On Solaris, in the runtime it defines the external name of
runtime.etext as _etext (runtime/os3_solaris.go:13). In CL 224939
we changed to put external names in the ELF symbol table more
consistently. In this case it will contain _etext but not
runtime.etext.
To be conservative, this CL defines both runtime.etext and _text
in the linker.
Change-Id: I79f196e87b655042be97b0fbbab02d0ebc8db2fa
Reviewed-on: https://go-review.googlesource.com/c/go/+/225537
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Than McIntosh <thanm@google.com>
The lookup is only used for DWARF section symbols, for which we
can just link the symbols to the sections.
Change-Id: Id8426fbf59bab2528f57e28e2043e0b405656a9f
Reviewed-on: https://go-review.googlesource.com/c/go/+/225204
Reviewed-by: Jeremy Faller <jeremy@golang.org>
Reviewed-by: Than McIntosh <thanm@google.com>
It is needed in Xcoffadddynrel. And it will be needed once we
move more things to new style (the sym.Symbol parameters will
also need to change).
Change-Id: Ie12683f9b44e21f1e6ea711bf2f4c5c32282e5b3
Reviewed-on: https://go-review.googlesource.com/c/go/+/225203
Reviewed-by: Jeremy Faller <jeremy@golang.org>
Reviewed-by: Than McIntosh <thanm@google.com>
This change moves datap from global space into the link context. Rather
than having it exist in context, we could have it returned from dodata,
and pass it as a parameter, but it is used in awkward places in the
Arch functions. Easiest for now is just keeping it in the context, until
we more formally move it to slices of loader.Sym.
This is a largely non-functional change.
Change-Id: Ica93bd857c39913ad470a61c63bc8d21704d6308
Reviewed-on: https://go-review.googlesource.com/c/go/+/222664
Reviewed-by: Than McIntosh <thanm@google.com>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
This is a non-functional change, just moving things around, making
dodata a more approachable piece of code.
Change-Id: I06fa047cbef2313040a31998fa8d242ccb2fedea
Reviewed-on: https://go-review.googlesource.com/c/go/+/222662
Run-TryBot: Jeremy Faller <jeremy@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Than McIntosh <thanm@google.com>
If the variable is not reachable, don't bother setting it.
The old behavior was to set it but not mark it reachable, nor the
string data it points to. This was changed in CL 219226, which
changed the variable and the string data to always reachable.
Typically it shouldn't matter much besides some waste of binary
size. But it does matter on AIX (crash in make.bash). I haven't
looked into why.
Fix AIX build.
Change-Id: I546a0c94ad77b10485ceb66e1288a408e2a2a3e2
Reviewed-on: https://go-review.googlesource.com/c/go/+/223380
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Jeremy Faller <jeremy@golang.org>
Reviewed-by: Than McIntosh <thanm@google.com>
I tried a couple of different architectures (goroutine per symbol, 8
goroutines handling symbols from channels, and this architecture), and
this was the best. Another possible approach could be to divide up the
space of relocations, forgo the channels, and just pass slices to the
relocation routines, which would possibly be faster.
Reloc 13.9ms ± 5% 9.0ms ±10% -35.09% (p=0.000 n=8+9)
Change-Id: I5111220e855313fae4b89d64277759c4dc33b697
Reviewed-on: https://go-review.googlesource.com/c/go/+/220842
Reviewed-by: Than McIntosh <thanm@google.com>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
This is the last step requried before relocsym can go parallel.
Change-Id: Id1c1c530c2b9277917208c3767eeb29e02c17a9c
Reviewed-on: https://go-review.googlesource.com/c/go/+/220841
Run-TryBot: Jeremy Faller <jeremy@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Than McIntosh <thanm@google.com>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Also correct a few places I hadn't switched over to Target from *Link
context.
Change-Id: I6de6b39723762de3fa5f8d12800085421aca76fb
Reviewed-on: https://go-review.googlesource.com/c/go/+/220840
Reviewed-by: Than McIntosh <thanm@google.com>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
We need to propogate Target through the relocation functions.
Change-Id: I1192d54a20a34569fd13c1511d2b21ebf2d1272e
Reviewed-on: https://go-review.googlesource.com/c/go/+/220839
Run-TryBot: Jeremy Faller <jeremy@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Than McIntosh <thanm@google.com>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
In an effort to make relocation application thread-safe remove another
dependence on context.
Change-Id: Ic53ea122cce72117fcebe56e386b710755f6eb68
Reviewed-on: https://go-review.googlesource.com/c/go/+/220838
Run-TryBot: Jeremy Faller <jeremy@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Than McIntosh <thanm@google.com>
In its current form, relocsym requires the Link context -- largely in a
readonly state. Rather than passing around such heavy-weight object to
the function, this CL separates out the link target. From here, the
number of touchpoints (and thread unsafe portions) of relocing symbols
can be mentally reasoned about.
(NB: My personal intent is to make this more universal -- passing only
the necessary variables/state to reloc functions. This is a taste to see
if we like this form.)
Change-Id: Id9177d03267fedf0bb572a9d61bc07b64309c3b9
Reviewed-on: https://go-review.googlesource.com/c/go/+/220837
Run-TryBot: Jeremy Faller <jeremy@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Austin Clements <austin@google.com>
Reviewed-by: Than McIntosh <thanm@google.com>
Otherwise we leave a gap at the start of Segrelrodata equal to the
size of the read-only non-relro data, which causes -buildmode=pie
executables to be noticeably larger than -buildmode=exe executables.
Change-Id: I98956ef29d5b7a57ad8e633c823ac09d9ca36a45
Reviewed-on: https://go-review.googlesource.com/c/go/+/208897
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Assorted fixups in the linker needed to enable turning back on
DWARF generation when building plugins for Darwin. Includes:
- don't suppress import of runtime/cgo in the linker for
Darwin if we are linking in plugin mode
- in calcCompUnitRanges handle the case where we encounter
linker-generated functions that have no associated Unit (and
also have no DWARF)
- generalize a guard in relocsym() include so as to avoid
triggering a spurious error on go.info symbols in plugin mode
Updates #21647.
Updates #27502.
Change-Id: I317fea97bef2f3461e31498e63f9fd6d8b8f4b23
Reviewed-on: https://go-review.googlesource.com/c/go/+/182959
Run-TryBot: Than McIntosh <thanm@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>
Factor out the direct CALL identification code from objabi.IsDirectJump and
use this in two places that have separately maintained lists of reloc types.
Provide an objabi.IsDirectCallOrJump function that implements the original
behaviour of objabi.IsDirectJump.
Change-Id: I48131bae92b2938fd7822110d53df0b4ffb35766
Reviewed-on: https://go-review.googlesource.com/c/go/+/196577
Run-TryBot: Joel Sing <joel@sing.id.au>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
In the dev.link branch we implemented the new object file format
and (part of) the linker improvements described in
https://golang.org/s/better-linker
The new object file is index-based and provides random access.
The linker maps the object files into read-only memory, and
access symbols on-demand using indices, as opposed to reading
all object files sequentially into the heap with the old format.
The linker carries symbol informations using indices (as opposed
to Symbol data structure). Symbols are created after the
reachability analysis, and only created for reachable symbols.
This reduces the linker's memory usage.
Linking cmd/compile, it creates ~25% fewer Symbols, and reduces
memory usage (inuse_space) by ~15%. (More results from Than.)
Currently, both the old and new object file formats are supported.
The old format is used by default. The new format can be turned
on by using the compiler/assembler/linker's -newobj flag. Note
that the flag needs to be specified consistently to all
compilations, i.e.
go build -gcflags=all=-newobj -asmflags=all=-newobj -ldflags=-newobj
Change-Id: Ia0e35306b5b9b5b19fdc7fa7c602d4ce36fa6abd
This CL adds experimental coverage instrumentation similar to what
github.com/dvyukov/go-fuzz produces in its -libfuzzer mode. The
coverage can be enabled by compiling with -d=libfuzzer. It's intended
to be used in conjunction with -buildmode=c-archive to produce an ELF
archive (.a) file that can be linked with libFuzzer. See #14565 for
example usage.
The coverage generates a unique 8-bit counter for each basic block in
the original source code, and emits an increment operation. These
counters are then collected into the __libfuzzer_extra_counters ELF
section for use by libFuzzer.
Updates #14565.
Change-Id: I239758cc0ceb9ca1220f2d9d3d23b9e761db9bf1
Reviewed-on: https://go-review.googlesource.com/c/go/+/202117
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
R_ADDRCUOFF refers to the offset from the start of the
compilation unit. Now that we could have multiple compilation
units per package, we should use the start of the compilation
unit, instead of the start of the package.
Change-Id: I3d6a3c5a5c47c9ccf88091ed05413ced826f9934
Reviewed-on: https://go-review.googlesource.com/c/go/+/204828
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Than McIntosh <thanm@google.com>
Allows Go asm calls referencing a function in a .syso file to be
passed through to the external linker, that would have otherwise
raised a "relocation target X not defined" error in cmd/link.
Fixes#33139
Change-Id: I2a8eb6063ebcd05fac96f141acf7652cf9189766
Reviewed-on: https://go-review.googlesource.com/c/go/+/198798
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Also a similar 'elapsed' function and its usages were deleted.
Fixes#19865.
Change-Id: Ib125365e69cf2eda60de64fa74290c8c7d1fd65a
Reviewed-on: https://go-review.googlesource.com/c/go/+/171730
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Than McIntosh <thanm@google.com>
This is part two if the nacl removal. Part 1 was CL 199499.
This CL removes amd64p32 support, which might be useful in the future
if we implement the x32 ABI. It also removes the nacl bits in the
toolchain, and some remaining nacl bits.
Updates #30439
Change-Id: I2475d5bb066d1b474e00e40d95b520e7c2e286e1
Reviewed-on: https://go-review.googlesource.com/c/go/+/200077
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Change some decodetype functions to operate on bytes nstead of
Symbol. This is in preparation of implementing live method
tracking in index-based deadcode pass, and reducing/eliminating
sym.Symbol in general.
Change-Id: Ia9809ad7b182884225e1bda577e8dbec0cd216c5
Reviewed-on: https://go-review.googlesource.com/c/go/+/199077
Reviewed-by: Austin Clements <austin@google.com>
Fix linking with a package having a .syso file in external link mode,
that would otherwise cause an error before executing the external
linker because it can't find symbols that are exported in the said
.syso file.
Fixes#33139
Change-Id: Id3ee737fba1c6f1e37910593dfedf9c84486d398
Reviewed-on: https://go-review.googlesource.com/c/go/+/186417
Reviewed-by: Ian Lance Taylor <iant@golang.org>
As we move the debug_line generation into the compiler, we need to
upgrade the notion of compilationUnit to not just be on a per package
basis. That won't be the case as it will be impossible for all
compilationUnits to have the same set of files names used to build the
debug_lines table. (For example, assembled files in a package don't know
about any files but themselves, so the debug_lines table could only
reference themseves. As such, we need to break the 1:1 relationship
between compUnit and package.)
Change-Id: I2e517bb6c01de0115bbf777af828a2fe59c09ce8
Reviewed-on: https://go-review.googlesource.com/c/go/+/189618
Run-TryBot: Jeremy Faller <jeremy@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Austin Clements <austin@google.com>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
For linking large binaries, the slice of Relocs consumes a large
amount of memory. We can reduce this memory consumption by
shrinking the size of the Reloc struct. This CL moves the fields
used only in external linking or only on PPC64 and S390X to a
lazily initialized side struct.
Linking k8s.io/kubernetes/cmd/kube-apiserver on Linux/AMD64,
before:
inuse_space 1240.25MB total
438.11MB 35.32% 35.32% 438.11MB 35.32% cmd/link/internal/objfile.(*objReader).readSlices
after:
inuse_space 1123.39MB total
306.85MB 27.31% 55.03% 306.85MB 27.31% cmd/link/internal/objfile.(*objReader).readSlices
Under GOGC=5 (to simulate system under memory pressure), the max
RSS reduces from ~2.05G to ~1.83G. Even with external linking the
max RSS doesn't increase.
Change-Id: I9bb8a8effaed24a8b3c4b1cfb93e6992b8740f91
Reviewed-on: https://go-review.googlesource.com/c/go/+/173437
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
It is useful to be able to dig the Go version out of a binary,
even a stripped binary. rsc.io/goversion does this for x86
binaries by disassembling the binary to find runtime/proc.go's
startup-time reference to runtime.buildVersion's address.
That approach is quite fragile: the implementation doesn't
work for non-x86 and must be updated as the generated
code changes.
rsc.io/goversion finds the module version string by looking
for random 16-byte framing around the actual string.
This is less fragile but fairly kludgy and requires scanning
the entire data segment.
cmd/buildid finds the build ID by looking for an ELF note
or else falling back to scanning the beginning of the text
segment for a magic string. This has proved quite reliable
and doesn't require scanning much of the binary.
This CL makes it possible to find the Go and module versions
using a scan more like the build ID scan: a symbol early in
the writable data segment starts with a magic number and
then has pointers to the two string variables.
Setting up for "go version <binary>".
For #31624.
Change-Id: I78ea8c52fe1686b5cc5a829ca5f198104d10ebf0
Reviewed-on: https://go-review.googlesource.com/c/go/+/173342
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Jay Conrod <jayconrod@google.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
When the linker's -X flag is used, it will overwrite the symbol's
content (sym.P) in addstrdata. The symbol's content may be in
read-only memory, in which case overwriting it will fault. Do
copy-on-write to fix this.
Change-Id: I34d583f44c30d187042757e19a14c1ef7d3e613c
Reviewed-on: https://go-review.googlesource.com/c/go/+/173937
Run-TryBot: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Than McIntosh <thanm@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
This resurrects CL 121198, except that this time we map read-only.
In case that we need to apply relocations to the symbol's
content that is backed by read-only memory, we do our own copy-
on-write. This can happen if we failed to mmap the output file,
or we build for Wasm.
Memory profile for building k8s.io/kubernetes/cmd/kube-apiserver
on Linux/AMD64:
Old (before this sequence of CLs):
inuse_space 1598.75MB total
669.87MB 41.90% 41.90% 669.87MB 41.90% cmd/link/internal/objfile.(*objReader).readSlices
New:
inuse_space 1280.45MB total
441.18MB 34.46% 34.46% 441.18MB 34.46% cmd/link/internal/objfile.(*objReader).readSlices
Change-Id: I6b4d29d6eee9828089ea3120eb38c212db21330b
Reviewed-on: https://go-review.googlesource.com/c/go/+/170741
Run-TryBot: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Move the phase of applying relocations later, after the sections
and segments are written to the mmap'd output region. Then apply
relocations directly in the output region, instead of the input.
So the input slices we read in don't need to be modified.
This is in preparation for mmap'ing input files read-only.
Change-Id: If9c80657b4469da36aec5a9ab6acf664f5af8fa0
Reviewed-on: https://go-review.googlesource.com/c/go/+/170739
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Austin Clements <austin@google.com>
We are preparing for applying relocations to the output buffer.
However, for DWARF compression, relocations need to be applied
before compression, but we don't have an output buffer at that
time. We also cannot delay DWARF compression to when we mmap the
output file, because we need the size of the DWARF sections to
compute the file size.
Instead of applying all the relocations together, we apply
relocations in DWARF sections one symbol at a time, right before
it is writing out for compression. As the symbol content may be
in read-only memory (in the future), we use a temporary buffer
for applying the relocations, and immediately write it out.
If compression is not used, relocations are still applied all
together.
This is in preparation for mmap'ing input files read-only.
Change-Id: Iae6d2dd71313897d5054bcc458d3bb78075b30c3
Reviewed-on: https://go-review.googlesource.com/c/go/+/171397
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Austin Clements <austin@google.com>
Apply R_DWARFFILEREF relocations later, along with other
relocations, so that we don't modify symbols' contents before
they are written to the output buffer.
This is in preparation for mmap'ing input files read-only.
Change-Id: I8e9ffb2f05acf8f198589b8770f277beb3847541
Reviewed-on: https://go-review.googlesource.com/c/go/+/170740
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Austin Clements <austin@google.com>
Use mmap for writing most of the output file content,
specifically, the sections and segments. After layout, we
already know the sizes and file offsets for the sections and
segments. So we can just write the bytes by copying to a mmap'd
backing store.
The writing of the output file is split into two parts. The first
part writes the sections and segments to the mmap'd region. The
second part writes some extra content, for which we don't know
the size, so we use direct file IO.
This is in preparation for mmap'ing input files read-only.
Change-Id: I9f3b4616a9f96bfd5c940d74c50aacd6d330f7d2
Reviewed-on: https://go-review.googlesource.com/c/go/+/170738
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Austin Clements <austin@google.com>
Currently the offset values of ELF relocations and Macho relocations
are 256 and 512 respectively, which means that the space reserved for
ELF relocations is only 256. But AARCH64 has more than 256 ELF relocation
types, in fact the maximum AARCH64 ELF relocation type recorded in file
src/debug/elf/elf.go is 1032 currently. So this CL increases the offset
of Macho relocations to 2048 to leave enough space for AARCH64 ELF
relocations.
Change-Id: I784ac38aeb3e102ac7825f6d621086849c8d3146
Reviewed-on: https://go-review.googlesource.com/c/go/+/172497
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
We're going to need a different TLS offset for Android Q, so the static
offsets used for 386 and amd64 are no longer viable on Android.
Introduce runtime·tls_g and use that for indexing into TLS storage. As
an added benefit, we can then merge the TLS setup code for all android
GOARCHs.
While we're at it, remove a bunch of android special cases no longer
needed.
Updates #29674
Updates #29249 (perhaps fixes it)
Change-Id: I77c7385aec7de8f1f6a4da7c9c79999157e39572
Reviewed-on: https://go-review.googlesource.com/c/go/+/169817
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Change-Id: Ia268b0d64dc89866aa09bfffcaa109741088a904
Reviewed-on: https://go-review.googlesource.com/c/go/+/169119
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
This change optimizes the data section in the wasm binary by
omitting blocks of zeroes and instead emitting data segments
with offsets skipping the zeroes.
This optimization is inspired by the memory-packing pass of the
wasm-opt tool and reduces the wasm binary size of "hello world" by 14%.
Change-Id: Iba3043df05bf6aab4745c5f8015c0337fc218aff
Reviewed-on: https://go-review.googlesource.com/c/go/+/167801
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Instead of writing an init function per package that does the same
thing for every package, just write that implementation once in the
runtime. Change the compiler to generate a data structure that encodes
the required initialization operations.
Reduces cmd/go binary size by 0.3%+. Most of the init code is gone,
including all the corresponding stack map info. The .inittask
structures that replace them are quite a bit smaller.
Most usefully to me, there is no longer an init function in every -S output.
(There is an .inittask global there, but it's much less distracting.)
After this CL we could change the name of the "init.ializers" function
back to just "init".
Update #6853
R=go1.13
Change-Id: Iec82b205cc52fe3ade4d36406933c97dbc9c01b1
Reviewed-on: https://go-review.googlesource.com/c/go/+/161337
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>
This commit fixes trampoline generation on aix/ppc64 which must use TOC
symbols.
It also adds a size to runtime.text.X symbols to prevent ld from moving
them, like runtime.text.
Change-Id: Ida033ec20ad8d7b7fb3faeb0ec4fa7bc4ce86b7e
Reviewed-on: https://go-review.googlesource.com/c/go/+/164009
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
