From 5ab0c12d54e7f47a64b476d41a7ed15104f79f5c Mon Sep 17 00:00:00 2001
From: Ian Moffett <ian@osmora.org>
Date: Sun, 30 Jun 2024 23:57:39 -0400
Subject: kernel: exec: Add execve()
Signed-off-by: Ian Moffett <ian@osmora.org>
---
sys/kern/kern_exec.c | 108 +++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 108 insertions(+)
create mode 100644 sys/kern/kern_exec.c
(limited to 'sys/kern/kern_exec.c')
diff --git a/sys/kern/kern_exec.c b/sys/kern/kern_exec.c
new file mode 100644
index 0000000..b21404b
--- /dev/null
+++ b/sys/kern/kern_exec.c
@@ -0,0 +1,108 @@
+/*
+ * 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/exec.h>
+#include <sys/types.h>
+#include <sys/errno.h>
+#include <sys/proc.h>
+#include <sys/sched.h>
+#include <vm/vm.h>
+#include <vm/map.h>
+#include <vm/physmem.h>
+#include <machine/pcb.h>
+
+/*
+ * Release the memory of the old stack
+ *
+ * @td: Target thread.
+ */
+static void
+release_stack(struct proc *td)
+{
+ struct pcb *pcbp = &td->pcb;
+ uintptr_t base = td->stack_base;
+
+ if (base >= VM_HIGHER_HALF) {
+ base -= VM_HIGHER_HALF;
+ vm_free_frame(base, PROC_STACK_PAGES);
+ } else {
+ vm_unmap(pcbp->addrsp, base, PROC_STACK_SIZE);
+ vm_free_frame(base, PROC_STACK_PAGES);
+ }
+}
+
+int
+execve(struct proc *td, const struct execve_args *args)
+{
+ int error;
+ struct exec_prog prog;
+ struct pcb *pcbp = &td->pcb;
+ uintptr_t stack_top, stack;
+
+ if (td == NULL || args == NULL)
+ return -EINVAL;
+ if ((error = elf64_load(args->pathname, td, &prog)) != 0)
+ return error;
+
+ /* Mark the thread as running exec */
+ td->flags |= (PROC_EXEC | PROC_INEXEC);
+
+ /* Create the new stack */
+ stack = vm_alloc_frame(PROC_STACK_PAGES);
+ if (stack == 0) {
+ elf_unload(td, &prog);
+ return -ENOMEM;
+ }
+
+ /* Release the old stack if it exists */
+ if (td->stack_base != 0)
+ release_stack(td);
+
+ /* Set new stack and map it to userspace */
+ td->stack_base = stack;
+ vm_map(pcbp->addrsp, td->stack_base, td->stack_base,
+ (PROT_READ | PROT_WRITE | PROT_USER), PROC_STACK_SIZE);
+
+ prog.argp = args->argv;
+ prog.envp = args->envp;
+ stack_top = td->stack_base + (PROC_STACK_SIZE - 1);
+
+ /* Setup registers and stack */
+ md_td_stackinit(td, (void *)(stack_top + VM_HIGHER_HALF), &prog);
+ setregs(td, &prog, stack_top);
+
+ /*
+ * Done, reset flags and yield
+ *
+ * XXX: PROC_EXEC is unset by the scheduler so it
+ * can properly start the new exec'd program.
+ */
+ td->flags &= ~PROC_INEXEC;
+ sched_enter();
+}
--
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