These were added in DWARF 5. They need to know the CU that they're being
evaluated in, but the parameters for drgn_eval_dwarf_expression() were
already getting unwieldy. Wrap the evaluation context in a new struct
drgn_dwarf_expression_context, add the additional CU information, and
implement the operations.
Signed-off-by: Omar Sandoval <osandov@osandov.com>
The main changes are:
1. Skipping the new attribute forms.
2. Handling DW_FORM_strx*, DW_FORM_line_strp, and DW_FORM_implicit_const
for the attributes that we care about.
3. Parsing the new unit header format.
4. Parsing the new line number program header format.
Note that Clang currently produces an incorrect DWARF 5 line number
program header for the Linux kernel (https://reviews.llvm.org/D105662),
so some types are not properly deduplicated in that case.
Closes#104.
Signed-off-by: Omar Sandoval <osandov@osandov.com>
dwfl_module_getsrc() relies on .debug_aranges to find the CU containing
the PC. If the module has a missing or incomplete .debug_aranges, it
fails. This lookup is actually redundant since we already found the CU
when we unwound the stack. Use the libdw helpers that take the CU DIE
instead to avoid this. We also need to save the CU for frames where we
found it but couldn't find the subprogram (typically assembly files).
Signed-off-by: Omar Sandoval <osandov@osandov.com>
Clang does not generate .debug_aranges by default, but the GNU toolchain
does. This means that a Linux kernel binary compiled with Clang and GNU
binutils will have ranges in .debug_aranges for assembly files and
nothing else. This breaks our assumption that a non-empty .debug_aranges
has ranges for every compilation unit. Fix it by always falling back to
checking every CU if a range was not found in .debug_aranges.
Signed-off-by: Omar Sandoval <osandov@osandov.com>
LEB128 allows for redundant zero/sign bits, but we currently always
treat extra bytes as overflow. Let's check those bytes correctly.
Signed-off-by: Omar Sandoval <osandov@osandov.com>
Somehow I missed this form, and I've never seen it used. It's the same
as DW_FORM_exprloc for our purposes, so it's an easy fix.
Signed-off-by: Omar Sandoval <osandov@osandov.com>
There are a few places in the DWARF indexing code that we skip a 64-bit
size. On 32-bit systems, this can wrap if the count is greater than
SIZE_MAX. Rather than requiring vigilance against this, change the size
to uint64_t.
Signed-off-by: Omar Sandoval <osandov@osandov.com>
Older versions of GCC and Clang don't accept const variables for
initializers ("error: initializer element is not constant"), so #define
the FNV constants instead.
Signed-off-by: Omar Sandoval <osandov@osandov.com>
We currently don't include the compilation directory when hashing file
names for deduplication. This can cause us to incorrectly deduplicate a
definition if, for example, two libraries have a definition with the
same name in files with the same name. Fix this by hashing the full file
path including the compilation directory.
This also requires reworking our strategy for path normalization to
better handle ".." components, since directories may end up outside of
the compilation directory. The new strategy keeps a linked list of
hashes (now FNV-1a instead of SipHash) for each parent directory. This
is actually more efficient than the previous approach, offsetting the
cost of the extra hash computations for the compilation directory. It
also correctly handles file names in the line number program header
which consist of multiple components.
Signed-off-by: Omar Sandoval <osandov@osandov.com>
I missed the drgn_program_set_kdump() code path when making sure that we
set the platform before adding memory segments.
Fixes: 0e3054a0ba ("libdrgn: make addresses wrap around when reading memory")
Signed-off-by: Omar Sandoval <osandov@osandov.com>
This workaround was originally present in commit e5874ad18a ("libdrgn:
use libdwfl"). We dropped in in commit 6a13d74c0c ("libdrgn: build
with bundled elfutils") because the bundled version of elfutils had the
fix. We forgot to bring it back in commit 4c5c5f3842 ("Remove bundled
version of elfutils") even though we support versions without the fix.
Reported-by: Serapheim Dimitropoulos <serapheim@delphix.com>
Signed-off-by: Omar Sandoval <osandov@osandov.com>
copy_lsbytes() doesn't copy enough bytes when copying from a smaller
little-endian value to a larger big-endian value. This was caught by the
test cases for DW_OP_deref{,_size}, but it can affect other places when
debugging a little-endian target from a big-endian host or vice-versa.
Closes#105.
Signed-off-by: Omar Sandoval <osandov@osandov.com>
The stack trace variable work introduced a regression that causes
objects with size zero to always be marked absent even if they have an
address. This matters because GCC sometimes seems to omit the complete
array type for arrays declared without a length, so an array variable
can end up with an incomplete array type. I saw this with the
"swapper_spaces" variable in mm/swap_state.c from the Linux kernel.
Make sure to use the address of an empty piece if the variable is also
empty.
Fixes: ffcb9ccb19 ("libdrgn: debug_info: implement creating objects from DWARF location descriptions")
Signed-off-by: Omar Sandoval <osandov@osandov.com>
drgn depends heavily on libelf and libdw, so it's useful to know what
version we're using. Add drgn._elfutils_version and use that in the CLI
and in the test cases where we currently check the libdw version.
Signed-off-by: Omar Sandoval <osandov@osandov.com>
After all of the preparatory work, the last two missing pieces are a way
to find a variable by name in the list of scopes that we saved while
unwinding, and a way to find the containing scopes of an inlined
function. With that, we can finally look up parameters and variables in
stack traces.
Signed-off-by: Omar Sandoval <osandov@osandov.com>
If we want to access a parameter or local variable in an inlined
function, then we need a stack frame for that function. It's also much
more useful to see inlined functions in the stack trace in general. So,
when we've unwound the registers for a stack frame, walk the debugging
information to find all of the (possibly inlined) functions at the
program counter, and add a drgn stack frame for each of those.
Also add StackFrame.name and StackFrame.is_inline so that we can
distinguish inline frames. Also add StackFrame.source() to get the
filename and line and column numbers. Finally, add the source code
location to pretty-printed stack traces and add pretty-printing for
individual stack frames that includes extra information.
Signed-off-by: Omar Sandoval <osandov@osandov.com>
This will be used for finding the ancestors of the abstract instance
root corresponding to a concrete inlined instance root for variable
lookups in inlined functions.
Signed-off-by: Omar Sandoval <osandov@osandov.com>
This will be used for finding functions, inlined functions, and blocks
containing a PC for stack unwinding and variable lookups.
Signed-off-by: Omar Sandoval <osandov@osandov.com>
We have a couple of upcoming use cases for iterating through all of the
DIEs in a module: searching for scopes and searching for a DIE's
ancestors. Add a DIE iterator interface to abstract away the details of
walking DIEs and allows us to efficiently track ancestors.
Signed-off-by: Omar Sandoval <osandov@osandov.com>
Add support for evaluating a DWARF location description and translating
it into a drgn object. In this commit, this is just used for global
variables, but an upcoming commit will wire this up to stack traces for
parameters and local variables.
There are a few locations that drgn's object model can't represent yet.
DW_OP_piece/DW_OP_bit_piece can describe objects that are only partially
known or partially in memory; we approximate these where we can. We
don't have a good way to support DW_OP_implicit_pointer at all yet.
This also adds test cases for DWARF expressions, which we couldn't
easily test before.
Signed-off-by: Omar Sandoval <osandov@osandov.com>
Implement looking up location descriptions and evaluating DW_OP_fbreg.
This isn't actually used yet since CFI expressions don't have a current
function DIE, but it will be used for parameters/local variables in
stack traces.
Signed-off-by: Omar Sandoval <osandov@osandov.com>
It doesn't make a difference anywhere it's currently used, but let's do
it just in case that changes in the future.
Signed-off-by: Omar Sandoval <osandov@osandov.com>
A malformed DWARF expression can easily get us into an infinite loop.
Avoid this by capping the number of operations that we'll execute.
Signed-off-by: Omar Sandoval <osandov@osandov.com>
Define that addresses for memory reads wrap around after the maximum
address rather than the current unpredictable behavior. This is done by:
1. Reworking drgn_memory_reader to work with an inclusive address range
so that a segment can contain UINT64_MAX. drgn_memory_reader remains
agnostic to the maximum address and requires that address ranges do
not overflow a uint64_t.
2. Adding the overflow/wrap-around logic to
drgn_program_add_memory_segment() and drgn_program_read_memory().
3. Changing direct uses of drgn_memory_reader_reader() to
drgn_program_read_memory() now that they are no longer equivalent.
(For some platforms, a fault might be more appropriate than wrapping
around, but this is a step in the right direction.)
Signed-off-by: Omar Sandoval <osandov@osandov.com>
If the program already had a platform set, we should its callbacks
instead of the ones from the ELF file's platform.
Signed-off-by: Omar Sandoval <osandov@osandov.com>
drgn.Program has supported the "in" operator since commit 25e7a9d3b8
("libdrgn/python: implement Program.__contains__"), but it's
undocumented and unannotated. Add a type annotation with a docstring
along with a METH_COEXIST method.
Signed-off-by: Omar Sandoval <osandov@osandov.com>
libomp (at least in LLVM 9 and 10) seems to have buggy OpenMP tasking
support. See commit 1cc3868955 ("CI: temporarily disable Clang") for
one example. OpenMP tasks aren't buying us much; they simplify DWARF
index updates in some places but complicate it in others. Let's ditch
tasks and go back to building an array of CUs to index similar to what
we did before commit f83bb7c71b ("libdrgn: move debugging information
tracking into drgn_debug_info"). There is no significant performance
difference.
Signed-off-by: Omar Sandoval <osandov@osandov.com>
First, add instructions for DW_FORM_indirect. Then, we can call the
function to convert a form to an instruction whenever we see an indirect
instruction.
Note that without elfutils commit d63b26b8d21f ("libdw: handle
DW_FORM_indirect when reading attributes") (queued for elfutils
0.184), DW_FORM_indirect will cause errors later when parsing with
libdw.
Signed-off-by: Jay Kamat <jaygkamat@gmail.com>
Rather than silently ignoring attributes whose form we don't recognize,
return an error. This way, we won't mysteriously skip indexing DIEs.
While we're doing this, split the form -> instruction mapping to its own
functions.
Signed-off-by: Omar Sandoval <osandov@osandov.com>
I often use examples/load_debug_info to benchmark loading/DWARF
indexing, so add a -T option that prints the time it takes to load debug
info.
Signed-off-by: Omar Sandoval <osandov@osandov.com>
When using type units, skeleton declarations are made instead of
concrete ones. However, these declarations have signature tags attached
that point to the type unit with the definition, so we can simply follow
the signature to get the concrete type.
Signed-off-by: Jay Kamat <jaygkamat@gmail.com>
Adds support for parsing of type units as enabled by
-fdebug-types-section. If a module has both a debug info section and
type unit section, both are read.
Signed-off-by: Jay Kamat <jaygkamat@gmail.com>
If the DIE passed to drgn_type_from_dwarf_internal() is a declaration,
then we overwrite it with dwarf_offdie(). As far as I can tell, this
doesn't break anything at the moment, but it's sketchy to overwrite an
input parameter and may cause issues in the future. Use a temporary DIE
on the stack in this case instead.
Signed-off-by: Omar Sandoval <osandov@osandov.com>
CPython commit fb5db7ec5862 ("bpo-42006: Stop using PyDict_GetItem,
PyDict_GetItemString and _PyDict_GetItemId. (GH-22648)") (in v3.10)
removed _PyDict_GetItemId() because it suppresses errors. Use
_PyDict_GetItemIdWithError() instead (which we should've been using
anyways).
Closes#101.
Signed-off-by: Omar Sandoval <osandov@osandov.com>
