In an executable, the debug_addr and debug_rnglists sections are
assembled by concatenating the input sections, and each input section
has a header, and each header may have different attributes. So just
parsing the single header isn't right. Parsing the header is not
necessary to handle offsets into these sections which is all we do.
Looking at the header is also problematic because GCC with
-gsplit-dwarf when using DWARF versions 2 through 4 emits a
.debug_addr section, but it has no header. The header was only added
for DWARF 5. So we can't parse the header at all for that case, and we
can't even detect that case in general.
This CL also fixes SeekPC with addrx and strx formats, by not using
the wrong compilation unit to find the address or string base.
To make that work when parsing the compilation unit itself, we add
support for delay the resolution of those values until we know the base.
New test binaries built with
gcc -gdwarf-5 -no-pie debug/dwarf/testdata/line[12].c
(gcc (Debian 10.2.0-15) 10.2.0)
clang -gdwarf-5 -no-pie debug/dwarf/testdata/line[12].c
(clang version 9.0.1-14)
Change-Id: I66783e0eded629bf80c467767f781164d344a54d
Reviewed-on: https://go-review.googlesource.com/c/go/+/277233
Trust: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Than McIntosh <thanm@google.com>
For a common pattern of iterating only over top-level compilation units (CU)
Reader.SkipChildren has decode and meterialize all CU subentries just
to skip them, because DW_TAG_compile_unit does not have DW_AT_sibling.
However, CUs have total size encoded before the unit and we already parse them
and know all unit sizes.
Optimize Reader.SkipChildren to use that size when skipping CUs children.
This speeds up iteration over a 1.3GB object file from 7.5s to 0.73s.
Change-Id: I2a8f00955159b4bd13571409f4817805f934cb69
Reviewed-on: https://go-review.googlesource.com/c/go/+/256217
Run-TryBot: Dmitry Vyukov <dvyukov@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Than McIntosh <thanm@google.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Trust: Than McIntosh <thanm@google.com>
Currently, dwarf.Reader exposes the current compilation unit's address
size, but doesn't expose its byte order. Both are important for
decoding many attributes. For example, location descriptions include
addresses that are encoded in native form for the CU.
This CL exposes the byte order of the compilation unit in the same way
we already expose its address size, which makes it possible to decode
attributes containing native addresses.
Change-Id: I92f156818fe92b049d1dfc1613816bb1689cfadf
Reviewed-on: https://go-review.googlesource.com/c/go/+/192698
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Also fix 64-bit DWARF to read a 64-bit abbrev offset in the
compilation unit.
Change-Id: Idc22e59ffb354d58e9973b62fdbd342acf695859
Reviewed-on: https://go-review.googlesource.com/71171
Reviewed-by: Austin Clements <austin@google.com>
These new methods help find the compilation unit to pass to the
LineReader method in order to find the line information for a PC.
The Ranges method also helps identify the specific function for a PC,
needed to determine the function name.
This uses the .debug.ranges section if necessary, and changes the object
file format packages to pass in the section contents if available.
Change-Id: I5ebc3d27faaf1a126ffb17a1e6027efdf64af836
Reviewed-on: https://go-review.googlesource.com/20769
Reviewed-by: Austin Clements <austin@google.com>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
This adds a test that debug/dwarf can read the skeleton DWARF data
from a split DWARF image (though it doesn't currently support piecing
the external DWARF data back together). This should work because
there's nothing particularly different about skeleton DWARF data, but
previously failed because of poor handling of unrecognized attributes.
Updates #12592.
Change-Id: I2fc5f4679883b05ebd7ec9f0b5c398a758181a32
Reviewed-on: https://go-review.googlesource.com/14542
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: jcd . <jcd@golang.org>
Ian Lance Taylor
Dmitry Vyukov
Austin Clements