- Directly call KdpGetMemorySizeInMBs() within KdpPrintBanner(),
instead of having the caller doing it.
- Use the miarm.h MiIsMemoryTypeInvisible() helper.
- Add Doxygen comments.
- Move local variables to the code blocks where they are used.
- if-s one-line bodies on their own lines.
- Massage the boot-images symbols loading, using a for-loop.
Override DbgPrint(), used by the debugger banner DPRINTs,
because KdInitSystem() can be called under the debugger lock
by KdEnableDebugger(WithLock)().
In this case, when DbgPrint() (re-)enters the debugger via an
interrupt and acquires the debugger lock, a deadlock occurs.
- The debugging banner helpers *CANNOT* be in the INIT section, because
it is possible for KdInitSystem() to enable the debugger **MUCH LATER**
after boot time. (Reverts part of commit f239ca0f0 (r72922).)
This can happen in two situations:
* When the debugger is in CRASHDEBUG mode, i.e. initialized at boot
time but not immediately enabled, and a BSOD happens later that
enables the debugger with a `KdInitSystem(0, NULL)` call.
* When the debugger was possibly manually disabled with a
KdDisableDebugger() call, then later re-enabled with a
KdEnableDebugger() call.
- In the same cases as described above, the KeLoaderBlock is freed after
boot time. Thus, KdpGetMemorySizeInMBs() cannot use it and enumerate
the MemoryDescriptors to evaluate the number of physical memory pages
available on the system. Instead, we can use what the memory manager
has already computed, since the latter is already initialized by now.
These two fixes avoid (invisible) crashes when (re-)enabling
the debugger at non-boot run time.
I.e. when LoaderBlock != NULL and we have loaded the initial hal and
ntoskrnl symbols. KdBreakAfterSymbolLoad is then checked for when the
other boot symbols have been loaded by ex/init.c!ExpLoadBootSymbols(),
invoked by ExpInitializeExecutive().
This basically avoids re-entering the debugger (via the embedded breakpoint)
while we are already running within its context.
In addition, this allows the tests for Kd/NtSystemDebugControl
(see PRs #7424 and #7426) to run without having ReactOS to crash.
Addendum to commit de81021ba.
Otherwise, we get the following build error:
\ntoskrnl\kd64\kddata.c(532,5): error: initializer element is not a compile-time constant
PtrToUL64(RtlpBreakWithStatusInstruction),
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
\ntoskrnl\kd64\kddata.c(526,26): note: expanded from macro 'PtrToUL64'
#define PtrToUL64(x) ((ULPTR64)(x))
^~~~~~~~~~~~
See this command's documentation:
https://docs.microsoft.com/en-us/windows-hardware/drivers/debugger/-dbgprint
and the section "DbgPrint buffer and the debugger"
https://docs.microsoft.com/en-us/windows-hardware/drivers/debugger/reading-and-filtering-debugging-messages#dbgprint-buffer-and-the-debugger
for more details.
- Loosely implement the function, based on our existing circular printout
buffers in kdio.c.
- Enable its usage in the KdpPrint() and KdpPrompt() functions.
Notice that this function will *only* capture the strings being sent **to**
the debugger, and not the strings the debugger itself produce. (This means
that we cannot use the KdPrintCircularBuffer as a replacement for our
KDBG dmesg one, for example...)
How to test:
Run ReactOS under WinDbg, and use the !dbgprint command to view the
buffer. You can also use the Memory Window, place yourself at the
address pointed by KdPrintCircularBuffer and KdPrintWritePointer, and
read its contents.
What you should observe:
Prior notice: The circular buffer in debug builds of ReactOS and Windows
is 0x8000 bytes large. In release builds, its size is down to 0x1000.
1- When you start e.g. the 2nd-stage GUI installation of ReactOS, going
past the initial "devices installation" and letting it stabilize on
the Welcome page, break into WinDbg and run the !dbgprint command. You
should notice that the end of its output is weirdly truncated, compared
to what has been actually emitted to the debug output. Comparing this
with the actual contents of the circular buffer (via Memory Window),
shows that the buffer contents is actually correct.
2- Copy all the text that has been output by the !dbgprint command and
paste it in an editor; count the number of all characters appearing +
newlines (only CR or LF), and observe that this number is "mysteriously"
equal to 16384 == 0x4000.
3- Continue running ReactOS installation for a little while, breaking back
back into WinDbg and looking at !dbgprint again. Its output seems to be
still stopping at the same place as before (but the actual buffer memory
contents shows otherwise). Continue running ROS installation, and break
into the debugger when ROS is about to restart. You should now observe
that the dbgprint buffer rolled over:
dd nt!KdPrintRolloverCount shows 1.
Carefully analysing the output of !dbgprint, however, you will notice
that it looks a bit garbage-y: the first part of the output is actually
truncated after 16384 characters, then you get a second part of the
buffer showing what ReactOS was printing while shutting down. Then
you get again what was shown at the top of the !dbgprint output.
(Of course, comparing with the actual contents of the circular buffer
in memory shows that its contents are fine...)
The reason of these strange observations, is because there is an intrinsic
bug in the !dbgprint command implementation (in kdexts.dll). Essentially,
it displays the contents of the circular buffer in two single dprintf()
calls: one for the "older" (bottom) part of the buffer:
[WritePointer, EndOfBuffer]
and one for the "newer" (upper) part of the buffer:
[CircularBuffer, WritePointer[ .
The first aspect of the bug (causing observation 3), is that those two
parts are not necessarily NULL-terminated strings (especially after
rollover), so for example, displaying the upper part of the buffer, will
potentially also display part of the buffer's bottom part.
The second aspect of the bug (explaining observations 1 and 2), is due
to the implementation of the dprintf() function (callback in dbgenv.dll).
There, it uses a fixed-sized buffer of size 0x4000 == 16384 characters.
Since the output of the circular buffer is not done by little chunks,
but by the two large parts, if any of those are larger than 0x4000 they
get truncated on display.
(This last observation is confirmed in a completely different context by
https://community.osr.com/discussion/112439/dprintf-s-max-string-length .)
But the underlying GCC stupidity is still there (15 years later).
However, enable it only in 32-bit GCC builds, not in 64-bits nor with MSVC.
See commit b9cd3f2d9 (r25845) for some details.
GCC is indeed still incapable of casting 32-bit pointers up to 64-bits,
when static-initializing arrays (**outside** a function) without emitting
the error:
"error: initializer element is not constant"
(which might somehow indicate it actually tries to generate executable
code for casting the pointers, instead of doing it at compile-time).
Going down the rabbit hole, other stupidities show up:
Our PVOID64 type and the related POINTER_64 (in 32-bit archs), or the
PVOID32 and POINTER_32 (in 64-bit archs), are all silently broken in
GCC builds, because the pointer size attributes __ptr64 and __ptr32,
which are originally MSVC-specific, are defined to nothing in _mingw.h.
(And similarly for the __uptr and __sptr sign-extension attributes.)
Clang and other sane ompilers has since then implemented those (enabled
with -fms-extensions), but not GCC. The closest thing that could exist
for GCC is to do:
#define __ptr64 __attribute__((mode(DI)))
in order to get a 64-bit-sized pointer type with
typedef void* __ptr64 PVOID64;
but even this does not work, with the error:
"error: invalid pointer mode 'DI'"
Addendum to 608032bd and 835c3023.
The IRQL is actually raised by KeFreezeExecution() and lowered by
KeThawExecution(), always to HIGH_IRQL on MP systems, or if necessary
on UP. These functions are called respectively by KdEnterDebugger()
and KdExitDebugger().
KD64: Raise to HIGH_LEVEL when entering trap
KDBG: lower to DISPATCH_LEVEL when applying IRQL hack & use a worker thread to load symbols
KD&KDBG: Actually unload symbols when required
Raise IRQL before entering debugger, so that KeAcquireSpinLockAtDpcLevel works as expected.
- HIGH_LEVEL since we don't know where we are coming from.
Do not try to read debug symbol from files in KDBG.
- There is no reason that this works if Mm didn't map it in the first place.
- Change INIT_FUNCTION and INIT_SECTION to CODE_SEG("INIT") and DATA_SEG("INIT") respectively
- Remove INIT_FUNCTION from function prototypes
- Remove alloc_text pragma calls as they are not needed anymore
