riscv, bpf: Factor common RISC-V JIT code

This patch factors out code that can be used by both the RV64 and RV32
BPF JITs to a common bpf_jit.h and bpf_jit_core.c.

Move struct definitions and macro-like functions to header. Rename
rv_sb_insn/rv_uj_insn to rv_b_insn/rv_j_insn to match the RISC-V
specification.

Move reusable functions emit_body() and bpf_int_jit_compile() to
bpf_jit_core.c with minor simplifications. Rename emit_insn() and
build_{prologue,epilogue}() to be prefixed with "bpf_jit_" as they are
no longer static.

Rename bpf_jit_comp.c to bpf_jit_comp64.c to be more explicit.
Co-developed-by: Xi Wang <xi.wang@gmail.com>
Signed-off-by: Xi Wang <xi.wang@gmail.com>
Signed-off-by: Luke Nelson <luke.r.nels@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Björn Töpel <bjorn.topel@gmail.com>
Acked-by: Björn Töpel <bjorn.topel@gmail.com>
Link: https://lore.kernel.org/bpf/20200305050207.4159-2-luke.r.nels@gmail.com

arch/riscv/net/Makefile

 # SPDX-License-Identifier: GPL-2.0-only
-obj-$(CONFIG_BPF_JIT) += bpf_jit_comp.o
+
+obj-$(CONFIG_BPF_JIT) += bpf_jit_core.o bpf_jit_comp64.o

arch/riscv/net/bpf_jit_core.c

+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Common functionality for RV32 and RV64 BPF JIT compilers
+ *
+ * Copyright (c) 2019 Björn Töpel <bjorn.topel@gmail.com>
+ *
+ */
+
+#include <linux/bpf.h>
+#include <linux/filter.h>
+#include "bpf_jit.h"
+
+/* Number of iterations to try until offsets converge. */
+#define NR_JIT_ITERATIONS	16
+
+static int build_body(struct rv_jit_context *ctx, bool extra_pass, int *offset)
+{
+	const struct bpf_prog *prog = ctx->prog;
+	int i;
+
+	for (i = 0; i < prog->len; i++) {
+		const struct bpf_insn *insn = &prog->insnsi[i];
+		int ret;
+
+		ret = bpf_jit_emit_insn(insn, ctx, extra_pass);
+		/* BPF_LD | BPF_IMM | BPF_DW: skip the next instruction. */
+		if (ret > 0)
+			i++;
+		if (offset)
+			offset[i] = ctx->ninsns;
+		if (ret < 0)
+			return ret;
+	}
+	return 0;
+}
+
+bool bpf_jit_needs_zext(void)
+{
+	return true;
+}
+
+struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
+{
+	bool tmp_blinded = false, extra_pass = false;
+	struct bpf_prog *tmp, *orig_prog = prog;
+	int pass = 0, prev_ninsns = 0, i;
+	struct rv_jit_data *jit_data;
+	struct rv_jit_context *ctx;
+	unsigned int image_size = 0;
+
+	if (!prog->jit_requested)
+		return orig_prog;
+
+	tmp = bpf_jit_blind_constants(prog);
+	if (IS_ERR(tmp))
+		return orig_prog;
+	if (tmp != prog) {
+		tmp_blinded = true;
+		prog = tmp;
+	}
+
+	jit_data = prog->aux->jit_data;
+	if (!jit_data) {
+		jit_data = kzalloc(sizeof(*jit_data), GFP_KERNEL);
+		if (!jit_data) {
+			prog = orig_prog;
+			goto out;
+		}
+		prog->aux->jit_data = jit_data;
+	}
+
+	ctx = &jit_data->ctx;
+
+	if (ctx->offset) {
+		extra_pass = true;
+		image_size = sizeof(u32) * ctx->ninsns;
+		goto skip_init_ctx;
+	}
+
+	ctx->prog = prog;
+	ctx->offset = kcalloc(prog->len, sizeof(int), GFP_KERNEL);
+	if (!ctx->offset) {
+		prog = orig_prog;
+		goto out_offset;
+	}
+	for (i = 0; i < prog->len; i++) {
+		prev_ninsns += 32;
+		ctx->offset[i] = prev_ninsns;
+	}
+
+	for (i = 0; i < NR_JIT_ITERATIONS; i++) {
+		pass++;
+		ctx->ninsns = 0;
+		if (build_body(ctx, extra_pass, ctx->offset)) {
+			prog = orig_prog;
+			goto out_offset;
+		}
+		bpf_jit_build_prologue(ctx);
+		ctx->epilogue_offset = ctx->ninsns;
+		bpf_jit_build_epilogue(ctx);
+
+		if (ctx->ninsns == prev_ninsns) {
+			if (jit_data->header)
+				break;
+
+			image_size = sizeof(u32) * ctx->ninsns;
+			jit_data->header =
+				bpf_jit_binary_alloc(image_size,
+						     &jit_data->image,
+						     sizeof(u32),
+						     bpf_fill_ill_insns);
+			if (!jit_data->header) {
+				prog = orig_prog;
+				goto out_offset;
+			}
+
+			ctx->insns = (u32 *)jit_data->image;
+			/*
+			 * Now, when the image is allocated, the image can
+			 * potentially shrink more (auipc/jalr -> jal).
+			 */
+		}
+		prev_ninsns = ctx->ninsns;
+	}
+
+	if (i == NR_JIT_ITERATIONS) {
+		pr_err("bpf-jit: image did not converge in <%d passes!\n", i);
+		bpf_jit_binary_free(jit_data->header);
+		prog = orig_prog;
+		goto out_offset;
+	}
+
+skip_init_ctx:
+	pass++;
+	ctx->ninsns = 0;
+
+	bpf_jit_build_prologue(ctx);
+	if (build_body(ctx, extra_pass, NULL)) {
+		bpf_jit_binary_free(jit_data->header);
+		prog = orig_prog;
+		goto out_offset;
+	}
+	bpf_jit_build_epilogue(ctx);
+
+	if (bpf_jit_enable > 1)
+		bpf_jit_dump(prog->len, image_size, pass, ctx->insns);
+
+	prog->bpf_func = (void *)ctx->insns;
+	prog->jited = 1;
+	prog->jited_len = image_size;
+
+	bpf_flush_icache(jit_data->header, ctx->insns + ctx->ninsns);
+
+	if (!prog->is_func || extra_pass) {
+out_offset:
+		kfree(ctx->offset);
+		kfree(jit_data);
+		prog->aux->jit_data = NULL;
+	}
+out:
+
+	if (tmp_blinded)
+		bpf_jit_prog_release_other(prog, prog == orig_prog ?
+					   tmp : orig_prog);
+	return prog;
+}