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[198.84.170.103]) by smtp.gmail.com with ESMTPSA id i26sm3804174qkh.14.2020.06.26.14.19.27 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 26 Jun 2020 14:19:28 -0700 (PDT) Subject: Re: [RFC PATCH 3/3] add r_debug multiple namespaces support To: Florian Weimer , Daniel Walker via Libc-alpha References: <20200626193228.1953-4-danielwa@cisco.com> <87ftah5yh8.fsf@oldenburg2.str.redhat.com> Organization: Red Hat Message-ID: <210c992f-b034-3ef7-440c-f67ab1b3acdb@redhat.com> Date: Fri, 26 Jun 2020 17:19:27 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: <87ftah5yh8.fsf@oldenburg2.str.redhat.com> Content-Language: en-US X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , From: Carlos O'Donell via Libc-alpha Reply-To: Carlos O'Donell Cc: Pedro Alves , Conan C Huang , Jeremy Stenglein , xe-linux-external@cisco.com Errors-To: libc-alpha-bounces@sourceware.org Sender: "Libc-alpha" On 6/26/20 5:05 PM, Florian Weimer via Libc-alpha wrote: > * Daniel Walker via Libc-alpha: > >> diff --git a/elf/link.h b/elf/link.h >> index 0048ad5d4d..5a42511636 100644 >> --- a/elf/link.h >> +++ b/elf/link.h >> @@ -61,6 +61,10 @@ struct r_debug >> } r_state; >> >> ElfW(Addr) r_ldbase; /* Base address the linker is loaded at. */ >> + >> + /* Link to next r_debug struct. Each r_debug struct represents a >> + different namespace. The first r_debug struct is the default. */ >> + struct r_debug *next; >> }; >> >> /* This is the instance of that structure used by the dynamic linker. */ > > How has this patch been tested? I expect that it will cause an abilist > mismatch for the _r_debug symbol in the dynamic linker. > > If we go this route to add this capability, I think we have to add a new > symbol version for the _r_debug symbol, and keep the old one at the > previous size. > > How is your compatibility experience with the size and version change? > How many tools need updating before they work again? > > A different approach would add another symbol (parallel to _r_debug) to > store this data. This would avoid the need for any immediate tool > updates. I mention this in my response to the cover letter in this series. This patch is probably unacceptable as-is because of application expectations. -- Cheers, Carlos.