linux/arch/powerpc/net/bpf_jit_comp.c
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   1// SPDX-License-Identifier: GPL-2.0-only
   2/*
   3 * eBPF JIT compiler
   4 *
   5 * Copyright 2016 Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
   6 *                IBM Corporation
   7 *
   8 * Based on the powerpc classic BPF JIT compiler by Matt Evans
   9 */
  10#include <linux/moduleloader.h>
  11#include <asm/cacheflush.h>
  12#include <asm/asm-compat.h>
  13#include <linux/netdevice.h>
  14#include <linux/filter.h>
  15#include <linux/if_vlan.h>
  16#include <asm/kprobes.h>
  17#include <linux/bpf.h>
  18
  19#include "bpf_jit.h"
  20
  21static void bpf_jit_fill_ill_insns(void *area, unsigned int size)
  22{
  23        memset32(area, BREAKPOINT_INSTRUCTION, size / 4);
  24}
  25
  26/* Fix the branch target addresses for subprog calls */
  27static int bpf_jit_fixup_subprog_calls(struct bpf_prog *fp, u32 *image,
  28                                       struct codegen_context *ctx, u32 *addrs)
  29{
  30        const struct bpf_insn *insn = fp->insnsi;
  31        bool func_addr_fixed;
  32        u64 func_addr;
  33        u32 tmp_idx;
  34        int i, ret;
  35
  36        for (i = 0; i < fp->len; i++) {
  37                /*
  38                 * During the extra pass, only the branch target addresses for
  39                 * the subprog calls need to be fixed. All other instructions
  40                 * can left untouched.
  41                 *
  42                 * The JITed image length does not change because we already
  43                 * ensure that the JITed instruction sequence for these calls
  44                 * are of fixed length by padding them with NOPs.
  45                 */
  46                if (insn[i].code == (BPF_JMP | BPF_CALL) &&
  47                    insn[i].src_reg == BPF_PSEUDO_CALL) {
  48                        ret = bpf_jit_get_func_addr(fp, &insn[i], true,
  49                                                    &func_addr,
  50                                                    &func_addr_fixed);
  51                        if (ret < 0)
  52                                return ret;
  53
  54                        /*
  55                         * Save ctx->idx as this would currently point to the
  56                         * end of the JITed image and set it to the offset of
  57                         * the instruction sequence corresponding to the
  58                         * subprog call temporarily.
  59                         */
  60                        tmp_idx = ctx->idx;
  61                        ctx->idx = addrs[i] / 4;
  62                        bpf_jit_emit_func_call_rel(image, ctx, func_addr);
  63
  64                        /*
  65                         * Restore ctx->idx here. This is safe as the length
  66                         * of the JITed sequence remains unchanged.
  67                         */
  68                        ctx->idx = tmp_idx;
  69                }
  70        }
  71
  72        return 0;
  73}
  74
  75struct powerpc64_jit_data {
  76        struct bpf_binary_header *header;
  77        u32 *addrs;
  78        u8 *image;
  79        u32 proglen;
  80        struct codegen_context ctx;
  81};
  82
  83bool bpf_jit_needs_zext(void)
  84{
  85        return true;
  86}
  87
  88struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp)
  89{
  90        u32 proglen;
  91        u32 alloclen;
  92        u8 *image = NULL;
  93        u32 *code_base;
  94        u32 *addrs;
  95        struct powerpc64_jit_data *jit_data;
  96        struct codegen_context cgctx;
  97        int pass;
  98        int flen;
  99        struct bpf_binary_header *bpf_hdr;
 100        struct bpf_prog *org_fp = fp;
 101        struct bpf_prog *tmp_fp;
 102        bool bpf_blinded = false;
 103        bool extra_pass = false;
 104
 105        if (!fp->jit_requested)
 106                return org_fp;
 107
 108        tmp_fp = bpf_jit_blind_constants(org_fp);
 109        if (IS_ERR(tmp_fp))
 110                return org_fp;
 111
 112        if (tmp_fp != org_fp) {
 113                bpf_blinded = true;
 114                fp = tmp_fp;
 115        }
 116
 117        jit_data = fp->aux->jit_data;
 118        if (!jit_data) {
 119                jit_data = kzalloc(sizeof(*jit_data), GFP_KERNEL);
 120                if (!jit_data) {
 121                        fp = org_fp;
 122                        goto out;
 123                }
 124                fp->aux->jit_data = jit_data;
 125        }
 126
 127        flen = fp->len;
 128        addrs = jit_data->addrs;
 129        if (addrs) {
 130                cgctx = jit_data->ctx;
 131                image = jit_data->image;
 132                bpf_hdr = jit_data->header;
 133                proglen = jit_data->proglen;
 134                alloclen = proglen + FUNCTION_DESCR_SIZE;
 135                extra_pass = true;
 136                goto skip_init_ctx;
 137        }
 138
 139        addrs = kcalloc(flen + 1, sizeof(*addrs), GFP_KERNEL);
 140        if (addrs == NULL) {
 141                fp = org_fp;
 142                goto out_addrs;
 143        }
 144
 145        memset(&cgctx, 0, sizeof(struct codegen_context));
 146        memcpy(cgctx.b2p, b2p, sizeof(cgctx.b2p));
 147
 148        /* Make sure that the stack is quadword aligned. */
 149        cgctx.stack_size = round_up(fp->aux->stack_depth, 16);
 150
 151        /* Scouting faux-generate pass 0 */
 152        if (bpf_jit_build_body(fp, 0, &cgctx, addrs, false)) {
 153                /* We hit something illegal or unsupported. */
 154                fp = org_fp;
 155                goto out_addrs;
 156        }
 157
 158        /*
 159         * If we have seen a tail call, we need a second pass.
 160         * This is because bpf_jit_emit_common_epilogue() is called
 161         * from bpf_jit_emit_tail_call() with a not yet stable ctx->seen.
 162         */
 163        if (cgctx.seen & SEEN_TAILCALL) {
 164                cgctx.idx = 0;
 165                if (bpf_jit_build_body(fp, 0, &cgctx, addrs, false)) {
 166                        fp = org_fp;
 167                        goto out_addrs;
 168                }
 169        }
 170
 171        bpf_jit_realloc_regs(&cgctx);
 172        /*
 173         * Pretend to build prologue, given the features we've seen.  This will
 174         * update ctgtx.idx as it pretends to output instructions, then we can
 175         * calculate total size from idx.
 176         */
 177        bpf_jit_build_prologue(0, &cgctx);
 178        bpf_jit_build_epilogue(0, &cgctx);
 179
 180        proglen = cgctx.idx * 4;
 181        alloclen = proglen + FUNCTION_DESCR_SIZE;
 182
 183        bpf_hdr = bpf_jit_binary_alloc(alloclen, &image, 4, bpf_jit_fill_ill_insns);
 184        if (!bpf_hdr) {
 185                fp = org_fp;
 186                goto out_addrs;
 187        }
 188
 189skip_init_ctx:
 190        code_base = (u32 *)(image + FUNCTION_DESCR_SIZE);
 191
 192        if (extra_pass) {
 193                /*
 194                 * Do not touch the prologue and epilogue as they will remain
 195                 * unchanged. Only fix the branch target address for subprog
 196                 * calls in the body.
 197                 *
 198                 * This does not change the offsets and lengths of the subprog
 199                 * call instruction sequences and hence, the size of the JITed
 200                 * image as well.
 201                 */
 202                bpf_jit_fixup_subprog_calls(fp, code_base, &cgctx, addrs);
 203
 204                /* There is no need to perform the usual passes. */
 205                goto skip_codegen_passes;
 206        }
 207
 208        /* Code generation passes 1-2 */
 209        for (pass = 1; pass < 3; pass++) {
 210                /* Now build the prologue, body code & epilogue for real. */
 211                cgctx.idx = 0;
 212                bpf_jit_build_prologue(code_base, &cgctx);
 213                bpf_jit_build_body(fp, code_base, &cgctx, addrs, extra_pass);
 214                bpf_jit_build_epilogue(code_base, &cgctx);
 215
 216                if (bpf_jit_enable > 1)
 217                        pr_info("Pass %d: shrink = %d, seen = 0x%x\n", pass,
 218                                proglen - (cgctx.idx * 4), cgctx.seen);
 219        }
 220
 221skip_codegen_passes:
 222        if (bpf_jit_enable > 1)
 223                /*
 224                 * Note that we output the base address of the code_base
 225                 * rather than image, since opcodes are in code_base.
 226                 */
 227                bpf_jit_dump(flen, proglen, pass, code_base);
 228
 229#ifdef PPC64_ELF_ABI_v1
 230        /* Function descriptor nastiness: Address + TOC */
 231        ((u64 *)image)[0] = (u64)code_base;
 232        ((u64 *)image)[1] = local_paca->kernel_toc;
 233#endif
 234
 235        fp->bpf_func = (void *)image;
 236        fp->jited = 1;
 237        fp->jited_len = alloclen;
 238
 239        bpf_flush_icache(bpf_hdr, (u8 *)bpf_hdr + (bpf_hdr->pages * PAGE_SIZE));
 240        bpf_jit_binary_lock_ro(bpf_hdr);
 241        if (!fp->is_func || extra_pass) {
 242                bpf_prog_fill_jited_linfo(fp, addrs);
 243out_addrs:
 244                kfree(addrs);
 245                kfree(jit_data);
 246                fp->aux->jit_data = NULL;
 247        } else {
 248                jit_data->addrs = addrs;
 249                jit_data->ctx = cgctx;
 250                jit_data->proglen = proglen;
 251                jit_data->image = image;
 252                jit_data->header = bpf_hdr;
 253        }
 254
 255out:
 256        if (bpf_blinded)
 257                bpf_jit_prog_release_other(fp, fp == org_fp ? tmp_fp : org_fp);
 258
 259        return fp;
 260}
 261