kern: os: Introduce support for OMAR initramfs

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

1 files changed, 205 insertions, 0 deletions

diff --git a/src/sys/os/os_omar.c b/src/sys/os/os_omar.c
new file mode 100644
index 0000000..63493b0
--- /dev/null
+++ b/src/sys/os/os_omar.c
@@ -0,0 +1,205 @@
+/*
+ * 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/types.h>
+#include <sys/errno.h>
+#include <sys/bootvars.h>
+#include <sys/cdefs.h>
+#include <sys/panic.h>
+#include <sys/syslog.h>
+#include <os/omar.h>
+#include <string.h>
+#include <stdbool.h>
+
+#define INITRD_PATH "/boot/initrd.omar"
+
+#define OMAR_EOF "RAMO"
+#define OMAR_REG    0
+#define OMAR_DIR    1
+#define BLOCK_SIZE 512
+
+static const char *__initrd_root = NULL;
+static size_t initrd_size = 0;
+
+/*
+ * File or directory.
+ */
+struct initrd_node {
+    const char *path;       /* Path */
+    void *data;             /* File data */
+    size_t size;            /* File size */
+    mode_t mode;            /* Perms and type */
+};
+
+/*
+ * The OMAR file header, describes the basics
+ * of a file.
+ *
+ * @magic: Header magic ("OMAR")
+ * @len: Length of the file
+ * @namelen: Length of the filename
+ * @rev: OMAR revision
+ * @mode: File permissions
+ */
+struct __packed omar_hdr {
+    char magic[4];
+    uint8_t type;
+    uint8_t namelen;
+    uint32_t len;
+    uint8_t rev;
+    uint32_t mode;
+};
+
+/*
+ * Get a file from initrd
+ *
+ * @path: Path of file to get.
+ * @res: Pointer to new resulting node.
+ */
+static int
+initrd_get_file(const char *path, struct initrd_node *res)
+{
+    struct initrd_node node;
+    const struct omar_hdr *hdr;
+    const char *p, *name;
+    char namebuf[256];
+    off_t off;
+
+    p = __initrd_root;
+    for (;;) {
+        hdr = (struct omar_hdr *)p;
+        if (strncmp(hdr->magic, OMAR_EOF, sizeof(OMAR_EOF)) == 0) {
+            break;
+        }
+
+        /* Ensure the file is valid */
+        if (strncmp(hdr->magic, "OMAR", 4) != 0) {
+            /* Bad magic */
+            return -EINVAL;
+        }
+        if (hdr->namelen > sizeof(namebuf) - 1) {
+            return -EINVAL;
+        }
+
+        name = (char *)p + sizeof(struct omar_hdr);
+        memcpy(namebuf, name, hdr->namelen);
+        namebuf[hdr->namelen] = '\0';
+
+        /* Compute offset to next block */
+        if (hdr->type == OMAR_DIR) {
+            off = 512;
+        } else {
+            off = ALIGN_UP(sizeof(*hdr) + hdr->namelen + hdr->len, BLOCK_SIZE);
+        }
+
+        /* Skip header and name, right to the data */
+        p = (char *)hdr + sizeof(struct omar_hdr);
+        p += hdr->namelen;
+
+        if (strcmp(namebuf, path) == 0) {
+            node.mode = hdr->mode;
+            node.size = hdr->len;
+            node.data = (void *)p;
+            *res = node;
+            return 0;
+        }
+
+        hdr = (struct omar_hdr *)((char *)hdr + off);
+        p = (char *)hdr;
+        memset(namebuf, 0, sizeof(namebuf));
+    }
+
+    return -ENOENT;
+}
+
+/*
+ * Initialize the initrd
+ */
+static int
+initrd_init(void)
+{
+    struct bootvars bootvars;
+    struct bootvar_io *bvio = NULL;
+    int error;
+
+    if (__initrd_root != NULL) {
+        panic("initrd: cannot re-init initrd\n");
+    }
+
+    error = bootvars_read(&bootvars, 0);
+    if (error < 0) {
+        return error;
+    }
+
+    bvio = &bootvars.iovars;
+    __initrd_root = bvio->get_module(INITRD_PATH, &initrd_size);
+    if (__initrd_root == NULL) {
+        panic("initrd: could not find '%s'\n", INITRD_PATH);
+    }
+
+    return 0;
+}
+
+/*
+ * Open an entry within the OMAR initrd
+ * image.
+ */
+ssize_t
+initrd_open(const char *path, char **res)
+{
+    struct initrd_node node;
+    int error = 0;
+
+    if (path == NULL || res == NULL) {
+        return -EINVAL;
+    }
+
+    /* Path must start with a '/' */
+    if (*path++ != '/') {
+        printf("initrd: bad path '%s'\n", path);
+        return -ENOENT;
+    }
+
+    if (__initrd_root == NULL) {
+        error = initrd_init();
+        if (error < 0) {
+            panic("initrd: failed to setup initrd\n");
+        }
+    }
+
+    error = initrd_get_file(path, &node);
+    if (error < 0) {
+        printf("initrd: failed to open '%s'\n", path);
+        return error;
+    }
+
+    *res = node.data;
+    return node.size;
+}