kernel: Add initial support for signals

Signed-off-by: Ian Moffett <ian@osmora.org>

1 files changed, 257 insertions, 0 deletions

diff --git a/sys/kern/kern_sig.c b/sys/kern/kern_sig.c
new file mode 100644
index 0000000..ed29397
--- /dev/null
+++ b/sys/kern/kern_sig.c
@@ -0,0 +1,257 @@
+/*
+ * Copyright (c) 2023-2024 Ian Marco Moffett and the Osmora Team.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of Hyra nor the names of its
+ *    contributors may be used to endorse or promote products derived from
+ *    this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <sys/signal.h>
+#include <sys/types.h>
+#include <sys/errno.h>
+#include <sys/syslog.h>
+#include <sys/param.h>
+#include <vm/dynalloc.h>
+#include <string.h>
+
+#define sigmask(SIGNO) BIT(SIGNO)
+
+static struct sigaction sa_tab[] = {
+    [SIGFPE] = {
+        .sa_handler = sigfpe_default,
+        .sa_mask = 0,
+        .sa_flags = 0,
+        .sa_sigaction = NULL
+    },
+
+    [SIGKILL] = {
+        .sa_handler = sigkill_default,
+        .sa_mask = 0,
+        .sa_flags = 0,
+        .sa_sigaction = NULL
+    },
+
+    [SIGSEGV] = {
+        .sa_handler = sigsegv_default,
+        .sa_mask = 0,
+        .sa_flags = 0,
+        .sa_sigaction = NULL
+    },
+};
+
+/*
+ * Register a new signal descriptor, set it in the process
+ * structure and return it in `ksig`.
+ *
+ * @td: Process to register signal to.
+ * @signo: Signal number to register.
+ * @ksig: Will contain a pointer to new signal descriptor.
+ */
+int
+newsig(struct proc *td, int signo, struct ksiginfo **ksig)
+{
+    struct ksiginfo *ksig_tmp;
+
+    /* Ensure we have valid args */
+    if (td == NULL || signo >= PROC_SIGMAX)
+        return -EINVAL;
+
+    /*
+     * Make sure we have a valid signal list. If we already
+     * have a signal registered in a slot, free up memory used
+     * for that signal descriptor so we can override it with the
+     * new one.
+     */
+    if (td->ksig_list == NULL)
+        return -EIO;
+    if ((ksig_tmp = td->ksig_list[signo]) != NULL)
+        dynfree(ksig_tmp);
+
+    /* Allocate our new signal */
+    ksig_tmp = dynalloc(sizeof(*ksig_tmp));
+    if (ksig_tmp == NULL)
+        return -ENOMEM;
+
+    memset(ksig_tmp, 0, sizeof(*ksig_tmp));
+    ksig_tmp->signo = signo;
+    td->ksig_list[signo] = ksig_tmp;
+    *ksig = ksig_tmp;
+    return 0;
+}
+
+/*
+ * Remove a signal from the signal table.
+ *
+ * @td: Process to remove signal from.
+ * @signo: Signal to remove.
+ */
+int
+delsig(struct proc *td, int signo)
+{
+    struct ksiginfo *ksig_tmp;
+
+    /* Ensure we have valid args */
+    if (td == NULL || signo >= PROC_SIGMAX)
+        return -EINVAL;
+
+    /* Don't do anything if it doesn't exist */
+    if ((ksig_tmp = td->ksig_list[signo]) == NULL)
+        return 0;
+
+    dynfree(ksig_tmp);
+    td->ksig_list[signo] = NULL;
+    return 0;
+}
+
+int
+sendsig(struct proc *td, const sigset_t *set)
+{
+    struct ksiginfo *ksig_tmp;
+
+    /* Ensure arguments are correct */
+    if (td == NULL || set == NULL)
+        return -EINVAL;
+
+    /* Enqueue required ksiginfo structures */
+    for (int i = 0; i < PROC_SIGMAX; ++i) {
+        if ((ksig_tmp = td->ksig_list[i]) == NULL) {
+            continue;
+        }
+
+        /* Enqueue if it is a member of the sigset */
+        if (sigismember(set, i)) {
+            spinlock_acquire(&td->ksigq_lock);
+            TAILQ_INSERT_TAIL(&td->ksigq, ksig_tmp, link);
+            spinlock_release(&td->ksigq_lock);
+        }
+    }
+
+    return 0;
+}
+
+int
+signals_init(struct proc *td)
+{
+    struct sigaction *sa;
+    struct ksiginfo *ksig;
+    int error, i;
+
+    TAILQ_INIT(&td->ksigq);
+
+    /* Populate process signal table with defaults */
+    for (i = 0; i < NELEM(sa_tab); ++i) {
+        sa = &sa_tab[i];
+
+        /* Drop actions that aren't set up */
+        if (sa->sa_handler == NULL && sa->sa_sigaction == NULL) {
+            continue;
+        }
+
+        /* Attempt to register the new signal */
+        if ((error = newsig(td, i, &ksig)) != 0) {
+            goto fail;
+        }
+
+        ksig->si = sa;
+    }
+
+    return 0;
+
+fail:
+    /*
+     * We do not want the process signal table to be in
+     * an inconsistent state so we clean up on failure.
+     */
+    for (int j = 0; j < i; ++j) {
+        if ((error = delsig(td, j)) != 0) {
+            kprintf("delsig() failed on signal %d (returned %d)\n",
+                j, error);
+        }
+    }
+
+    return error;
+}
+
+void
+dispatch_signals(struct proc *td)
+{
+    struct ksiginfo *ksig_tmp;
+    struct sigaction *action;
+
+    spinlock_acquire(&td->ksigq_lock);
+    while (!TAILQ_EMPTY(&td->ksigq)) {
+        /* Dequeue signal descriptor */
+        ksig_tmp = TAILQ_FIRST(&td->ksigq);
+        TAILQ_REMOVE(&td->ksigq, ksig_tmp, link);
+
+        /* Invoke handler */
+        action = ksig_tmp->si;
+        action->sa_handler(ksig_tmp->signo);
+    }
+
+    spinlock_release(&td->ksigq_lock);
+}
+
+int
+sigemptyset(sigset_t *set)
+{
+    *set = 0;
+    return 0;
+}
+
+int
+sigfillset(sigset_t *set)
+{
+    *set = ~(sigset_t)0;
+    return 0;
+}
+
+int
+sigaddset(sigset_t *set, int signo)
+{
+    if (signo <= 0 || signo >= PROC_SIGMAX)
+        return -EINVAL;
+
+    *set |= sigmask(signo);
+    return 0;
+}
+
+int
+sigdelset(sigset_t *set, int signo)
+{
+    if (signo <= 0 || signo >= PROC_SIGMAX)
+        return -EINVAL;
+
+    *set &= ~sigmask(signo);
+    return 0;
+}
+
+int
+sigismember(const sigset_t *set, int signo)
+{
+    if (signo <= 0 || signo >= PROC_SIGMAX)
+        return -EINVAL;
+
+    return (*set & sigmask(signo)) != 0;
+}