os: boot: Add boot variable information

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

2 files changed, 252 insertions, 0 deletions

diff --git a/src/sys/include/sys/bootvars.h b/src/sys/include/sys/bootvars.h
new file mode 100644
index 0000000..d2f0cf6
--- /dev/null
+++ b/src/sys/include/sys/bootvars.h
@@ -0,0 +1,87 @@
+/*
+ * 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 _SYS_BOOTVARS_H_
+#define _SYS_BOOTVARS_H_  1
+
+#include <sys/types.h>
+#include <sys/param.h>
+
+#define BOOTVARS_MAGIC 0xDECAFE
+
+/* Flags for bootvars_read() */
+#define BV_BYPASS_CACHE BIT(0)   /* Don't read cached entries */
+
+/*
+ * Framebuffer information
+ *
+ * @io: MMIO address for pixel plotting
+ * @width: Framebuffer width
+ * @height: Framebuffer height
+ * @pitch: Framebuffer pitch
+ * @bpp: Bytes per pixel
+ */
+struct bootvar_fb {
+    uint32_t *io;
+    uint32_t width;
+    uint32_t height;
+    uint32_t pitch;
+    uint32_t bpp;
+};
+
+/*
+ * Various callbacks that are related in one
+ * way or another to the features of the bootloader.
+ */
+struct bootvar_io {
+    char *(*get_module)(const char *path, uint64_t *size);
+};
+
+/*
+ * Boot variables given to us by the bootloader
+ *
+ * @magic: Magic number (see BOOTVARS_MAGIC)
+ * @fbvars: Framebuffer information
+ * @iovars: I/O callbacks
+ * @rsdp: ACPI Root System Descriptor Pointer [vaddr]
+ */
+struct bootvars {
+    uint32_t magic;
+    struct bootvar_fb fbvars;
+    struct bootvar_io iovars;
+    void *rsdp;
+};
+
+#if defined(_KERNEL)
+
+off_t get_kernel_base(void);
+int bootvars_read(struct bootvars *bvp, int flags);
+
+#endif  /* _KERNEL */
+#endif  /* !_SYS_BOOTVARS_H_ */
diff --git a/src/sys/os/os_bootvars.c b/src/sys/os/os_bootvars.c
new file mode 100644
index 0000000..a72ccf4
--- /dev/null
+++ b/src/sys/os/os_bootvars.c
@@ -0,0 +1,165 @@
+/*
+ * Copyright (c) 2025 Ian Marco Moffett and Ethos0 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/bootvars.h>
+#include <sys/cdefs.h>
+#include <sys/errno.h>
+#include <sys/types.h>
+#include <sys/panic.h>
+#include <vm/vm.h>
+#include <limine.h>
+#include <string.h>
+#include <stdbool.h>
+
+#define FRAMEBUFFER framebuffer_req.response->framebuffers[0]
+
+static off_t __hhdm_offset = 0;
+static volatile struct limine_hhdm_request hhdm_req = {
+    .id = LIMINE_HHDM_REQUEST,
+    .revision = 0
+};
+
+/* Request from bootloader */
+static volatile struct limine_framebuffer_request framebuffer_req = {
+    .id = LIMINE_FRAMEBUFFER_REQUEST,
+    .revision = 0
+};
+
+static volatile struct limine_module_request mod_req = {
+    .id = LIMINE_MODULE_REQUEST,
+    .revision = 0
+};
+
+static volatile struct limine_rsdp_request rsdp_req = {
+    .id = LIMINE_RSDP_REQUEST,
+    .revision = 0
+};
+
+/*
+ * Get a module from the bootloader, this can be used for
+ * things like configuration or initramfs.
+ *
+ * @path: Path to lookup
+ * @size: Size of found data written here
+ */
+static char *
+get_module(const char *path, uint64_t *size) {
+    for (uint64_t i = 0; i < mod_req.response->module_count; ++i) {
+        if (strcmp(mod_req.response->modules[i]->path, path) == 0) {
+            *size = mod_req.response->modules[i]->size;
+            return mod_req.response->modules[i]->address;
+        }
+    }
+
+    return NULL;
+}
+
+static void
+read_fbvars(struct bootvar_fb *fbvars)
+{
+    fbvars->io = FRAMEBUFFER->address;
+    fbvars->width = FRAMEBUFFER->width;
+    fbvars->height = FRAMEBUFFER->height;
+    fbvars->pitch = FRAMEBUFFER->pitch;
+    fbvars->bpp = FRAMEBUFFER->bpp;
+}
+
+static void
+read_iovars(struct bootvar_io *iovp)
+{
+    iovp->get_module = get_module;
+}
+
+/*
+ * Return the kernel base offset which is used to convert
+ * certain lower half physical addresses to higher half
+ * physical addresses.
+ */
+off_t
+get_kernel_base(void)
+{
+    static struct limine_hhdm_response *hhdm_resp = NULL;
+
+    if (hhdm_resp == NULL) {
+        if ((hhdm_resp = hhdm_req.response) == NULL) {
+            panic("bootvars: could not get HHDM\n");
+        }
+    }
+
+    if (__hhdm_offset == 0) {
+        __hhdm_offset = hhdm_resp->offset;
+    }
+
+    return __hhdm_offset;
+}
+
+/*
+ * Read bootvars given to us on boot that we will
+ * use to set up the system.
+ *
+ * @bvp: Bootvars result
+ * @flags: Optional flags (see BV_*)
+ *
+ * XXX: BV_BYPASS_CACHE calls are still cached however entries are
+ *      guaranteed to not be stale.
+ */
+int
+bootvars_read(struct bootvars *bvp, int flags)
+{
+    static struct bootvars cache;
+    static short cached = false;
+    struct limine_rsdp_response *rsdp_resp;
+
+    if (bvp == NULL) {
+        return -EINVAL;
+    }
+
+    /*
+     * If BV_BYPASS_CACHE is not set and we have a cache
+     * entry, use it.
+     */
+    if (cached && !ISSET(flags, BV_BYPASS_CACHE)) {
+        *bvp = cache;
+        return 0;
+    }
+
+    cache.magic = BOOTVARS_MAGIC;
+    read_fbvars(&cache.fbvars);
+    read_iovars(&cache.iovars);
+
+    /* We need this for proper operation */
+    if ((rsdp_resp = rsdp_req.response) == NULL) {
+        panic("bootvars: could not get ACPI RSDP\n");
+    }
+
+    cache.rsdp = rsdp_resp->address;
+    cached = true;
+    *bvp = cache;
+    return 0;
+}