a simple compressor API which can be
used to select an algorithm.

Also change the (non-default) GZIO kernel option to not enable
compressed user cores by default. It's not clear that such a default
would be desirable with support for multiple algorithms implemented,
and it's inconsistent in that it isn't applied to kernel dumps.

Reviewed by:	cem
Differential Revision:	https://reviews.freebsd.org/D13632
2018-01-08 21:27:41 +00:00
Andriy Gapon
6e1c5d187c ddb: fix validation of cpu id in 'set db_cpu=x'
MFC after:	1 week
2017-12-05 14:22:08 +00:00
Pedro F. Giffuni
c967e4ffa6 SPDX: oops .. not from CMU. 2017-11-30 15:58:38 +00:00
Pedro F. Giffuni
796df753f4 SPDX: Consider code from Carnegie-Mellon University.
Interesting cases, most likely from CMU Mach sources.
2017-11-30 15:48:35 +00:00
Edward Tomasz Napierala
2276703108 Make the ddb(4) "set" command list variables when called without parameters.
Obtained from:	CheriBSD
MFC after:	2 weeks
Sponsored by:	DARPA, AFRL
2017-11-30 12:22:15 +00:00
Edward Tomasz Napierala
212ff84f4a Make kdb_reenter() silent when explicitly called from db_error().
This removes the useless backtrace on various ddb(4) user errors.

Reviewed by:	jhb@
Obtained from:	CheriBSD
MFC after:	2 weeks
Sponsored by:	DARPA, AFRL
Differential Revision:	https://reviews.freebsd.org/D13212
2017-11-28 12:53:55 +00:00
Pedro F. Giffuni
753c4e83fc sys/ddb: further adoption of SPDX licensing ID tags.
Mainly focus on files that use BSD 2-Clause license, however the tool I
was using misidentified many licenses so this was mostly a manual - error
prone - task.

The Software Package Data Exchange (SPDX) group provides a specification
to make it easier for automated tools to detect and summarize well known
opensource licenses. We are gradually adopting the specification, noting
that the tags are considered only advisory and do not, in any way,
superceed or replace the license texts.
2017-11-27 15:14:46 +00:00
Pedro F. Giffuni
51369649b0 sys: further adoption of SPDX licensing ID tags.
Mainly focus on files that use BSD 3-Clause license.

The Software Package Data Exchange (SPDX) group provides a specification
to make it easier for automated tools to detect and summarize well known
opensource licenses. We are gradually adopting the specification, noting
that the tags are considered only advisory and do not, in any way,
superceed or replace the license texts.

Special thanks to Wind River for providing access to "The Duke of
Highlander" tool: an older (2014) run over FreeBSD tree was useful as a
starting point.
2017-11-20 19:43:44 +00:00
Gavin Atkinson
c6404e6690 Point people towards our https web site for documentation, http accesses are
just redirected anyway.

MFC after:	1 week
2017-11-09 13:38:24 +00:00
Mark Johnston
01938d3666 Rename mkdumpheader() and group EKCD functions in kern_shutdown.c.
This helps simplify the code in kern_shutdown.c and reduces the number
of globally visible functions.

No functional change intended.

Reviewed by:	cem, def
Sponsored by:	Dell EMC Isilon
Differential Revision:	https://reviews.freebsd.org/D11603
2017-08-18 04:04:09 +00:00
Warner Losh
4e38d89520 Include opt files in the kernel with "" instead of <>. 2017-07-10 05:08:01 +00:00
Edward Tomasz Napierala
81e12dd187 Make ^c work in ddb(4).
Obtained from:	CheriBSD
MFC after:	2 weeks
Sponsored by:	DARPA, AFRL
2017-07-06 15:27:34 +00:00
Edward Tomasz Napierala
eeb6101e04 Make ^w work in ddb(4).
Obtained from:	CheriBSD
MFC after:	2 weeks
Sponsored by:	DARPA, AFRL
2017-07-06 15:21:57 +00:00
Edward Tomasz Napierala
9990da25ea Improve ddb(4) error reporting a bit.
Obtained from:	CheriBSD
MFC after:	2 weeks
Sponsored by:	DARPA, AFRL
2017-07-06 12:30:39 +00:00
Edward Tomasz Napierala
b5bd6c7383 Make ddb(4) a bit more user-friendly by improving "help".
Obtained from:	CheriBSD
MFC after:	2 weeks
Sponsored by:	DARPA, AFRL
2017-07-06 12:27:14 +00:00
Ed Maste
3e85b721d6 Remove register keyword from sys/ and ANSIfy prototypes
A long long time ago the register keyword told the compiler to store
the corresponding variable in a CPU register, but it is not relevant
for any compiler used in the FreeBSD world today.

ANSIfy related prototypes while here.

Reviewed by:	cem, jhb
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D10193
2017-05-17 00:34:34 +00:00
Bruce Evans
f434f3515b Fix printing of negative offsets (typically from frame pointers) again.
I fixed this in 1997, but the fix was over-engineered and fragile and
was broken in 2003 if not before.  i386 parameters were copied to 8
other arches verbatim, mostly after they stopped working on i386, and
mostly without the large comment saying how the values were chosen on
i386.  powerpc has a non-verbatim copy which just changes the uncritical
parameter and seems to add a sign extension bug to it.

Just treat negative offsets as offsets if they are no more negative than
-db_offset_max (default -64K), and remove all the broken parameters.

-64K is not very negative, but it is enough for frame and stack pointer
offsets since kernel stacks are small.

The over-engineering was mainly to go more negative than -64K for the
negative offset format, without affecting printing for more than a
single address.

Addresses in the top 64K of a (full 32-bit or 64-bit) address space
are now printed less well, but there aren't many interesting ones.
For arches that have many interesting ones very near the top (e.g.,
68k has interrupt vectors there), there would be no good limit for
the negative offset format and -64K is a good as anything.
2017-03-26 18:46:35 +00:00
Bruce Evans
82b93348db Fix right shifts on arches with db_expr_t larger than u_int (LP64 arches
in practice).

db_expr_t is a signed type, but right shifts are fudged to evaluate
them in an unsigned type, and the unsigned type was broken by hard-
coding it as 'unsigned', so casting to it lost the top bits on arches
with db_expr_t larger than u_int.

The unsigned type with the same size as db_expr_t is not declared;
assume that db_addr_t gives it.  Fixing this properly is less important
than using the correct type for db_expr_t (originally always long for
C90, but always intmax_t since C99).
2017-03-18 07:01:18 +00:00
Warner Losh
fbbd9655e5 Renumber copyright clause 4
Renumber cluase 4 to 3, per what everybody else did when BSD granted
them permission to remove clause 3. My insistance on keeping the same
numbering for legal reasons is too pedantic, so give up on that point.

Submitted by:	Jan Schaumann <jschauma@stevens.edu>
Pull Request:	https://github.com/freebsd/freebsd/pull/96
2017-02-28 23:42:47 +00:00
Baptiste Daroussin
b4b4b5304b Revert crap accidentally committed 2017-01-28 16:31:23 +00:00
Baptiste Daroussin
814aaaa7da Revert r312923 a better approach will be taken later 2017-01-28 16:30:14 +00:00
Mark Johnston
c2718b428e Revert r311952.
It broke DDB type-ahead since it caused db_check_interrupt() to drop
unrecognized characters.

Reported by:	bde
2017-01-14 22:06:25 +00:00
Mark Johnston
5fddef7999 Enable the use of ^C and ^S/^Q in DDB.
This lets one interrupt DDB's output, which is useful if paging is
disabled and the output device is slow.

Submitted by:	Anton Rang <rang@acm.org>
Reviewed by:	jhb
MFC after:	1 week
Differential Revision:	https://reviews.freebsd.org/D9138
2017-01-12 00:22:36 +00:00
John Baldwin
ecb65f66c6 Use casts to force an unsigned comparison in db_search_symbol().
On all of our platforms, db_expr_t is a signed integer while
db_addr_t is an unsigned integer value.  db_search_symbol used variables
of type db_expr_t to hold the current offset of the requested address from
the "best" symbol found so far.  This value was initialized to '~0'.
When a new symbol is found from a symbol table, the associated diff for the
new symbol is compared against the existing value as 'if (newdiff < diff)'
to determine if the new symbol had a smaller diff and was thus a closer
match.

On 64-bit MIPS, the '~0' was treated as a negative value (-1).  A lookup
that found a perfect match of an address against a symbol returned a diff
of 0.  However, in signed comparisons, 0 is not less than -1.  As a result,
DDB on 64-bit MIPS never resolved any addresses to symbols.  Workaround
this by using casts to force an unsigned comparison.

Probably the diff returned from db_search_symbol() and X_db_search_symbol()
should be changed to a db_addr_t instead of a db_expr_t as it is an
unsigned value (and is an offset of an address, so should fit in the same
size as an address).

Sponsored by:	DARPA / AFRL
2016-12-14 00:18:12 +00:00
Konrad Witaszczyk
480f31c214 Add support for encrypted kernel crash dumps.
Changes include modifications in kernel crash dump routines, dumpon(8) and
savecore(8). A new tool called decryptcore(8) was added.

A new DIOCSKERNELDUMP I/O control was added to send a kernel crash dump
configuration in the diocskerneldump_arg structure to the kernel.
The old DIOCSKERNELDUMP I/O control was renamed to DIOCSKERNELDUMP_FREEBSD11 for
backward ABI compatibility.

dumpon(8) generates an one-time random symmetric key and encrypts it using
an RSA public key in capability mode. Currently only AES-256-CBC is supported
but EKCD was designed to implement support for other algorithms in the future.
The public key is chosen using the -k flag. The dumpon rc(8) script can do this
automatically during startup using the dumppubkey rc.conf(5) variable.  Once the
keys are calculated dumpon sends them to the kernel via DIOCSKERNELDUMP I/O
control.

When the kernel receives the DIOCSKERNELDUMP I/O control it generates a random
IV and sets up the key schedule for the specified algorithm. Each time the
kernel tries to write a crash dump to the dump device, the IV is replaced by
a SHA-256 hash of the previous value. This is intended to make a possible
differential cryptanalysis harder since it is possible to write multiple crash
dumps without reboot by repeating the following commands:
# sysctl debug.kdb.enter=1
db> call doadump(0)
db> continue
# savecore

A kernel dump key consists of an algorithm identifier, an IV and an encrypted
symmetric key. The kernel dump key size is included in a kernel dump header.
The size is an unsigned 32-bit integer and it is aligned to a block size.
The header structure has 512 bytes to match the block size so it was required to
make a panic string 4 bytes shorter to add a new field to the header structure.
If the kernel dump key size in the header is nonzero it is assumed that the
kernel dump key is placed after the first header on the dump device and the core
dump is encrypted.

Separate functions were implemented to write the kernel dump header and the
kernel dump key as they need to be unencrypted. The dump_write function encrypts
data if the kernel was compiled with the EKCD option. Encrypted kernel textdumps
are not supported due to the way they are constructed which makes it impossible
to use the CBC mode for encryption. It should be also noted that textdumps don't
contain sensitive data by design as a user decides what information should be
dumped.

savecore(8) writes the kernel dump key to a key.# file if its size in the header
is nonzero. # is the number of the current core dump.

decryptcore(8) decrypts the core dump using a private RSA key and the kernel
dump key. This is performed by a child process in capability mode.
If the decryption was not successful the parent process removes a partially
decrypted core dump.

Description on how to encrypt crash dumps was added to the decryptcore(8),
dumpon(8), rc.conf(5) and savecore(8) manual pages.

EKCD was tested on amd64 using bhyve and i386, mipsel and sparc64 using QEMU.
The feature still has to be tested on arm and arm64 as it wasn't possible to run
FreeBSD due to the problems with QEMU emulation and lack of hardware.

Designed by:	def, pjd
Reviewed by:	cem, oshogbo, pjd
Partial review:	delphij, emaste, jhb, kib
Approved by:	pjd (mentor)
Differential Revision:	https://reviews.freebsd.org/D4712
2016-12-10 16:20:39 +00:00
Bruce Evans
808cf02c24 Determine the operand/address size of %cs in a new function
db_segsize().

Use db_segsize() to set the default operand/address size for
disassembling.  Allow overriding this with the "alternate" display
format /I.  The API of db_disasm() should be debooleanized to pass a
more general request (amd64 needs overrides to sizes of 16, 32, and
64, but this commit doesn't implement anything for amd64 since much
larger changes are needed to restore the amd64 disassmbler's support
for non-default sizes).

Fix db_print_loc_and_inst() to ask for the normal format and not the
alternate in normal operation.

This is most useful for vm86 mode, but also works for 16-bit protected
mode.

Use db_segsize() to avoid trying to print a garbage stack trace if %cs
is 16 bits.  Print something like the stack trace termination message
for a trap boundary instead.

Document that the alternate format is now useful on i386.
2016-09-25 16:30:29 +00:00
Bruce Evans
e1e554a382 Silently ignore unexpected single-step traps (except for turning
off single-stepping).  Only do this on arches (only x86 so far)
which classify single-step traps unambiguously.

This allows other parts of the kernel to be intentionally and
unintentionally sloppy about generating single-step traps.  On
x86, at least the following places were unintentionally sloppy:
- all operations that context-switched [er]flags.  Especially
  spinlock_enter()/exit() and cpu_switch().  When single-stepped,
  saving the flags leaves PSL_T set in the saved flags, so
  restoring gives a trap that is spurious if it occurs after
  single-step mode has been left.  Switching contexts away from
  a low priority thread gives especially long-lived saved copies.
- the vm86 emulation allows user mode to set PSL_T.  This was
  correct until vm86 bios call mode was unintentionally given
  access to kdb handling its single-step traps.
Now these places are intentionally sloppy, but unexpected
debugger traps still cause panics if no debugger that handles
the trap is attached when the trap is delivered.
2016-09-17 11:43:51 +00:00
Bruce Evans
1e24fd3bd9 Statically initialize the run mode to the one that will become
current on first entry.  This fixes a spurious "Stepping aborted"
message when the first entry is for a breakpoint.

Don't reset to the run mode to STEP_NONE when stopping, and remove
STEP_NONE.  This mode was never really used, except transiently to
mis-decide whether to print the message on first entry.
2016-09-16 06:31:10 +00:00
Bruce Evans
bd20334ca0 Abort single stepping in ddb if the trap is not for single-stepping.
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.
2016-09-15 17:24:23 +00:00
Bruce Evans
5c48342f16 Pass the trap type and code down from db_trap() to db_stop_at_pc() so
that the latter can easily determine what the trap type actually is
after callers are fixed to encode the type unambigously.

ddb currently barely understands breakpoints, and it treats all
non-breakpoints as single-step traps.  This works OK for stopping
after every instruction when single-stepping, but is broken for
single-stepping with a count > 1 (especially with a large count).
ddb needs to stop on the first non-single-step trap while single-
stepping.  Otherwise, ddb doesn't even stop the first time for
fatal traps and external breakpoints like the one in kdb_enter().
2016-09-09 15:53:42 +00:00
Bruce Evans
10c458cc3b Fix stopping when the specified breakpoint count is reached. The
countdown was done correctly, but the action when the count was not
reduced to 0 was to fall through to generic code which almost always
stopped.
2016-09-09 14:09:50 +00:00