From nobody Mon Jan 10 23:27:00 2022 X-Original-To: dev-commits-src-all@mlmmj.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mlmmj.nyi.freebsd.org (Postfix) with ESMTP id 3AD2A194CE83; Mon, 10 Jan 2022 23:27:42 +0000 (UTC) (envelope-from cognet@ci0.org) Received: from kanar.ci0.org (kanar.ci0.org [IPv6:2001:bc8:35e6::1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256 client-signature RSA-PSS (2048 bits) client-digest SHA256) (Client CN "sd-143795", Issuer "sd-143795" (not verified)) by mx1.freebsd.org (Postfix) with ESMTPS id 4JXqk607Zpz4vk9; Mon, 10 Jan 2022 23:27:41 +0000 (UTC) (envelope-from cognet@ci0.org) Received: from kanar.ci0.org (localhost [127.0.0.1]) by kanar.ci0.org (8.16.1/8.16.1) with ESMTPS id 20ANR1Fb075512 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NO); Tue, 11 Jan 2022 00:27:01 +0100 (CET) (envelope-from cognet@ci0.org) Received: (from doginou@localhost) by kanar.ci0.org (8.16.1/8.16.1/Submit) id 20ANR1Ro075511; Tue, 11 Jan 2022 00:27:01 +0100 (CET) (envelope-from cognet@ci0.org) X-Authentication-Warning: kanar.ci0.org: doginou set sender to cognet@ci0.org using -f Date: Tue, 11 Jan 2022 00:27:00 +0100 From: Olivier Houchard To: John Baldwin Cc: Warner Losh , src-committers , dev-commits-src-all@freebsd.org, dev-commits-src-main@freebsd.org Subject: Re: git: d6c0538dae8d - main - ddb: Remove SOFTWARE_SSTEP support Message-ID: References: <202201071627.207GRsGX062055@gitrepo.freebsd.org> <45275428-75e2-aaae-bed3-e5e84b39e17c@FreeBSD.org> <61fa2498-3516-0f1b-fb24-270d38f0472f@FreeBSD.org> List-Id: Commit messages for all branches of the src repository List-Archive: https://lists.freebsd.org/archives/dev-commits-src-all List-Help: List-Post: List-Subscribe: List-Unsubscribe: Sender: owner-dev-commits-src-all@freebsd.org X-BeenThere: dev-commits-src-all@freebsd.org MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <61fa2498-3516-0f1b-fb24-270d38f0472f@FreeBSD.org> X-Rspamd-Queue-Id: 4JXqk607Zpz4vk9 X-Spamd-Bar: ---- Authentication-Results: mx1.freebsd.org; none X-Spamd-Result: default: False [-4.00 / 15.00]; REPLY(-4.00)[] X-ThisMailContainsUnwantedMimeParts: N On Mon, Jan 10, 2022 at 02:50:40PM -0800, John Baldwin wrote: > On 1/10/22 1:37 PM, Olivier Houchard wrote: > > On Mon, Jan 10, 2022 at 02:14:54PM -0700, Warner Losh wrote: > >> On Mon, Jan 10, 2022 at 12:48 PM John Baldwin wrote: > >> > >>> On 1/7/22 8:27 AM, Warner Losh wrote: > >>>> The branch main has been updated by imp: > >>>> > >>>> URL: > >>> https://cgit.FreeBSD.org/src/commit/?id=d6c0538dae8d138219dfd051994a44c50e741212 > >>>> > >>>> commit d6c0538dae8d138219dfd051994a44c50e741212 > >>>> Author: Warner Losh > >>>> AuthorDate: 2022-01-07 16:25:33 +0000 > >>>> Commit: Warner Losh > >>>> CommitDate: 2022-01-07 16:25:33 +0000 > >>>> > >>>> ddb: Remove SOFTWARE_SSTEP support > >>>> > >>>> It was needed for mips only, and only kinda sorta worked for mips. > >>> It > >>>> can be brought back if we grow another architecture that need it. > >>>> > >>>> Sponsored by: Netflix > >>> > >>> RISC-V would need it in theory (no hardware single step), but no one has > >>> felt the > >>> need to implement the backend support for it. I think 32-bit arm doesn't > >>> support > >>> hardware single step either (but again, no one has bothered to add the > >>> backend > >>> support). > >>> > >> > >> Generally, I agree with these thoughts. I went ahead with the removal > >> because I > >> knew it would be easy to bring back, even years from now should someone[tm] > >> have an implementation for those platforms (though I thought 32-bit arm did > >> have > >> single step in hardware). > >> > >> Should I put it back? Or should we wait until someone shows up with support > >> for > >> a supported platform? > >> > > > > It was used for arm, but only older arm, ie v4/v5, pretty sure newer > > cores do have hardware breakpoints. > > They have hardware breakpoints/watchpoints, not sure if they have single step. > > In GDB 32-bit arm only supports software single step, even on Linux. > Seems true, the newer code just seems to use hardware breakpoints, but the logic is the same as what was done with SOFTWARE_SSTEP. Olivier