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Sat, 14 Mar 2026 06:21:10 -0700 (PDT) Received: from gpc ([2400:8902:e002:de08:5754:7dac:85df:935a]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-35a03005f7fsm11288866a91.15.2026.03.14.06.21.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 14 Mar 2026 06:21:10 -0700 (PDT) From: WANG Rui To: ryan.roberts@arm.com Cc: Liam.Howlett@oracle.com, ajd@linux.ibm.com, akpm@linux-foundation.org, anshuman.khandual@arm.com, apopple@nvidia.com, baohua@kernel.org, baolin.wang@linux.alibaba.com, brauner@kernel.org, catalin.marinas@arm.com, david@kernel.org, dev.jain@arm.com, hannes@cmpxchg.org, jack@suse.cz, kas@kernel.org, kees@kernel.org, kernel-team@meta.com, kevin.brodsky@arm.com, lance.yang@linux.dev, linux-arm-kernel@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, lorenzo.stoakes@oracle.com, npache@redhat.com, rmclure@linux.ibm.com, shakeel.butt@linux.dev, usama.arif@linux.dev, viro@zeniv.linux.org.uk, will@kernel.org, willy@infradead.org, ziy@nvidia.com, WANG Rui Subject: Re: [PATCH 0/4] arm64/mm: contpte-sized exec folios for 16K and 64K pages Date: Sat, 14 Mar 2026 21:20:38 +0800 Message-ID: <20260314132038.223901-1-r@hev.cc> X-Mailer: git-send-email 2.53.0 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: CCD4580009 X-Stat-Signature: qsg7jkhfs5i1kcki1ywg4s98rnqfmmz6 X-Rspam-User: X-HE-Tag: 1773494471-844269 X-HE-Meta: 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 /LkLv/CQ 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hi Ryan, > I don't see how you can reliably influence this from the kernel? The ELF file > alignment is, by default, 64K (16K on Android) and there is no guarrantee that > the text section is the first section in the file. You need to align the start > of the text section to the 2M boundary and to do that, you'll need to align the > start of the file to some 64K boundary at a specific offset to the 2M boundary, > based on the size of any sections before the text section. That's a job for the > dynamic loader I think? Perhaps I've misunderstood what you're doing... On Arch Linux for AArch64 and LoongArch64 I've observed that most binaries place the executable segment in the first PT_LOAD. In that case both the virtual address and file offset are 0, which happens to satisfy the alignment requirements for PMD-sized or large folio mappings. x86 looks quite different. The executable segment is usually not the first one. After digging into this I realized this mostly comes from the linker defaults. With GNU ld, -z noseparate-code merges the read-only and read-only-executable segments into one, while -z separate-code splits them, placing a non-executable read-only segment first. The latter is the default on x86, partly to avoid making the ELF headers executable when mappings start from the beginning of the file. Other architectures tend to default to -z noseparate-code, which makes it more likely that the text segment is the first PT_LOAD. LLVM lld behaves differently again: --rosegment (equivalent to -z separate-code) is enabled by default on all architectures, which similarly tends to place the executable segment after an initial read-only one. That default is clearly less friendly to large-page text mappings. Thanks, Rui