Commit 4dd31243 authored by Puranjay Mohan's avatar Puranjay Mohan Committed by Alexei Starovoitov
Browse files

bpf: Add arm64 JIT support for bpf_addr_space_cast instruction. 



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: default avatarPuranjay Mohan <puranjay12@gmail.com>
Link: https://lore.kernel.org/r/20240325150716.4387-3-puranjay12@gmail.com


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent 339af577

arch/arm64/net/bpf_jit_comp.c

+16 −0
Original line number Diff line number Diff line
@@ -82,6 +82,7 @@ struct jit_ctx { 
	__le32 *ro_image;

	u32 stack_size;

	int fpb_offset;

	u64 user_vm_start;

};



struct bpf_plt {
@@ -868,6 +869,15 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx, 
	/* dst = src */

	case BPF_ALU | BPF_MOV | BPF_X:

	case BPF_ALU64 | BPF_MOV | BPF_X:

		if (insn_is_cast_user(insn)) {

			emit(A64_MOV(0, tmp, src), ctx); // 32-bit mov clears the upper 32 bits

			emit_a64_mov_i(0, dst, ctx->user_vm_start >> 32, ctx);

			emit(A64_LSL(1, dst, dst, 32), ctx);

			emit(A64_CBZ(1, tmp, 2), ctx);

			emit(A64_ORR(1, tmp, dst, tmp), ctx);

			emit(A64_MOV(1, dst, tmp), ctx);

			break;

		}

		switch (insn->off) {

		case 0:

			emit(A64_MOV(is64, dst, src), ctx);
@@ -1690,6 +1700,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog) 
	}



	ctx.fpb_offset = find_fpb_offset(prog);

	ctx.user_vm_start = bpf_arena_get_user_vm_start(prog->aux->arena);



	/*

	 * 1. Initial fake pass to compute ctx->idx and ctx->offset.
@@ -2511,6 +2522,11 @@ bool bpf_jit_supports_exceptions(void) 
	return true;

}



bool bpf_jit_supports_arena(void)

{

	return true;

}



void bpf_jit_free(struct bpf_prog *prog)

{

	if (prog->jited) {

tools/testing/selftests/bpf/DENYLIST.aarch64

+0 −2
Original line number Diff line number Diff line
@@ -10,5 +10,3 @@ fill_link_info/kprobe_multi_link_info # bpf_program__attach_kprobe_mu 
fill_link_info/kretprobe_multi_link_info         # bpf_program__attach_kprobe_multi_opts unexpected error: -95

fill_link_info/kprobe_multi_invalid_ubuff        # bpf_program__attach_kprobe_multi_opts unexpected error: -95

missed/kprobe_recursion                          # missed_kprobe_recursion__attach unexpected error: -95 (errno 95)
 
verifier_arena                                   # JIT does not support arena

arena_htab                                       # JIT does not support arena