bpf, riscv: Support riscv jit to provide bpf_line_info

Add support for riscv jit to provide bpf_line_info. We need to
consider the prologue offset in ctx->offset, but unlike x86 and
arm64, ctx->offset of riscv does not provide an extra slot for
the prologue, so here we just calculate the len of prologue and
add it to ctx->offset at the end. Both RV64 and RV32 have been
tested.
Signed-off-by: Pu Lehui <pulehui@huawei.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20220530092815.1112406-3-pulehui@huawei.com

arch/riscv/net/bpf_jit.h

@@ -69,6 +69,7 @@ struct rv_jit_context {
 	struct bpf_prog *prog;
 	u16 *insns;		/* RV insns */
 	int ninsns;
+	int body_len;
 	int epilogue_offset;
 	int *offset;		/* BPF to RV */
 	int nexentries;

arch/riscv/net/bpf_jit_core.c

@@ -44,7 +44,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
 	unsigned int prog_size = 0, extable_size = 0;
 	bool tmp_blinded = false, extra_pass = false;
 	struct bpf_prog *tmp, *orig_prog = prog;
-	int pass = 0, prev_ninsns = 0, i;
+	int pass = 0, prev_ninsns = 0, prologue_len, i;
 	struct rv_jit_data *jit_data;
 	struct rv_jit_context *ctx;
 
@@ -95,6 +95,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
 			prog = orig_prog;
 			goto out_offset;
 		}
+		ctx->body_len = ctx->ninsns;
 		bpf_jit_build_prologue(ctx);
 		ctx->epilogue_offset = ctx->ninsns;
 		bpf_jit_build_epilogue(ctx);
@@ -161,6 +162,11 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
 
 	if (!prog->is_func || extra_pass) {
 		bpf_jit_binary_lock_ro(jit_data->header);
+		prologue_len = ctx->epilogue_offset - ctx->body_len;
+		for (i = 0; i < prog->len; i++)
+			ctx->offset[i] = ninsns_rvoff(prologue_len +
+						      ctx->offset[i]);
+		bpf_prog_fill_jited_linfo(prog, ctx->offset);
 out_offset:
 		kfree(ctx->offset);
 		kfree(jit_data);