src/bpfloader/UprobeStatsBpfLoad.cpp

/*
 * Copyright (C) 2024 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#define LOG_TAG "UprobeStatsBpfLoad"

#include <errno.h>
#include <fcntl.h>
#include <linux/bpf.h>
#include <linux/elf.h>
#include <log/log.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/utsname.h>
#include <sys/wait.h>
#include <sysexits.h>
#include <unistd.h>

#include "BpfSyscallWrappers.h"
#include "bpf/BpfUtils.h"
#include "bpf_map_def.h"

#include <cstdlib>
#include <fstream>
#include <iostream>
#include <optional>
#include <string>
#include <unordered_map>
#include <vector>

#include <android-base/cmsg.h>
#include <android-base/file.h>
#include <android-base/logging.h>
#include <android-base/strings.h>
#include <android-base/unique_fd.h>

#define BPF_FS_PATH "/sys/fs/bpf/"

// Size of the BPF log buffer for verifier logging
#define BPF_LOAD_LOG_SZ 0xfffff

using android::base::EndsWith;
using android::base::StartsWith;
using android::base::unique_fd;
using std::ifstream;
using std::ios;
using std::optional;
using std::strerror;
using std::string;
using std::vector;

namespace android {
namespace bpf {

static unsigned int page_size = static_cast<unsigned int>(getpagesize());

static string pathToObjName(const string &path) {
  // extract everything after the final slash, ie. this is the filename
  // '[email protected]' or 'bar.o'
  string filename = android::base::Split(path, "/").back();
  // strip off everything from the final period onwards (strip '.o' suffix), ie.
  // 'foo@1' or 'bar'
  string name = filename.substr(0, filename.find_last_of('.'));
  // strip any potential @1 suffix, this will leave us with just 'foo' or 'bar'
  // this can be used to provide duplicate programs (mux based on the bpfloader
  // version)
  return name.substr(0, name.find_last_of('@'));
}

typedef struct {
  const char *name;
  enum bpf_prog_type type;
} sectionType;

/*
 * Map section name prefixes to program types, the section name will be:
 *   SECTION(<prefix>/<name-of-program>)
 * For example:
 *   SECTION("tracepoint/sched_switch_func") where sched_switch_funcs
 * is the name of the program, and tracepoint is the type.
 *
 * However, be aware that you should not be directly using the SECTION() macro.
 * Instead use the DEFINE_(BPF|XDP)_(PROG|MAP)... & LICENSE/CRITICAL macros.
 */
sectionType sectionNameTypes[] = {
    {"kprobe/", BPF_PROG_TYPE_KPROBE},
    {"kretprobe/", BPF_PROG_TYPE_KPROBE},
    {"perf_event/", BPF_PROG_TYPE_PERF_EVENT},
    {"skfilter/", BPF_PROG_TYPE_SOCKET_FILTER},
    {"tracepoint/", BPF_PROG_TYPE_TRACEPOINT},
    {"uprobe/", BPF_PROG_TYPE_KPROBE},
    {"uretprobe/", BPF_PROG_TYPE_KPROBE},
};

typedef struct {
  enum bpf_prog_type type;
  string name;
  vector<char> data;
  vector<char> rel_data;
  optional<struct bpf_prog_def> prog_def;

  unique_fd prog_fd; /* fd after loading */
} codeSection;

static int readElfHeader(ifstream &elfFile, Elf64_Ehdr *eh) {
  elfFile.seekg(0);
  if (elfFile.fail())
    return -1;

  if (!elfFile.read((char *)eh, sizeof(*eh)))
    return -1;

  return 0;
}

/* Reads all section header tables into an Shdr array */
static int readSectionHeadersAll(ifstream &elfFile,
                                 vector<Elf64_Shdr> &shTable) {
  Elf64_Ehdr eh;
  int ret = 0;

  ret = readElfHeader(elfFile, &eh);
  if (ret)
    return ret;

  elfFile.seekg(eh.e_shoff);
  if (elfFile.fail())
    return -1;

  /* Read shdr table entries */
  shTable.resize(eh.e_shnum);

  if (!elfFile.read((char *)shTable.data(), (eh.e_shnum * eh.e_shentsize)))
    return -ENOMEM;

  return 0;
}

/* Read a section by its index - for ex to get sec hdr strtab blob */
static int readSectionByIdx(ifstream &elfFile, int id, vector<char> &sec) {
  vector<Elf64_Shdr> shTable;
  int ret = readSectionHeadersAll(elfFile, shTable);
  if (ret)
    return ret;

  elfFile.seekg(shTable[id].sh_offset);
  if (elfFile.fail())
    return -1;

  sec.resize(shTable[id].sh_size);
  if (!elfFile.read(sec.data(), shTable[id].sh_size))
    return -1;

  return 0;
}

/* Read whole section header string table */
static int readSectionHeaderStrtab(ifstream &elfFile, vector<char> &strtab) {
  Elf64_Ehdr eh;
  int ret = readElfHeader(elfFile, &eh);
  if (ret)
    return ret;

  ret = readSectionByIdx(elfFile, eh.e_shstrndx, strtab);
  if (ret)
    return ret;

  return 0;
}

/* Get name from offset in strtab */
static int getSymName(ifstream &elfFile, int nameOff, string &name) {
  int ret;
  vector<char> secStrTab;

  ret = readSectionHeaderStrtab(elfFile, secStrTab);
  if (ret)
    return ret;

  if (nameOff >= (int)secStrTab.size())
    return -1;

  name = string((char *)secStrTab.data() + nameOff);
  return 0;
}

/* Reads a full section by name - example to get the GPL license */
static int readSectionByName(const char *name, ifstream &elfFile,
                             vector<char> &data) {
  vector<char> secStrTab;
  vector<Elf64_Shdr> shTable;
  int ret;

  ret = readSectionHeadersAll(elfFile, shTable);
  if (ret)
    return ret;

  ret = readSectionHeaderStrtab(elfFile, secStrTab);
  if (ret)
    return ret;

  for (int i = 0; i < (int)shTable.size(); i++) {
    char *secname = secStrTab.data() + shTable[i].sh_name;
    if (!secname)
      continue;

    if (!strcmp(secname, name)) {
      vector<char> dataTmp;
      dataTmp.resize(shTable[i].sh_size);

      elfFile.seekg(shTable[i].sh_offset);
      if (elfFile.fail())
        return -1;

      if (!elfFile.read((char *)dataTmp.data(), shTable[i].sh_size))
        return -1;

      data = dataTmp;
      return 0;
    }
  }
  return -2;
}

unsigned int readSectionUint(const char *name, ifstream &elfFile,
                             unsigned int defVal) {
  vector<char> theBytes;
  int ret = readSectionByName(name, elfFile, theBytes);
  if (ret) {
    ALOGV("Couldn't find section %s (defaulting to %u [0x%x]).", name, defVal,
          defVal);
    return defVal;
  } else if (theBytes.size() < sizeof(unsigned int)) {
    ALOGE("Section %s too short (defaulting to %u [0x%x]).", name, defVal,
          defVal);
    return defVal;
  } else {
    // decode first 4 bytes as LE32 uint, there will likely be more bytes due to
    // alignment.
    unsigned int value = static_cast<unsigned char>(theBytes[3]);
    value <<= 8;
    value += static_cast<unsigned char>(theBytes[2]);
    value <<= 8;
    value += static_cast<unsigned char>(theBytes[1]);
    value <<= 8;
    value += static_cast<unsigned char>(theBytes[0]);
    ALOGV("Section %s value is %u [0x%x]", name, value, value);
    return value;
  }
}

static int readSectionByType(ifstream &elfFile, int type, vector<char> &data) {
  int ret;
  vector<Elf64_Shdr> shTable;

  ret = readSectionHeadersAll(elfFile, shTable);
  if (ret)
    return ret;

  for (int i = 0; i < (int)shTable.size(); i++) {
    if ((int)shTable[i].sh_type != type)
      continue;

    vector<char> dataTmp;
    dataTmp.resize(shTable[i].sh_size);

    elfFile.seekg(shTable[i].sh_offset);
    if (elfFile.fail())
      return -1;

    if (!elfFile.read((char *)dataTmp.data(), shTable[i].sh_size))
      return -1;

    data = dataTmp;
    return 0;
  }
  return -2;
}

static bool symCompare(Elf64_Sym a, Elf64_Sym b) {
  return (a.st_value < b.st_value);
}

static int readSymTab(ifstream &elfFile, int sort, vector<Elf64_Sym> &data) {
  int ret, numElems;
  Elf64_Sym *buf;
  vector<char> secData;

  ret = readSectionByType(elfFile, SHT_SYMTAB, secData);
  if (ret)
    return ret;

  buf = (Elf64_Sym *)secData.data();
  numElems = (secData.size() / sizeof(Elf64_Sym));
  data.assign(buf, buf + numElems);

  if (sort)
    std::sort(data.begin(), data.end(), symCompare);
  return 0;
}

static enum bpf_prog_type getFuseProgType() {
  int result = BPF_PROG_TYPE_UNSPEC;
  ifstream("/sys/fs/fuse/bpf_prog_type_fuse") >> result;
  return static_cast<bpf_prog_type>(result);
}

static enum bpf_prog_type getSectionType(string &name) {
  for (auto &snt : sectionNameTypes)
    if (StartsWith(name, snt.name))
      return snt.type;

  // TODO Remove this code when fuse-bpf is upstream and this BPF_PROG_TYPE_FUSE
  // is fixed
  if (StartsWith(name, "fuse/"))
    return getFuseProgType();

  return BPF_PROG_TYPE_UNSPEC;
}

static string getSectionName(enum bpf_prog_type type) {
  for (auto &snt : sectionNameTypes)
    if (snt.type == type)
      return string(snt.name);

  return "UNKNOWN SECTION NAME " + std::to_string(type);
}

static int readProgDefs(ifstream &elfFile, vector<struct bpf_prog_def> &pd) {
  vector<char> pdData;
  int ret = readSectionByName("progs", elfFile, pdData);
  if (ret)
    return ret;

  if (pdData.size() % sizeof(struct bpf_prog_def)) {
    ALOGE("readProgDefs failed due to improper sized progs section, %zu %% %zu "
          "!= 0",
          pdData.size(), sizeof(struct bpf_prog_def));
    return -1;
  };

  pd.resize(pdData.size() / sizeof(struct bpf_prog_def));
  memcpy(pd.data(), pdData.data(), pdData.size());
  return 0;
}

static int getSectionSymNames(ifstream &elfFile, const string &sectionName,
                              vector<string> &names,
                              optional<unsigned> symbolType = std::nullopt) {
  int ret;
  string name;
  vector<Elf64_Sym> symtab;
  vector<Elf64_Shdr> shTable;

  ret = readSymTab(elfFile, 1 /* sort */, symtab);
  if (ret)
    return ret;

  /* Get index of section */
  ret = readSectionHeadersAll(elfFile, shTable);
  if (ret)
    return ret;

  int sec_idx = -1;
  for (int i = 0; i < (int)shTable.size(); i++) {
    ret = getSymName(elfFile, shTable[i].sh_name, name);
    if (ret)
      return ret;

    if (!name.compare(sectionName)) {
      sec_idx = i;
      break;
    }
  }

  /* No section found with matching name*/
  if (sec_idx == -1) {
    ALOGW("No %s section could be found in elf object", sectionName.c_str());
    return -1;
  }

  for (int i = 0; i < (int)symtab.size(); i++) {
    if (symbolType.has_value() && ELF_ST_TYPE(symtab[i].st_info) != symbolType)
      continue;

    if (symtab[i].st_shndx == sec_idx) {
      string s;
      ret = getSymName(elfFile, symtab[i].st_name, s);
      if (ret)
        return ret;
      names.push_back(s);
    }
  }

  return 0;
}

static bool IsAllowed(bpf_prog_type type, const bpf_prog_type *allowed,
                      size_t numAllowed) {
  if (allowed == nullptr)
    return true;

  for (size_t i = 0; i < numAllowed; i++) {
    if (allowed[i] == BPF_PROG_TYPE_UNSPEC) {
      if (type == getFuseProgType())
        return true;
    } else if (type == allowed[i])
      return true;
  }

  return false;
}

/* Read a section by its index - for ex to get sec hdr strtab blob */
static int readCodeSections(ifstream &elfFile, vector<codeSection> &cs,
                            const bpf_prog_type *allowed, size_t numAllowed) {
  vector<Elf64_Shdr> shTable;
  int entries, ret = 0;

  ret = readSectionHeadersAll(elfFile, shTable);
  if (ret)
    return ret;
  entries = shTable.size();

  vector<struct bpf_prog_def> pd;
  ret = readProgDefs(elfFile, pd);
  if (ret)
    return ret;
  vector<string> progDefNames;
  ret = getSectionSymNames(elfFile, "progs", progDefNames);
  if (!pd.empty() && ret)
    return ret;

  for (int i = 0; i < entries; i++) {
    string name;
    codeSection cs_temp;
    cs_temp.type = BPF_PROG_TYPE_UNSPEC;

    ret = getSymName(elfFile, shTable[i].sh_name, name);
    if (ret)
      return ret;

    enum bpf_prog_type ptype = getSectionType(name);

    if (ptype == BPF_PROG_TYPE_UNSPEC)
      continue;

    if (!IsAllowed(ptype, allowed, numAllowed)) {
      ALOGE("Program type %s not permitted here",
            getSectionName(ptype).c_str());
      return -1;
    }

    string oldName = name;

    // convert all slashes to underscores
    std::replace(name.begin(), name.end(), '/', '_');

    cs_temp.type = ptype;
    cs_temp.name = name;

    ret = readSectionByIdx(elfFile, i, cs_temp.data);
    if (ret)
      return ret;
    ALOGV("Loaded code section %d (%s)", i, name.c_str());

    vector<string> csSymNames;
    ret = getSectionSymNames(elfFile, oldName, csSymNames, STT_FUNC);
    if (ret || !csSymNames.size())
      return ret;
    for (size_t i = 0; i < progDefNames.size(); ++i) {
      if (!progDefNames[i].compare(csSymNames[0] + "_def")) {
        cs_temp.prog_def = pd[i];
        break;
      }
    }

    /* Check for rel section */
    if (cs_temp.data.size() > 0 && i < entries) {
      ret = getSymName(elfFile, shTable[i + 1].sh_name, name);
      if (ret)
        return ret;

      if (name == (".rel" + oldName)) {
        ret = readSectionByIdx(elfFile, i + 1, cs_temp.rel_data);
        if (ret)
          return ret;
        ALOGV("Loaded relo section %d (%s)", i, name.c_str());
      }
    }

    if (cs_temp.data.size() > 0) {
      cs.push_back(std::move(cs_temp));
      ALOGV("Adding section %d to cs list", i);
    }
  }
  return 0;
}

static int getSymNameByIdx(ifstream &elfFile, int index, string &name) {
  vector<Elf64_Sym> symtab;
  int ret = 0;

  ret = readSymTab(elfFile, 0 /* !sort */, symtab);
  if (ret)
    return ret;

  if (index >= (int)symtab.size())
    return -1;

  return getSymName(elfFile, symtab[index].st_name, name);
}

static bool mapMatchesExpectations(const unique_fd &fd, const string &mapName,
                                   const struct bpf_map_def &mapDef,
                                   const enum bpf_map_type type) {
  // Assuming fd is a valid Bpf Map file descriptor then
  // all the following should always succeed on a 4.14+ kernel.
  // If they somehow do fail, they'll return -1 (and set errno),
  // which should then cause (among others) a key_size mismatch.
  int fd_type = bpfGetFdMapType(fd);
  int fd_key_size = bpfGetFdKeySize(fd);
  int fd_value_size = bpfGetFdValueSize(fd);
  int fd_max_entries = bpfGetFdMaxEntries(fd);
  int fd_map_flags = bpfGetFdMapFlags(fd);

  // DEVMAPs are readonly from the bpf program side's point of view, as such
  // the kernel in kernel/bpf/devmap.c dev_map_init_map() will set the flag
  int desired_map_flags = (int)mapDef.map_flags;
  if (type == BPF_MAP_TYPE_DEVMAP || type == BPF_MAP_TYPE_DEVMAP_HASH)
    desired_map_flags |= BPF_F_RDONLY_PROG;

  // The .h file enforces that this is a power of two, and page size will
  // also always be a power of two, so this logic is actually enough to
  // force it to be a multiple of the page size, as required by the kernel.
  unsigned int desired_max_entries = mapDef.max_entries;
  if (type == BPF_MAP_TYPE_RINGBUF) {
    if (desired_max_entries < page_size)
      desired_max_entries = page_size;
  }

  // The following checks should *never* trigger, if one of them somehow does,
  // it probably means a bpf .o file has been changed/replaced at runtime
  // and bpfloader was manually rerun (normally it should only run *once*
  // early during the boot process).
  // Another possibility is that something is misconfigured in the code:
  // most likely a shared map is declared twice differently.
  // But such a change should never be checked into the source tree...
  if ((fd_type == type) && (fd_key_size == (int)mapDef.key_size) &&
      (fd_value_size == (int)mapDef.value_size) &&
      (fd_max_entries == (int)desired_max_entries) &&
      (fd_map_flags == desired_map_flags)) {
    return true;
  }

  ALOGE("bpf map name %s mismatch: desired/found: "
        "type:%d/%d key:%u/%d value:%u/%d entries:%u/%d flags:%u/%d",
        mapName.c_str(), type, fd_type, mapDef.key_size, fd_key_size,
        mapDef.value_size, fd_value_size, mapDef.max_entries, fd_max_entries,
        desired_map_flags, fd_map_flags);
  return false;
}

static int createMaps(const char *elfPath, ifstream &elfFile,
                      vector<unique_fd> &mapFds, const char *prefix) {
  int ret;
  vector<char> mdData;
  vector<struct bpf_map_def> md;
  vector<string> mapNames;
  string objName = pathToObjName(string(elfPath));

  ret = readSectionByName("maps", elfFile, mdData);
  if (ret == -2)
    return 0; // no maps to read
  if (ret)
    return ret;

  if (mdData.size() % sizeof(struct bpf_map_def)) {
    ALOGE(
        "createMaps failed due to improper sized maps section, %zu %% %zu != 0",
        mdData.size(), sizeof(struct bpf_map_def));
    return -1;
  }
  md.resize(mdData.size() / sizeof(struct bpf_map_def));
  memcpy(md.data(), mdData.data(), mdData.size());

  ret = getSectionSymNames(elfFile, "maps", mapNames);
  if (ret)
    return ret;

  unsigned kvers = kernelVersion();

  for (int i = 0; i < (int)mapNames.size(); i++) {
    if (md[i].zero != 0)
      abort();

    if (kvers < md[i].min_kver) {
      ALOGD("skipping map %s which requires kernel version 0x%x >= 0x%x",
            mapNames[i].c_str(), kvers, md[i].min_kver);
      mapFds.push_back(unique_fd());
      continue;
    }

    if (kvers >= md[i].max_kver) {
      ALOGD("skipping map %s which requires kernel version 0x%x < 0x%x",
            mapNames[i].c_str(), kvers, md[i].max_kver);
      mapFds.push_back(unique_fd());
      continue;
    }

    enum bpf_map_type type = md[i].type;
    if (type == BPF_MAP_TYPE_DEVMAP_HASH && !isAtLeastKernelVersion(5, 4, 0)) {
      // On Linux Kernels older than 5.4 this map type doesn't exist, but it can
      // kind of be approximated: HASH has the same userspace visible api.
      // However it cannot be used by ebpf programs in the same way.
      // Since bpf_redirect_map() only requires 4.14, a program using a
      // DEVMAP_HASH map would fail to load (due to trying to redirect to a HASH
      // instead of DEVMAP_HASH). One must thus tag any BPF_MAP_TYPE_DEVMAP_HASH
      // + bpf_redirect_map() using programs as being 5.4+...
      type = BPF_MAP_TYPE_HASH;
    }

    // The .h file enforces that this is a power of two, and page size will
    // also always be a power of two, so this logic is actually enough to
    // force it to be a multiple of the page size, as required by the kernel.
    unsigned int max_entries = md[i].max_entries;
    if (type == BPF_MAP_TYPE_RINGBUF) {
      if (max_entries < page_size)
        max_entries = page_size;
    }

    // Format of pin location is /sys/fs/bpf/<prefix>map_<objName>_<mapName>
    // except that maps shared across .o's have empty <objName>
    // Note: <objName> refers to the extension-less basename of the .o file
    // (without @ suffix).
    string mapPinLoc = string(BPF_FS_PATH) + prefix + "map_" +
                       (md[i].shared ? "" : objName) + "_" + mapNames[i];
    bool reuse = false;
    unique_fd fd;
    int saved_errno;

    if (access(mapPinLoc.c_str(), F_OK) == 0) {
      fd.reset(mapRetrieveRO(mapPinLoc.c_str()));
      saved_errno = errno;
      ALOGV("bpf_create_map reusing map %s, ret: %d", mapNames[i].c_str(),
            fd.get());
      reuse = true;
    } else {
      union bpf_attr req = {
          .map_type = type,
          .key_size = md[i].key_size,
          .value_size = md[i].value_size,
          .max_entries = max_entries,
          .map_flags = md[i].map_flags,
      };
      strlcpy(req.map_name, mapNames[i].c_str(), sizeof(req.map_name));
      fd.reset(bpf(BPF_MAP_CREATE, req));
      saved_errno = errno;
      ALOGV("bpf_create_map name %s, ret: %d", mapNames[i].c_str(), fd.get());
    }

    if (!fd.ok())
      return -saved_errno;

    // When reusing a pinned map, we need to check the map type/sizes/etc match,
    // but for safety (since reuse code path is rare) run these checks even if
    // we just created it. We assume failure is due to pinned map mismatch,
    // hence the 'NOT UNIQUE' return code.
    if (!mapMatchesExpectations(fd, mapNames[i], md[i], type))
      return -ENOTUNIQ;

    if (!reuse) {
      ret = bpfFdPin(fd, mapPinLoc.c_str());
      if (ret) {
        int err = errno;
        ALOGE("pin %s -> %d [%d:%s]", mapPinLoc.c_str(), ret, err,
              strerror(err));
        return -err;
      }
      ret = chmod(mapPinLoc.c_str(), md[i].mode);
      if (ret) {
        int err = errno;
        ALOGE("chmod(%s, 0%o) = %d [%d:%s]", mapPinLoc.c_str(), md[i].mode, ret,
              err, strerror(err));
        return -err;
      }
      ret = chown(mapPinLoc.c_str(), (uid_t)md[i].uid, (gid_t)md[i].gid);
      if (ret) {
        int err = errno;
        ALOGE("chown(%s, %u, %u) = %d [%d:%s]", mapPinLoc.c_str(), md[i].uid,
              md[i].gid, ret, err, strerror(err));
        return -err;
      }
    }

    int mapId = bpfGetFdMapId(fd);
    if (mapId == -1) {
      ALOGE("bpfGetFdMapId failed, ret: %d [%d]", mapId, errno);
    } else {
      ALOGD("map %s id %d", mapPinLoc.c_str(), mapId);
    }

    mapFds.push_back(std::move(fd));
  }

  return ret;
}

static void applyRelo(void *insnsPtr, Elf64_Addr offset, int fd) {
  int insnIndex;
  struct bpf_insn *insn, *insns;

  insns = (struct bpf_insn *)(insnsPtr);

  insnIndex = offset / sizeof(struct bpf_insn);
  insn = &insns[insnIndex];

  // Occasionally might be useful for relocation debugging, but pretty spammy
  if (0) {
    ALOGV("applying relo to instruction at byte offset: %llu, "
          "insn offset %d, insn %llx",
          (unsigned long long)offset, insnIndex, *(unsigned long long *)insn);
  }

  if (insn->code != (BPF_LD | BPF_IMM | BPF_DW)) {
    ALOGE("invalid relo for insn %d: code 0x%x", insnIndex, insn->code);
    return;
  }

  insn->imm = fd;
  insn->src_reg = BPF_PSEUDO_MAP_FD;
}

static void applyMapRelo(ifstream &elfFile, vector<unique_fd> &mapFds,
                         vector<codeSection> &cs) {
  vector<string> mapNames;

  int ret = getSectionSymNames(elfFile, "maps", mapNames);
  if (ret)
    return;

  for (int k = 0; k != (int)cs.size(); k++) {
    Elf64_Rel *rel = (Elf64_Rel *)(cs[k].rel_data.data());
    int n_rel = cs[k].rel_data.size() / sizeof(*rel);

    for (int i = 0; i < n_rel; i++) {
      int symIndex = ELF64_R_SYM(rel[i].r_info);
      string symName;

      ret = getSymNameByIdx(elfFile, symIndex, symName);
      if (ret)
        return;

      /* Find the map fd and apply relo */
      for (int j = 0; j < (int)mapNames.size(); j++) {
        if (!mapNames[j].compare(symName)) {
          applyRelo(cs[k].data.data(), rel[i].r_offset, mapFds[j]);
          break;
        }
      }
    }
  }
}

static int loadCodeSections(const char *elfPath, vector<codeSection> &cs,
                            const string &license, const char *prefix) {
  unsigned kvers = kernelVersion();

  if (!kvers) {
    ALOGE("unable to get kernel version");
    return -EINVAL;
  }

  string objName = pathToObjName(string(elfPath));

  for (int i = 0; i < (int)cs.size(); i++) {
    unique_fd &fd = cs[i].prog_fd;
    int ret;
    string name = cs[i].name;

    if (!cs[i].prog_def.has_value()) {
      ALOGE("[%d] '%s' missing program definition! bad bpf.o build?", i,
            name.c_str());
      return -EINVAL;
    }

    unsigned min_kver = cs[i].prog_def->min_kver;
    unsigned max_kver = cs[i].prog_def->max_kver;
    if (kvers < min_kver || kvers >= max_kver) {
      ALOGD(
          "skipping program cs[%d].name:%s min_kver:%x max_kver:%x (kvers:%x)",
          i, name.c_str(), min_kver, max_kver, kvers);
      continue;
    }

    // strip any potential $foo suffix
    // this can be used to provide duplicate programs
    // conditionally loaded based on running kernel version
    name = name.substr(0, name.find_last_of('$'));

    bool reuse = false;
    // Format of pin location is
    // /sys/fs/bpf/<prefix>prog_<objName>_<progName>
    string progPinLoc =
        string(BPF_FS_PATH) + prefix + "prog_" + objName + '_' + string(name);
    if (access(progPinLoc.c_str(), F_OK) == 0) {
      fd.reset(retrieveProgram(progPinLoc.c_str()));
      ALOGV("New bpf prog load reusing prog %s, ret: %d (%s)",
            progPinLoc.c_str(), fd.get(),
            (!fd.ok() ? std::strerror(errno) : "no error"));
      reuse = true;
    } else {
      vector<char> log_buf(BPF_LOAD_LOG_SZ, 0);

      union bpf_attr req = {
          .prog_type = cs[i].type,
          .kern_version = kvers,
          .license = ptr_to_u64(license.c_str()),
          .insns = ptr_to_u64(cs[i].data.data()),
          .insn_cnt =
              static_cast<__u32>(cs[i].data.size() / sizeof(struct bpf_insn)),
          .log_level = 1,
          .log_buf = ptr_to_u64(log_buf.data()),
          .log_size = static_cast<__u32>(log_buf.size()),
      };
      strlcpy(req.prog_name, cs[i].name.c_str(), sizeof(req.prog_name));
      fd.reset(bpf(BPF_PROG_LOAD, req));

      if (!fd.ok()) {
        ALOGW("BPF_PROG_LOAD call for %s (%s) returned fd: %d (%s)", elfPath,
              cs[i].name.c_str(), fd.get(), std::strerror(errno));

        vector<string> lines = android::base::Split(log_buf.data(), "\n");

        ALOGW("BPF_PROG_LOAD - BEGIN log_buf contents:");
        for (const auto &line : lines)
          ALOGW("%s", line.c_str());
        ALOGW("BPF_PROG_LOAD - END log_buf contents.");

        if (cs[i].prog_def->optional) {
          ALOGW("failed program is marked optional - continuing...");
          continue;
        }
        ALOGE("non-optional program failed to load.");
      }
    }

    if (!fd.ok())
      return fd.get();

    if (!reuse) {
      ret = bpfFdPin(fd, progPinLoc.c_str());
      if (ret) {
        int err = errno;
        ALOGE("create %s -> %d [%d:%s]", progPinLoc.c_str(), ret, err,
              strerror(err));
        return -err;
      }
      if (chmod(progPinLoc.c_str(), 0440)) {
        int err = errno;
        ALOGE("chmod %s 0440 -> [%d:%s]", progPinLoc.c_str(), err,
              strerror(err));
        return -err;
      }
      if (chown(progPinLoc.c_str(), (uid_t)cs[i].prog_def->uid,
                (gid_t)cs[i].prog_def->gid)) {
        int err = errno;
        ALOGE("chown %s %d %d -> [%d:%s]", progPinLoc.c_str(),
              cs[i].prog_def->uid, cs[i].prog_def->gid, err, strerror(err));
        return -err;
      }
    }

    int progId = bpfGetFdProgId(fd);
    if (progId == -1) {
      ALOGE("bpfGetFdProgId failed, ret: %d [%d]", progId, errno);
    } else {
      ALOGD("prog %s id %d", progPinLoc.c_str(), progId);
    }
  }

  return 0;
}

struct Location {
  const char *const dir = "";
  const char *const prefix = "";
  const bpf_prog_type *allowedProgTypes = nullptr;
  size_t allowedProgTypesLength = 0;
};

int loadProg(const char *elfPath, bool *isCritical, const Location &location) {
  vector<char> license;
  vector<char> critical;
  vector<codeSection> cs;
  vector<unique_fd> mapFds;
  int ret;

  if (!isCritical)
    return -1;
  *isCritical = false;

  ifstream elfFile(elfPath, ios::in | ios::binary);
  if (!elfFile.is_open())
    return -1;

  ret = readSectionByName("critical", elfFile, critical);
  *isCritical = !ret;

  ret = readSectionByName("license", elfFile, license);
  if (ret) {
    ALOGE("Couldn't find license in %s", elfPath);
    return ret;
  }

  ALOGI("UprobeStatsBpfLoad loading %s%s ELF object %s with license %s",
        *isCritical ? "critical for " : "optional",
        *isCritical ? (char *)critical.data() : "", elfPath,
        (char *)license.data());

  ret = readCodeSections(elfFile, cs, location.allowedProgTypes,
                         location.allowedProgTypesLength);
  if (ret) {
    ALOGE("Couldn't read all code sections in %s", elfPath);
    return ret;
  }

  ret = createMaps(elfPath, elfFile, mapFds, location.prefix);
  if (ret) {
    ALOGE("Failed to create maps: (ret=%d) in %s", ret, elfPath);
    return ret;
  }

  for (int i = 0; i < (int)mapFds.size(); i++)
    ALOGV("map_fd found at %d is %d in %s", i, mapFds[i].get(), elfPath);

  applyMapRelo(elfFile, mapFds, cs);

  ret = loadCodeSections(elfPath, cs, string(license.data()), location.prefix);
  if (ret)
    ALOGE("Failed to load programs, loadCodeSections ret=%d", ret);

  return ret;
}

// Networking-related program types are limited to the Tethering Apex
// to prevent things from breaking due to conflicts on mainline updates
// (exception made for socket filters, ie. xt_bpf for potential use in iptables,
// or for attaching to sockets directly)
constexpr bpf_prog_type kPlatformAllowedProgTypes[] = {
    BPF_PROG_TYPE_KPROBE,        BPF_PROG_TYPE_PERF_EVENT,
    BPF_PROG_TYPE_SOCKET_FILTER, BPF_PROG_TYPE_TRACEPOINT,
    BPF_PROG_TYPE_UNSPEC, // Will be replaced with fuse bpf program type
};

constexpr bpf_prog_type kMemEventsAllowedProgTypes[] = {
    BPF_PROG_TYPE_TRACEPOINT,
    BPF_PROG_TYPE_SOCKET_FILTER,
};

constexpr bpf_prog_type kUprobestatsAllowedProgTypes[] = {
    BPF_PROG_TYPE_KPROBE,
};

// see b/162057235. For arbitrary program types, the concern is that due to the
// lack of SELinux access controls over BPF program attachpoints, we have no way
// to control the attachment of programs to shared resources (or to detect when
// a shared resource has one BPF program replace another that is attached there)
constexpr bpf_prog_type kVendorAllowedProgTypes[] = {
    BPF_PROG_TYPE_SOCKET_FILTER,
};

const Location locations[] = {
    // uprobestats
    {
        .dir = "/apex/com.android.uprobestats/etc/bpf/uprobestats/",
        .prefix = "uprobestats/",
        .allowedProgTypes = kUprobestatsAllowedProgTypes,
        .allowedProgTypesLength = arraysize(kUprobestatsAllowedProgTypes),
    },
};

int loadAllElfObjects(const Location &location) {
  int retVal = 0;
  DIR *dir;
  struct dirent *ent;

  if ((dir = opendir(location.dir)) != NULL) {
    while ((ent = readdir(dir)) != NULL) {
      string s = ent->d_name;
      if (!EndsWith(s, ".o"))
        continue;

      string progPath(location.dir);
      progPath += s;

      bool critical;
      int ret = loadProg(progPath.c_str(), &critical, location);
      if (ret) {
        if (critical)
          retVal = ret;
        ALOGE("Failed to load object: %s, ret: %s", progPath.c_str(),
              strerror(-ret));
      } else {
        ALOGV("Loaded object: %s", progPath.c_str());
      }
    }
    closedir(dir);
  }
  return retVal;
}

int createSysFsBpfSubDir(const char *const prefix) {
  if (*prefix) {
    mode_t prevUmask = umask(0);

    string s = "/sys/fs/bpf/";
    s += prefix;

    errno = 0;
    int ret = mkdir(s.c_str(), S_ISVTX | S_IRWXU | S_IRWXG | S_IRWXO);
    if (ret && errno != EEXIST) {
      const int err = errno;
      ALOGE("Failed to create directory: %s, ret: %s", s.c_str(),
            strerror(err));
      return -err;
    }

    umask(prevUmask);
  }
  return 0;
}

} // namespace bpf
} // namespace android

// ----- extern C stuff for rust below here -----

void initLogging() {
  // since we only ever get called from mainline NetBpfLoad
  // (see packages/modules/Connectivity/netbpfload/NetBpfLoad.cpp around line
  // 516) and there no arguments, so we can just pretend/assume this is the
  // case.
  const char *argv[] = {"/system/bin/bpfloader", NULL};
  android::base::InitLogging(const_cast<char **>(argv),
                             &android::base::KernelLogger);
}

bool createBpfFsSubDirectories() {
  for (const auto &location : android::bpf::locations) {
    if (android::bpf::createSysFsBpfSubDir(location.prefix)) {
      ALOGE("=== Failed to create subdir %s ===", location.prefix);
      return true;
    }
  }
  return false;
}

void legacyBpfLoader() {
  // Load all ELF objects, create programs and maps, and pin them
  for (const auto &location : android::bpf::locations) {
    if (android::bpf::loadAllElfObjects(location)) {
      ALOGE("=== FAILURE LOADING BPF PROGRAMS FROM %s ===", location.dir);
    }
  }
}

void load() {
  if (createBpfFsSubDirectories()) {
    return;
  }
  legacyBpfLoader();
}

const char *const platformBpfLoader = "/system/bin/bpfloader";

int main(int, char **, char *const envp[]) {
  initLogging();
  load();

  const char *args[] = {
      platformBpfLoader,
      NULL,
  };
  execve(args[0], (char **)args, envp);
  ALOGE("FATAL: execve('%s'): %d[%s]", platformBpfLoader, errno,
        strerror(errno));
  return 1;
}