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30e29ee9b6
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
29 lines
547 B
Go
29 lines
547 B
Go
// Copyright 2013 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package cgotlstest
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// #include <pthread.h>
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// extern void setTLS(int);
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// extern int getTLS();
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import "C"
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import (
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"runtime"
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"testing"
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)
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func testTLS(t *testing.T) {
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var keyVal C.int = 1234
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runtime.LockOSThread()
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defer runtime.UnlockOSThread()
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C.setTLS(C.int(keyVal))
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storedVal := C.getTLS()
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if storedVal != keyVal {
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t.Fatalf("stored %d want %d", storedVal, keyVal)
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}
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}
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