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[221.241.217.81]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-725d899efe4sm10403960b3a.161.2024.12.12.23.19.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 12 Dec 2024 23:19:50 -0800 (PST) Date: Fri, 13 Dec 2024 16:19:46 +0900 Message-ID: From: Hajime Tazaki To: ebiederm@xmission.com Cc: linux-um@lists.infradead.org, ricarkol@google.com, Liam.Howlett@oracle.com, kees@kernel.org, viro@zeniv.linux.org.uk, brauner@kernel.org, jack@suse.cz, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org Subject: Re: [PATCH v5 02/13] x86/um: nommu: elf loader for fdpic In-Reply-To: <87r06d0ymg.fsf@email.froward.int.ebiederm.org> References: <87r06d0ymg.fsf@email.froward.int.ebiederm.org> User-Agent: Wanderlust/2.15.9 (Almost Unreal) Emacs/26.3 Mule/6.0 MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII X-Rspamd-Queue-Id: 7EDA818000F X-Rspam-User: X-Rspamd-Server: rspam07 X-Stat-Signature: qop5qpn66rn3gzt4w1eq9w7199txpz5m X-HE-Tag: 1734074389-34641 X-HE-Meta: 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 y+9jEBqn 1Gv7sgXbF8xVkHzwxxuaACDddNXfkA1F/1EEIpUDKwXwomXUKQzzDx/roS2togBc+4jIYZGLWxM5+QO5Y7BSOmudx1eyVE8z0X/AkfxWR22eLE0nOXlJeNBFqAUHd62ycE3cb94+VopJgJkI/xknhODvNCcv+V1XlsevCbrSQfYcq0R5HT8PdG5VwkmTz64t5Uo08JrZehlWhToaOai8TLa2+TfIXOaQD0/R4vXi0cxDvD3xpqDwy/dDM6tqzih9bOmNdTQG3/YYa2EUVp9XFtWypD71I+rZT0PyjereG9mh7jLl7AY1vZ+oeoXwQzGpDMnQUnfWUhDaeB3OEvIhsr6i5lA== X-Bogosity: Unsure, tests=bogofilter, spamicity=0.489778, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hello Eric, thanks for the feedback. On Thu, 12 Dec 2024 23:22:47 +0900, Eric W. Biederman wrote: > > Hajime Tazaki writes: > > > As UML supports CONFIG_MMU=n case, it has to use an alternate ELF > > loader, FDPIC ELF loader. In this commit, we added necessary > > definitions in the arch, as UML has not been used so far. It also > > updates Kconfig file to use BINFMT_ELF_FDPIC under !MMU environment. > > Why does the no mmu case need an alternative elf loader? I was simply following the way how other nommu architectures (riscv, etc) did. > Last time I looked the regular binfmt_elf works just fine > without an mmu. I looked again and at a quick skim the > regular elf loader still looks like it will work without > an MMU. I'm wondering how you looked at it and how you see that it works without MMU. > You would need ET_DYN binaries just so they will load and run > in a position independent way. But even that seems a common > configuration even with a MMU these days. Yes, our perquisite for this nommu port is to use PIE binaries so, ET_DYN assumption works fine for the moment. > There are some funny things in elf_fdpic where it departs > from the ELF standard and is no fun to support unless it > is necessary. So I am not excited to see more architectures > supporting ELF_FDPIC. I understand. I also wish to use the regular binfmt_elf, but it doesn't allow me to compile with !CONFIG_MMU right now. I've played a little bit with touching binfmt_elf.c, but not finished yet with a trivial attempt. sorry, i'm not familiar with this part but wish to fix it for nommu+ET_EYN if possible with a right background information. -- Hajime