On Mon, Nov 7, 2022 at 2:41 PM Song Liu <song@xxxxxxxxxx> wrote: > [...] > > > This set enables bpf programs and bpf dispatchers to share huge pages with > new API: > execmem_alloc() > execmem_alloc() > execmem_fill() > > The idea is similar to Peter's suggestion in [1]. > > execmem_alloc() manages a set of PMD_SIZE RO+X memory, and allocates these > memory to its users. execmem_alloc() is used to free memory allocated by > execmem_alloc(). execmem_fill() is used to update memory allocated by > execmem_alloc(). Sigh, I just realized this thread made through linux-mm@xxxxxxxxx, but got dropped by bpf@xxxxxxxxxxxxxxx, so I guess I will have to resend v3. Currently, I have got the following action items for v3: 1. Add unify API to allocate text memory to motivation; 2. Update Documentation/x86/x86_64/mm.rst; 3. Allow none PMD_SIZE allocation for powerpc. 1 and 2 are relatively simple. We can probably do 3 in a follow up patch (as I don't have powerpc environments for testing). Did I miss anything? Besides these, does this set look reasonable? Andrew and Peter, could you please share your comments on this? Thanks, Song > > Memory allocated by execmem_alloc() is RO+X, so this doesnot violate W^X. > The caller has to update the content with text_poke like mechanism. > Specifically, execmem_fill() is provided to update memory allocated by > execmem_alloc(). execmem_fill() also makes sure the update stays in the > boundary of one chunk allocated by execmem_alloc(). Please refer to patch > 1/5 for more details of > > Patch 3/5 uses these new APIs in bpf program and bpf dispatcher. > > Patch 4/5 and 5/5 allows static kernel text (_stext to _etext) to share > PMD_SIZE pages with dynamic kernel text on x86_64. This is achieved by > allocating PMD_SIZE pages to roundup(_etext, PMD_SIZE), and then use > _etext to roundup(_etext, PMD_SIZE) for dynamic kernel text. > > [1] https://lore.kernel.org/bpf/Ys6cWUMHO8XwyYgr@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/ > [2] RFC v1: https://lore.kernel.org/linux-mm/20220818224218.2399791-3-song@xxxxxxxxxx/T/ > [3] v1: https://lore.kernel.org/bpf/20221031222541.1773452-1-song@xxxxxxxxxx/ > [4] https://lore.kernel.org/bpf/Y2ioTodn+mBXdIqp@ziqianlu-desk2/ > [5] https://lore.kernel.org/bpf/20220707223546.4124919-1-song@xxxxxxxxxx/ > > Changes PATCH v1 => v2: > 1. Rename the APIs as execmem_* (Christoph Hellwig) > 2. Add more information about the motivation of this work (and follow up > works in for kernel modules, various trampolines, etc). > (Luis Chamberlain, Rick Edgecombe, Mike Rapoport, Aaron Lu) > 3. Include expermential results from previous bpf_prog_pack and the > community. (Aaron Lu, Luis Chamberlain, Rick Edgecombe) > > Changes RFC v2 => PATCH v1: > 1. Add vcopy_exec(), which updates memory allocated by vmalloc_exec(). It > also ensures vcopy_exec() is only used to update memory from one single > vmalloc_exec() call. (Christoph Hellwig) > 2. Add arch_vcopy_exec() and arch_invalidate_exec() as wrapper for the > text_poke() like logic. > 3. Drop changes for kernel modules and focus on BPF side changes. > > Changes RFC v1 => RFC v2: > 1. Major rewrite of the logic of vmalloc_exec and vfree_exec. They now > work fine with BPF programs (patch 1, 2, 4). But module side (patch 3) > still need some work. > > Song Liu (5): > vmalloc: introduce execmem_alloc, execmem_free, and execmem_fill > x86/alternative: support execmem_alloc() and execmem_free() > bpf: use execmem_alloc for bpf program and bpf dispatcher > vmalloc: introduce register_text_tail_vm() > x86: use register_text_tail_vm > > arch/x86/include/asm/pgtable_64_types.h | 1 + > arch/x86/kernel/alternative.c | 12 + > arch/x86/mm/init_64.c | 4 +- > arch/x86/net/bpf_jit_comp.c | 23 +- > include/linux/bpf.h | 3 - > include/linux/filter.h | 5 - > include/linux/vmalloc.h | 9 + > kernel/bpf/core.c | 180 +----------- > kernel/bpf/dispatcher.c | 11 +- > mm/nommu.c | 12 + > mm/vmalloc.c | 354 ++++++++++++++++++++++++ > 11 files changed, 412 insertions(+), 202 deletions(-) > > -- > 2.30.2
