Date: Mon, 10 Jan 2022 14:50:40 -0800 From: John Baldwin <jhb@FreeBSD.org> To: Olivier Houchard <cognet@ci0.org>, Warner Losh <imp@bsdimp.com> Cc: Warner Losh <imp@freebsd.org>, src-committers <src-committers@freebsd.org>, dev-commits-src-all@freebsd.org, dev-commits-src-main@freebsd.org Subject: Re: git: d6c0538dae8d - main - ddb: Remove SOFTWARE_SSTEP support Message-ID: <61fa2498-3516-0f1b-fb24-270d38f0472f@FreeBSD.org> In-Reply-To: <YdynB3Omo4RK16Fx@ci0.org> References: <202201071627.207GRsGX062055@gitrepo.freebsd.org> <45275428-75e2-aaae-bed3-e5e84b39e17c@FreeBSD.org> <CANCZdfq0UCZvdcsuaWx3KXqrKBBYoxDHqc=_P3U7L4QpCyh=rw@mail.gmail.com> <YdynB3Omo4RK16Fx@ci0.org>
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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 <jhb@freebsd.org> 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 <imp@FreeBSD.org> >>>> AuthorDate: 2022-01-07 16:25:33 +0000 >>>> Commit: Warner Losh <imp@FreeBSD.org> >>>> 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. -- John Baldwin
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