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@@ -0,0 +1,694 @@
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+/* bpf_jit_comp.c: BPF JIT compiler for PPC64
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+ *
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+ * Copyright 2011 Matt Evans <matt@ozlabs.org>, IBM Corporation
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+ *
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+ * Based on the x86 BPF compiler, by Eric Dumazet (eric.dumazet@gmail.com)
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+ *
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+ * This program is free software; you can redistribute it and/or
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+ * modify it under the terms of the GNU General Public License
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+ * as published by the Free Software Foundation; version 2
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+ * of the License.
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+ */
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+#include <linux/moduleloader.h>
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+#include <asm/cacheflush.h>
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+#include <linux/netdevice.h>
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+#include <linux/filter.h>
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+#include "bpf_jit.h"
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+
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+#ifndef __BIG_ENDIAN
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+/* There are endianness assumptions herein. */
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+#error "Little-endian PPC not supported in BPF compiler"
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+#endif
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+
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+int bpf_jit_enable __read_mostly;
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+
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+
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+static inline void bpf_flush_icache(void *start, void *end)
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+{
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+ smp_wmb();
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+ flush_icache_range((unsigned long)start, (unsigned long)end);
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+}
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+
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+static void bpf_jit_build_prologue(struct sk_filter *fp, u32 *image,
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+ struct codegen_context *ctx)
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+{
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+ int i;
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+ const struct sock_filter *filter = fp->insns;
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+
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+ if (ctx->seen & (SEEN_MEM | SEEN_DATAREF)) {
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+ /* Make stackframe */
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+ if (ctx->seen & SEEN_DATAREF) {
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+ /* If we call any helpers (for loads), save LR */
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+ EMIT(PPC_INST_MFLR | __PPC_RT(0));
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+ PPC_STD(0, 1, 16);
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+
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+ /* Back up non-volatile regs. */
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+ PPC_STD(r_D, 1, -(8*(32-r_D)));
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+ PPC_STD(r_HL, 1, -(8*(32-r_HL)));
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+ }
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+ if (ctx->seen & SEEN_MEM) {
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+ /*
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+ * Conditionally save regs r15-r31 as some will be used
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+ * for M[] data.
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+ */
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+ for (i = r_M; i < (r_M+16); i++) {
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+ if (ctx->seen & (1 << (i-r_M)))
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+ PPC_STD(i, 1, -(8*(32-i)));
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+ }
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+ }
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+ EMIT(PPC_INST_STDU | __PPC_RS(1) | __PPC_RA(1) |
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+ (-BPF_PPC_STACKFRAME & 0xfffc));
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+ }
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+
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+ if (ctx->seen & SEEN_DATAREF) {
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+ /*
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+ * If this filter needs to access skb data,
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+ * prepare r_D and r_HL:
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+ * r_HL = skb->len - skb->data_len
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+ * r_D = skb->data
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+ */
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+ PPC_LWZ_OFFS(r_scratch1, r_skb, offsetof(struct sk_buff,
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+ data_len));
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+ PPC_LWZ_OFFS(r_HL, r_skb, offsetof(struct sk_buff, len));
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+ PPC_SUB(r_HL, r_HL, r_scratch1);
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+ PPC_LD_OFFS(r_D, r_skb, offsetof(struct sk_buff, data));
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+ }
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+
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+ if (ctx->seen & SEEN_XREG) {
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+ /*
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+ * TODO: Could also detect whether first instr. sets X and
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+ * avoid this (as below, with A).
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+ */
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+ PPC_LI(r_X, 0);
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+ }
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+
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+ switch (filter[0].code) {
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+ case BPF_S_RET_K:
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+ case BPF_S_LD_W_LEN:
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+ case BPF_S_ANC_PROTOCOL:
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+ case BPF_S_ANC_IFINDEX:
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+ case BPF_S_ANC_MARK:
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+ case BPF_S_ANC_RXHASH:
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+ case BPF_S_ANC_CPU:
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+ case BPF_S_ANC_QUEUE:
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+ case BPF_S_LD_W_ABS:
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+ case BPF_S_LD_H_ABS:
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+ case BPF_S_LD_B_ABS:
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+ /* first instruction sets A register (or is RET 'constant') */
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+ break;
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+ default:
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+ /* make sure we dont leak kernel information to user */
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+ PPC_LI(r_A, 0);
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+ }
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+}
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+
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+static void bpf_jit_build_epilogue(u32 *image, struct codegen_context *ctx)
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+{
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+ int i;
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+
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+ if (ctx->seen & (SEEN_MEM | SEEN_DATAREF)) {
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+ PPC_ADDI(1, 1, BPF_PPC_STACKFRAME);
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+ if (ctx->seen & SEEN_DATAREF) {
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+ PPC_LD(0, 1, 16);
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+ PPC_MTLR(0);
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+ PPC_LD(r_D, 1, -(8*(32-r_D)));
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+ PPC_LD(r_HL, 1, -(8*(32-r_HL)));
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+ }
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+ if (ctx->seen & SEEN_MEM) {
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+ /* Restore any saved non-vol registers */
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+ for (i = r_M; i < (r_M+16); i++) {
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+ if (ctx->seen & (1 << (i-r_M)))
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+ PPC_LD(i, 1, -(8*(32-i)));
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+ }
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+ }
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+ }
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+ /* The RETs have left a return value in R3. */
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+
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+ PPC_BLR();
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+}
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+
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+/* Assemble the body code between the prologue & epilogue. */
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+static int bpf_jit_build_body(struct sk_filter *fp, u32 *image,
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+ struct codegen_context *ctx,
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+ unsigned int *addrs)
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+{
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+ const struct sock_filter *filter = fp->insns;
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+ int flen = fp->len;
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+ u8 *func;
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+ unsigned int true_cond;
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+ int i;
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+
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+ /* Start of epilogue code */
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+ unsigned int exit_addr = addrs[flen];
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+
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+ for (i = 0; i < flen; i++) {
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+ unsigned int K = filter[i].k;
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+
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+ /*
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+ * addrs[] maps a BPF bytecode address into a real offset from
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+ * the start of the body code.
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+ */
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+ addrs[i] = ctx->idx * 4;
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+
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+ switch (filter[i].code) {
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+ /*** ALU ops ***/
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+ case BPF_S_ALU_ADD_X: /* A += X; */
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+ ctx->seen |= SEEN_XREG;
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+ PPC_ADD(r_A, r_A, r_X);
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+ break;
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+ case BPF_S_ALU_ADD_K: /* A += K; */
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+ if (!K)
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+ break;
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+ PPC_ADDI(r_A, r_A, IMM_L(K));
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+ if (K >= 32768)
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+ PPC_ADDIS(r_A, r_A, IMM_HA(K));
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+ break;
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+ case BPF_S_ALU_SUB_X: /* A -= X; */
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+ ctx->seen |= SEEN_XREG;
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+ PPC_SUB(r_A, r_A, r_X);
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+ break;
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+ case BPF_S_ALU_SUB_K: /* A -= K */
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+ if (!K)
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+ break;
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+ PPC_ADDI(r_A, r_A, IMM_L(-K));
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+ if (K >= 32768)
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+ PPC_ADDIS(r_A, r_A, IMM_HA(-K));
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+ break;
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+ case BPF_S_ALU_MUL_X: /* A *= X; */
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+ ctx->seen |= SEEN_XREG;
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+ PPC_MUL(r_A, r_A, r_X);
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+ break;
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+ case BPF_S_ALU_MUL_K: /* A *= K */
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+ if (K < 32768)
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+ PPC_MULI(r_A, r_A, K);
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+ else {
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+ PPC_LI32(r_scratch1, K);
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+ PPC_MUL(r_A, r_A, r_scratch1);
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+ }
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+ break;
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+ case BPF_S_ALU_DIV_X: /* A /= X; */
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+ ctx->seen |= SEEN_XREG;
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+ PPC_CMPWI(r_X, 0);
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+ if (ctx->pc_ret0 != -1) {
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+ PPC_BCC(COND_EQ, addrs[ctx->pc_ret0]);
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+ } else {
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+ /*
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+ * Exit, returning 0; first pass hits here
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+ * (longer worst-case code size).
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+ */
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+ PPC_BCC_SHORT(COND_NE, (ctx->idx*4)+12);
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+ PPC_LI(r_ret, 0);
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+ PPC_JMP(exit_addr);
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+ }
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+ PPC_DIVWU(r_A, r_A, r_X);
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+ break;
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+ case BPF_S_ALU_DIV_K: /* A = reciprocal_divide(A, K); */
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+ PPC_LI32(r_scratch1, K);
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+ /* Top 32 bits of 64bit result -> A */
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+ PPC_MULHWU(r_A, r_A, r_scratch1);
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+ break;
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+ case BPF_S_ALU_AND_X:
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+ ctx->seen |= SEEN_XREG;
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+ PPC_AND(r_A, r_A, r_X);
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+ break;
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+ case BPF_S_ALU_AND_K:
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+ if (!IMM_H(K))
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+ PPC_ANDI(r_A, r_A, K);
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+ else {
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+ PPC_LI32(r_scratch1, K);
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+ PPC_AND(r_A, r_A, r_scratch1);
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+ }
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+ break;
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+ case BPF_S_ALU_OR_X:
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+ ctx->seen |= SEEN_XREG;
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+ PPC_OR(r_A, r_A, r_X);
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+ break;
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+ case BPF_S_ALU_OR_K:
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+ if (IMM_L(K))
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+ PPC_ORI(r_A, r_A, IMM_L(K));
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+ if (K >= 65536)
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+ PPC_ORIS(r_A, r_A, IMM_H(K));
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+ break;
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+ case BPF_S_ALU_LSH_X: /* A <<= X; */
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+ ctx->seen |= SEEN_XREG;
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+ PPC_SLW(r_A, r_A, r_X);
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+ break;
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+ case BPF_S_ALU_LSH_K:
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+ if (K == 0)
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+ break;
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+ else
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+ PPC_SLWI(r_A, r_A, K);
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+ break;
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+ case BPF_S_ALU_RSH_X: /* A >>= X; */
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+ ctx->seen |= SEEN_XREG;
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+ PPC_SRW(r_A, r_A, r_X);
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+ break;
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+ case BPF_S_ALU_RSH_K: /* A >>= K; */
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+ if (K == 0)
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+ break;
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+ else
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+ PPC_SRWI(r_A, r_A, K);
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+ break;
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+ case BPF_S_ALU_NEG:
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+ PPC_NEG(r_A, r_A);
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+ break;
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+ case BPF_S_RET_K:
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+ PPC_LI32(r_ret, K);
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+ if (!K) {
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+ if (ctx->pc_ret0 == -1)
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+ ctx->pc_ret0 = i;
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+ }
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+ /*
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+ * If this isn't the very last instruction, branch to
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+ * the epilogue if we've stuff to clean up. Otherwise,
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+ * if there's nothing to tidy, just return. If we /are/
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+ * the last instruction, we're about to fall through to
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+ * the epilogue to return.
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+ */
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+ if (i != flen - 1) {
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+ /*
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+ * Note: 'seen' is properly valid only on pass
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+ * #2. Both parts of this conditional are the
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+ * same instruction size though, meaning the
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+ * first pass will still correctly determine the
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+ * code size/addresses.
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+ */
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+ if (ctx->seen)
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+ PPC_JMP(exit_addr);
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+ else
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+ PPC_BLR();
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+ }
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+ break;
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+ case BPF_S_RET_A:
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+ PPC_MR(r_ret, r_A);
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+ if (i != flen - 1) {
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+ if (ctx->seen)
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+ PPC_JMP(exit_addr);
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+ else
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+ PPC_BLR();
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+ }
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+ break;
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+ case BPF_S_MISC_TAX: /* X = A */
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+ PPC_MR(r_X, r_A);
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+ break;
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+ case BPF_S_MISC_TXA: /* A = X */
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+ ctx->seen |= SEEN_XREG;
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+ PPC_MR(r_A, r_X);
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+ break;
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+
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+ /*** Constant loads/M[] access ***/
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+ case BPF_S_LD_IMM: /* A = K */
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+ PPC_LI32(r_A, K);
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+ break;
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+ case BPF_S_LDX_IMM: /* X = K */
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+ PPC_LI32(r_X, K);
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+ break;
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+ case BPF_S_LD_MEM: /* A = mem[K] */
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+ PPC_MR(r_A, r_M + (K & 0xf));
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+ ctx->seen |= SEEN_MEM | (1<<(K & 0xf));
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+ break;
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+ case BPF_S_LDX_MEM: /* X = mem[K] */
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+ PPC_MR(r_X, r_M + (K & 0xf));
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+ ctx->seen |= SEEN_MEM | (1<<(K & 0xf));
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+ break;
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+ case BPF_S_ST: /* mem[K] = A */
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+ PPC_MR(r_M + (K & 0xf), r_A);
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+ ctx->seen |= SEEN_MEM | (1<<(K & 0xf));
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+ break;
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+ case BPF_S_STX: /* mem[K] = X */
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+ PPC_MR(r_M + (K & 0xf), r_X);
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+ ctx->seen |= SEEN_XREG | SEEN_MEM | (1<<(K & 0xf));
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+ break;
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+ case BPF_S_LD_W_LEN: /* A = skb->len; */
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+ BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, len) != 4);
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+ PPC_LWZ_OFFS(r_A, r_skb, offsetof(struct sk_buff, len));
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+ break;
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+ case BPF_S_LDX_W_LEN: /* X = skb->len; */
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+ PPC_LWZ_OFFS(r_X, r_skb, offsetof(struct sk_buff, len));
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+ break;
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+
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+ /*** Ancillary info loads ***/
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+
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+ /* None of the BPF_S_ANC* codes appear to be passed by
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+ * sk_chk_filter(). The interpreter and the x86 BPF
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+ * compiler implement them so we do too -- they may be
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+ * planted in future.
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+ */
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+ case BPF_S_ANC_PROTOCOL: /* A = ntohs(skb->protocol); */
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+ BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff,
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+ protocol) != 2);
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+ PPC_LHZ_OFFS(r_A, r_skb, offsetof(struct sk_buff,
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+ protocol));
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+ /* ntohs is a NOP with BE loads. */
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+ break;
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+ case BPF_S_ANC_IFINDEX:
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+ PPC_LD_OFFS(r_scratch1, r_skb, offsetof(struct sk_buff,
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+ dev));
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+ PPC_CMPDI(r_scratch1, 0);
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+ if (ctx->pc_ret0 != -1) {
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+ PPC_BCC(COND_EQ, addrs[ctx->pc_ret0]);
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+ } else {
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+ /* Exit, returning 0; first pass hits here. */
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+ PPC_BCC_SHORT(COND_NE, (ctx->idx*4)+12);
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+ PPC_LI(r_ret, 0);
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+ PPC_JMP(exit_addr);
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+ }
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+ BUILD_BUG_ON(FIELD_SIZEOF(struct net_device,
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+ ifindex) != 4);
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+ PPC_LWZ_OFFS(r_A, r_scratch1,
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+ offsetof(struct net_device, ifindex));
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+ break;
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+ case BPF_S_ANC_MARK:
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+ BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, mark) != 4);
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+ PPC_LWZ_OFFS(r_A, r_skb, offsetof(struct sk_buff,
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+ mark));
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+ break;
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+ case BPF_S_ANC_RXHASH:
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+ BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, rxhash) != 4);
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+ PPC_LWZ_OFFS(r_A, r_skb, offsetof(struct sk_buff,
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+ rxhash));
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+ break;
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+ case BPF_S_ANC_QUEUE:
|
|
|
+ BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff,
|
|
|
+ queue_mapping) != 2);
|
|
|
+ PPC_LHZ_OFFS(r_A, r_skb, offsetof(struct sk_buff,
|
|
|
+ queue_mapping));
|
|
|
+ break;
|
|
|
+ case BPF_S_ANC_CPU:
|
|
|
+#ifdef CONFIG_SMP
|
|
|
+ /*
|
|
|
+ * PACA ptr is r13:
|
|
|
+ * raw_smp_processor_id() = local_paca->paca_index
|
|
|
+ */
|
|
|
+ BUILD_BUG_ON(FIELD_SIZEOF(struct paca_struct,
|
|
|
+ paca_index) != 2);
|
|
|
+ PPC_LHZ_OFFS(r_A, 13,
|
|
|
+ offsetof(struct paca_struct, paca_index));
|
|
|
+#else
|
|
|
+ PPC_LI(r_A, 0);
|
|
|
+#endif
|
|
|
+ break;
|
|
|
+
|
|
|
+ /*** Absolute loads from packet header/data ***/
|
|
|
+ case BPF_S_LD_W_ABS:
|
|
|
+ func = sk_load_word;
|
|
|
+ goto common_load;
|
|
|
+ case BPF_S_LD_H_ABS:
|
|
|
+ func = sk_load_half;
|
|
|
+ goto common_load;
|
|
|
+ case BPF_S_LD_B_ABS:
|
|
|
+ func = sk_load_byte;
|
|
|
+ common_load:
|
|
|
+ /*
|
|
|
+ * Load from [K]. Reference with the (negative)
|
|
|
+ * SKF_NET_OFF/SKF_LL_OFF offsets is unsupported.
|
|
|
+ */
|
|
|
+ ctx->seen |= SEEN_DATAREF;
|
|
|
+ if ((int)K < 0)
|
|
|
+ return -ENOTSUPP;
|
|
|
+ PPC_LI64(r_scratch1, func);
|
|
|
+ PPC_MTLR(r_scratch1);
|
|
|
+ PPC_LI32(r_addr, K);
|
|
|
+ PPC_BLRL();
|
|
|
+ /*
|
|
|
+ * Helper returns 'lt' condition on error, and an
|
|
|
+ * appropriate return value in r3
|
|
|
+ */
|
|
|
+ PPC_BCC(COND_LT, exit_addr);
|
|
|
+ break;
|
|
|
+
|
|
|
+ /*** Indirect loads from packet header/data ***/
|
|
|
+ case BPF_S_LD_W_IND:
|
|
|
+ func = sk_load_word;
|
|
|
+ goto common_load_ind;
|
|
|
+ case BPF_S_LD_H_IND:
|
|
|
+ func = sk_load_half;
|
|
|
+ goto common_load_ind;
|
|
|
+ case BPF_S_LD_B_IND:
|
|
|
+ func = sk_load_byte;
|
|
|
+ common_load_ind:
|
|
|
+ /*
|
|
|
+ * Load from [X + K]. Negative offsets are tested for
|
|
|
+ * in the helper functions, and result in a 'ret 0'.
|
|
|
+ */
|
|
|
+ ctx->seen |= SEEN_DATAREF | SEEN_XREG;
|
|
|
+ PPC_LI64(r_scratch1, func);
|
|
|
+ PPC_MTLR(r_scratch1);
|
|
|
+ PPC_ADDI(r_addr, r_X, IMM_L(K));
|
|
|
+ if (K >= 32768)
|
|
|
+ PPC_ADDIS(r_addr, r_addr, IMM_HA(K));
|
|
|
+ PPC_BLRL();
|
|
|
+ /* If error, cr0.LT set */
|
|
|
+ PPC_BCC(COND_LT, exit_addr);
|
|
|
+ break;
|
|
|
+
|
|
|
+ case BPF_S_LDX_B_MSH:
|
|
|
+ /*
|
|
|
+ * x86 version drops packet (RET 0) when K<0, whereas
|
|
|
+ * interpreter does allow K<0 (__load_pointer, special
|
|
|
+ * ancillary data). common_load returns ENOTSUPP if K<0,
|
|
|
+ * so we fall back to interpreter & filter works.
|
|
|
+ */
|
|
|
+ func = sk_load_byte_msh;
|
|
|
+ goto common_load;
|
|
|
+ break;
|
|
|
+
|
|
|
+ /*** Jump and branches ***/
|
|
|
+ case BPF_S_JMP_JA:
|
|
|
+ if (K != 0)
|
|
|
+ PPC_JMP(addrs[i + 1 + K]);
|
|
|
+ break;
|
|
|
+
|
|
|
+ case BPF_S_JMP_JGT_K:
|
|
|
+ case BPF_S_JMP_JGT_X:
|
|
|
+ true_cond = COND_GT;
|
|
|
+ goto cond_branch;
|
|
|
+ case BPF_S_JMP_JGE_K:
|
|
|
+ case BPF_S_JMP_JGE_X:
|
|
|
+ true_cond = COND_GE;
|
|
|
+ goto cond_branch;
|
|
|
+ case BPF_S_JMP_JEQ_K:
|
|
|
+ case BPF_S_JMP_JEQ_X:
|
|
|
+ true_cond = COND_EQ;
|
|
|
+ goto cond_branch;
|
|
|
+ case BPF_S_JMP_JSET_K:
|
|
|
+ case BPF_S_JMP_JSET_X:
|
|
|
+ true_cond = COND_NE;
|
|
|
+ /* Fall through */
|
|
|
+ cond_branch:
|
|
|
+ /* same targets, can avoid doing the test :) */
|
|
|
+ if (filter[i].jt == filter[i].jf) {
|
|
|
+ if (filter[i].jt > 0)
|
|
|
+ PPC_JMP(addrs[i + 1 + filter[i].jt]);
|
|
|
+ break;
|
|
|
+ }
|
|
|
+
|
|
|
+ switch (filter[i].code) {
|
|
|
+ case BPF_S_JMP_JGT_X:
|
|
|
+ case BPF_S_JMP_JGE_X:
|
|
|
+ case BPF_S_JMP_JEQ_X:
|
|
|
+ ctx->seen |= SEEN_XREG;
|
|
|
+ PPC_CMPLW(r_A, r_X);
|
|
|
+ break;
|
|
|
+ case BPF_S_JMP_JSET_X:
|
|
|
+ ctx->seen |= SEEN_XREG;
|
|
|
+ PPC_AND_DOT(r_scratch1, r_A, r_X);
|
|
|
+ break;
|
|
|
+ case BPF_S_JMP_JEQ_K:
|
|
|
+ case BPF_S_JMP_JGT_K:
|
|
|
+ case BPF_S_JMP_JGE_K:
|
|
|
+ if (K < 32768)
|
|
|
+ PPC_CMPLWI(r_A, K);
|
|
|
+ else {
|
|
|
+ PPC_LI32(r_scratch1, K);
|
|
|
+ PPC_CMPLW(r_A, r_scratch1);
|
|
|
+ }
|
|
|
+ break;
|
|
|
+ case BPF_S_JMP_JSET_K:
|
|
|
+ if (K < 32768)
|
|
|
+ /* PPC_ANDI is /only/ dot-form */
|
|
|
+ PPC_ANDI(r_scratch1, r_A, K);
|
|
|
+ else {
|
|
|
+ PPC_LI32(r_scratch1, K);
|
|
|
+ PPC_AND_DOT(r_scratch1, r_A,
|
|
|
+ r_scratch1);
|
|
|
+ }
|
|
|
+ break;
|
|
|
+ }
|
|
|
+ /* Sometimes branches are constructed "backward", with
|
|
|
+ * the false path being the branch and true path being
|
|
|
+ * a fallthrough to the next instruction.
|
|
|
+ */
|
|
|
+ if (filter[i].jt == 0)
|
|
|
+ /* Swap the sense of the branch */
|
|
|
+ PPC_BCC(true_cond ^ COND_CMP_TRUE,
|
|
|
+ addrs[i + 1 + filter[i].jf]);
|
|
|
+ else {
|
|
|
+ PPC_BCC(true_cond, addrs[i + 1 + filter[i].jt]);
|
|
|
+ if (filter[i].jf != 0)
|
|
|
+ PPC_JMP(addrs[i + 1 + filter[i].jf]);
|
|
|
+ }
|
|
|
+ break;
|
|
|
+ default:
|
|
|
+ /* The filter contains something cruel & unusual.
|
|
|
+ * We don't handle it, but also there shouldn't be
|
|
|
+ * anything missing from our list.
|
|
|
+ */
|
|
|
+ if (printk_ratelimit())
|
|
|
+ pr_err("BPF filter opcode %04x (@%d) unsupported\n",
|
|
|
+ filter[i].code, i);
|
|
|
+ return -ENOTSUPP;
|
|
|
+ }
|
|
|
+
|
|
|
+ }
|
|
|
+ /* Set end-of-body-code address for exit. */
|
|
|
+ addrs[i] = ctx->idx * 4;
|
|
|
+
|
|
|
+ return 0;
|
|
|
+}
|
|
|
+
|
|
|
+void bpf_jit_compile(struct sk_filter *fp)
|
|
|
+{
|
|
|
+ unsigned int proglen;
|
|
|
+ unsigned int alloclen;
|
|
|
+ u32 *image = NULL;
|
|
|
+ u32 *code_base;
|
|
|
+ unsigned int *addrs;
|
|
|
+ struct codegen_context cgctx;
|
|
|
+ int pass;
|
|
|
+ int flen = fp->len;
|
|
|
+
|
|
|
+ if (!bpf_jit_enable)
|
|
|
+ return;
|
|
|
+
|
|
|
+ addrs = kzalloc((flen+1) * sizeof(*addrs), GFP_KERNEL);
|
|
|
+ if (addrs == NULL)
|
|
|
+ return;
|
|
|
+
|
|
|
+ /*
|
|
|
+ * There are multiple assembly passes as the generated code will change
|
|
|
+ * size as it settles down, figuring out the max branch offsets/exit
|
|
|
+ * paths required.
|
|
|
+ *
|
|
|
+ * The range of standard conditional branches is +/- 32Kbytes. Since
|
|
|
+ * BPF_MAXINSNS = 4096, we can only jump from (worst case) start to
|
|
|
+ * finish with 8 bytes/instruction. Not feasible, so long jumps are
|
|
|
+ * used, distinct from short branches.
|
|
|
+ *
|
|
|
+ * Current:
|
|
|
+ *
|
|
|
+ * For now, both branch types assemble to 2 words (short branches padded
|
|
|
+ * with a NOP); this is less efficient, but assembly will always complete
|
|
|
+ * after exactly 3 passes:
|
|
|
+ *
|
|
|
+ * First pass: No code buffer; Program is "faux-generated" -- no code
|
|
|
+ * emitted but maximum size of output determined (and addrs[] filled
|
|
|
+ * in). Also, we note whether we use M[], whether we use skb data, etc.
|
|
|
+ * All generation choices assumed to be 'worst-case', e.g. branches all
|
|
|
+ * far (2 instructions), return path code reduction not available, etc.
|
|
|
+ *
|
|
|
+ * Second pass: Code buffer allocated with size determined previously.
|
|
|
+ * Prologue generated to support features we have seen used. Exit paths
|
|
|
+ * determined and addrs[] is filled in again, as code may be slightly
|
|
|
+ * smaller as a result.
|
|
|
+ *
|
|
|
+ * Third pass: Code generated 'for real', and branch destinations
|
|
|
+ * determined from now-accurate addrs[] map.
|
|
|
+ *
|
|
|
+ * Ideal:
|
|
|
+ *
|
|
|
+ * If we optimise this, near branches will be shorter. On the
|
|
|
+ * first assembly pass, we should err on the side of caution and
|
|
|
+ * generate the biggest code. On subsequent passes, branches will be
|
|
|
+ * generated short or long and code size will reduce. With smaller
|
|
|
+ * code, more branches may fall into the short category, and code will
|
|
|
+ * reduce more.
|
|
|
+ *
|
|
|
+ * Finally, if we see one pass generate code the same size as the
|
|
|
+ * previous pass we have converged and should now generate code for
|
|
|
+ * real. Allocating at the end will also save the memory that would
|
|
|
+ * otherwise be wasted by the (small) current code shrinkage.
|
|
|
+ * Preferably, we should do a small number of passes (e.g. 5) and if we
|
|
|
+ * haven't converged by then, get impatient and force code to generate
|
|
|
+ * as-is, even if the odd branch would be left long. The chances of a
|
|
|
+ * long jump are tiny with all but the most enormous of BPF filter
|
|
|
+ * inputs, so we should usually converge on the third pass.
|
|
|
+ */
|
|
|
+
|
|
|
+ cgctx.idx = 0;
|
|
|
+ cgctx.seen = 0;
|
|
|
+ cgctx.pc_ret0 = -1;
|
|
|
+ /* Scouting faux-generate pass 0 */
|
|
|
+ if (bpf_jit_build_body(fp, 0, &cgctx, addrs))
|
|
|
+ /* We hit something illegal or unsupported. */
|
|
|
+ goto out;
|
|
|
+
|
|
|
+ /*
|
|
|
+ * Pretend to build prologue, given the features we've seen. This will
|
|
|
+ * update ctgtx.idx as it pretends to output instructions, then we can
|
|
|
+ * calculate total size from idx.
|
|
|
+ */
|
|
|
+ bpf_jit_build_prologue(fp, 0, &cgctx);
|
|
|
+ bpf_jit_build_epilogue(0, &cgctx);
|
|
|
+
|
|
|
+ proglen = cgctx.idx * 4;
|
|
|
+ alloclen = proglen + FUNCTION_DESCR_SIZE;
|
|
|
+ image = module_alloc(max_t(unsigned int, alloclen,
|
|
|
+ sizeof(struct work_struct)));
|
|
|
+ if (!image)
|
|
|
+ goto out;
|
|
|
+
|
|
|
+ code_base = image + (FUNCTION_DESCR_SIZE/4);
|
|
|
+
|
|
|
+ /* Code generation passes 1-2 */
|
|
|
+ for (pass = 1; pass < 3; pass++) {
|
|
|
+ /* Now build the prologue, body code & epilogue for real. */
|
|
|
+ cgctx.idx = 0;
|
|
|
+ bpf_jit_build_prologue(fp, code_base, &cgctx);
|
|
|
+ bpf_jit_build_body(fp, code_base, &cgctx, addrs);
|
|
|
+ bpf_jit_build_epilogue(code_base, &cgctx);
|
|
|
+
|
|
|
+ if (bpf_jit_enable > 1)
|
|
|
+ pr_info("Pass %d: shrink = %d, seen = 0x%x\n", pass,
|
|
|
+ proglen - (cgctx.idx * 4), cgctx.seen);
|
|
|
+ }
|
|
|
+
|
|
|
+ if (bpf_jit_enable > 1)
|
|
|
+ pr_info("flen=%d proglen=%u pass=%d image=%p\n",
|
|
|
+ flen, proglen, pass, image);
|
|
|
+
|
|
|
+ if (image) {
|
|
|
+ if (bpf_jit_enable > 1)
|
|
|
+ print_hex_dump(KERN_ERR, "JIT code: ",
|
|
|
+ DUMP_PREFIX_ADDRESS,
|
|
|
+ 16, 1, code_base,
|
|
|
+ proglen, false);
|
|
|
+
|
|
|
+ bpf_flush_icache(code_base, code_base + (proglen/4));
|
|
|
+ /* Function descriptor nastiness: Address + TOC */
|
|
|
+ ((u64 *)image)[0] = (u64)code_base;
|
|
|
+ ((u64 *)image)[1] = local_paca->kernel_toc;
|
|
|
+ fp->bpf_func = (void *)image;
|
|
|
+ }
|
|
|
+out:
|
|
|
+ kfree(addrs);
|
|
|
+ return;
|
|
|
+}
|
|
|
+
|
|
|
+static void jit_free_defer(struct work_struct *arg)
|
|
|
+{
|
|
|
+ module_free(NULL, arg);
|
|
|
+}
|
|
|
+
|
|
|
+/* run from softirq, we must use a work_struct to call
|
|
|
+ * module_free() from process context
|
|
|
+ */
|
|
|
+void bpf_jit_free(struct sk_filter *fp)
|
|
|
+{
|
|
|
+ if (fp->bpf_func != sk_run_filter) {
|
|
|
+ struct work_struct *work = (struct work_struct *)fp->bpf_func;
|
|
|
+
|
|
|
+ INIT_WORK(work, jit_free_defer);
|
|
|
+ schedule_work(work);
|
|
|
+ }
|
|
|
+}
|