Commit Graph

17 Commits

Author SHA1 Message Date
Omar Sandoval
87b7292aa5 Relicense drgn from GPLv3+ to LGPLv2.1+
drgn is currently licensed as GPLv3+. Part of the long term vision for
drgn is that other projects can use it as a library providing
programmatic interfaces for debugger functionality. A more permissive
license is better suited to this goal. We decided on LGPLv2.1+ as a good
balance between software freedom and permissiveness.

All contributors not employed by Meta were contacted via email and
consented to the license change. The only exception was the author of
commit c4fbf7e589 ("libdrgn: fix for compilation error"), who did not
respond. That commit reverted a single line of code to one originally
written by me in commit 640b1c011d ("libdrgn: embed DWARF index in
DWARF info cache").

Signed-off-by: Omar Sandoval <osandov@osandov.com>
2022-11-01 17:05:16 -07:00
Omar Sandoval
04d2dee964 libdrgn: elaborate on core dump p_filesz < p_memsz ambiguity
There's a lot more context here that we should write down. It's also
worth noting that it appears that GDB always zero fills the range
between p_filesz and p_memsz, so if we end up having any other issues
because of this, we might have to concede and go back to the behavior
before commit 02912ca7d0 ("libdrgn: fix handling of p_filesz < p_memsz
in core dumps").

Signed-off-by: Omar Sandoval <osandov@osandov.com>
2022-08-26 12:43:20 -07:00
Glen McCready
9684771d61 libdrgn: Zero fill excluded pages in kernel core dumps rather than FaultError
makedumpfile will exclude zero pages. We found a core file where a
structure straddled a page boundary and the end of the structure
was all zeros so the page was excluded and we were generating a
FaultError trying to access the structure.

This change reverts a portion of that behaviour such that when we are
debugging a kernel core we go back to the zero fill behaviour. To do this
we go back to creating segments based on memsz instead of filesz and
handling the filesz->memsz gap in drgn_read_memory_file.

Fixes: 02912ca7d0 ("libdrgn: fix handling of p_filesz < p_memsz in core dumps")
Signed-off-by: Glen McCready <gkm@mysteryinc.ca>
2022-08-25 11:59:39 -07:00
Omar Sandoval
3595c81a8c libdrgn: binary_search_tree: move member and entry_to_key to DEFINE_BINARY_SEARCH_TREE_FUNCTIONS()
DEFINE_BINARY_SEARCH_TREE_TYPE() doesn't need these. This is preparation
for a potential new use of a BST. But, it's also a good cleanup on its
own and allows us to move some code out of memory_reader.h and into
memory_reader.c. (This is similar to commit 1339dc6a2f ("libdrgn:
hash_table: move entry_to_key to DEFINE_HASH_TABLE_FUNCTIONS()").)

Signed-off-by: Omar Sandoval <osandov@osandov.com>
2022-05-24 15:26:39 -07:00
Omar Sandoval
02912ca7d0 libdrgn: fix handling of p_filesz < p_memsz in core dumps
I implemented the case of a segment in a core file with p_filesz <
p_memsz by treating the difference as zero bytes. This is correct for
ET_EXEC and ET_DYN, but for ET_CORE, it actually means that the memory
existed in the program but was not saved. For userspace core dumps, this
typically happens for read-only file mappings. For kernel core dumps,
makedumpfile does this to indicate memory that was excluded.

Instead, let's return a DRGN_FAULT_ERROR if an attempt is made to read
from these bytes. In the future, we need to read from the
executable/library files when we can.

Signed-off-by: Omar Sandoval <osandov@osandov.com>
2021-12-08 00:02:44 -08:00
Omar Sandoval
c0d8709b45 Update copyright headers to Meta
Signed-off-by: Omar Sandoval <osandov@osandov.com>
2021-11-21 15:59:44 -08:00
Omar Sandoval
0e3054a0ba libdrgn: make addresses wrap around when reading memory
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>
2021-06-03 17:49:29 -07:00
Omar Sandoval
a4b9d68a8c Use GPL-3.0-or-later license identifier instead of GPL-3.0+
Apparently the latter is deprecated and the former is preferred.

Signed-off-by: Omar Sandoval <osandov@osandov.com>
2021-04-03 01:10:35 -07:00
Omar Sandoval
de6a4e07ae libdrgn: fix Doxygen
The Doxygen documentation for libdrgn has bit-rotted over time. Bring
back the Internal module, clean up a few renamed members and parameters,
and fix broken parsing caused by the generic definition macros.

Signed-off-by: Omar Sandoval <osandov@osandov.com>
2020-09-30 01:32:33 -07:00
Omar Sandoval
286c09844e Clean up #includes with include-what-you-use
I recently hit a couple of CI failures caused by relying on transitive
includes that weren't always present. include-what-you-use is a
Clang-based tool that helps with this. It's a bit finicky and noisy, so
this adds scripts/iwyu.py to make running it more convenient (but not
reliable enough to automate it in Travis).

This cleans up all reasonable include-what-you-use warnings and
reorganizes a few header files.

Signed-off-by: Omar Sandoval <osandov@osandov.com>
2020-09-23 16:29:42 -07:00
Omar Sandoval
8b264f8823 Update copyright headers to Facebook and add missing headers
drgn was originally my side project, but for awhile now it's also been
my work project. Update the copyright headers to reflect this, and add a
copyright header to various files that were missing it.
2020-05-15 15:13:02 -07:00
Omar Sandoval
4a8152175b libdrgn: translate EIO from /proc/$pid/mem to DRGN_ERROR_FAULT
For live userspace processes, we add a single [0, UINT64_MAX) memory
file segment for /proc/$pid/mem. Of course, not every address in that
range is valid; reading from an invalid address returns EIO. We should
translate this to a DRGN_ERROR_FAULT instead of DRGN_ERROR_OS, but only
for /proc/$pid/mem.
2019-12-10 13:30:34 -08:00
Omar Sandoval
c0bc72b0ea libdrgn: use splay tree for memory reader
The current array-based memory reader has a bug in the following
scenario:

    prog.add_memory_segment(0xffff0000, 128, ...)
    # This should replace a subset of the first segment.
    prog.add_memory_segment(0xffff0020, 32, ...)
    # This moves the first segment back to the front of the array.
    prog.read(0xffff0000, 32)
    # This finds the first segment instead of the second segment.
    prog.read(0xffff0032, 32)

Fix it by using the newly-added splay tree. This also splits up the
virtual and physical memory segments into separate trees.
2019-05-24 17:48:08 -07:00
Omar Sandoval
baba1ff3f0 libdrgn: make program components pluggable
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.
2019-05-10 12:41:07 -07:00
Omar Sandoval
5200a6652c libdrgn: embed memory reader, type index, and symbol index in program 2019-05-06 14:55:34 -07:00
Omar Sandoval
417a6f0d76 libdrgn: make memory reader pluggable with callbacks
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.
2019-05-06 14:55:34 -07:00
Omar Sandoval
75c3679147 Rewrite drgn core in C
The current mixed Python/C implementation works well, but it has a
couple of important limitations:

- It's too slow for some common use cases, like iterating over large
  data structures.
- It can't be reused in utilities written in other languages.

This replaces the internals with a new library written in C, libdrgn. It
includes Python bindings with mostly the same public interface as
before, with some important improvements:

- Types are now represented by a single Type class rather than the messy
  polymorphism in the Python implementation.
- Qualifiers are a bitmask instead of a set of strings.
- Bit fields are not considered a separate type.
- The lvalue/rvalue terminology is replaced with reference/value.
- Structure, union, and array values are better supported.
- Function objects are supported.
- Program distinguishes between lookups of variables, constants, and
  functions.

The C rewrite is about 6x as fast as the original Python when using the
Python bindings, and about 8x when using the C API directly.

Currently, the exposed API in C is fairly conservative. In the future,
the memory reader, type index, and object index APIs will probably be
exposed for more flexibility.
2019-04-02 14:12:07 -07:00