kernel: Add initial support for signals

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

7 files changed, 385 insertions, 1 deletions

diff --git a/sys/include/sys/proc.h b/sys/include/sys/proc.h
index b9db603..b10ee41 100644
--- a/sys/include/sys/proc.h
+++ b/sys/include/sys/proc.h
@@ -38,6 +38,7 @@
 #include <sys/syscall.h>
 #include <sys/exec.h>
 #include <sys/filedesc.h>
+#include <sys/signal.h>
 #if defined(_KERNEL)
 #include <machine/frame.h>
 #include <machine/pcb.h>
@@ -48,10 +49,12 @@
 #define PROC_STACK_PAGES 8
 #define PROC_STACK_SIZE  (PROC_STACK_PAGES * DEFAULT_PAGESIZE)
 #define PROC_MAX_FILEDES 256
+#define PROC_SIGMAX 64
 
 struct proc {
     pid_t pid;
     struct exec_prog exec;
+    struct ksiginfo *ksig_list[PROC_SIGMAX];
     struct filedesc *fds[PROC_MAX_FILEDES];
     struct trapframe tf;
     struct pcb pcb;
@@ -59,6 +62,8 @@ struct proc {
     bool rested;
     uint32_t flags;
     uintptr_t stack_base;
+    struct spinlock ksigq_lock;
+    TAILQ_HEAD(, ksiginfo) ksigq;
     TAILQ_ENTRY(proc) link;
 };
 
diff --git a/sys/include/sys/signal.h b/sys/include/sys/signal.h
new file mode 100644
index 0000000..f35ff82
--- /dev/null
+++ b/sys/include/sys/signal.h
@@ -0,0 +1,84 @@
+/*
+ * 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.
+ */
+
+#ifndef _SYS_SIGNAL_H_
+#define _SYS_SIGNAL_H_
+
+#include <sys/types.h>
+#include <sys/queue.h>
+#include <sys/proc.h>
+
+#define SIGFPE      8   /* Floating point exception */
+#define SIGKILL     9   /* Kill */
+#define SIGSEGV     11  /* Segmentation violation */
+
+typedef uint32_t sigset_t;
+
+typedef struct {
+    int si_signo;
+    int si_code;
+} siginfo_t;
+
+struct sigaction {
+    void(*sa_handler)(int signo);
+    sigset_t sa_mask;
+    int sa_flags;
+    void(*sa_sigaction)(int signo, siginfo_t *si, void *p);
+};
+
+#if defined(_KERNEL)
+struct proc;
+
+struct ksiginfo {
+    int signo;
+    int sigcode;
+    struct sigaction *si;
+    TAILQ_ENTRY(ksiginfo) link;
+};
+
+/* Signal management */
+int newsig(struct proc *td, int signo, struct ksiginfo **ksig);
+int delsig(struct proc *td, int signo);
+int sendsig(struct proc *td, const sigset_t *set);
+void dispatch_signals(struct proc *td);
+int signals_init(struct proc *td);
+
+/* Sigset functions */
+int sigemptyset(sigset_t *set);
+int sigfillset(sigset_t *set);
+int sigaddset(sigset_t *set, int signo);
+int sigdelset(sigset_t *set, int signo);
+int sigismember(const sigset_t *set, int signo);
+
+/* Default handlers */
+void sigfpe_default(int signo);
+void sigkill_default(int signo);
+void sigsegv_default(int signo);
+#endif  /* _KERNEL */
+#endif  /* !_SYS_SIGNAL_H_ */
diff --git a/sys/kern/kern_exec.c b/sys/kern/kern_exec.c
index ceb08f6..863f4ae 100644
--- a/sys/kern/kern_exec.c
+++ b/sys/kern/kern_exec.c
@@ -32,6 +32,7 @@
 #include <sys/errno.h>
 #include <sys/proc.h>
 #include <sys/sched.h>
+#include <sys/signal.h>
 #include <vm/vm.h>
 #include <vm/map.h>
 #include <vm/physmem.h>
@@ -97,9 +98,10 @@ execve(struct proc *td, const struct execve_args *args)
     prog.envp = args->envp;
     stack_top = td->stack_base + (PROC_STACK_SIZE - 1);
 
-    /* Setup registers and stack */
+    /* Setup registers, signals and stack */
     md_td_stackinit(td, (void *)(stack_top + VM_HIGHER_HALF), &prog);
     setregs(td, &prog, stack_top);
+    signals_init(td);
 
     /* Done, reset flags and start the user thread */
     td->flags &= ~PROC_EXEC;
diff --git a/sys/kern/kern_fork.c b/sys/kern/kern_fork.c
index 037026b..7bcff4b 100644
--- a/sys/kern/kern_fork.c
+++ b/sys/kern/kern_fork.c
@@ -31,6 +31,7 @@
 #include <sys/proc.h>
 #include <sys/errno.h>
 #include <sys/sched.h>
+#include <sys/signal.h>
 #include <vm/dynalloc.h>
 #include <string.h>
 
@@ -64,6 +65,7 @@ fork1(struct proc *cur, int flags, void(*ip)(void), struct proc **newprocp)
         *newprocp = newproc;
 
     newproc->pid = ++nthreads;
+    signals_init(newproc);
     sched_enqueue_td(newproc);
 done:
     if (status != 0)
diff --git a/sys/kern/kern_sched.c b/sys/kern/kern_sched.c
index 6d85330..5f2b019 100644
--- a/sys/kern/kern_sched.c
+++ b/sys/kern/kern_sched.c
@@ -187,6 +187,7 @@ sched_switch(struct trapframe *tf)
     td = ci->curtd;
 
     if (td != NULL) {
+        dispatch_signals(td);
         td_pri_update(td);
     }
 
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;
+}
diff --git a/sys/kern/kern_stub.c b/sys/kern/kern_stub.c
index 65688e2..5a53cc1 100644
--- a/sys/kern/kern_stub.c
+++ b/sys/kern/kern_stub.c
@@ -30,6 +30,39 @@
 #include <sys/device.h>
 #include <sys/types.h>
 #include <sys/errno.h>
+#include <sys/syslog.h>
+#include <sys/proc.h>
+#include <sys/signal.h>
+
+void
+sigfpe_default(int signo)
+{
+    static struct proc *td;
+
+    td = this_td();
+    kprintf("Floating point exception (pid=%d)\n", td->pid);
+    exit1(td);
+}
+
+void
+sigkill_default(int signo)
+{
+    static struct proc *td;
+
+    td = this_td();
+    kprintf("Terminated (pid=%d)\n", td->pid);
+    exit1(td);
+}
+
+void
+sigsegv_default(int signo)
+{
+    static struct proc *td;
+
+    td = this_td();
+    kprintf("Segmentation fault (pid=%d)\n", td->pid);
+    exit1(td);
+}
 
 int
 dev_noread(void)