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bh=/Ja6GFNF6qtDRTD2jbRnjHnkG93QpxBc5lSinA0vdSo=; b=rKpR24dTM5oTAA4JbzfdMwyEO9is7yuInB3LMR3RZ0sWQodCIjHSnk3bUe7rFf9/0q hIXlXULWkUwFzVneUsY5N61u1dfp/MsiaMusWpQbn5KU8N3JbkZPQX3Et1O4ixjujM6a 89A1qyAj+Hqhjb49rZ94al7GxQwomu1mFLO1tqg69R7wQ3BXs0R85XRRw7zNdxpM8b/p CoVwIsKloFQg5/iLfQlXjV1UCFvWjGfuyBUYxHFPyO5Wzs6+kJGtaukNI/v7b6RPU4e6 4JHmm4Vjeg5pGQ+FjdpR1q535fc05t1xhDcMghYJkzsw/7vXGadi51B+lAQ7KK4lxyqx cxLQ== X-Gm-Message-State: APjAAAXMh8NkB/D1UvSV15fzpeHpkGH4czQIYyf1vQ+SkdKRygeu4qvN 9yn+FDAI32y1ca91ZB7i1/Bqo0MLCgg= X-Google-Smtp-Source: APXvYqyfivg7GAZt24pXsjt6uHZCeKM4jzjkbtiOk5k8o8Q69fdmSIiWTAJklEqF356ZrBoeYT2SCQ== X-Received: by 2002:a67:f505:: with SMTP id u5mr42753024vsn.159.1555416668519; Tue, 16 Apr 2019 05:11:08 -0700 (PDT) Received: from [192.168.1.132] ([177.194.125.152]) by smtp.googlemail.com with ESMTPSA id m23sm88277692vsl.24.2019.04.16.05.11.06 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 16 Apr 2019 05:11:07 -0700 (PDT) To: Florian Weimer , hpa@zytor.com References: <875zrnlakd.fsf@oldenburg2.str.redhat.com> <284e9c76-2411-b8f4-c4bc-c25c60c04cf7@linaro.org> <87imvker6t.fsf@oldenburg2.str.redhat.com> <87lg0fbr1q.fsf@oldenburg2.str.redhat.com> <87lg0az2xk.fsf@oldenburg2.str.redhat.com> From: Adhemerval Zanella Openpgp: preference=signencrypt Autocrypt: addr=adhemerval.zanella@linaro.org; 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Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <87lg0az2xk.fsf@oldenburg2.str.redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-GB Content-Transfer-Encoding: 8bit X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-api@vger.kernel.org, libc-alpha@sourceware.org, linuxppc-dev@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On 16/04/2019 06:59, Florian Weimer wrote: > * hpa: > >> Using symbol versioning doesn't really help much since the real >> problem is that struct termios can be passed around in userspace, and >> the interfaces between user space libraries don't have any >> versioning. However, my POC code deals with that too by only seeing >> BOTHER when necessary, so if the structure is extended garbage in the >> extra fields will be ignored unless new baud rates are in use. > > That still doesn't solve the problem of changing struct offsets after a > struct field of type struct termios. We will need symbol versioning at least on sparc, since currently it defines NCSS 17 and termios-c_cc.h defines 16 control characters (there is no space to squeeze more fields one termios). ANd The WIP branch gratuitously change the termios struct size on the architecture. I am not sure which would be the best option to avoid the the user space libraries compatibility issue. It is unlikely to happen, it would require one to use old libraries along with newer libraries build against a newer glibc. Not sure how often this scenarios arises in realworld (specially on sparc). I think MIPS would be fine to lower NCSS to 24, as WIP branch does. And alpha is also fine since it already provides the c_* fields. > >> Exporting termios2 to user space feels a bit odd at this stage as it >> would only be usable as a fallback on old glibc. Call it >> kernel_termios2 at least. > > I'm not sure why we should do that? The kernel calls it struct termios2 > in its UAPI headers. If that name is not appropriate, it should be > changed first in the UAPI headers. > > Thanks, > Florian >