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From: Kent Overstreet To: Mike Rapoport Cc: linux-kernel@vger.kernel.org, Alexandre Ghiti , Andrew Morton , =?utf-8?B?QmrDtnJuIFTDtnBlbA==?= , Catalin Marinas , Christophe Leroy , "David S. Miller" , Dinh Nguyen , Donald Dutile , Eric Chanudet , Heiko Carstens , Helge Deller , Huacai Chen , Luis Chamberlain , Mark Rutland , Michael Ellerman , Nadav Amit , Palmer Dabbelt , Puranjay Mohan , Rick Edgecombe , Russell King , Song Liu , Steven Rostedt , Thomas Bogendoerfer , Thomas Gleixner , Will Deacon , bpf@vger.kernel.org, linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mips@vger.kernel.org, linux-mm@kvack.org, linux-modules@vger.kernel.org, linux-parisc@vger.kernel.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, loongarch@lists.linux.dev, netdev@vger.kernel.org, sparclinux@vger.kernel.org, x86@kernel.org Subject: Re: [PATCH v4 00/15] mm: jit/text allocator Message-ID: References: <20240411160051.2093261-1-rppt@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240411160051.2093261-1-rppt@kernel.org> X-Migadu-Flow: FLOW_OUT X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 5EABD2002D X-Stat-Signature: ao6ppm94bzrj5x4yy87f64jhjgq9u9bc X-HE-Tag: 1712858433-691078 X-HE-Meta: U2FsdGVkX18jbVHUKF4t+pAs6HgzUaW0HPARd4ldqyysy5Qaxt6/7Mdsw1vef9D4q35I/SKrPf5lALVWm9Q+vdvf+YxI73ScwBRfN7zPHlvsYEb6h5c3uxqdSQ3bMoyWEDRpn2rF3RWNH7nzfOQYNfw3KrpJEgY9D+GtXznJnomw0d4IFpYqX6pq7glN4rRNoIlEHfZVm6jlLm2Gu7fHcIhpMJS9y4qLR/mDMUwP33+QR4PbImv14UthaKiEtWZrTG8/hkmsp5HV0kHLWzbhfvdthUkc8u1Kncvc5gwr3PK8jbirhWH7i5Ufgw0JwBtD3/u/lkd67nUaxIZhJj+SSJ5ghM1P/Lg98Qh8z4ltc+tYspktRy2UrZpT97OGmI/do/9ZfzFc3IjuQluVElga5DnjcLA87JzV4wgO95GcUakMEd/OPuproB1oH0yiGxioTuzAhxKKUmxwoTviFQjkGxnUGhqRDFxlgsfwdvR+MFxgVya1GNTBmtm1IfgA0kW/Iy4ACf7PxWg5qZ7nVcwuYPXqTGzWPJU6f32H0U2PWjnk74P/5mQBTRfd7um48vlsEKVrqdAQoekSujQxkduJub3Oaq0jnnbTaDTZWeEkTeruIyURM54T7tjKya4dAijf9M8zIh2TH1mFzvUcK3arCmpSEtZZQicJRnmJwEhmiu1ef+BhljoG8dsxwPOdwqFlFhtOEJENnyb06iOfTecSubnekiwrHwJLrPlEeyl7x7XVApq2Wj3chJJquY5a4dcceV/xZMtsfsyHv0sry+ddYCUj0bsMnGJpLYjuiyIbZTwagGqlTD/B6YzcotNBKurWcbbnFDW7rNr3z94caOmpJa3ZIIRHopT5D7nH1T9m++1wMt39Wo++OA== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Apr 11, 2024 at 07:00:36PM +0300, Mike Rapoport wrote: > From: "Mike Rapoport (IBM)" > > Hi, > > Since v3 I looked into making execmem more of an utility toolbox, as we > discussed at LPC with Mark Rutland, but it was getting more hairier than > having a struct describing architecture constraints and a type identifying > the consumer of execmem. > > And I do think that having the description of architecture constraints for > allocations of executable memory in a single place is better that having it > spread all over the place. > > The patches available via git: > https://git.kernel.org/pub/scm/linux/kernel/git/rppt/linux.git/log/?h=execmem/v4 > > v4 changes: > * rebase on v6.9-rc2 > * rename execmem_params to execmem_info and execmem_arch_params() to > execmem_arch_setup() > * use single execmem_alloc() API instead of execmem_{text,data}_alloc() (Song) > * avoid extra copy of execmem parameters (Rick) > * run execmem_init() as core_initcall() except for the architectures that > may allocated text really early (currently only x86) (Will) > * add acks for some of arm64 and riscv changes, thanks Will and Alexandre > * new commits: > - drop call to kasan_alloc_module_shadow() on arm64 because it's not > needed anymore > - rename MODULE_START to MODULES_VADDR on MIPS > - use CONFIG_EXECMEM instead of CONFIG_MODULES on powerpc as per Christophe: > https://lore.kernel.org/all/79062fa3-3402-47b3-8920-9231ad05e964@csgroup.eu/ > > v3: https://lore.kernel.org/all/20230918072955.2507221-1-rppt@kernel.org > * add type parameter to execmem allocation APIs > * remove BPF dependency on modules > > v2: https://lore.kernel.org/all/20230616085038.4121892-1-rppt@kernel.org > * Separate "module" and "others" allocations with execmem_text_alloc() > and jit_text_alloc() > * Drop ROX entailment on x86 > * Add ack for nios2 changes, thanks Dinh Nguyen > > v1: https://lore.kernel.org/all/20230601101257.530867-1-rppt@kernel.org > > = Cover letter from v1 (sligtly updated) = > > module_alloc() is used everywhere as a mean to allocate memory for code. > > Beside being semantically wrong, this unnecessarily ties all subsystmes > that need to allocate code, such as ftrace, kprobes and BPF to modules and > puts the burden of code allocation to the modules code. > > Several architectures override module_alloc() because of various > constraints where the executable memory can be located and this causes > additional obstacles for improvements of code allocation. > > A centralized infrastructure for code allocation allows allocations of > executable memory as ROX, and future optimizations such as caching large > pages for better iTLB performance and providing sub-page allocations for > users that only need small jit code snippets. > > Rick Edgecombe proposed perm_alloc extension to vmalloc [1] and Song Liu > proposed execmem_alloc [2], but both these approaches were targeting BPF > allocations and lacked the ground work to abstract executable allocations > and split them from the modules core. > > Thomas Gleixner suggested to express module allocation restrictions and > requirements as struct mod_alloc_type_params [3] that would define ranges, > protections and other parameters for different types of allocations used by > modules and following that suggestion Song separated allocations of > different types in modules (commit ac3b43283923 ("module: replace > module_layout with module_memory")) and posted "Type aware module > allocator" set [4]. > > I liked the idea of parametrising code allocation requirements as a > structure, but I believe the original proposal and Song's module allocator > was too module centric, so I came up with these patches. > > This set splits code allocation from modules by introducing execmem_alloc() > and and execmem_free(), APIs, replaces call sites of module_alloc() and > module_memfree() with the new APIs and implements core text and related > allocations in a central place. > > Instead of architecture specific overrides for module_alloc(), the > architectures that require non-default behaviour for text allocation must > fill execmem_info structure and implement execmem_arch_setup() that returns > a pointer to that structure. If an architecture does not implement > execmem_arch_setup(), the defaults compatible with the current > modules::module_alloc() are used. > > Since architectures define different restrictions on placement, > permissions, alignment and other parameters for memory that can be used by > different subsystems that allocate executable memory, execmem APIs > take a type argument, that will be used to identify the calling subsystem > and to allow architectures to define parameters for ranges suitable for that > subsystem. > > The new infrastructure allows decoupling of BPF, kprobes and ftrace from > modules, and most importantly it paves the way for ROX allocations for > executable memory. It looks like you're just doing API cleanup first, then improving the implementation later? Patch set looks nice and clean; previous versions did seem to leak too much arch/module details (or perhaps we were just bikeshedding too much ;) - but the API first approach is nice. Looking forward to seeing this merged.