kern: Add initial signals work

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

7 files changed, 245 insertions, 4 deletions

diff --git a/src/sys/compat/unix/os/os_signal.c b/src/sys/compat/unix/os/os_signal.c
new file mode 100644
index 0000000..4093c98
--- /dev/null
+++ b/src/sys/compat/unix/os/os_signal.c
@@ -0,0 +1,99 @@
+/*
+ * Copyright (c) 2025 Ian Marco Moffett and L5 engineers
+ * 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 the project 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/errno.h>
+#include <sys/signal.h>
+#include <sys/cdefs.h>
+#include <sys/proc.h>
+#include <os/signal.h>
+
+/*
+ * Handle a POSIX sigaction
+ */
+static int
+do_sigaction(int sig, const struct sigaction *act, struct sigaction *oact)
+{
+    struct proc *self;
+
+    if (act == NULL || oact == NULL) {
+        return -EINVAL;
+    }
+
+    if ((self = proc_self()) == NULL) {
+        return -ESRCH;
+    }
+
+    /* Don't overflow the signal table */
+    if (sig >= NELEM(self->sigtab) || sig < 0) {
+        return -EINVAL;
+    }
+
+    if (oact != NULL) {
+        *oact = self->sigtab[sig];
+    }
+
+    if (act != NULL) {
+        self->sigtab[sig] = *act;
+    }
+
+    return 0;
+}
+
+/*
+ * ARG0: Signal number
+ * ARG1: Action to set (act)
+ * ARG2: Old action (old sigaction written here)
+ */
+scret_t
+sys_sigaction(struct syscall_args *scargs)
+{
+    struct proc *self = proc_self();
+    int sig;
+    struct sigaction *sap, *sap_old;
+    int error;
+
+    sig = SCARG(scargs, int, 0);
+    sap = SCARG(scargs, struct sigaction *, 1);
+    sap_old = SCARG(scargs, struct sigaction *, 2);
+
+    /* Sigactions at a valid address? */
+    error = proc_check_addr(self, (uintptr_t)sap, sizeof(*sap));
+    if (error < 0) {
+        return error;
+    }
+
+    /* Old sigactions at a valid address? */
+    error = proc_check_addr(self, (uintptr_t)sap_old, sizeof(sap_old));
+    if (error < 0) {
+        return error;
+    }
+
+    return do_sigaction(sig, sap, sap_old);
+
+}
diff --git a/src/sys/include/os/signal.h b/src/sys/include/os/signal.h
new file mode 100644
index 0000000..b77a51f
--- /dev/null
+++ b/src/sys/include/os/signal.h
@@ -0,0 +1,55 @@
+/*
+ * Copyright (c) 2025 Ian Marco Moffett and L5 engineers
+ * 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 the project 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 _OS_SIGNAL_H_
+#define _OS_SIGNAL_H_
+
+#include <sys/types.h>
+#include <sys/proc.h>
+#include <sys/signal.h>
+
+typedef struct sigaction sigtab_t[32];
+
+/*
+ * Initialize the signals framework
+ */
+int signal_init(struct proc *procp);
+
+/* Default handlers */
+void sigfpe_default(int signo);
+void sigkill_default(int signo);
+void sigsegv_default(int signo);
+void sigterm_default(int signo);
+
+/*
+ * POSIX sigaction system call
+ */
+scret_t sys_sigaction(struct syscall_args *scargs);
+
+#endif  /* !_OS_SIGNAL_H_ */
diff --git a/src/sys/include/sys/proc.h b/src/sys/include/sys/proc.h
index c5b0fda..c268693 100644
--- a/src/sys/include/sys/proc.h
+++ b/src/sys/include/sys/proc.h
@@ -36,6 +36,7 @@
 #include <sys/param.h>
 #include <sys/queue.h>
 #include <os/mac.h>
+#include <os/signal.h>
 #include <os/spinlock.h>
 #include <os/filedesc.h>
 #include <vm/vm.h>
@@ -57,6 +58,8 @@
  * @pcb: Process control block
  * @scdom: Syscall domain
  * @level: Access level
+ * @maplist_lock: Protects the maplist
+ * @sigtab: Signal table
  * @maplist: List of mapped regions
  * @link: TAILQ link
  */
@@ -68,6 +71,7 @@ struct proc {
     struct filedesc *fdtab[FD_MAX];
     mac_level_t level;
     struct spinlock maplist_lock;
+    sigtab_t sigtab;
     TAILQ_HEAD(, vm_range) maplist;
     TAILQ_ENTRY(proc) link;
 };
diff --git a/src/sys/include/sys/signal.h b/src/sys/include/sys/signal.h
new file mode 100644
index 0000000..85d0dbb
--- /dev/null
+++ b/src/sys/include/sys/signal.h
@@ -0,0 +1,54 @@
+/*
+ * Copyright (c) 2025 Ian Marco Moffett and L5 engineers
+ * 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 the project 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 _SIGNAL_H_
+#define _SIGNAL_H_
+
+#include <sys/types.h>
+
+#define SIGFPE      8   /* Floating point exception */
+#define SIGKILL     9   /* Kill */
+#define SIGSEGV     11  /* Segmentation violation */
+#define SIGTERM     15  /* Terminate gracefully */
+
+typedef __uint32_t sigset_t;
+
+/*
+ * POSIX sigaction
+ *
+ * Represents the action associated with
+ * a specific signal
+ */
+struct sigaction {
+    void(*sa_handler)(int);
+    sigset_t sa_mask;
+    int sa_flags;
+};
+
+#endif /* _SIGNAL_H_ */
diff --git a/src/sys/include/sys/syscall.h b/src/sys/include/sys/syscall.h
index 3f8ab10..5ec48c3 100644
--- a/src/sys/include/sys/syscall.h
+++ b/src/sys/include/sys/syscall.h
@@ -42,10 +42,11 @@
  * Defines marked as (mandatory) must be implemented
  * between latches.
  */
-#define SYS_none    0x00
-#define SYS_exit    0x01
-#define SYS_write   0x02
-#define SYS_cross   0x03    /* cross a border (mandatory) */
+#define SYS_none        0x00
+#define SYS_exit        0x01
+#define SYS_write       0x02
+#define SYS_cross       0x03    /* cross a border (mandatory) */
+#define SYS_sigaction   0x04
 
 typedef __ssize_t scret_t;
 typedef __ssize_t scarg_t;
diff --git a/src/sys/os/os_proc.c b/src/sys/os/os_proc.c
index ef98ce2..ef80b76 100644
--- a/src/sys/os/os_proc.c
+++ b/src/sys/os/os_proc.c
@@ -35,6 +35,7 @@
 #include <sys/proc.h>
 #include <vm/vm.h>
 #include <vm/physseg.h>
+#include <os/signal.h>
 #include <os/kalloc.h>
 #include <os/filedesc.h>
 #include <string.h>
diff --git a/src/sys/os/os_stub.c b/src/sys/os/os_stub.c
index f78df68..76a5828 100644
--- a/src/sys/os/os_stub.c
+++ b/src/sys/os/os_stub.c
@@ -30,6 +30,8 @@
 #include <sys/cdefs.h>
 #include <sys/cpuvar.h>
 #include <sys/syslog.h>
+#include <sys/panic.h>
+#include <os/signal.h>
 #include <io/pci/cam.h>
 
 __weak void
@@ -45,3 +47,28 @@ pci_cam_init(struct cam_hook *chp)
     printf("pci_cam_init: unimplemented\n");
     return 0;
 }
+
+/* Default handlers */
+void
+sigfpe_default(int signo)
+{
+    panic("Floating point exception\n");
+}
+
+void
+sigkill_default(int signo)
+{
+    panic("Killed\n");
+}
+
+void
+sigsegv_default(int signo)
+{
+    panic("Segmentation fault\n");
+}
+
+void
+sigterm_default(int signo)
+{
+    panic("Terminated\n");
+}