From owner-svn-src-all@freebsd.org Thu May 24 18:32:55 2018 Return-Path: Delivered-To: svn-src-all@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id D0604EFAB73; Thu, 24 May 2018 18:32:55 +0000 (UTC) (envelope-from brooks@FreeBSD.org) Received: from mxrelay.nyi.freebsd.org (mxrelay.nyi.freebsd.org [IPv6:2610:1c1:1:606c::19:3]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client CN "mxrelay.nyi.freebsd.org", Issuer "Let's Encrypt Authority X3" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 82A517C89C; Thu, 24 May 2018 18:32:55 +0000 (UTC) (envelope-from brooks@FreeBSD.org) Received: from repo.freebsd.org (repo.freebsd.org [IPv6:2610:1c1:1:6068::e6a:0]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mxrelay.nyi.freebsd.org (Postfix) with ESMTPS id 63D2315FA4; Thu, 24 May 2018 18:32:55 +0000 (UTC) (envelope-from brooks@FreeBSD.org) Received: from repo.freebsd.org ([127.0.1.37]) by repo.freebsd.org (8.15.2/8.15.2) with ESMTP id w4OIWtPo032660; Thu, 24 May 2018 18:32:55 GMT (envelope-from brooks@FreeBSD.org) Received: (from brooks@localhost) by repo.freebsd.org (8.15.2/8.15.2/Submit) id w4OIWtNV032659; Thu, 24 May 2018 18:32:55 GMT (envelope-from brooks@FreeBSD.org) Message-Id: <201805241832.w4OIWtNV032659@repo.freebsd.org> X-Authentication-Warning: repo.freebsd.org: brooks set sender to brooks@FreeBSD.org using -f From: Brooks Davis Date: Thu, 24 May 2018 18:32:55 +0000 (UTC) To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r334176 - head/lib/libc/sys X-SVN-Group: head X-SVN-Commit-Author: brooks X-SVN-Commit-Paths: head/lib/libc/sys X-SVN-Commit-Revision: 334176 X-SVN-Commit-Repository: base MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-BeenThere: svn-src-all@freebsd.org X-Mailman-Version: 2.1.26 Precedence: list List-Id: "SVN commit messages for the entire src tree \(except for " user" and " projects" \)" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 24 May 2018 18:32:56 -0000 Author: brooks Date: Thu May 24 18:32:54 2018 New Revision: 334176 URL: https://svnweb.freebsd.org/changeset/base/334176 Log: Indicate the brk/sbrk are deprecated and not portable. More firmly suggest mmap(2) instead. Include the history of arm64 and riscv shipping without brk/sbrk. Mention that sbrk(0) produces unreliable results. Reviewed by: emaste, Marcin Cieślak MFC after: 3 days Sponsored by: DARPA, AFRL Differential Revision: https://reviews.freebsd.org/D15535 Modified: head/lib/libc/sys/brk.2 Modified: head/lib/libc/sys/brk.2 ============================================================================== --- head/lib/libc/sys/brk.2 Thu May 24 18:22:13 2018 (r334175) +++ head/lib/libc/sys/brk.2 Thu May 24 18:32:54 2018 (r334176) @@ -28,7 +28,7 @@ .\" @(#)brk.2 8.4 (Berkeley) 5/1/95 .\" $FreeBSD$ .\" -.Dd December 15, 2015 +.Dd May 24, 2018 .Dt BRK 2 .Os .Sh NAME @@ -51,6 +51,10 @@ and .Fn sbrk functions are legacy interfaces from before the advent of modern virtual memory management. +They are deprecated and not present on the arm64 or riscv architectures. +The +.Xr mmap 2 +interface should be used to allocate pages instead. .Ef .Pp The @@ -152,6 +156,11 @@ The .Fn brk function appeared in .At v7 . +.Fx 11.0 +introduced the arm64 and riscv architectures which do not support +.Fn brk +or +.Fn sbrk . .Sh BUGS Mixing .Fn brk @@ -168,3 +177,9 @@ It is not possible to distinguish this from a failure caused by exceeding the maximum size of the data segment without consulting .Xr getrlimit 2 . +.Pp +.Fn sbrk +is sometimes used to monitor heap use by calling with an argument of 0. +The result is unlikely to reflect actual utilization in combination with an +.Xr mmap 2 +based malloc.