We're too inconsistent with how we use these for them to be useful (and
it's impossible to distinguish between a format error and some other
error from libelf/libdw/libdwfl), so let's just get rid of them and make
it all DRGN_ERROR_OTHER/Exception.
For now, we only support stack traces for the Linux kernel (at least
v4.9) on x86-64, and we only support getting the program counter and
corresponding function symbol from each stack frame.
For stack trace support, we'll need to have some architecture-specific
functionality. drgn's current notion of an architecture doesn't actually
include the instruction set architecture. This change expands it to a
"platform", which includes the ISA as well as the existing flags.
Now that we're not overloading the name "symbol", we can define struct
drgn_symbol as a symbol table entry. For now, this is very minimal: it's
just a name, address, and size. We can then add a way to find the symbol
for a given address, drgn_program_find_symbol(). For now, this is only
supported through the actual ELF symbol tables. However, in the future,
we can probably support adding "symbol finders".
struct drgn_symbol doesn't really represent a symbol; it's just an
object which hasn't been fully initialized (see c2be52dff0 ("libdrgn:
rename object index to symbol index"), it used to be called a "partial
object"). For stack traces, we're going to have a notion of a symbol
that more closely represents an ELF symbol, so let's get rid of the
temporary struct drgn_symbol representation and just return an object
directly.
Currently, programs can be created for three main use-cases: core dumps,
the running kernel, and a running process. However, internally, the
program memory, types, and symbols are pluggable. Expose that as a
callback API, which makes it possible to use drgn in much more creative
ways.
Similar to "libdrgn: make memory reader pluggable with callbacks", we
want to support custom type indexes (imagine, e.g., using drgn to parse
a binary format). For now, this disables the dwarf index tests; we'll
have a better way to test them later, so let's not bother adding more
test scaffolding.
I've been planning to make memory readers pluggable (in order to support
use cases like, e.g., reading a core file over the network), but the
C-style "inheritance" drgn uses internally is awkward as a library
interface; it's much easier to just register a callback. This change
effectively makes drgn_memory_reader a mapping from a memory range to an
arbitrary callback. As a bonus, this means that read callbacks can be
mixed and matched; a part of memory can be in a core file, another part
can be in the executable file, and another part could be filled from an
arbitrary buffer.
drgn has pretty thorough in-program documentation, but it doesn't have a
nice overview or introduction to the basic concepts. This commit adds
that using Sphinx. In order to avoid documenting everything in two
places, the libdrgn bindings have their docstrings generated from the
API documentation. The alternative would be to use Sphinx's autodoc
extension, but that's not as flexible and would also require building
the extension to build the docs. The documentation for the helpers is
generated using autodoc and a small custom extension.
I went back and forth on using setuptools or autotools for the Python
extension, but I eventually settled on using only setuptools after
fighting to get the two to integrate well. However, setuptools is kind
of crappy; for one, it rebuilds every source file when rebuilding the
extension, which is really annoying for development. automake is a
better designed build system overall, so let's use that for the
extension. We override the build_ext command to build using autotools
and copy things where setuptools expects them.
