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@xxxxxxxxx>
---
arch/arm64/net/bpf_jit_comp.c | 16 ++++++++++++++++
tools/testing/selftests/bpf/DENYLIST.aarch64 | 2 --
2 files changed, 16 insertions(+), 2 deletions(-)
diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c
index ba6dabf62712..8967388446d5 100644
--- a/arch/arm64/net/bpf_jit_comp.c
+++ b/arch/arm64/net/bpf_jit_comp.c
@@ -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) {
diff --git a/tools/testing/selftests/bpf/DENYLIST.aarch64 b/tools/testing/selftests/bpf/DENYLIST.aarch64
index d8ade15e2789..0445ac38bc07 100644
--- a/tools/testing/selftests/bpf/DENYLIST.aarch64
+++ b/tools/testing/selftests/bpf/DENYLIST.aarch64
@@ -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
--
2.40.1
