kernel: Add initial ELF loader implementation

This is the initial ELF loader implementation, this will obviously need some fixups
and refactoring in the future but it works as of now.

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

1 files changed, 112 insertions, 0 deletions

diff --git a/sys/kern/kern_loader.c b/sys/kern/kern_loader.c
new file mode 100644
index 0000000..cf51c72
--- /dev/null
+++ b/sys/kern/kern_loader.c
@@ -0,0 +1,112 @@
+/*
+ * 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/loader.h>
+#include <sys/cdefs.h>
+#include <sys/elf.h>
+#include <sys/types.h>
+#include <sys/syslog.h>
+#include <vm/vm.h>
+#include <vm/map.h>
+#include <vm/physseg.h>
+#include <string.h>
+#include <assert.h>
+
+__MODULE_NAME("kern_loader");
+__KERNEL_META("$Hyra$: kern_loader.c, Ian Marco Moffett, "
+              "Kernel ELF loader");
+
+#if !defined(DEBUG)
+#define DBG(...) __nothing
+#else
+#define DBG(...) KDEBUG(__VA_ARGS__)
+#endif
+
+#define PHDR(hdrptr, IDX) \
+    (void *)((uintptr_t)hdr + (hdrptr)->e_phoff + (hdrptr->e_phentsize*IDX))
+
+int
+loader_load(const void *dataptr, struct auxval *auxv)
+{
+    const Elf64_Ehdr *hdr = dataptr;
+    Elf64_Phdr *phdr;
+    vm_prot_t prot = 0;
+
+    uintptr_t physmem;
+    size_t misalign, page_count;
+
+    int status;
+    const size_t GRANULE = vm_get_page_size();
+
+    void *tmp_ptr;
+
+    if (auxv == NULL) {
+        DBG("Auxval argument NULL\n");
+        return -1;
+    }
+
+    if (memcmp(hdr->e_ident, ELFMAG, 4) != 0) {
+        /* Bad ELF header */
+        DBG("ELF header bad! (Magic incorrect)\n");
+        return -1;
+    }
+
+    /* Parse program headers */
+    for (size_t i = 0; i < hdr->e_phnum; ++i) {
+        phdr = PHDR(hdr, i);
+        switch (phdr->p_type) {
+        case PT_LOAD:
+            if (__TEST(phdr->p_flags, PF_W))
+                prot |= PROT_WRITE;
+            if (__TEST(phdr->p_flags, PF_X)) {
+                prot |= PROT_EXEC;
+            }
+
+            misalign = phdr->p_vaddr & (GRANULE - 1);
+            page_count = __DIV_ROUNDUP(phdr->p_memsz + misalign, GRANULE);
+
+            physmem = vm_alloc_pageframe(page_count);
+            __assert(physmem != 0);     /* TODO: Handle better */
+
+            status = vm_map_create(phdr->p_vaddr, physmem, prot,
+                                   page_count * GRANULE);
+
+            __assert(status == 0);  /* TODO: Handle better */
+
+            /* Now we want to copy the data */
+            tmp_ptr = (void *)((uintptr_t)hdr + phdr->p_offset);
+            memcpy((void *)phdr->p_vaddr, tmp_ptr, phdr->p_filesz);
+        }
+    }
+
+    auxv->at_entry = hdr->e_entry;
+    auxv->at_phent = hdr->e_phentsize;
+    auxv->at_phnum = hdr->e_phnum;
+    return 0;
+}