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On 32-bit architectures (or if we fail to map a 64-bit-style arena), we try to map the heap arena just above the end of the process image. While we can accept any address, using lower addresses is preferable because lower addresses cause us to map less of the heap bitmap. However, if a program is linked against C code that has global constructors, those constructors may call brk/sbrk to allocate memory (e.g., many C malloc implementations do this for small allocations). The brk also starts just above the process image, so this may adjust the brk past the beginning of where we want to put the heap arena. In this case, the kernel will pick a different address for the arena and it will usually be very high (at least, as these things go in a 32-bit address space). Fix this by consulting the current value of the brk and using this in addition to the end of the process image to compute the initial arena placement. This is implemented only on Linux currently, since we have no evidence that it's an issue on any other OSes. Fixes #19831. Change-Id: Id64b45d08d8c91e4f50d92d0339146250b04f2f8 Reviewed-on: https://go-review.googlesource.com/39810 Run-TryBot: Austin Clements <austin@google.com> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Ian Lance Taylor <iant@golang.org>
10 lines
215 B
Go
10 lines
215 B
Go
// Copyright 2017 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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// +build linux
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package runtime
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func sbrk0() uintptr
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