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I tried to reproduce a problem in test-case gdb.python/py-disasm.exp on a
s390x machine, but when running with target board unix/-m31 I saw that the
required libraries were missing, so I couldn't generate an executable.
However, I realized that I did have an object file, and the test-case should
mostly also work with an object file.
I've renamed gdb.python/py-disasm.exp to gdb.python/py-disasm.exp.tcl and
included it from two new minimal test-case wrappers:
- gdb.python/py-disasm-exec.exp, and
- gdb.python/py-disasm-obj.exp
where the former uses an executable as before, and the latter uses an object
file.
Using an object file required changing the info.read_memory calls in
gdb.python/py-disasm.py:
...
- info.read_memory(1, -info.address + 2)
+ info.read_memory(1, -info.address - 1)
...
because reading from address 2 succeeds. Using address -1 instead does
generate the expected gdb.MemoryError.
Tested on x86_64-linux.
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After fixing test-case gdb.python/py-disasm.exp to recognize the arm nop:
...
nop {0}
...
we run into:
...
disassemble test^M
Dump of assembler code for function test:^M
0x004004d8 <+0>: push {r11} @ (str r11, [sp, #-4]!)^M
0x004004dc <+4>: add r11, sp, #0^M
0x004004e0 <+8>: nop {0}^M
=> 0x004004e4 <+12>: Python Exception <class 'ValueError'>: Buffer \
returned from read_memory is sized 0 instead of the expected 4^M
^M
unknown disassembler error (error = -1)^M
(gdb) FAIL: $exp: global_disassembler=ShowInfoRepr: disassemble test
...
This is caused by this code in gdbpy_disassembler::read_memory_func:
...
gdbpy_ref<> result_obj (PyObject_CallMethod ((PyObject *) obj,
"read_memory",
"KL", len, offset));
...
where len has type "unsigned int", while "K" means "unsigned long long" [1].
Fix this by using "I" instead, meaning "unsigned int".
Also, offset has type LONGEST, which is typedef'ed to int64_t, while "L" means
"long long".
Fix this by using type gdb_py_longest for offset, in combination with format
character "GDB_PY_LL_ARG". Likewise in disasmpy_info_read_memory.
Tested on arm-linux.
Reviewed-By: Alexandra Petlanova Hajkova <ahajkova@redhat.com>
Approved-By: Tom Tromey <tom@tromey.com>
PR python/31845
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=31845
[1] https://docs.python.org/3/c-api/arg.html
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This patch is the result of running 'isort .' in the gdb directory.
Approved-By: Simon Marchi <simon.marchi@efficios.com>
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This commit is the result of the following actions:
- Running gdb/copyright.py to update all of the copyright headers to
include 2024,
- Manually updating a few files the copyright.py script told me to
update, these files had copyright headers embedded within the
file,
- Regenerating gdbsupport/Makefile.in to refresh it's copyright
date,
- Using grep to find other files that still mentioned 2023. If
these files were updated last year from 2022 to 2023 then I've
updated them this year to 2024.
I'm sure I've probably missed some dates. Feel free to fix them up as
you spot them.
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Run black on gdb.python/py-disasm.py file and commit the changes.
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This commit extends the Python Disassembler API to allow for styling
of the instructions.
Before this commit the Python Disassembler API allowed the user to do
two things:
- They could intercept instruction disassembly requests and return a
string of their choosing, this string then became the disassembled
instruction, or
- They could call builtin_disassemble, which would call back into
libopcode to perform the disassembly. As libopcode printed the
instruction GDB would collect these print requests and build a
string. This string was then returned from the builtin_disassemble
call, and the user could modify or extend this string as needed.
Neither of these approaches allowed for, or preserved, disassembler
styling, which is now available within libopcodes for many of the more
popular architectures GDB supports.
This commit aims to fill this gap. After this commit a user will be
able to do the following things:
- Implement a custom instruction disassembler entirely in Python
without calling back into libopcodes, the custom disassembler will
be able to return styling information such that GDB will display
the instruction fully styled. All of GDB's existing style
settings will affect how instructions coming from the Python
disassembler are displayed in the expected manner.
- Call builtin_disassemble and receive a result that represents how
libopcode would like the instruction styled. The user can then
adjust or extend the disassembled instruction before returning the
result to GDB. Again, the instruction will be styled as expected.
To achieve this I will add two new classes to GDB,
DisassemblerTextPart and DisassemblerAddressPart.
Within builtin_disassemble, instead of capturing the print calls from
libopcodes and building a single string, we will now create either a
text part or address part and store these parts in a vector.
The DisassemblerTextPart will capture a small piece of text along with
the associated style that should be used to display the text. This
corresponds to the disassembler calling
disassemble_info::fprintf_styled_func, or for disassemblers that don't
support styling disassemble_info::fprintf_func.
The DisassemblerAddressPart is used when libopcodes requests that an
address be printed, and takes care of printing the address and
associated symbol, this corresponds to the disassembler calling
disassemble_info::print_address_func.
These parts are then placed within the DisassemblerResult when
builtin_disassemble returns.
Alternatively, the user can directly create parts by calling two new
methods on the DisassembleInfo class: DisassembleInfo.text_part and
DisassembleInfo.address_part.
Having created these parts the user can then pass these parts when
initializing a new DisassemblerResult object.
Finally, when we return from Python to gdbpy_print_insn, one way or
another, the result being returned will have a list of parts. Back in
GDB's C++ code we walk the list of parts and call back into GDB's core
to display the disassembled instruction with the correct styling.
The new API lives in parallel with the old API. Any existing code
that creates a DisassemblerResult using a single string immediately
creates a single DisassemblerTextPart containing the entire
instruction and gives this part the default text style. This is also
what happens if the user calls builtin_disassemble for an architecture
that doesn't (yet) support libopcode styling.
This matches up with what happens when the Python API is not involved,
an architecture without disassembler styling support uses the old
libopcodes printing API (the API that doesn't pass style info), and
GDB just prints everything using the default text style.
The reason that parts are created by calling methods on
DisassembleInfo, rather than calling the class constructor directly,
is DisassemblerAddressPart. Ideally this part would only hold the
address which the part represents, but in order to support backwards
compatibility we need to be able to convert the
DisassemblerAddressPart into a string. To do that we need to call
GDB's internal print_address function, and to do that we need an
gdbarch.
What this means is that the DisassemblerAddressPart needs to take a
gdb.Architecture object at creation time. The only valid place a user
can pull this from is from the DisassembleInfo object, so having the
DisassembleInfo act as a factory ensures that the correct gdbarch is
passed over each time. I implemented both solutions (the one
presented here, and an alternative where parts could be constructed
directly), and this felt like the cleanest solution.
Reviewed-By: Eli Zaretskii <eliz@gnu.org>
Reviewed-By: Tom Tromey <tom@tromey.com>
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This commit is a refactor ahead of the next change which will make
disassembler styling available through the Python API.
Unfortunately, in order to make the styling support available, I think
the easiest solution is to make a very small change to the existing
API.
The current API relies on returning a DisassemblerResult object to
represent each disassembled instruction. Currently GDB allows the
DisassemblerResult class to be sub-classed, which could mean that a
user tries to override the various attributes that exist on the
DisassemblerResult object.
This commit removes this ability, effectively making the
DisassemblerResult class final.
Though this is a change to the existing API, I'm hoping this isn't
going to cause too many issues:
- The Python disassembler API was only added in the previous release
of GDB, so I don't expect it to be widely used yet, and
- It's not clear to me why a user would need to sub-class the
DisassemblerResult type, I allowed it in the original patch
because at the time I couldn't see any reason to NOT allow it.
Having prevented sub-classing I can now rework the tail end of the
gdbpy_print_insn function; instead of pulling the results out of the
DisassemblerResult object by calling back into Python, I now cast the
Python object back to its C++ type (disasm_result_object), and access
the fields directly from there. In later commits I will be reworking
the disasm_result_object type in order to hold information about the
styled disassembler output.
The tests that dealt with sub-classing DisassemblerResult have been
removed, and a new test that confirms that DisassemblerResult can't be
sub-classed has been added.
Reviewed-By: Eli Zaretskii <eliz@gnu.org>
Reviewed-By: Tom Tromey <tom@tromey.com>
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Add the DisassemblerResult.__str__ method. This gives the same result
as the DisassemblerResult.string attribute, but can be useful
sometimes depending on how the user is trying to print the object.
There's a test for the new functionality.
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Add a __repr__ method for the DisassembleInfo and DisassemblerResult
types, and add some tests for these new methods.
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This commit is the result of running the gdb/copyright.py script,
which automated the update of the copyright year range for all
source files managed by the GDB project to be updated to include
year 2023.
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On s390x-linux, I run into:
...
(gdb) disassemble test^M
Dump of assembler code for function test:^M
0x0000000001000638 <+0>: stg %r11,88(%r15)^M
0x000000000100063e <+6>: lgr %r11,%r15^M
0x0000000001000642 <+10>: nop 0^M
=> 0x0000000001000646 <+14>: nop 0^M
0x000000000100064a <+18>: nop 0^M
0x000000000100064e <+22>: lhi %r1,0^M
0x0000000001000652 <+26>: lgfr %r1,%r1^M
0x0000000001000656 <+30>: lgr %r2,%r1^M
0x000000000100065a <+34>: lg %r11,88(%r11)^M
0x0000000001000660 <+40>: br %r14^M
End of assembler dump.^M
(gdb) FAIL: gdb.python/py-disasm.exp: global_disassembler=: disassemble test
...
The problem is that the test-case expects "nop" but on s390x we have instead
"nop\t0".
Fix this by allowing the insn.
Tested on s390x-linux and x86_64-linux.
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After this commit:
commit 81384924cdcc9eb2676dd9084b76845d7d0e0759
Date: Tue Apr 5 11:06:16 2022 +0100
gdb: have gdb_disassemble_info carry 'this' in its stream pointer
The disassemble_info::stream field will no longer be a ui_file*. That
commit failed to update one location in py-disasm.c though.
While running some tests using the Python disassembler API, I
triggered a call to gdbpy_disassembler::print_address_func, and, as I
had compiled GDB with the undefined behaviour sanitizer, GDB crashed
as the code currently (incorrectly) casts the stream field to be a
ui_file*.
In this commit I fix this error.
In order to test this case I had to tweak the existing test case a
little. I also spotted some debug printf statements in py-disasm.py,
which I have removed.
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This commit extends the Python API to include disassembler support.
The motivation for this commit was to provide an API by which the user
could write Python scripts that would augment the output of the
disassembler.
To achieve this I have followed the model of the existing libopcodes
disassembler, that is, instructions are disassembled one by one. This
does restrict the type of things that it is possible to do from a
Python script, i.e. all additional output has to fit on a single line,
but this was all I needed, and creating something more complex would,
I think, require greater changes to how GDB's internal disassembler
operates.
The disassembler API is contained in the new gdb.disassembler module,
which defines the following classes:
DisassembleInfo
Similar to libopcodes disassemble_info structure, has read-only
properties: address, architecture, and progspace. And has methods:
__init__, read_memory, and is_valid.
Each time GDB wants an instruction disassembled, an instance of
this class is passed to a user written disassembler function, by
reading the properties, and calling the methods (and other support
methods in the gdb.disassembler module) the user can perform and
return the disassembly.
Disassembler
This is a base-class which user written disassemblers should
inherit from. This base class provides base implementations of
__init__ and __call__ which the user written disassembler should
override.
DisassemblerResult
This class can be used to hold the result of a call to the
disassembler, it's really just a wrapper around a string (the text
of the disassembled instruction) and a length (in bytes). The user
can return an instance of this class from Disassembler.__call__ to
represent the newly disassembled instruction.
The gdb.disassembler module also provides the following functions:
register_disassembler
This function registers an instance of a Disassembler sub-class
as a disassembler, either for one specific architecture, or, as a
global disassembler for all architectures.
builtin_disassemble
This provides access to GDB's builtin disassembler. A common
use case that I see is augmenting the existing disassembler output.
The user code can call this function to have GDB disassemble the
instruction in the normal way. The user gets back a
DisassemblerResult object, which they can then read in order to
augment the disassembler output in any way they wish.
This function also provides a mechanism to intercept the
disassemblers reads of memory, thus the user can adjust what GDB
sees when it is disassembling.
The included documentation provides a more detailed description of the
API.
There is also a new CLI command added:
maint info python-disassemblers
This command is defined in the Python gdb.disassemblers module, and
can be used to list the currently registered Python disassemblers.
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