feat: establish bootable new architecture checkpoint

Replace the compressed boot path with a relocatable higher-half RISC-V entry, expand memory and SMP support, and add the driver, TTY, VFS, exec, signal, syscall, initramfs, and self-test infrastructure needed for a bootable kernel checkpoint.

1 files changed, 250 insertions, 0 deletions

diff --git a/na/kernel/poll.cc b/na/kernel/poll.cc
new file mode 100644
index 0000000..3674491
--- /dev/null
+++ b/na/kernel/poll.cc
@@ -0,0 +1,250 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/* Copyright (C) 2026 Richard Qin */
+
+/*
+ * sys_ppoll — POSIX ppoll() implementation.
+ *
+ * Linux fs/select.c:do_sys_poll() pattern, simplified for our needs:
+ *   - Two-phase loop: "register-then-check".  First pass calls every
+ *     f_op->poll() with a real poll_table so drivers can register their
+ *     wait queues; if any fd is already ready we return immediately.
+ *     Otherwise schedule() until a wq fires (or timeout/signal), then
+ *     re-check with poll_table=nullptr (probe-only).
+ *
+ * Limitations vs. Linux:
+ *   - Only a single wait queue per ppoll call is tracked (the first one
+ *     a driver hands to poll_wait).  Multi-fd polls work, but only the
+ *     first wq's wake actually re-runs the loop; other fds becoming
+ *     ready won't be noticed until the timer fires or another wake.
+ *     BusyBox interactive shell polls one fd (stdin), so this matches.
+ *
+ * Reference: Linux fs/select.c
+ */
+
+#include <lume/poll.h>
+#include <lume/file.h>
+#include <lume/fdtable.h>
+#include <lume/task.h>
+#include <lume/sched.h>
+#include <lume/timer.h>
+#include <lume/waitqueue.h>
+#include <lume/signal.h>
+#include <lume/signal_types.h>
+#include <lume/uaccess.h>
+#include <lume/errno.h>
+#include <lume/klog.h>
+#include <lume/new.h>
+
+/* ================================================================== */
+/*  poll_wait — called by file_operations->poll() implementations     */
+/* ================================================================== */
+
+void poll_wait(file* /*fp*/, WaitQueue* wq, poll_table* pt)
+{
+    /* Probe-only pass: pt is null, drivers skip registration. */
+    if (!pt || !wq) return;
+    /* Single-wq design: keep the first one we see.  A more complete
+     * implementation would chain entries onto a list. */
+    if (!pt->wq) pt->wq = wq;
+}
+
+/* ================================================================== */
+/*  Linux-compatible timespec                                         */
+/* ================================================================== */
+
+struct linux_timespec_pp {
+    int64 tv_sec;
+    int64 tv_nsec;
+};
+
+/*
+ * Convert a timespec into a deadline in jiffies (g_jiffies clock).
+ * Returns 0 if the input is null (= infinite wait), or a deadline
+ * jiffy value otherwise.  Caller treats 0 deadline as "no timeout".
+ */
+static uint64 timespec_to_deadline(const linux_timespec_pp* ts)
+{
+    if (!ts) return 0;
+    /* g_jiffies advances at 100 Hz (HZ=100) — 1 jiffy = 10 ms */
+    uint64 ticks = static_cast<uint64>(ts->tv_sec) * 100ULL;
+    ticks += ts->tv_nsec / 10'000'000;          /* 10 ms granularity */
+    /* Round up sub-jiffy nsec so a tiny timeout doesn't truncate to 0. */
+    if (ts->tv_nsec % 10'000'000 != 0) ticks++;
+    return g_jiffies + ticks;
+}
+
+/* ================================================================== */
+/*  do_poll — one scan over all fds                                   */
+/* ================================================================== */
+
+/*
+ * For each fd: look up the file, call its poll() callback.  If `pt` is
+ * non-null, drivers register their wait queues onto it.  Returns the
+ * number of fds that have any non-zero revents.
+ */
+static int do_poll_scan(pollfd* fds, uint32 nfds, poll_table* pt)
+{
+    TaskControlBlock* c = current_task();
+    files_struct* files = c ? c->files : nullptr;
+    if (!files) return 0;
+    int ready = 0;
+
+    for (uint32 i = 0; i < nfds; i++) {
+        if (fds[i].fd < 0) {
+            fds[i].revents = 0;
+            continue;
+        }
+        file* fp = fcheck(files, fds[i].fd);
+        if (!fp) {
+            fds[i].revents = POLLNVAL;
+            ready++;
+            continue;
+        }
+        uint32 mask = 0;
+        if (fp->f_op && fp->f_op->poll) {
+            mask = fp->f_op->poll(fp, pt);
+        } else {
+            /* No poll handler — treat as always readable/writable so
+             * a missing implementation doesn't permanently block sh. */
+            mask = POLLIN | POLLOUT;
+        }
+        /* Filter: revents always include error/hup; userland event bits
+         * only set if requested in events. */
+        uint32 always = POLLERR | POLLHUP | POLLNVAL;
+        uint32 want = static_cast<uint32>(fds[i].events) | always;
+        fds[i].revents = static_cast<int16>(mask & want);
+        if (fds[i].revents) ready++;
+    }
+    return ready;
+}
+
+/* ================================================================== */
+/*  sys_ppoll                                                         */
+/* ================================================================== */
+
+/*
+ * a0 = struct pollfd __user *ufds
+ * a1 = nfds_t nfds
+ * a2 = const struct __kernel_timespec __user *tsp  (nullable = infinite)
+ * a3 = const sigset_t __user *sigmask              (nullable = no override)
+ * a4 = size_t sigsetsize
+ */
+int64 sys_ppoll(uint64 a0, uint64 a1, uint64 a2, uint64 a3,
+                uint64 a4, uint64 /*a5*/)
+{
+    uint64 ufds   = a0;
+    uint32 nfds   = static_cast<uint32>(a1);
+    uint64 utsp   = a2;
+    uint64 usigmask = a3;
+    uint64 sigsetsize = a4;
+
+    if (nfds > 1024) return -EINVAL;        /* Linux RLIMIT_NOFILE-ish cap */
+    if (usigmask && sigsetsize != sizeof(sigset_t)) return -EINVAL;
+
+    /* Copy timespec from user.  Null pointer means "wait forever". */
+    bool have_timeout = (utsp != 0);
+    linux_timespec_pp ts{};
+    if (have_timeout) {
+        if (copy_from_user(&ts, utsp, sizeof(ts)) < 0) return -EFAULT;
+        if (ts.tv_sec < 0 || ts.tv_nsec < 0 || ts.tv_nsec >= 1'000'000'000)
+            return -EINVAL;
+    }
+    uint64 deadline = have_timeout ? timespec_to_deadline(&ts) : 0;
+
+    /* Apply temporary sigmask if requested.  Linux semantics: the new
+     * mask is in effect for the duration of the call; on return we
+     * restore the old mask.  If a signal interrupts us mid-wait, the
+     * original mask is restored before returning -EINTR. */
+    TaskControlBlock* curr = current_task();
+    sigset_t saved_mask{};
+    bool mask_swapped = false;
+    if (usigmask && curr && curr->sighand) {
+        sigset_t newmask{};
+        if (copy_from_user(&newmask, usigmask, sizeof(newmask)) < 0)
+            return -EFAULT;
+        newmask.del(SIGKILL);
+        newmask.del(SIGSTOP);
+        LockGuard guard(curr->sighand->siglock);
+        saved_mask = curr->blocked;
+        curr->blocked = newmask;
+        mask_swapped = true;
+    }
+
+    /* Copy pollfd array from user.  Allocate a kernel buffer; for the
+     * common nfds<=8 case this is one slab object. */
+    pollfd* kfds = nullptr;
+    uint64 fds_bytes = static_cast<uint64>(nfds) * sizeof(pollfd);
+    int64 ret = 0;
+
+    if (nfds > 0) {
+        kfds = static_cast<pollfd*>(operator new[](fds_bytes));
+        if (!kfds) { ret = -ENOMEM; goto out_restore_mask; }
+        if (copy_from_user(kfds, ufds, fds_bytes) < 0) {
+            ret = -EFAULT; goto out_free;
+        }
+    }
+
+    /* The main poll loop. */
+    {
+        poll_table pt{};
+        pt.wq = nullptr;
+        int n_ready = do_poll_scan(kfds, nfds, &pt);
+
+        while (n_ready == 0) {
+            /* Timeout==0 means non-blocking probe. */
+            if (have_timeout && deadline <= g_jiffies) break;
+
+            /* No registered wait queue?  Nothing to sleep on.  This
+             * happens when no fd has a poll handler that calls
+             * poll_wait — fall back to a short reschedule loop so we
+             * don't burn the CPU. */
+            if (!pt.wq) {
+                schedule();
+                if (signal_pending(curr)) { ret = -EINTR; goto out_free; }
+                pt.wq = nullptr;
+                n_ready = do_poll_scan(kfds, nfds, &pt);
+                continue;
+            }
+
+            /* Standard prepare-check-schedule pattern. */
+            pt.wq->prepare_to_wait(curr, TaskState::Sleeping);
+
+            /* Re-probe with pt=nullptr (no extra registration) so we
+             * see any state change that arrived between the previous
+             * scan and prepare_to_wait. */
+            n_ready = do_poll_scan(kfds, nfds, nullptr);
+            if (n_ready > 0) {
+                pt.wq->finish_wait(curr);
+                break;
+            }
+            if (signal_pending(curr)) {
+                pt.wq->finish_wait(curr);
+                ret = -EINTR; goto out_free;
+            }
+
+            schedule();
+            pt.wq->finish_wait(curr);
+
+            /* Reset the registration and rescan — drivers may register
+             * fresh wait queues this pass. */
+            pt.wq = nullptr;
+            n_ready = do_poll_scan(kfds, nfds, &pt);
+        }
+        ret = n_ready;
+    }
+
+    /* Copy revents back to user (events bits stay as user wrote them). */
+    if (nfds > 0) {
+        if (copy_to_user(ufds, kfds, fds_bytes) < 0) ret = -EFAULT;
+    }
+
+out_free:
+    if (kfds) operator delete[](kfds);
+
+out_restore_mask:
+    if (mask_swapped && curr && curr->sighand) {
+        LockGuard guard(curr->sighand->siglock);
+        curr->blocked = saved_mask;
+    }
+    return ret;
+}