kernel: elf: Add ELF64 loader

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

1 files changed, 240 insertions, 0 deletions

diff --git a/sys/kern/exec_elf64.c b/sys/kern/exec_elf64.c
new file mode 100644
index 0000000..568c7c8
--- /dev/null
+++ b/sys/kern/exec_elf64.c
@@ -0,0 +1,240 @@
+/*
+ * 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/elf.h>
+#include <sys/exec.h>
+#include <sys/param.h>
+#include <sys/namei.h>
+#include <sys/vnode.h>
+#include <sys/errno.h>
+#include <vm/pmap.h>
+#include <vm/physmem.h>
+#include <vm/dynalloc.h>
+#include <vm/vm.h>
+#include <vm/map.h>
+#include <string.h>
+#include <machine/pcb.h>
+
+#define PHDR(HDRP, IDX) \
+    (void *)((uintptr_t)HDRP + (HDRP)->e_phoff + (HDRP->e_phentsize * IDX))
+
+struct elf_file {
+    char *data;
+    size_t size;
+};
+
+/*
+ * Load the file and give back an "elf_file"
+ * structure.
+ */
+static int
+elf_get_file(const char *pathname, struct elf_file *res)
+{
+    struct vnode *vp = NULL;
+    struct nameidata nd;
+    struct vattr vattr;
+    struct vop_getattr_args getattr_args;
+    struct sio_txn read_txn;
+    int status = 0;
+
+    nd.path = pathname;
+    nd.flags = 0;
+
+    if (res == NULL)
+        return -EINVAL;
+    if ((status = namei(&nd)) != 0)
+        return status;
+
+    vp = nd.vp;
+
+    getattr_args.res = &vattr;
+    getattr_args.vp = vp;
+    status = vfs_vop_getattr(nd.vp, &getattr_args);
+    if (status != 0)
+        goto done;
+
+    /* Can we use the size field? */
+    if (vattr.size == VNOVAL) {
+        status = -EIO;
+        goto done;
+    }
+
+    res->size = vattr.size;
+    res->data = dynalloc(sizeof(char) * res->size);
+    if (res->data == NULL) {
+        status = -ENOMEM;
+        goto done;
+    }
+
+    /* Read data into our buffer */
+    read_txn.buf = res->data;
+    read_txn.len = res->size;
+    read_txn.offset = 0;
+    vfs_vop_read(vp, &read_txn);
+
+done:
+    if (vp != NULL) {
+        vfs_release_vnode(nd.vp);
+    }
+    return status;
+}
+
+/*
+ * Verify the validity of the ELF header.
+ * Returns 0 on success.
+ */
+static int
+elf64_verify(Elf64_Ehdr *hdr)
+{
+    const char *mag = &hdr->e_ident[EI_MAG0];
+
+    if (memcmp(mag, ELFMAG, SELFMAG) != 0) {
+        /* Bad magic */
+        return -ENOEXEC;
+    }
+
+    if (hdr->e_ident[EI_OSABI] != ELFOSABI_SYSV) {
+        /* ABI used is not System V */
+        return -ENOEXEC;
+    }
+
+    if (hdr->e_ident[EI_DATA] != ELFDATA2LSB) {
+        /* Not little-endian */
+        return -ENOEXEC;
+    }
+
+    if (hdr->e_ident[EI_CLASS] != ELFCLASS64) {
+        /* Not 64-bits */
+        return -ENOEXEC;
+    }
+
+    if (hdr->e_type != ET_EXEC) {
+        /* Not executable */
+        return -ENOEXEC;
+    }
+
+    if (hdr->e_phnum > MAX_PHDRS) {
+        /* Too many program headers */
+        return -ENOEXEC;
+    }
+
+    return 0;
+}
+
+void
+elf_unload(struct proc *td, struct exec_prog *prog)
+{
+    size_t map_len;
+    struct pcb *pcbp = &td->pcb;
+    struct auxval auxval = prog->auxval;
+    struct exec_range *loadmap = prog->loadmap;
+
+    for (size_t i = 0; i < auxval.at_phnum; ++i) {
+        map_len = (loadmap[i].end - loadmap[i].start);
+        vm_unmap(pcbp->addrsp, loadmap[i].start, map_len);
+        vm_free_frame(loadmap[i].start, map_len / DEFAULT_PAGESIZE);
+    }
+}
+
+int
+elf64_load(const char *pathname, struct proc *td, struct exec_prog *prog)
+{
+    vm_prot_t prot = (PROT_READ | PROT_USER);
+    Elf64_Ehdr *hdr;
+    Elf64_Phdr *phdr;
+    paddr_t physmem;
+    off_t misalign;
+    void *tmp;
+    size_t page_count, map_len;
+    struct elf_file file;
+    struct pcb *pcbp;
+    struct exec_range loadmap[MAX_PHDRS];
+    struct auxval *auxvalp;
+    int error = 0;
+
+    if ((error = elf_get_file(pathname, &file)) != 0)
+        return error;
+
+    hdr = (Elf64_Ehdr *)file.data;
+    if ((error = elf64_verify(hdr)) != 0)
+        return error;
+
+    pcbp = &td->pcb;
+
+    /* Load program headers */
+    for (size_t i = 0; i < hdr->e_phnum; ++i) {
+        phdr = PHDR(hdr, i);
+        switch (phdr->p_type) {
+        case PT_LOAD:
+            if (ISSET(phdr->p_flags, PF_W))
+                prot |= PROT_WRITE;
+            if (ISSET(phdr->p_flags, PF_X))
+                prot |= PROT_EXEC;
+
+            misalign = phdr->p_vaddr & (DEFAULT_PAGESIZE - 1);
+            map_len = ALIGN_UP(phdr->p_memsz + misalign, DEFAULT_PAGESIZE);
+            page_count = map_len / DEFAULT_PAGESIZE;
+
+            /* Try to allocate page frames */
+            physmem = vm_alloc_frame(page_count);
+            if (physmem == 0) {
+                error = -ENOMEM;
+                break;
+            }
+
+            error = vm_map(pcbp->addrsp, phdr->p_vaddr, physmem,
+                prot, map_len);
+
+            if (error != 0) {
+                break;
+            }
+
+            tmp = (void *)((uintptr_t)hdr + phdr->p_offset);
+            memcpy(PHYS_TO_VIRT(physmem), tmp, phdr->p_filesz);
+
+            loadmap[i].start = physmem;
+            loadmap[i].end = physmem + map_len;
+        }
+    }
+
+    memcpy(prog->loadmap, loadmap, sizeof(loadmap));
+    auxvalp = &prog->auxval;
+    auxvalp->at_entry = hdr->e_entry;
+    auxvalp->at_phent = hdr->e_phentsize;
+    auxvalp->at_phnum = hdr->e_phnum;
+
+    /* Did program header loading fail? */
+    if (error != 0) {
+        elf_unload(td, prog);
+        return error;
+    }
+
+    dynfree(file.data);
+    return 0;
+}