// SPDX-License-Identifier: GPL-3.0-only
// SPDX-FileCopyrightText: Copyright (C) 2026 Catcrafts®

// lint-disable-file fixed-width-types
// lint-disable-file no-char-pointer
/*
fingerprintd — the daemon shell.

Everything that touches hardware lives here; the decisions live in
fingerprintd-core, which is tested without a phone. Right now this reaches QTEE
and stops: root object, credentials, client env, the QSEECOM-compat loader.
Enough to prove the transport, not yet to drive the sensor.

Why the process must be long-lived, once it does more: a listener registration
is held for as long as the process lives and QTEE's listener table is global to
the boot, and one sensor reset buys exactly one trustlet init. So the process
that powers the sensor has to be the process that holds the session.
*/
// libqcomtee is a C library and its headers carry no extern "C" guard -- it
// has only ever been consumed from C. Without one every symbol would be
// C++-mangled and none would link.
//
// The headers pull in <stdarg.h>, <stdatomic.h> and <stdio.h>, and under
// libc++ those drag in C++ templates, which may not appear inside an
// extern "C" block. Including them first makes the nested includes no-ops.
#include <stdarg.h>
#include <stdio.h>
#include <stdatomic.h>
extern "C" {
#include <qcomtee_object.h>
#include <qcomtee_object_types.h>
#include <qcomtee_errno.h>
}

#include <linux/gpio.h>
#include <linux/bsg.h>
#include <scsi/sg.h>
#include <pthread.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <sys/time.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <stdarg.h>

import std;
import Fingerprintd;

namespace {

constexpr const char* Version = "0.0.3";

bool g_verbose = false;
bool g_listeners = false;
bool g_auth = false;
int g_frames = 40;
int g_frameGapMs = 500;
std::string g_logDir = "/var/log/fingerprintd";
int g_rescan = -1;          // -1 = leave the config's value alone
std::uint32_t g_gid = 0;
std::string g_taPath = "/lib/firmware/focal64.mbn";
std::string g_cfgPath = "/lib/firmware/fingerprintd.json";

qcomtee_object* g_root = QCOMTEE_OBJECT_NULL;

// The ioctl trampoline libqcomtee calls. Cancellation is made asynchronous
// around it so the supplicant thread can be stopped while blocked in the
// kernel waiting for QTEE.
//
// Every run writes its own timestamped transcript. Not a convenience: a run
// whose result nobody recorded is a run that has to be repeated on a human's
// finger. And a SINGLE shared log path is worse than none -- the next run,
// including a quick control, destroys the interesting one, which is how the
// first successful authentication in this project was very nearly lost.
//
// Done at the file-descriptor level rather than by wrapping a stream, because
// std::println writes to stdout through C stdio: an ostream wrapper would
// capture nothing. Routing fd 1 through tee catches every line including the
// ones libqcomtee prints.
bool StartTranscript(const std::string& dir) {
    std::error_code ec;
    std::filesystem::create_directories(dir, ec);
    auto now = std::chrono::system_clock::now();
    std::string path = std::format("{}/{:%Y%m%d-%H%M%S}.log", dir,
                                   std::chrono::floor<std::chrono::seconds>(now));
    FILE* t = ::popen(std::format("tee {}", path).c_str(), "w");
    if (!t) return false;
    ::dup2(::fileno(t), 1);
    ::setvbuf(stdout, nullptr, _IOLBF, 0);
    std::println("transcript: {}", path);
    return true;
}

// tee_call_t's second parameter is `unsigned long` on glibc and `int` on musl
// (qcomtee_object.h keys it off __GLIBC__), so the signature has to match or
// the function pointer will not convert. The native build is glibc and the
// phone is musl, so both forms are compiled here.
#ifdef __GLIBC__
int TeeCall(int fd, unsigned long op, ...) {
#else
int TeeCall(int fd, int op, ...) {
#endif
    va_list ap;
    va_start(ap, op);
    void* arg = va_arg(ap, void*);
    va_end(ap);
    pthread_setcanceltype(PTHREAD_CANCEL_ASYNCHRONOUS, nullptr);
    int ret = ::ioctl(fd, static_cast<unsigned long>(op), arg);
    pthread_setcanceltype(PTHREAD_CANCEL_DEFERRED, nullptr);
    return ret;
}

// QTEE's callbacks are serviced here. Nothing QTEE asks of us happens without
// this running.
void* Supplicant(void*) {
    for (;;) {
        pthread_testcancel();
        if (qcomtee_object_process_one(g_root))
            break;
    }
    return nullptr;
}

std::uint64_t NowMs() {
    timeval tv{};
    ::gettimeofday(&tv, nullptr);
    return static_cast<std::uint64_t>(tv.tv_sec) * 1000
         + static_cast<std::uint64_t>(tv.tv_usec) / 1000;
}

// ---- The credentials object
//
// QTEE will not take the credentials blob directly on the Register path: it
// takes an object and calls back into it, twice, while our invoke is still in
// flight. Two ops, GET_LENGTH then READ_AT_OFFSET.
//
// libqcomtee ships one of these, but only by pulling in QCBOR to build the
// map. The map is thirteen bytes and lives in Fingerprintd:Tee under test, so
// this serves it and the library needs no dependency beyond libc.
struct CredentialsObject {
    qcomtee_object object;              // must be first: we cast between them
    std::vector<std::byte> blob;
    std::uint64_t lenStorage = 0;       // op 0's answer, pointed at not copied
};

void CredentialsRelease(qcomtee_object* object) {
    delete reinterpret_cast<CredentialsObject*>(object);
}

qcomtee_result_t CredentialsDispatch(qcomtee_object* object, qcomtee_op_t op,
                                     qcomtee_param* params, int num) {
    auto* self = reinterpret_cast<CredentialsObject*>(object);

    // On the CALLBACK path a QCOMTEE_UBUF_OUTPUT param arrives with
    // addr = NULL and size = the capacity QTEE will accept: the dispatcher
    // supplies the buffer, so the handler POINTS the param at storage of its
    // own and lets the framework marshal it. Writing through the incoming addr
    // is a null dereference, which is exactly how this crashed the first time
    // it ran against real QTEE.
    if (op == static_cast<qcomtee_op_t>(fingerprintd::tee::CredOp::GetLength)) {
        if (num != 1 || params[0].attr != QCOMTEE_UBUF_OUTPUT)
            return QCOMTEE_ERROR_INVALID;
        if (params[0].ubuf.size < fingerprintd::tee::CredLengthReplySize)
            return QCOMTEE_ERROR_INVALID;
        self->lenStorage = static_cast<std::uint64_t>(self->blob.size());
        params[0].ubuf.addr = &self->lenStorage;
        params[0].ubuf.size = sizeof(self->lenStorage);
        return QCOMTEE_OK;
    }

    if (op == static_cast<qcomtee_op_t>(fingerprintd::tee::CredOp::ReadAtOffset)) {
        if (num != 2 || params[0].attr != QCOMTEE_UBUF_INPUT
                     || params[1].attr != QCOMTEE_UBUF_OUTPUT)
            return QCOMTEE_ERROR_INVALID;
        // An INPUT param does carry a real address; only outputs arrive NULL.
        if (params[0].ubuf.size < sizeof(std::uint64_t) || !params[0].ubuf.addr)
            return QCOMTEE_ERROR_INVALID;
        std::uint64_t offset = 0;
        ::memcpy(&offset, params[0].ubuf.addr, sizeof(offset));

        auto plan = fingerprintd::tee::PlanRead(self->blob.size(), offset,
                                                params[1].ubuf.size);
        if (!plan.valid)
            return QCOMTEE_ERROR_INVALID;
        // Same again: point at the blob, do not copy into QTEE's buffer. The
        // storage has to outlive the dispatch, which the object owns.
        params[1].ubuf.addr = self->blob.data() + plan.offset;
        params[1].ubuf.size = plan.count;
        return QCOMTEE_OK;
    }

    return QCOMTEE_ERROR_INVALID;
}

qcomtee_object_ops g_credOps = {
    /* release   */ CredentialsRelease,
    /* dispatch  */ CredentialsDispatch,
    /* error     */ nullptr,
    /* supported */ nullptr,
};

qcomtee_object* MakeCredentials(std::uint32_t uid) {
    auto* c = new CredentialsObject{};
    c->blob = fingerprintd::tee::BuildCredentials(uid, NowMs());
    if (qcomtee_object_cb_init(&c->object, &g_credOps, g_root)) {
        delete c;
        return QCOMTEE_OBJECT_NULL;
    }
    return &c->object;
}

// ROOT op 2: hand QTEE a live credentials object and get a client env back.
// QTEE calls into the object while this invoke is outstanding, which is why
// the supplicant has to be running first.
qcomtee_object* GetClientEnv(std::uint32_t uid) {
    qcomtee_object* creds = MakeCredentials(uid);
    if (creds == QCOMTEE_OBJECT_NULL) {
        std::println(std::cerr, "credentials object init failed");
        return QCOMTEE_OBJECT_NULL;
    }
    qcomtee_param p[2] = {};
    p[0].attr = QCOMTEE_OBJREF_INPUT;
    p[0].object = creds;
    p[1].attr = QCOMTEE_OBJREF_OUTPUT;
    qcomtee_result_t result = 0;
    if (qcomtee_object_invoke(g_root,
                              static_cast<qcomtee_op_t>(fingerprintd::tee::ClientEnvOp),
                              p, 2, &result) || result) {
        std::println(std::cerr, "ROOT op {} failed, result={}",
                     static_cast<unsigned>(fingerprintd::tee::ClientEnvOp),
                     static_cast<int>(result));
        return QCOMTEE_OBJECT_NULL;
    }
    return p[1].object;
}

// IClientEnv op 0: open a service by UID on the env.
qcomtee_object* OpenService(qcomtee_object* env, std::uint32_t uid) {
    qcomtee_param p[2] = {};
    p[0].attr = QCOMTEE_UBUF_INPUT;
    p[0].ubuf.addr = &uid;
    p[0].ubuf.size = sizeof(uid);
    p[1].attr = QCOMTEE_OBJREF_OUTPUT;
    qcomtee_result_t result = 0;
    if (qcomtee_object_invoke(env, 0, p, 2, &result) || result) {
        std::println(std::cerr, "IClientEnv.open({}) failed, result={}", uid,
                     static_cast<int>(result));
        return QCOMTEE_OBJECT_NULL;
    }
    return p[1].object;
}

// ---- The storage listeners
//
// QTEE cannot reach a filesystem, so it calls back into the normal world for
// every template read and write. This serves those callbacks. The framing is
// Fingerprintd:Sfs; what lives here is the file I/O and the registration.
//
// READ-ONLY MODE EXISTS FOR A REASON. QTEE deletes a container whose keyed
// integrity tag does not verify, so a listener that serves bytes at the wrong
// offset does not merely fail -- it makes QTEE unlink an enrolled template.
// That is unrecoverable. Until a build has been shown to round-trip a
// container, it should serve read-only, where an unlink is refused with EROFS
// and the store cannot be damaged.
bool g_sfsReadOnly = true;
std::string g_sfsRoot = "/var/lib/fingerprintd/sfs";

struct ListenerObject {
    qcomtee_object object;          // must be first
    std::uint32_t id = 0;
    qcomtee_object* shared = QCOMTEE_OBJECT_NULL;
    std::array<std::array<std::byte, 64>, 8> outBufs{};
};

void ListenerRelease(qcomtee_object* object) {
    delete reinterpret_cast<ListenerObject*>(object);
}

// Serve one gpfile request out of the shared buffer, in place.
void ServeGpFile(std::span<std::byte> sb) {
    namespace sfs = fingerprintd::sfs;

    auto req = sfs::ParseRequest(sb);
    if (!req) {
        std::println("    gpfile: undecodable request");
        sfs::WriteReply(sb, EINVAL, 0);
        return;
    }
    if (req->op == sfs::OpConfigPathInit) {
        // Asked first, with an empty frame. The answer is LATCHED for the
        // whole boot, so an experiment on its value needs a fresh boot.
        std::println("    gpfile op 12 (path init) -> {}", sfs::ConfigPathInitReply);
        sfs::WriteConfigPathInitReply(sb);
        return;
    }

    auto full = sfs::ResolvePath(g_sfsRoot, req->root, req->path);
    if (!full) {
        std::println("    gpfile: refusing path '{}' under root {}", req->path, req->root);
        sfs::WriteReply(sb, EINVAL, 0);
        return;
    }

    switch (req->action) {
    case sfs::Action::Read: {
        std::println("    gpfile READ  {} off={} len={}", *full, req->offset, req->length);
        std::ifstream f(*full, std::ios::binary);
        if (!f) { sfs::WriteReply(sb, ENOENT, 0); return; }
        if (req->offset > 0) f.seekg(req->offset);
        std::size_t want = std::min<std::size_t>(req->length,
                                                 sfs::Capacity(sb, sfs::Action::Read));
        f.read(reinterpret_cast<char*>(sb.data() + sfs::ReadDataOff),
               static_cast<std::streamsize>(want));
        auto got = static_cast<std::uint32_t>(f.gcount());
        std::println("      read {} bytes into +0x{:03x}", got, sfs::ReadDataOff);
        sfs::WriteReply(sb, 0, got);
        return;
    }
    case sfs::Action::Write: {
        std::println("    gpfile WRITE {} off={} len={}", *full, req->offset, req->length);
        if (g_sfsReadOnly) {
            std::println("      REFUSED: read-only");
            sfs::WriteReply(sb, EROFS, 0);
            return;
        }
        // O_RDWR | O_CREAT | O_SYNC and never O_TRUNC: QTEE writes a container
        // as write(0,4096), write(4096,N), write(0,4096), so truncating on open
        // leaves 4096 bytes where a 258850-byte template belongs.
        int fd = ::open(full->c_str(), O_RDWR | O_CREAT | O_SYNC, 0600);
        if (fd < 0) { sfs::WriteReply(sb, errno, 0); return; }
        if (req->offset > 0 && ::lseek(fd, req->offset, SEEK_SET) < 0) {
            int e = errno; ::close(fd); sfs::WriteReply(sb, e, 0); return;
        }
        std::size_t want = std::min<std::size_t>(req->length,
                                                 sfs::Capacity(sb, sfs::Action::Write));
        std::size_t done = 0;
        while (done < want) {   // short writes are real; the reference loops
            ssize_t n = ::write(fd, sb.data() + sfs::WriteDataOff + done, want - done);
            if (n <= 0) break;
            done += static_cast<std::size_t>(n);
        }
        ::fsync(fd);
        ::close(fd);
        sfs::WriteReply(sb, 0, static_cast<std::uint32_t>(done));
        return;
    }
    case sfs::Action::Unlink:
        std::println("    gpfile UNLINK {}", *full);
        if (g_sfsReadOnly) {
            std::println("      REFUSED: read-only (this is what protects an enrolled template)");
            sfs::WriteReply(sb, EROFS, 0);
            return;
        }
        sfs::WriteReply(sb, ::unlink(full->c_str()) ? errno : 0, 0);
        return;
    case sfs::Action::Rename: {
        auto to = sfs::ResolvePath(g_sfsRoot, req->root, req->path2);
        std::println("    gpfile RENAME {} -> {}", *full, to ? *to : std::string("?"));
        if (g_sfsReadOnly || !to) { sfs::WriteReply(sb, EROFS, 0); return; }
        sfs::WriteReply(sb, ::rename(full->c_str(), to->c_str()) ? errno : 0, 0);
        return;
    }
    }
}

// ---- RPMB
//
// The anti-rollback half. QTEE will not trust a container until it has read
// its counter record out of the UFS device's replay-protected area, and it
// cannot reach the device itself. This serves that read.
//
// A WRITE advances a monotonic counter that can never be moved back, so it is
// refused unless explicitly enabled. Key programming is refused ALWAYS -- the
// RPMB key is one-time programmable and relaying such a frame destroys this
// part's RPMB permanently.
bool g_rpmbWrite = false;

// SECURITY PROTOCOL IN/OUT against the RPMB well-known LUN. Returns 0 on
// success, 1 on unit attention (retryable), -1 on error.
int SecurityProtocol(int fd, bool isIn, std::byte* buf, std::uint32_t len) {
    namespace rp = fingerprintd::rpmb;
    std::array<unsigned char, 12> cdb{};
    std::array<unsigned char, 64> sense{};

    cdb[0] = isIn ? 0xA2 : 0xB5;
    cdb[1] = rp::SecurityProtocolUfs;
    cdb[2] = (rp::SecurityProtocolSpecific >> 8) & 0xFF;
    cdb[3] = rp::SecurityProtocolSpecific & 0xFF;
    cdb[4] = 0;                       // INC_512 = 0: the length is in bytes
    cdb[6] = (len >> 24) & 0xFF;
    cdb[7] = (len >> 16) & 0xFF;
    cdb[8] = (len >> 8) & 0xFF;
    cdb[9] = len & 0xFF;

    sg_io_v4 io{};
    io.guard = 'Q';
    io.protocol = BSG_PROTOCOL_SCSI;
    io.subprotocol = BSG_SUB_PROTOCOL_SCSI_CMD;
    io.request_len = cdb.size();
    io.request = reinterpret_cast<std::uintptr_t>(cdb.data());
    io.max_response_len = sense.size();
    io.response = reinterpret_cast<std::uintptr_t>(sense.data());
    io.timeout = 15000;
    if (isIn) {
        io.din_xfer_len = len;
        io.din_xferp = reinterpret_cast<std::uintptr_t>(buf);
    } else {
        io.dout_xfer_len = len;
        io.dout_xferp = reinterpret_cast<std::uintptr_t>(buf);
    }

    if (::ioctl(fd, SG_IO, &io) < 0) {
        std::println("      SP{} ioctl failed: {}", isIn ? "I" : "O", ::strerror(errno));
        return -1;
    }
    if (io.driver_status || io.transport_status || io.device_status) {
        unsigned key = sense[2] & 0x0F;
        std::println("      SP{} status drv={} trans={} dev={} sense key={} asc=0x{:02x}/{:02x}",
                     isIn ? "I" : "O", io.driver_status, io.transport_status,
                     io.device_status, key, sense[12], sense[13]);
        // The RPMB LUN raises UNIT ATTENTION on the first command after a
        // reset and clears it by reporting it once. Retryable, not an error.
        return key == fingerprintd::rpmb::SenseKeyUnitAttention ? 1 : -1;
    }
    return 0;
}

int SecurityProtocolRetry(int fd, bool isIn, std::byte* buf, std::uint32_t len) {
    for (int t = 0; t < 4; t++) {
        int rc = SecurityProtocol(fd, isIn, buf, len);
        if (rc != 1) return rc;
        std::println("      (unit attention cleared, retrying)");
    }
    return -1;
}

void ServeRpmb(std::span<std::byte> sb) {
    namespace rp = fingerprintd::rpmb;

    auto req = rp::ParseRequest(sb);
    if (!req) { rp::WriteReply(sb, rp::StatusRefused, 0); return; }
    if (g_verbose)
        std::println("    rpmb op=0x{:x} nblocks={} framesz={} dataoff=0x{:x}",
                     static_cast<unsigned>(req->op), req->nblocks, req->frameSize,
                     req->dataOff);

    if (!rp::FramesInBounds(sb, *req)) {
        std::println("    rpmb: frames out of bounds, refusing");
        rp::WriteReply(sb, rp::StatusRefused, 0);
        return;
    }

    // NEVER RELAYED, whatever the write policy says. The RPMB authentication
    // key is one-time programmable: reprogramming it destroys this part's RPMB
    // permanently and no reflash recovers it. QTEE has no legitimate reason to
    // send one.
    if (rp::AnyKeyProgramming(sb, *req)) {
        std::println("    *** REFUSED: RPMB KEY PROGRAMMING frame. Irreversible. ***");
        rp::WriteReply(sb, rp::StatusRefused, 0);
        return;
    }

    if (req->op == rp::Op::Write && !g_rpmbWrite) {
        std::println("    rpmb WRITE refused (advances an irreversible counter)");
        rp::WriteReply(sb, rp::StatusRefused, 0);
        return;
    }
    if (req->op != rp::Op::Read && req->op != rp::Op::Write) {
        rp::WriteReply(sb, rp::StatusRefused, 0);
        return;
    }

    int fd = ::open(std::string(rp::BsgDevice).c_str(), O_RDWR);
    if (fd < 0) {
        std::println("    rpmb: open {}: {}", rp::BsgDevice, ::strerror(errno));
        rp::WriteReply(sb, rp::StatusRefused, 0);
        return;
    }
    std::byte* frames = sb.data() + req->dataOff;
    std::uint32_t total = req->nblocks * static_cast<std::uint32_t>(rp::FrameSize);

    int rc = -1;
    if (req->op == rp::Op::Read) {
        // A read posts ONE request frame however large nblocks is, then
        // collects nblocks * 512 back.
        if (SecurityProtocolRetry(fd, false, frames, rp::FrameSize) == 0)
            rc = SecurityProtocolRetry(fd, true, frames, total);
    }
    ::close(fd);

    if (rc != 0) {
        rp::WriteReply(sb, rp::StatusRefused, 0);
        return;
    }
    if (g_verbose)
        std::println("      rpmb read ok: resp=0x{:04x} result=0x{:04x} counter={}",
                     rp::ReqRespOf(std::span(frames, rp::FrameSize)),
                     rp::ResultOf(std::span(frames, rp::FrameSize)),
                     rp::WriteCounterOf(std::span(frames, rp::FrameSize)));
    // +0x08 is an OUT parameter QTEE checks against what it expected to be
    // transferred; leaving the request's frame size there fails every
    // transaction. +0x0c is left exactly as the request supplied it.
    rp::WriteReply(sb, rp::StatusOk, rp::BytesTransferred(req->op, req->nblocks));
}

qcomtee_result_t ListenerDispatch(qcomtee_object* object, qcomtee_op_t op,
                                  qcomtee_param* params, int num) {
    auto* self = reinterpret_cast<ListenerObject*>(object);
    if (g_verbose)
        std::println("  *** QTEE called listener 0x{:x} op={} params={}", self->id,
                     static_cast<unsigned>(op), num);

    for (int i = 0; i < num; i++) {
        switch (params[i].attr) {
        case QCOMTEE_UBUF_OUTPUT: {
            // addr arrives NULL on the callback path; point it at our own
            // storage. Zeros are the answer QTEE expects here.
            std::size_t want = std::min<std::size_t>(params[i].ubuf.size,
                                                     self->outBufs[0].size());
            if (i < 8) {
                self->outBufs[i].fill(std::byte{0});
                params[i].ubuf.addr = self->outBufs[i].data();
                params[i].ubuf.size = want;
            }
            break;
        }
        case QCOMTEE_OBJREF_OUTPUT:
            // MUST be set. cb_marshal_in leaves .object uninitialised and
            // marshal_out then calls typeof() on stack garbage -- a SIGSEGV in
            // the supplicant the moment QTEE first dispatches.
            params[i].object = QCOMTEE_OBJECT_NULL;
            break;
        default:
            break;
        }
    }

    // The request itself rides in the registered shared buffer, not in params.
    void* addr = qcomtee_memory_object_addr(self->shared);
    std::size_t size = qcomtee_memory_object_size(self->shared);
    if (addr) {
        std::span<std::byte> sb(static_cast<std::byte*>(addr), size);
        if (self->id == 0x7000)
            ServeGpFile(sb);
        else if (self->id == 0x2000)
            ServeRpmb(sb);
        else
            std::println("    (listener 0x{:x}: no handler yet)", self->id);
    }
    return QCOMTEE_OK;
}

qcomtee_object_ops g_listenerOps = {
    /* release   */ ListenerRelease,
    /* dispatch  */ ListenerDispatch,
    /* error     */ nullptr,
    /* supported */ nullptr,
};

// One callback object PER registration. Sharing one across registrations
// overwrites its id and buffer, and every multi-listener result taken that way
// is void -- six sessions of hypotheses rested on exactly that bug.
bool RegisterListener(qcomtee_object* env, std::uint32_t id, std::size_t bufSize) {
    qcomtee_object* svc = OpenService(env, fingerprintd::tee::UidListenerCbo);
    if (svc == QCOMTEE_OBJECT_NULL) return false;

    qcomtee_object* shared = QCOMTEE_OBJECT_NULL;
    if (qcomtee_memory_object_alloc(bufSize, g_root, &shared)) {
        std::println(std::cerr, "listener 0x{:x}: shared buffer alloc failed", id);
        return false;
    }
    auto* lo = new ListenerObject{};
    lo->id = id;
    lo->shared = shared;
    if (qcomtee_object_cb_init(&lo->object, &g_listenerOps, g_root)) {
        delete lo;
        return false;
    }

    std::uint32_t lid = id;
    qcomtee_param p[3] = {};
    p[0].attr = QCOMTEE_UBUF_INPUT;   p[0].ubuf.addr = &lid; p[0].ubuf.size = sizeof(lid);
    p[1].attr = QCOMTEE_OBJREF_INPUT; p[1].object = &lo->object;
    p[2].attr = QCOMTEE_OBJREF_INPUT; p[2].object = shared;
    qcomtee_result_t result = 0;
    if (qcomtee_object_invoke(svc, 0, p, 3, &result)) {
        std::println(std::cerr, "listener 0x{:x}: invoke failed", id);
        return false;
    }
    std::println("listener 0x{:<5x} sb={:<7} -> result={}{}", id, bufSize,
                 static_cast<int>(result),
                 result == 0 ? "  REGISTERED"
                 : static_cast<int>(result) == fingerprintd::tee::ResultIdAlreadyTaken
                   ? "  (id already taken)" : "");
    return result == 0;
}

// ---- The sensor rail
//
// GPIO v2 chardev ioctls directly: libgpiod is not on the phone and this is
// three lines. The chip is found by LABEL, never by index -- /dev/gpiochipN
// ordering is not stable and driving the wrong controller's pins is the kind
// of mistake that is not recoverable over ssh.
class Sensor {
public:
    ~Sensor() { PowerOff(); }

    bool Open() {
        namespace sn = fingerprintd::sensor;
        chip_ = FindChip(sn::ChipLabel);
        if (chip_ < 0) {
            std::println(std::cerr, "no gpiochip labelled '{}'", sn::ChipLabel);
            return false;
        }
        power_ = RequestLine(sn::PowerLine, GPIO_V2_LINE_FLAG_OUTPUT, "fpd-pwr");
        reset_ = RequestLine(sn::ResetLine, GPIO_V2_LINE_FLAG_OUTPUT, "fpd-rst");
        irq_   = RequestLine(sn::IrqLine,   GPIO_V2_LINE_FLAG_INPUT,  "fpd-irq");
        return power_ >= 0 && reset_ >= 0 && irq_ >= 0;
    }

    // Rail up, settle, release reset, settle. Both lines are driven low first
    // so a warm restart starts where a cold one does.
    bool PowerOn() {
        namespace sn = fingerprintd::sensor;
        if (!Set(power_, 0) || !Set(reset_, 0)) return false;
        if (!Set(power_, 1)) return false;
        std::this_thread::sleep_for(sn::PowerSettle);
        if (!Set(reset_, 1)) return false;
        std::this_thread::sleep_for(sn::ResetSettle);
        on_ = true;
        return true;
    }

    void PowerOff() {
        if (!on_) return;
        Set(reset_, 0);
        Set(power_, 0);
        on_ = false;
    }

    std::optional<int> ReadIrq() const { return Get(irq_); }

private:
    static int FindChip(std::string_view label) {
        for (int i = 0; i < 32; i++) {
            std::string path = std::format("/dev/gpiochip{}", i);
            int fd = ::open(path.c_str(), O_RDWR | O_CLOEXEC);
            if (fd < 0) continue;
            gpiochip_info info{};
            if (::ioctl(fd, GPIO_GET_CHIPINFO_IOCTL, &info) == 0
                && label == info.label
                && info.lines >= fingerprintd::sensor::MinChipLines) {
                std::println("gpiochip '{}' is {} ({} lines)", info.label, path,
                             info.lines);
                return fd;
            }
            ::close(fd);
        }
        return -1;
    }

    int RequestLine(unsigned line, std::uint64_t flags, const char* consumer) {
        // The guard, enforced where the line is actually opened rather than
        // only asserted in the core. gpio8-11 are XPU-protected and touching
        // one is an immediate SError, not an error return.
        if (!fingerprintd::sensor::IsSafeLine(line)) {
            std::println(std::cerr,
                         "REFUSING to open gpio{}: XPU-protected fingerprint SPI", line);
            return -1;
        }
        gpio_v2_line_request req{};
        req.offsets[0] = line;
        req.num_lines = 1;
        req.config.flags = flags;
        std::snprintf(req.consumer, sizeof(req.consumer), "%s", consumer);
        if (::ioctl(chip_, GPIO_V2_GET_LINE_IOCTL, &req) < 0) {
            std::println(std::cerr, "gpio{} request failed: {}", line, ::strerror(errno));
            return -1;
        }
        return req.fd;
    }

    static bool Set(int fd, int v) {
        if (fd < 0) return false;
        gpio_v2_line_values vals{};
        vals.mask = 1;
        vals.bits = v ? 1 : 0;
        return ::ioctl(fd, GPIO_V2_LINE_SET_VALUES_IOCTL, &vals) == 0;
    }

    static std::optional<int> Get(int fd) {
        if (fd < 0) return std::nullopt;
        gpio_v2_line_values vals{};
        vals.mask = 1;
        if (::ioctl(fd, GPIO_V2_LINE_GET_VALUES_IOCTL, &vals) < 0) return std::nullopt;
        return static_cast<int>(vals.bits & 1);
    }

    int chip_ = -1, power_ = -1, reset_ = -1, irq_ = -1;
    bool on_ = false;
};

// ---- The trustlet
//
// The loader is IQSEEComCompatAppLoader (UID 122): op 1 loadFromBuffer, op 2
// lookupTA. A stale instance from a crashed run is unloaded first, which is
// what stops a bad experiment costing a reboot.
constexpr const char* TaName = "focal64";

void UnloadStale(qcomtee_object* loader) {
    qcomtee_param p[3] = {};
    std::array<std::byte, 4> ob{};
    p[0].attr = QCOMTEE_UBUF_INPUT;
    p[0].ubuf.addr = const_cast<char*>(TaName);
    p[0].ubuf.size = std::strlen(TaName);
    p[1].attr = QCOMTEE_UBUF_OUTPUT;
    p[1].ubuf.addr = ob.data();
    p[1].ubuf.size = ob.size();
    p[2].attr = QCOMTEE_OBJREF_OUTPUT;
    qcomtee_result_t result = 0;
    if (qcomtee_object_invoke(loader, 2, p, 3, &result) || result) {
        std::println("lookupTA('{}') -> result={} (nothing to unload)", TaName,
                     static_cast<int>(result));
        return;
    }
    if (!qcomtee_object_invoke(p[2].object, 2, nullptr, 0, &result))
        std::println("unloaded a stale '{}' -> result={}", TaName, static_cast<int>(result));
    qcomtee_object_refs_dec(p[2].object);
}

qcomtee_object* LoadTrustlet(qcomtee_object* loader, const std::string& path) {
    UnloadStale(loader);

    std::ifstream f(path, std::ios::binary);
    if (!f) {
        std::println(std::cerr, "cannot open {}", path);
        return QCOMTEE_OBJECT_NULL;
    }
    std::vector<char> image((std::istreambuf_iterator<char>(f)),
                            std::istreambuf_iterator<char>());
    if (image.empty()) {
        std::println(std::cerr, "{} is empty", path);
        return QCOMTEE_OBJECT_NULL;
    }

    std::array<char, 128> distName{};
    qcomtee_param p[4] = {};
    p[0].attr = QCOMTEE_UBUF_INPUT;
    p[0].ubuf.addr = image.data();
    p[0].ubuf.size = image.size();
    p[1].attr = QCOMTEE_UBUF_INPUT;
    p[1].ubuf.addr = const_cast<char*>(TaName);
    p[1].ubuf.size = std::strlen(TaName);
    p[2].attr = QCOMTEE_UBUF_OUTPUT;
    p[2].ubuf.addr = distName.data();
    p[2].ubuf.size = distName.size();
    p[3].attr = QCOMTEE_OBJREF_OUTPUT;
    qcomtee_result_t result = 0;
    if (qcomtee_object_invoke(loader, 1, p, 4, &result) || result) {
        std::println(std::cerr, "loadFromBuffer failed, result={}",
                     static_cast<int>(result));
        return QCOMTEE_OBJECT_NULL;
    }
    std::println("trustlet loaded from {} ({} bytes), distName='{}'", path,
                 image.size(), distName.data());
    return p[3].object;
}

// sendRequest is op 0 with arity 0x0424: four input buffers, two output, four
// object slots. The request and response buffers go in and come back out; the
// trustlet's own return code rides in the returned request's header.
struct CommandResult {
    bool invoked = false;
    qcomtee_result_t result = 0;
    std::int32_t rc = 0;
    std::int32_t metric = 0;
    // Only meaningful for REPORT_EVENT: the matcher's verdict rides in the
    // returned request's payload.
    std::uint32_t gid = 0;
    std::uint32_t fid = 0;
    std::int32_t samplesRemaining = -1;
};

CommandResult SendCommand(qcomtee_object* app, fingerprintd::ta::Cmd cmd,
                          std::span<const std::byte> payload) {
    namespace ta = fingerprintd::ta;
    namespace tee = fingerprintd::tee;
    static std::vector<std::byte> req(8192), rsp(16384), reqOut(8192), rspOut(16384);
    std::ranges::fill(rsp, std::byte{0});
    std::ranges::fill(reqOut, std::byte{0});
    std::ranges::fill(rspOut, std::byte{0});
    ta::BuildRequest(req, cmd, payload);

    // CAPTURE_IMAGE's flags word sits at payload+0x18, PAST the declared
    // length of 0x14 -- the trustlet range-checks the length to exactly that
    // and reads the flags anyway. Without bit 1 or bit 30 it skips
    // preprocessing, the classifier and the enrol grouper entirely and returns
    // success having done nothing but a raw scan.
    if (cmd == ta::Cmd::CaptureImage) {
        for (std::size_t i = 0; i < 4; i++)
            req[ta::ReqPayloadOff + ta::CaptureFlagsOff + i] =
                static_cast<std::byte>((ta::CaptureFlagsEnrol >> (8 * i)) & 0xFF);
    }

    std::uint32_t is64 = 1;
    qcomtee_param p[10] = {};
    p[0].attr = QCOMTEE_UBUF_INPUT;  p[0].ubuf.addr = req.data();    p[0].ubuf.size = req.size();
    p[1].attr = QCOMTEE_UBUF_INPUT;  p[1].ubuf.addr = rsp.data();    p[1].ubuf.size = rsp.size();
    p[2].attr = QCOMTEE_UBUF_INPUT;  p[2].ubuf.addr = nullptr;       p[2].ubuf.size = 0;
    p[3].attr = QCOMTEE_UBUF_INPUT;  p[3].ubuf.addr = &is64;         p[3].ubuf.size = sizeof(is64);
    p[4].attr = QCOMTEE_UBUF_OUTPUT; p[4].ubuf.addr = reqOut.data(); p[4].ubuf.size = reqOut.size();
    p[5].attr = QCOMTEE_UBUF_OUTPUT; p[5].ubuf.addr = rspOut.data(); p[5].ubuf.size = rspOut.size();
    for (int i = 6; i < 10; i++) {
        p[i].attr = QCOMTEE_OBJREF_INPUT;
        p[i].object = QCOMTEE_OBJECT_NULL;
    }

    // A capture needs a real shared memory REGION or the trustlet answers
    // -201: it reads an output-buffer pointer out of payload+0x00, and QTEE
    // only patches an address in there if we name the location in
    // embeddedBufOffsets (IB2) and hand it the region in an object slot.
    // Without that the pointer is NULL. This is the whole difference between a
    // flat metric and a real scan.
    //
    // Two traps: the offsets array applies to EVERY command in a run, so it is
    // scoped to this one command -- patching a pointer into SYNC_CONFIG's
    // request breaks it. And an invoke CONSUMES its input objects, so the
    // region is allocated fresh each time.
    qcomtee_object* region = QCOMTEE_OBJECT_NULL;
    std::uint32_t offsets = tee::EmbeddedBufOffsetValue;
    if (cmd == static_cast<ta::Cmd>(tee::RegionScopedToCommand)) {
        if (qcomtee_memory_object_alloc(tee::CaptureRegionSize, g_root, &region)) {
            std::println(std::cerr, "  memory region alloc failed");
            region = QCOMTEE_OBJECT_NULL;
        } else {
            void* addr = qcomtee_memory_object_addr(region);
            std::size_t sz = qcomtee_memory_object_size(region);
            if (g_verbose)
                std::println("    region: addr={} size={} offsets=[0x{:x}] slot=IO0",
                             addr, sz, offsets);
            std::memset(addr, 0, sz);
            p[2].ubuf.addr = &offsets;
            p[2].ubuf.size = sizeof(offsets);
            p[6].object = region;
        }
    }

    CommandResult out;
    if (qcomtee_object_invoke(app, tee::AppSendRequestOp, p, 10, &out.result)) {
        if (region != QCOMTEE_OBJECT_NULL)
            qcomtee_memory_object_release(region);
        return out;
    }
    out.invoked = true;
    out.rc = ta::ResultCode(reqOut);
    out.metric = ta::CaptureMetric(reqOut);
    if (cmd == ta::Cmd::ReportEvent) {
        out.gid = ta::MatchedGid(reqOut);
        out.fid = ta::MatchedFid(reqOut);
        out.samplesRemaining = ta::SamplesRemaining(reqOut);
    }
    if (g_verbose && cmd == ta::Cmd::CaptureImage) {
        std::string hex;
        for (std::size_t i = 0; i < 0x30; i++)
            hex += std::format("{:02x}{}", std::to_integer<unsigned>(reqOut[i]),
                               (i % 16 == 15) ? "\n      " : " ");
        std::println("    reqOut[0x00..0x2f]:\n      {}", hex);
    }
    return out;
}

void Report(fingerprintd::ta::Cmd cmd, const CommandResult& r) {
    namespace ta = fingerprintd::ta;
    if (!r.invoked) {
        std::println("  CMD 0x{:04x} -> INVOKE FAILED", static_cast<unsigned>(cmd));
        return;
    }
    // A POSITIVE rc is not an error code. ENUMERATE returns the template
    // count there, so running it through the error table prints "unknown" for
    // a perfectly good answer.
    if (r.rc > 0)
        std::println("  CMD 0x{:04x} -> result={} rc={}", static_cast<unsigned>(cmd),
                     static_cast<int>(r.result), r.rc);
    else
        std::println("  CMD 0x{:04x} -> result={} rc={} ({})", static_cast<unsigned>(cmd),
                     static_cast<int>(r.result), r.rc, ta::StrError(r.rc));
}

int Probe() {
    namespace tee = fingerprintd::tee;

    std::string dev(tee::DevTee);
    g_root = qcomtee_object_root_init(dev.c_str(), TeeCall, nullptr, nullptr);
    if (g_root == QCOMTEE_OBJECT_NULL) {
        std::println(std::cerr, "root object on {}: {}", tee::DevTee,
                     ::strerror(errno));
        return 1;
    }
    std::println("root object on {}", tee::DevTee);

    pthread_t th{};
    if (pthread_create(&th, nullptr, Supplicant, nullptr) != 0) {
        std::println(std::cerr, "supplicant thread failed to start");
        return 1;
    }

    std::uint32_t uid = ::getuid();
    qcomtee_object* env = GetClientEnv(uid);
    if (env == QCOMTEE_OBJECT_NULL)
        return 1;
    std::println("client env obtained (uid {}, {}-byte credentials)", uid,
                 tee::BuildCredentials(uid, 0).size());

    // Register the storage listeners BEFORE loading the trustlet, so any
    // storage QTEE wants during init has somewhere to go.
    if (g_listeners) {
        for (const auto& l : tee::Listeners) {
            if (l.id == 10) continue;   // never called on the fingerprint path
            RegisterListener(env, l.id, l.bufferSize);
        }
        std::println("SFS root {} ({})", g_sfsRoot,
                     g_sfsReadOnly ? "READ-ONLY" : "writable");
    }

    qcomtee_object* loader = OpenService(env, tee::UidQseecomCompatAppLoader);
    if (loader == QCOMTEE_OBJECT_NULL)
        return 1;
    std::println("QSEECOM-compat app loader (UID {}) opened",
                 tee::UidQseecomCompatAppLoader);

    qcomtee_object* app = LoadTrustlet(loader, g_taPath);
    if (app == QCOMTEE_OBJECT_NULL)
        return 1;

    // SYNC_CONFIG first, always. The trustlet reads its whole configuration
    // from this one JSON payload, and two keys in it are load-bearing:
    // algorithm.enrolling_overlap_intervals must be PRESENT (its default is
    // the empty string, which faults the trustlet's own sscanf), and
    // device.preferred_device_id selects the chip driver.
    std::ifstream cf(g_cfgPath);
    if (!cf) {
        std::println(std::cerr, "cannot open config {}", g_cfgPath);
        return 1;
    }
    std::string json((std::istreambuf_iterator<char>(cf)),
                     std::istreambuf_iterator<char>());

    // common.max_authentication_rescan_times bounds how many frames the
    // matcher may answer "not identified yet" before it has to produce a
    // verdict. At the stock default a whole run can end undecided, which is
    // the right shipping behaviour and useless as a measurement: a
    // wrong-finger control that never reaches a verdict has not demonstrated
    // a rejection. Setting it to 0 forces every frame terminal.
    //
    // MEASUREMENT ONLY. A rate measured this way is a per-frame figure taken
    // with the retry mechanism disabled and is not a shipping reject rate.
    if (g_rescan >= 0) {
        auto at = json.find("\"common\":{");
        if (at == std::string::npos) at = json.find("\"common\": {");
        if (at == std::string::npos) {
            std::println(std::cerr, "config has no \"common\" object to patch");
            return 1;
        }
        auto brace = json.find('{', at);
        json.insert(brace + 1,
                    std::format("\"max_authentication_rescan_times\":{},", g_rescan));
        std::println("forcing max_authentication_rescan_times={} (MEASUREMENT ONLY)",
                     g_rescan);
    }
    // The trustlet wants the terminating NUL counted.
    std::vector<std::byte> cfg(json.size() + 1, std::byte{0});
    for (std::size_t i = 0; i < json.size(); i++)
        cfg[i] = static_cast<std::byte>(json[i]);
    std::println("config {}: {} bytes", g_cfgPath, cfg.size());

    auto r = SendCommand(app, fingerprintd::ta::Cmd::SyncConfig, cfg);
    Report(fingerprintd::ta::Cmd::SyncConfig, r);
    if (!r.invoked || r.result != 0 || r.rc != 0) {
        std::println(std::cerr, "SYNC_CONFIG did not succeed; stopping here");
        return 1;
    }


    // ---- The sensor, and the init chain that needs it powered
    Sensor sensor;
    if (!sensor.Open()) {
        std::println(std::cerr, "sensor lines unavailable; stopping before init");
        return 1;
    }
    if (!sensor.PowerOn()) {
        std::println(std::cerr, "sensor power-up failed");
        return 1;
    }
    auto irq = sensor.ReadIrq();
    std::println("sensor powered, reset released, irq={}",
                 irq ? std::to_string(*irq) : std::string("?"));

    // The chain, in order. Every step answers rc=0 on a healthy sensor and the
    // last one is not optional: without SYNC_STATISTICS the trustlet's
    // g_statistics stays NULL and the first enrol frame that gets far enough
    // writes through it.
    //
    // One reset buys one init. If this fails, the rail has to go down and come
    // back up -- re-running the chain answers -205.
    bool ok = true;
    for (fingerprintd::ta::Cmd c : fingerprintd::ta::InitChain) {
        std::vector<std::byte> payload;
        if (c == fingerprintd::ta::Cmd::WorkMode) {
            // WORK_MODE takes a u32 mode; 1 = WAIT_TOUCH.
            payload.assign(0x10, std::byte{0});
            payload[0] = static_cast<std::byte>(
                static_cast<std::uint32_t>(fingerprintd::ta::WorkMode::WaitTouch));
        } else if (c == fingerprintd::ta::Cmd::SyncStatistics) {
            payload.assign(fingerprintd::ta::SyncStatisticsPayloadSize, std::byte{0});
        }
        auto ir = SendCommand(app, c, payload);
        Report(c, ir);
        if (!ir.invoked || ir.result != 0 || ir.rc != 0) {
            ok = false;
            if (ir.rc == fingerprintd::sensor::RcDeviceNotFound)
                std::println(std::cerr,
                             "  -205: a second init in one power cycle. "
                             "Power-cycle the rail, do not retry.");
            break;
        }
    }
    if (!ok) {
        std::println(std::cerr, "init chain did not complete");
        return 1;
    }

    // NOW the store can be read. A template reload needs the device init
    // chain to have run first: the per-slot enroll-template array is allocated
    // by that chain, and without it FtInitEnrollTplData writes through a NULL
    // the moment a template becomes reachable. Running SET_ACTIVE_GROUP before
    // the chain answers -2 and loads nothing, which reads like a missing
    // container and is an ordering bug.
    if (g_listeners) {
        auto sag = fingerprintd::ta::BuildSetActiveGroup(g_gid);
        std::println("\nSET_ACTIVE_GROUP gid={} path='{}'", g_gid,
                     fingerprintd::ta::GroupNamespacePath);
        auto g = SendCommand(app, fingerprintd::ta::Cmd::SetActiveGroup, sag);
        Report(fingerprintd::ta::Cmd::SetActiveGroup, g);

        auto e = SendCommand(app, fingerprintd::ta::Cmd::Enumerate, {});
        Report(fingerprintd::ta::Cmd::Enumerate, e);
        std::println("  templates loaded: {}", e.rc);
    }

    // With the sensor initialised and a region supplied, a capture returns a
    // real metric. No finger is needed to establish the idle floor, and the
    // floor is the only meaningful reference: the metric is per frame and
    // drifts, so a fixed threshold is wrong by construction.
    fingerprintd::engine::Baseline baseline;
    std::println("calibrating the idle floor ({} samples)",
                 fingerprintd::engine::Baseline::DefaultSamples);
    for (std::size_t i = 0; i < fingerprintd::engine::Baseline::DefaultSamples; i++) {
        std::vector<std::byte> cap(fingerprintd::ta::CaptureDeclaredLen);
        fingerprintd::ta::BuildCapturePayload(cap);
        auto c = SendCommand(app, fingerprintd::ta::Cmd::CaptureImage, cap);
        if (!c.invoked || c.result != 0) {
            Report(fingerprintd::ta::Cmd::CaptureImage, c);
            std::println(std::cerr, "capture failed during calibration");
            return 1;
        }
        std::println("  idle {}/{}: rc={} metric={}", i + 1,
                     fingerprintd::engine::Baseline::DefaultSamples, c.rc, c.metric);
        baseline.Observe(c.metric);
    }
    if (!baseline.Ready()) {
        std::println(std::cerr, "baseline did not calibrate (floor stayed 0)");
        return 1;
    }
    std::println("idle floor = {}, finger threshold = {}", baseline.Floor(),
                 baseline.Threshold());

    // ---- Authentication
    //
    // Needs no writes of any kind: no SAVE_DATA, no RPMB write, no SFS write.
    // So it runs safely against an existing template with the store read-only,
    // which is what makes it the right thing to try before enrolment.
    if (g_auth) {
        namespace ta = fingerprintd::ta;
        namespace en = fingerprintd::engine;

        // AUTHENTICATE arms the scan session. Its gid must match the one
        // SET_ACTIVE_GROUP used or the trustlet answers -200.
        std::vector<std::byte> au(ta::AuthPayloadSize);
        ta::BuildAuthPayload(au, 1, g_gid);
        std::println("\nAUTHENTICATE gid={}", g_gid);
        auto a = SendCommand(app, ta::Cmd::Authenticate, au);
        Report(ta::Cmd::Authenticate, a);
        if (!a.invoked || a.result != 0 || a.rc != 0) {
            std::println(std::cerr, "could not arm authentication");
            return 1;
        }

        for (int c = 3; c > 0; c--) {
            std::println("*** press and lift your finger in {}... ***", c);
            std::fflush(stdout);
            std::this_thread::sleep_for(std::chrono::seconds(1));
        }
        std::println("\n*** GO -- {} frames, about {} seconds ***\n", g_frames,
                     (g_frames * g_frameGapMs) / 1000);
        en::TouchTracker tracker;
        en::AuthTally tally;

        // The reference frame loop is {QUERY, CAPTURE, REPORT, QUERY, REPORT}.
        // QUERY_EVENT_STATUS returns its answer in rc -- 5 while an event is
        // pending, 0 once REPORT_EVENT has consumed it -- and the trailing
        // query is not decoration: without it the trustlet's event state is
        // never acknowledged, and after the first verdict every later frame
        // answers "not identified yet" forever.
        for (int i = 0; i < g_frames; i++) {
            std::vector<std::byte> q(0x10, std::byte{0});
            auto q0 = SendCommand(app, ta::Cmd::QueryEventStatus, q);

            std::vector<std::byte> cap(ta::CaptureDeclaredLen);
            ta::BuildCapturePayload(cap);
            auto c = SendCommand(app, ta::Cmd::CaptureImage, cap);
            bool finger = baseline.IsFinger(c.metric);

            auto events = tracker.Observe(finger, en::Mode::Authenticate);
            std::string verdicts;
            for (ta::Event ev : events) {
                std::vector<std::byte> evbuf(ta::EventContextSize);
                ta::BuildEventContext(evbuf, { .event = ev });
                // Poison the fid field before the call. A zero-initialised
                // buffer cannot tell "the matcher never ran" from "the matcher
                // ran and rejected the finger" -- the failure path writes zero
                // there too, so zero is ambiguous and 0xAAAAAAAA is not.
                // PoisonFid already writes at RespFidOff within the PAYLOAD.
                // Handing it a span that is itself already offset by the
                // payload offset double-counts and poisons payload+0x20, so
                // the real fid field stays zero -- and a released finger then
                // classifies as a REJECTION, inventing failures that never
                // happened.
                ta::PoisonFid(evbuf);

                auto r = SendCommand(app, ta::Cmd::ReportEvent, evbuf);
                if (!r.invoked) continue;

                ta::Verdict v = ta::Classify(r.rc, r.fid);
                tally.Observe(v, finger);
                verdicts += std::format("  {}", [&] {
                    switch (v) {
                        case ta::Verdict::Match:
                            return std::format("*** MATCH *** gid={} fid={}", r.gid, r.fid);
                        case ta::Verdict::Rejected:      return std::string("REJECTED");
                        case ta::Verdict::NotIdentifiedYet: return std::string("not identified yet");
                        case ta::Verdict::MatcherNeverRan:  return std::string("released");
                    }
                    return std::string("?");
                }());
            }
            // Acknowledge the event state before the next frame.
            auto q1 = SendCommand(app, ta::Cmd::QueryEventStatus, q);

            std::println("  frame {:2}/{}: metric={:<4}{} evst {}->{}{}", i + 1, g_frames,
                         c.metric, finger ? "  FINGER" : "        ",
                         q0.invoked ? q0.rc : -999, q1.invoked ? q1.rc : -999, verdicts);
            std::this_thread::sleep_for(std::chrono::milliseconds(g_frameGapMs));
        }
        // Only a terminal verdict is an attempt. Counting rescan frames as
        // rejections invents failures that never happened.
        std::println("\n=== {} MATCH / {} REJECTED over {} terminal frames ===",
                     tally.Matches(), tally.Rejections(), tally.TerminalFrames());
        std::println("    ({} answered 'not identified yet', {} never reached the matcher)",
                     tally.NotIdentifiedYet(), tally.NeverRan());
        if (tally.Presses() > 0)
            std::println("    presses: {} total, {} reached a verdict, {} matched",
                         tally.Presses(), tally.PressesDecided(), tally.PressesMatched());
        std::println("    {}", tally.Identified() ? "FINGER IDENTIFIED" : "no match");
    }

    std::println("\ntrustlet initialised against a powered sensor.");
    pthread_cancel(th);
    pthread_join(th, nullptr);
    return 0;
}

}  // namespace

int main(int argc, char** argv) {
    std::span<char*> args(argv, static_cast<std::size_t>(argc));
    bool probe = false;
    for (std::string_view a : args.subspan(1)) {
        if (a == "--version") {
            std::println("fingerprintd {}", Version);
            return 0;
        }
        if (a == "--probe-tee") probe = true;
        if (a.starts_with("--ta=")) g_taPath = a.substr(5);
        if (a.starts_with("--config=")) g_cfgPath = a.substr(9);
        if (a == "--verbose") g_verbose = true;
        if (a == "--listeners") g_listeners = true;
        // Serving the store writable lets QTEE UNLINK a container it rejects,
        // which destroys an enrolled template. Opt in explicitly.
        if (a == "--sfs-writable") g_sfsReadOnly = false;
        if (a == "--rpmb-write") g_rpmbWrite = true;
        if (a == "--auth") { g_auth = true; g_listeners = true; }
        if (a.starts_with("--frames=")) g_frames = std::stoi(std::string(a.substr(9)));
        if (a.starts_with("--log-dir=")) g_logDir = a.substr(10);
        if (a.starts_with("--rescan=")) g_rescan = std::stoi(std::string(a.substr(9)));
        if (a.starts_with("--sfs-root=")) g_sfsRoot = a.substr(11);
        if (a.starts_with("--gid=")) g_gid = static_cast<std::uint32_t>(
            std::stoul(std::string(a.substr(6))));
    }
    if (probe) {
        StartTranscript(g_logDir);
        return Probe();
    }

    std::println(std::cerr,
                 "fingerprintd {}: no runtime yet. --probe-tee reaches QTEE; "
                 "`crafter-build test` covers the core.", Version);
    return 1;
}