| Message ID | 20230616085038.4121892-1-rppt@kernel.org (mailing list archive) |
|---|---|
| Headers | show |
| Series | mm: jit/text allocator | expand |
On Fri, 2023-06-16 at 11:50 +0300, Mike Rapoport wrote: > From: "Mike Rapoport (IBM)" <rppt@kernel.org> > > Hi, > > 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. I like how this series leaves the allocation code centralized at the end of it because it will be much easier when we get to ROX, huge page, text_poking() type stuff. I guess that's the idea. I'm just catching up on what you and Song have been up to.
From: "Mike Rapoport (IBM)" <rppt@kernel.org> Hi, 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's 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 were too module centric, so I came up with these patches. This set splits code allocation from modules by introducing execmem_text_alloc(), execmem_data_alloc(), execmem_free(), jit_text_alloc() and jit_free() APIs, replaces call sites of module_alloc() and module_memfree() with the new APIs and implements core text and related allocation 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_alloc_params structure and implement execmem_arch_params() that returns a pointer to that structure. If an architecture does not implement execmem_arch_params(), the defaults compatible with the current modules::module_alloc() are used. The intended semantics of the new APIs is that execmem APIs should be used to allocate memory that must reside close to the kernel image because of addressing mode restrictions, e.g modules on many architectures or dynamic ftrace trampolines on x86. The jit APIs are intended for users that can place code anywhere in vmalloc area, like kprobes on most architectures and BPF on arm/arm64. While two distinct API cover the major cases, there is still might be need for arch-specific overrides for some of the usecases. For example, riscv uses a dedicated range for BPF allocations in order to be able to use relative addressing, but for kprobes riscv can use the entire vmalloc area. For such overrides we might introduce jit_text_alloc variant that gets start + end parameters to restrict the range like Mark Rutland suggested and then use that variant in arch override. The new infrastructure allows decoupling of kprobes and ftrace from modules, and most importantly it paves the way for ROX allocations for executable memory. For now I've dropped patches that enable ROX allocations on x86 because with them modprobe takes ten times more. To make modprobe fast with ROX allocations more work is required to text poking infrastructure, but this work is not a prerequisite for this series. [1] https://lore.kernel.org/lkml/20201120202426.18009-1-rick.p.edgecombe@intel.com/ [2] https://lore.kernel.org/all/20221107223921.3451913-1-song@kernel.org/ [3] https://lore.kernel.org/all/87v8mndy3y.ffs@tglx/ [4] https://lore.kernel.org/all/20230526051529.3387103-1-song@kernel.org v2 changes: * Separate "module" and "others" allocations with execmem_text_alloc() and jit_text_alloc() * Drop ROX entablement on x86 * Add ack for nios2 changes, thanks Dinh Nguyen v1: https://lore.kernel.org/all/20230601101257.530867-1-rppt@kernel.org Mike Rapoport (IBM) (12): nios2: define virtual address space for modules mm: introduce execmem_text_alloc() and jit_text_alloc() mm/execmem, arch: convert simple overrides of module_alloc to execmem mm/execmem, arch: convert remaining overrides of module_alloc to execmem modules, execmem: drop module_alloc mm/execmem: introduce execmem_data_alloc() arm64, execmem: extend execmem_params for generated code definitions riscv: extend execmem_params for kprobes allocations powerpc: extend execmem_params for kprobes allocations arch: make execmem setup available regardless of CONFIG_MODULES x86/ftrace: enable dynamic ftrace without CONFIG_MODULES kprobes: remove dependcy on CONFIG_MODULES arch/Kconfig | 2 +- arch/arm/kernel/module.c | 32 ------ arch/arm/mm/init.c | 36 ++++++ arch/arm64/include/asm/memory.h | 8 ++ arch/arm64/include/asm/module.h | 6 - arch/arm64/kernel/kaslr.c | 3 +- arch/arm64/kernel/module.c | 47 -------- arch/arm64/kernel/probes/kprobes.c | 7 -- arch/arm64/mm/init.c | 56 +++++++++ arch/loongarch/kernel/module.c | 6 - arch/loongarch/mm/init.c | 20 ++++ arch/mips/kernel/module.c | 10 +- arch/mips/mm/init.c | 19 ++++ arch/nios2/include/asm/pgtable.h | 5 +- arch/nios2/kernel/module.c | 28 +++-- arch/parisc/kernel/module.c | 12 +- arch/parisc/mm/init.c | 22 +++- arch/powerpc/kernel/kprobes.c | 16 +-- arch/powerpc/kernel/module.c | 37 ------ arch/powerpc/mm/mem.c | 59 ++++++++++ arch/riscv/kernel/module.c | 10 -- arch/riscv/kernel/probes/kprobes.c | 10 -- arch/riscv/mm/init.c | 34 ++++++ arch/s390/kernel/ftrace.c | 4 +- arch/s390/kernel/kprobes.c | 4 +- arch/s390/kernel/module.c | 42 +------ arch/s390/mm/init.c | 41 +++++++ arch/sparc/kernel/module.c | 33 +----- arch/sparc/mm/Makefile | 2 + arch/sparc/mm/execmem.c | 25 ++++ arch/sparc/net/bpf_jit_comp_32.c | 8 +- arch/x86/Kconfig | 1 + arch/x86/kernel/ftrace.c | 16 +-- arch/x86/kernel/kprobes/core.c | 4 +- arch/x86/kernel/module.c | 51 --------- arch/x86/mm/init.c | 54 +++++++++ include/linux/execmem.h | 155 +++++++++++++++++++++++++ include/linux/moduleloader.h | 15 --- kernel/bpf/core.c | 14 +-- kernel/kprobes.c | 51 +++++---- kernel/module/Kconfig | 1 + kernel/module/main.c | 45 ++------ kernel/trace/trace_kprobe.c | 11 ++ mm/Kconfig | 3 + mm/Makefile | 1 + mm/execmem.c | 177 +++++++++++++++++++++++++++++ mm/mm_init.c | 2 + 47 files changed, 813 insertions(+), 432 deletions(-) create mode 100644 arch/sparc/mm/execmem.c create mode 100644 include/linux/execmem.h create mode 100644 mm/execmem.c base-commit: 44c026a73be8038f03dbdeef028b642880cf1511