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.
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().
On big endian hardware that uses 1 byte bool a type mismatch of bool vs int will
cause the least signifcant byte of db_cmd_loop_done to be set, but the MSB to be
read, and read as 0. This causes ddb to stay in an infinite loop.
MFC after: 1 week
and negative shift counts.
Fix error messages: print "Division" instead of "Divide"; print
multiplier-like, addition-like and logical operator tokens instead of
garbage (usually the command name).
ddb has a primitive lexer with excessive information hiding that makes
it hard to find even the point in the line where a syntax error is
detected. Old ddb just printed "Syntax error" and this was unimproved
in most places by printing a garbage token.
'show active trace', or 'acttrace' for short, prints backtraces from running
threads only.
Reviewed by: mjg
Differential Revision: https://reviews.freebsd.org/D7646
the fixed-width numeric field 'wchan', as in ps(1). They were sort
of centered, although the template shows 'state' as right-justified.
The `wmesg' field very rarely has a prefix of '*' (for lock names)
that is still to the left of the header, and the width of this field
is reduced from 8 to 7 (more than 6 is an error).
The 'wmesg' and 'wchan' fields are still misnamed and poorly handled.
They are named sort of backwards relative to ps(1):
- wmesg in ddb = mwchan in ps
- wmesg in ddb = wchan in ps (if it is a wait channel name, not a lock name)
- wchan in ddb = nwchan in ps
ddb ps wastes lots of space for the unimportant 'wchan' field (20
columns altogether on 64-bit arches). ps(1) documents using a
compressed format, but the compression only omits leading nybbles of
0 so it has neveqr worked on arches that put the kernel in the top half
of the address space. It just avoids wasting space for an 0x prefix.
single stepping of multiple instructions (e.g., s/p,<count> and n/p).
db_print_loc_and_inst() already prints a newline on all arches although
it probably shouldn't.
Especially on SMP systems, single stepping tends to deadlock or panic
too quickly to be useful for anything except finding bugs in itself,
but with printing "itself" includes console drivers so it is useful
for generating stress tests for console drivers.
specifics of callout KPI. Esp., do not depend on the exact interface
of callout_stop(9) return values.
The main change is that instead of requiring precise callouts, code
maintains absolute time to wake up. Callouts now should ensure that a
wake occurs at the requested moment, but we can tolerate both run-away
callout, and callout_stop(9) lying about running callout either way.
As consequence, it removes the constant source of the bugs where
sleepq_check_timeout() causes uninterruptible thread state where the
thread is detached from CPU, see e.g. r234952 and r296320.
Patch also removes dual meaning of the TDF_TIMEOUT flag, making code
(IMO much) simpler to reason about.
Tested by: pho
Reviewed by: jhb
Sponsored by: The FreeBSD Foundation
MFC after: 1 month
Differential revision: https://reviews.freebsd.org/D7137
This are based on Mach3.
Documentation is pending but has been promised.
Submitted by: Dan Partelly
Reviewed by: adrian, jhb (older version)
Differential Revision: https://reviews.freebsd.org/D4230
RelNotes: yes
* Change x/a to work similar to gdb. The content of the memory is
treated as an address, printed symbolically and the address is advanced.
This way you can x/a <stack_address> and then just hit return a bunch
of times to locate useful data on the stack.
* Add x/p. The content of the memory is treated as an address and
printed as hex.
This is based on the similar commit from DragonFlyBSD without the
cosmetic changes.
Relnotes: yes
Obtained from: DragonflyBSD (Matthew Dillon)
Reference: 0624d20e86affcd708609cbf9014207537537a72
Some architectures (including ARMv6/v7) do not have separate single step
events and cannot see difference between breakpoint and single step.
Add db_pc_is_singlestep() to avoid skipping instruction we stepped on
to trigger debug event.
This commit does not change the existing functionality but adds possibility
to implement custom db_pc_is_singlestep().
Reviewed by: imp
Submitted by: Zbigniew Bodek <zbb@semihalf.com>
Obtained from: Semihalf
Sponsored by: Juniper Networks Inc.
Differential Revision: https://reviews.freebsd.org/D4036
initial thread stack is not adjusted by the tunable, the stack is
allocated too early to get access to the kernel environment. See
TD0_KSTACK_PAGES for the thread0 stack sizing on i386.
The tunable was tested on x86 only. From the visual inspection, it
seems that it might work on arm and powerpc. The arm
USPACE_SVC_STACK_TOP and powerpc USPACE macros seems to be already
incorrect for the threads with non-default kstack size. I only
changed the macros to use variable instead of constant, since I cannot
test.
On arm64, mips and sparc64, some static data structures are sized by
KSTACK_PAGES, so the tunable is disabled.
Sponsored by: The FreeBSD Foundation
MFC after: 2 week
- Fix segment registers to only display the low 16 bits.
- Remove unused handlers and entries for the debug registers.
- Display xcr0 (if valid) in 'show sysregs'.
- Add '0x' prefix to MSR values to match other values in 'show sysregs'.
- MFamd64: Display various MSRs in 'show sysregs'.
- Add a 'show dbregs' to display the value of debug registers.
- Dynamically size the column width for register values to properly
align columns on 64-bit platforms.
- Display %gs for i386 in 'show registers'.
Differential Revision: https://reviews.freebsd.org/D2784
Reviewed by: kib, markj
MFC after: 2 weeks
Undefined symbols have a value of zero, so it makes no sense to return
such a symbol when performing a lookup by value. This occurs for example
when unwinding the stack after calling a NULL function pointer, and we
confusingly report the faulting function as uart_sab82532_class() on
amd64.
Convert db_print_loc_and_inst() to only attempt disassembly if we managed
to find a symbol corresponding to the IP. Otherwise we may fault and
re-enter the debugger.
Reviewed by: jhb
Sponsored by: EMC / Isilon Storage Division
Differential Revision: https://reviews.freebsd.org/D2858
If KSTACK_PAGES was changed to anything alse than the default,
the value from param.h was taken instead in some places and
the value from KENRCONF in some others. This resulted in
inconsistency which caused corruption in SMP envorinment.
Ensure all places where KSTACK_PAGES are used the opt_kstack_pages.h
is included.
The file opt_kstack_pages.h could not be included in param.h
because was breaking the toolchain compilation.
Reviewed by: kib
Obtained from: Semihalf
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D3094
The replacement started at r283088 was necessarily incomplete without
replacing boolean_t with bool. This also involved cleaning some type
mismatches and ansifying old C function declarations.
Pointed out by: bde
Discussed with: bde, ian, jhb
When the FreeBSD kernel is loaded from Xen the symtab and strtab are
not loaded the same way as the native boot loader. This patch adds
three new global variables to ddb that can be used to specify the
exact position and size of those tables, so they can be directly used
as parameters to db_add_symbol_table. A new helper is introduced, so callers
that used to set ksym_start and ksym_end can use this helper to set the new
variables.
It also adds support for loading them from the Xen PVH port, that was
previously missing those tables.
Sponsored by: Citrix Systems R&D
Reviewed by: kib
ddb/db_main.c:
- Add three new global variables: ksymtab, kstrtab, ksymtab_size that
can be used to specify the position and size of the symtab and
strtab.
- Use those new variables in db_init in order to call db_add_symbol_table.
- Move the logic in db_init to db_fetch_symtab in order to set ksymtab,
kstrtab, ksymtab_size from ksym_start and ksym_end.
ddb/ddb.h:
- Add prototype for db_fetch_ksymtab.
- Declate the extern variables ksymtab, kstrtab and ksymtab_size.
x86/xen/pv.c:
- Add support for finding the symtab and strtab when booted as a Xen
PVH guest. Since Xen loads the symtab and strtab as NetBSD expects
to find them we have to adapt and use the same method.
amd64/amd64/machdep.c:
arm/arm/machdep.c:
i386/i386/machdep.c:
mips/mips/machdep.c:
pc98/pc98/machdep.c:
powerpc/aim/machdep.c:
powerpc/booke/machdep.c:
sparc64/sparc64/machdep.c:
- Use the newly introduced db_fetch_ksymtab in order to set ksymtab,
kstrtab and ksymtab_size.
Allow textdumps to be called explicitly from DDB.
If "dump" is called in DDB and textdumps are enabled then abort the
dump and tell the user to turn off textdumps.
Add options TEXTDUMP_PREFERRED to turn textdumps on by default.
Add options TEXTDUMP_VERBOSE to be a bit more verbose while textdumping.
Reviewed by: rwatson
MFC after: 2 weeks
It is implemented via db_trace_thread() for DDB and not implemented
for GDB. This should have been part of r234190.
Pointy hat to: jhb
Reported by: jkim
MFC after: 1 week
It seems strchr() and strrchr() are used more often than index() and
rindex(). Therefore, simply migrate all kernel code to use it.
For the XFS code, remove an empty line to make the code identical to
the code in the Linux kernel.
improvements:
(1) Implement new model in previously missed at91 UART driver
(2) Move BREAK_TO_DEBUGGER and ALT_BREAK_TO_DEBUGGER from opt_comconsole.h
to opt_kdb.h (spotted by np)
(3) Garbage collect now-unused opt_comconsole.h
MFC after: 3 weeks
Approved by: re (bz)
for it. Do not not expect a developer to call doadump(). Calling
doadump does not necessarily work when it's declared static. Nor
does it necessarily do what was intended in the context of text
dumps. The dump command always creates a core dump.
Move printing of error messages from doadump to the dump command,
now that we don't have to worry about being called from DDB.
the watchdog, via the watchdog(9) interface.
For that, the WD_LASTVAL bitwise operation is used. It is mutually
exclusive with any explicit timout passing to the watchdogs.
The last timeout can be returned via the wdog_kern_last_timeout()
KPI.
- Add the possibility to pat the watchdogs installed via the watchdog(9)
interface from the kernel.
In order to do that the new KPI wdog_kern_pat() is offered and it does
accept normalized nanoseconds or WD_LASTVAL.
- Avoid to pass WD_ACTIVE down in the watchdog handlers. All the control
bit processing should over to the upper layer functions and not passed
down to the handlers at all.
These changes are intended to be used in order to fix up the watchdog
tripping in situation when the userland is busted, but protection is still
wanted (examples: shutdown syncing / disk dumping).
Sponsored by: Sandvine Incorporated
Reviewed by: emaste, des, cognet
MFC after: 2 weeks
value.
The timeout is expressed in the form T(N) = (2^N * nanoseconds) and can
be easilly extracted from the watchdog interface as a WD_TO_* macro.
That new functionality is supposed to fix re-entering the kernel from DDB
re-enabling the watchdog again (previously disabled) and also offer the
possibility to break for deadlocked DDB commands.
Please note that retro-compatibility is retained.
Sponsored by: Sandvine Incorporated
Approved by: des
MFC after: 10 days
the debugger back-end has changed. This means that switching from ddb
to gdb no longer requires a "step" which can be dangerous on an
already-crashed kernel.
Also add a capability to get from the gdb back-end back to ddb, by
typing ^C in the console window.
While here, simplify kdb_sysctl_available() by using
sbuf_new_for_sysctl(), and use strlcpy() instead of strncpy() since the
strlcpy semantic is desired.
MFC after: 1 month
