delta/go-git.git/src/debug/dwarf, branch dev.cmdgo

debug/dwarf: delay array type fixup to handle type cycles

2021-05-13T12:32:21+00:00

A user encountered a debug/dwarf crash when running the dwarf2json
tool (https://github.com/volatilityfoundation/dwarf2json) on a
debug-built copy of the linux kernel. In this crash, the DWARF type
reader was trying to examine the contents of an array type while that
array type was still in the process of being constructed (due to
cycles in the type graph).

To avoid such situations, this patch extends the mechanism introduced
in https://go-review.googlesource.com/18459 (which handles typedef
types) to delay fixup of array types as well.

Change-Id: I303f6ce5db1ca4bd79da3581957dfc2bfc17cc01
Reviewed-on: https://go-review.googlesource.com/c/go/+/319329
Trust: Than McIntosh 
Run-TryBot: Than McIntosh 
Reviewed-by: Cherry Mui 
Reviewed-by: Yi Chou 
TryBot-Result: Go Bot

debug/dwarf: skip over zero-length compilation units

2021-04-23T21:42:56+00:00

DWARF sections generated by mingw-clang seem to include these
(not often - only one out of many in the binary that I am looking at).
Skipping over them, everything parses correctly.

This makes TestDefaultLinkerDWARF pass on windows/arm64.

Change-Id: Ie4a7daa1423f51cbc8c4aac88b1d27c3b52ee880
Reviewed-on: https://go-review.googlesource.com/c/go/+/312031
Trust: Russ Cox 
Run-TryBot: Russ Cox 
TryBot-Result: Go Bot 
Reviewed-by: Cherry Zhang

debug/dwarf: support DW_FORM_rnglistx aka formRnglistx

2021-03-17T00:54:09+00:00

Change-Id: I7df915978af3488f46a27595a1b04d0d33f81f7b
Reviewed-on: https://go-review.googlesource.com/c/go/+/302369
Trust: Ian Lance Taylor 
Run-TryBot: Ian Lance Taylor 
TryBot-Result: Go Bot 
Reviewed-by: Than McIntosh

all: remove duplicate words

2021-03-13T11:56:59+00:00

Change-Id: Ib0469232a2b69a869e58d5d24990ad74ac96ea56
GitHub-Last-Rev: eb38e049ee1e773392ff3747e1eb2af20dd50dcd
GitHub-Pull-Request: golang/go#44805
Reviewed-on: https://go-review.googlesource.com/c/go/+/299109
Trust: Emmanuel Odeke 
Run-TryBot: Emmanuel Odeke 
TryBot-Result: Go Bot 
Reviewed-by: Bryan C. Mills

debug/dwarf: don't try to parse addr/rnglists header

2020-12-14T18:06:06+00:00

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 
Reviewed-by: Than McIntosh

all: update to use os.ReadFile, os.WriteFile, os.CreateTemp, os.MkdirTemp

2020-12-09T19:12:23+00:00

As part of #42026, these helpers from io/ioutil were moved to os.
(ioutil.TempFile and TempDir became os.CreateTemp and MkdirTemp.)

Update the Go tree to use the preferred names.

As usual, code compiled with the Go 1.4 bootstrap toolchain
and code vendored from other sources is excluded.

ReadDir changes are in a separate CL, because they are not a
simple search and replace.

For #42026.

Change-Id: If318df0216d57e95ea0c4093b89f65e5b0ababb3
Reviewed-on: https://go-review.googlesource.com/c/go/+/266365
Trust: Russ Cox 
Run-TryBot: Russ Cox 
TryBot-Result: Go Bot 
Reviewed-by: Ian Lance Taylor

cmd/link: emit include directories in DWARF line table prologue

2020-10-30T18:01:54+00:00

This patch changes the way the linker emits the DWARF line table
prologue, specifically the file table. Previously files were left
unmodified, and the directory table was empty. For each compilation
unit we now scan the unit file table and build up a common set of
directories, emit them into the directory table, and then emit file
entries that refer to the dirs. This provides a modest binary size
savings.

For kubernetes kubelet:

$ objdump -h /tmp/kubelet.old | fgrep debug_line
 36 .zdebug_line  019a55f5  0000000000000000  0000000000000000  084a5123  2**0
$ objdump -h /tmp/kubelet.new | fgrep debug_line
 36 .zdebug_line  01146fd2  0000000000000000  0000000000000000  084a510a  2**0

[where the value following the section name above is the section size
in hex, so roughly a 30% decrease in this case.]

The actual savings will depend on the length of the pathnames
involved, so it's hard to really pin down how much savings we'll see
here. In addition, emitting the files this way reduces the
"compressibility" of the line table, so there could even be cases
where we don't win at all.

Updates #6853, #19784, #36495.

Change-Id: I298d8561da5ed3ebc9d38aa772874851baa2f4f4
Reviewed-on: https://go-review.googlesource.com/c/go/+/263017
Run-TryBot: Than McIntosh 
TryBot-Result: Go Bot 
Reviewed-by: Austin Clements 
Trust: Than McIntosh

debug/dwarf: add support for DWARFv5 to (*Data).Ranges

2020-10-24T04:11:41+00:00

Updates the (*Data).Ranges method to work with DWARFv5 which uses the
new debug_rnglists section instead of debug_ranges.

This does not include supporting DW_FORM_rnglistx.

General support for DWARFv5 was added by CL 175138.

Change-Id: I01f919a865616a3ff12f5bf649c2c9abf89fcf52
Reviewed-on: https://go-review.googlesource.com/c/go/+/236657
Run-TryBot: Ian Lance Taylor 
TryBot-Result: Go Bot 
Reviewed-by: Ian Lance Taylor 
Trust: Emmanuel Odeke

debug/dwarf: speed up SkipChildren for compilation units

2020-09-21T20:14:27+00:00

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 
TryBot-Result: Go Bot 
Reviewed-by: Than McIntosh 
Reviewed-by: Ian Lance Taylor 
Trust: Than McIntosh

debug/dwarf: call strings.EqualFold instead of calling Lower twice

2019-10-26T02:36:26+00:00

Change-Id: I8dcb425c37a067277549ba3bda6a21206459890a
GitHub-Last-Rev: dc51b9b425ca51cd0a4ac494d4c7a3c0e2306951
GitHub-Pull-Request: golang/go#35132
Reviewed-on: https://go-review.googlesource.com/c/go/+/203097
Run-TryBot: Ian Lance Taylor 
TryBot-Result: Gobot Gobot 
Reviewed-by: Ian Lance Taylor