This set enables bpf programs and bpf dispatchers to share huge pages with new API: vmalloc_exec() vfree_exec() vcopy_exec() The idea is similar to Peter's suggestion in [1]. vmalloc_exec() manages a set of PMD_SIZE RO+X memory, and allocates these memory to its users. vfree_exec() is used to free memory allocated by vmalloc_exec(). vcopy_exec() is used to update memory allocated by vmalloc_exec(). Memory allocated by vmalloc_exec() is RO+X, so this doesnot violate W^X. The caller has to update the content with text_poke like mechanism. Specifically, vcopy_exec() is provided to update memory allocated by vmalloc_exec(). vcopy_exec() also makes sure the update stays in the boundary of one chunk allocated by vmalloc_exec(). 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/ 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 vmalloc_exec, vfree_exec, and vcopy_exec x86/alternative: support vmalloc_exec() and vfree_exec() bpf: use vmalloc_exec 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 | 7 + mm/vmalloc.c | 351 ++++++++++++++++++++++++ 11 files changed, 404 insertions(+), 202 deletions(-) -- 2.30.2
