Merge "NetlinkEvent: use isKernel64Bit in KernelUtils.h" am: 97055b7e am:...

        "liblog",

    ],

    header_libs: [

        "bpf_headers",

    ],

    export_include_dirs: ["include"],

    tidy: true,

#include <sys/utsname.h>

#include <android-base/parseint.h>

#include <bpf/KernelUtils.h>

#include <log/log.h>

#include <sysutils/NetlinkEvent.h>

using android::base::ParseInt;

using android::bpf::isKernel64Bit;

/* From kernel's net/netfilter/xt_quota2.c */

const int LOCAL_QLOG_NL_EVENT = 112;

static_assert(sizeof(ulog_packet_msg32_t) == 168);

static_assert(sizeof(ulog_packet_msg64_t) == 192);

// Figure out the bitness of userspace.

// Trivial and known at compile time.

static bool isUserspace64bit(void) {

    return sizeof(long) == 8;

}

// Figure out the bitness of the kernel.

static bool isKernel64Bit(void) {

    // a 64-bit userspace requires a 64-bit kernel

    if (isUserspace64bit()) return true;

    static bool init = false;

    static bool cache = false;

    if (init) return cache;

    // Retrieve current personality - on Linux this system call *cannot* fail.

    int p = personality(0xffffffff);

    // But if it does just assume kernel and userspace (which is 32-bit) match...

    if (p == -1) return false;

    // This will effectively mask out the bottom 8 bits, and switch to 'native'

    // personality, and then return the previous personality of this thread

    // (likely PER_LINUX or PER_LINUX32) with any extra options unmodified.

    int q = personality((p & ~PER_MASK) | PER_LINUX);

    // Per man page this theoretically could error out with EINVAL,

    // but kernel code analysis suggests setting PER_LINUX cannot fail.

    // Either way, assume kernel and userspace (which is 32-bit) match...

    if (q != p) return false;

    struct utsname u;

    (void)uname(&u);  // only possible failure is EFAULT, but u is on stack.

    // Switch back to previous personality.

    // Theoretically could fail with EINVAL on arm64 with no 32-bit support,

    // but then we wouldn't have fetched 'p' from the kernel in the first place.

    // Either way there's nothing meaningul we can do in case of error.

    // Since PER_LINUX32 vs PER_LINUX only affects uname.machine it doesn't

    // really hurt us either.  We're really just switching back to be 'clean'.

    (void)personality(p);

    // Possible values of utsname.machine observed on x86_64 desktop (arm via qemu):

    //   x86_64 i686 aarch64 armv7l

    // additionally observed on arm device:

    //   armv8l

    // presumably also might just be possible:

    //   i386 i486 i586

    // and there might be other weird arm32 cases.

    // We note that the 64 is present in both 64-bit archs,

    // and in general is likely to be present in only 64-bit archs.

    cache = !!strstr(u.machine, "64");

    init = true;

    return cache;

}

/******************************************************************************/

NetlinkEvent::NetlinkEvent() {