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go/misc/cgo/testtls/tls_test.go

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cmd/ld: emit TLS relocations during external linking This CL was written by rsc. I just tweaked 8l. This CL adds TLS relocation to the ELF .o file we write during external linking, so that the host linker (gcc) can decide the final location of m and g. Similar relocations are not necessary on OS X because we use an alternate program start-time mechanism to acquire thread-local storage. Similar relocations are not necessary on ARM or Plan 9 or Windows because external linking mode is not yet supported on those systems. On almost all ELF systems, the references we use are like %fs:-0x4 or %gs:-0x4, which we write in 6a/8a as -0x4(FS) or -0x4(GS). On Linux/ELF, however, Xen's lack of support for this mode forced us long ago to use a two-instruction sequence: first we load %gs:0x0 into a register r, and then we use -0x4(r). (The ELF program loader arranges that %gs:0x0 contains a regular pointer to that same memory location.) In order to relocate those -0x4(r) references, the linker must know where they are. This CL adds the equivalent notation -0x4(r)(GS*1) for this purpose: it assembles to the same encoding as -0x4(r) but the (GS*1) indicates to the linker that this is one of those thread-local references that needs relocation. Thanks to Elias Naur for reminding me about this missing piece and also for writing the test. R=r CC=golang-dev https://golang.org/cl/7891047
2013-03-27 14:27:35 -06:00
// Copyright 2013 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
all: gofmt more (but vendor, testdata, and top-level test directories) CL 294430 made packages in std and cmd modules use Go 1.17 gofmt format, adding //go:build lines. This change applies the same formatting to some more packages that 'go fmt' missed (e.g., syscall/js, runtime/msan), and everything else that is easy and safe to modify in bulk. Consider the top-level test directory, testdata, and vendor directories out of scope, since there are many files that don't follow strict gofmt formatting, often for intentional and legitimate reasons (testing gofmt itself, invalid Go programs that shouldn't crash the compiler, etc.). That makes it easy and safe to gofmt -w the .go files that are found with gofmt -l with aforementioned directories filtered out: $ gofmt -l . 2>/dev/null | \ grep -v '^test/' | \ grep -v '/testdata/' | \ grep -v '/vendor/' | wc -l 51 None of the 51 files are generated. After this change, the same command prints 0. For #41184. Change-Id: Ia96ee2a0f998d6a167d4473bcad17ad09bc1d86e Reviewed-on: https://go-review.googlesource.com/c/go/+/341009 Run-TryBot: Dmitri Shuralyov <dmitshur@golang.org> TryBot-Result: Go Bot <gobot@golang.org> Reviewed-by: Ian Lance Taylor <iant@golang.org> Trust: Dmitri Shuralyov <dmitshur@golang.org>
2021-08-09 18:29:14 -06:00
//go:build !windows
cmd/ld: emit TLS relocations during external linking This CL was written by rsc. I just tweaked 8l. This CL adds TLS relocation to the ELF .o file we write during external linking, so that the host linker (gcc) can decide the final location of m and g. Similar relocations are not necessary on OS X because we use an alternate program start-time mechanism to acquire thread-local storage. Similar relocations are not necessary on ARM or Plan 9 or Windows because external linking mode is not yet supported on those systems. On almost all ELF systems, the references we use are like %fs:-0x4 or %gs:-0x4, which we write in 6a/8a as -0x4(FS) or -0x4(GS). On Linux/ELF, however, Xen's lack of support for this mode forced us long ago to use a two-instruction sequence: first we load %gs:0x0 into a register r, and then we use -0x4(r). (The ELF program loader arranges that %gs:0x0 contains a regular pointer to that same memory location.) In order to relocate those -0x4(r) references, the linker must know where they are. This CL adds the equivalent notation -0x4(r)(GS*1) for this purpose: it assembles to the same encoding as -0x4(r) but the (GS*1) indicates to the linker that this is one of those thread-local references that needs relocation. Thanks to Elias Naur for reminding me about this missing piece and also for writing the test. R=r CC=golang-dev https://golang.org/cl/7891047
2013-03-27 14:27:35 -06:00
package cgotlstest
import "testing"
func TestTLS(t *testing.T) {
testTLS(t)
}
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