Bpf arm64 arena #6641
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Bpf arm64 arena #6641
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Implement a helper function to check if an instruction is addr_space_cast from as(0) to as(1). Use this helper in the x86 JIT. Other JITs can use this helper when they add support for this instruction. Signed-off-by: Puranjay Mohan <puranjay12@gmail.com>
The arena_list selftest uses (1ull << 32) in the mmap address computation for arm64. Use the same in the verifier_arena selftest. This makes the selftest pass for arm64 on the CI[1]. [1] kernel-patches#6622 Signed-off-by: Puranjay Mohan <puranjay12@gmail.com> Link: https://lore.kernel.org/r/20240322133552.70681-1-puranjay12@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org>
The selftests use to tell LLVM about special pointers. For LLVM there is nothing "arena" about them. They are simply pointers in a different address space. Hence LLVM diff llvm/llvm-project#85161 renamed: . macro __BPF_FEATURE_ARENA_CAST -> __BPF_FEATURE_ADDR_SPACE_CAST . global variables in __attribute__((address_space(N))) are now placed in section named ".addr_space.N" instead of ".arena.N". Adjust libbpf, bpftool, and selftests to match LLVM. Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Acked-by: Stanislav Fomichev <sdf@google.com> Link: https://lore.kernel.org/bpf/20240315021834.62988-3-alexei.starovoitov@gmail.com
Add support for [LDX | STX | ST], PROBE_MEM32, [B | H | W | DW] instructions. They are similar to PROBE_MEM instructions with the following differences: - PROBE_MEM32 supports store. - PROBE_MEM32 relies on the verifier to clear upper 32-bit of the src/dst register - PROBE_MEM32 adds 64-bit kern_vm_start address (which is stored in R28 in the prologue). Due to bpf_arena constructions such R28 + reg + off16 access is guaranteed to be within arena virtual range, so no address check at run-time. - PROBE_MEM32 allows STX and ST. If they fault the store is a nop. When LDX faults the destination register is zeroed. To support these on arm64, we do tmp2 = R28 + src/dst reg and then use tmp2 as the new src/dst register. This allows us to reuse most of the code for normal [LDX | STX | ST]. Signed-off-by: Puranjay Mohan <puranjay12@gmail.com>
LLVM generates bpf_addr_space_cast instruction while translating pointers between native (zero) address space and __attribute__((address_space(N))). The addr_space=0 is reserved as bpf_arena address space. rY = addr_space_cast(rX, 0, 1) is processed by the verifier and converted to normal 32-bit move: wX = wY. rY = addr_space_cast(rX, 1, 0) : used to convert a bpf arena pointer to a pointer in the userspace vma. This has to be converted by the JIT. Signed-off-by: Puranjay Mohan <puranjay12@gmail.com>
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Puranjay Mohan says: ==================== bpf,arm64: Add support for BPF Arena Changes in V4 V3: https://lore.kernel.org/bpf/20240323103057.26499-1-puranjay12@gmail.com/ - Use more descriptive variable names. - Use insn_is_cast_user() helper. Changes in V3 V2: https://lore.kernel.org/bpf/20240321153102.103832-1-puranjay12@gmail.com/ - Optimize bpf_addr_space_cast as suggested by Xu Kuohai Changes in V2 V1: https://lore.kernel.org/bpf/20240314150003.123020-1-puranjay12@gmail.com/ - Fix build warnings by using 5 in place of 32 as DONT_CLEAR marker. R5 is not mapped to any BPF register so it can safely be used here. This series adds the support for PROBE_MEM32 and bpf_addr_space_cast instructions to the ARM64 BPF JIT. These two instructions allow the enablement of BPF Arena. All arena related selftests are passing. [root@ip-172-31-6-62 bpf]# ./test_progs -a "*arena*" #3/1 arena_htab/arena_htab_llvm:OK #3/2 arena_htab/arena_htab_asm:OK #3 arena_htab:OK #4/1 arena_list/arena_list_1:OK #4/2 arena_list/arena_list_1000:OK #4 arena_list:OK #434/1 verifier_arena/basic_alloc1:OK #434/2 verifier_arena/basic_alloc2:OK #434/3 verifier_arena/basic_alloc3:OK #434/4 verifier_arena/iter_maps1:OK #434/5 verifier_arena/iter_maps2:OK #434/6 verifier_arena/iter_maps3:OK #434 verifier_arena:OK Summary: 3/10 PASSED, 0 SKIPPED, 0 FAILED This will need the patch [1] that introduced insn_is_cast_user() helper to build. The verifier_arena selftest could fail in the CI because the following commit[2] is missing from bpf-next: [1] https://lore.kernel.org/bpf/20240324183226.29674-1-puranjay12@gmail.com/ [2] https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf.git/commit/?id=fa3550dca8f02ec312727653a94115ef3ab68445 Here is a CI run with all dependencies added: kernel-patches/bpf#6641 ==================== Link: https://lore.kernel.org/r/20240325150716.4387-1-puranjay12@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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