1 files changed, 162 insertions, 0 deletions
diff --git a/roms/openbios/arch/x86/context.c b/roms/openbios/arch/x86/context.c
new file mode 100644
index 000000000..5ed387542
--- /dev/null
+++ b/roms/openbios/arch/x86/context.c
@@ -0,0 +1,162 @@
+/* tag: x86  context switching
+ *
+ * 2003-10 by SONE Takeshi
+ *
+ * See the file "COPYING" for further information about
+ * the copyright and warranty status of this work.
+ */
+
+#include "config.h"
+#include "kernel/kernel.h"
+#include "segment.h"
+#include "context.h"
+#include "libopenbios/bindings.h"
+#include "libopenbios/initprogram.h"
+#include "libopenbios/sys_info.h"
+#include "boot.h"
+#include "openbios.h"
+
+#define MAIN_STACK_SIZE 16384
+#define IMAGE_STACK_SIZE 4096
+
+#define debug printk
+
+static void start_main(void); /* forward decl. */
+void __exit_context(void); /* assembly routine */
+
+/*
+ * Main context structure
+ * It is placed at the bottom of our stack, and loaded by assembly routine
+ * to start us up.
+ */
+static struct context main_ctx __attribute__((section (".initctx"))) = {
+    .gdt_base = (uint32_t) gdt,
+    .gdt_limit = GDT_LIMIT,
+    .cs = FLAT_CS,
+    .ds = FLAT_DS,
+    .es = FLAT_DS,
+    .fs = FLAT_DS,
+    .gs = FLAT_DS,
+    .ss = FLAT_DS,
+    .esp = (uint32_t) ESP_LOC(&main_ctx),
+    .eip = (uint32_t) start_main,
+    .return_addr = (uint32_t) __exit_context,
+};
+
+/* This is used by assembly routine to load/store the context which
+ * it is to switch/switched.  */
+struct context * volatile __context = &main_ctx;
+
+/* Client program context */
+static struct context *client_ctx;
+
+/* Stack for loaded ELF image */
+static uint8_t image_stack[IMAGE_STACK_SIZE];
+
+/* Pointer to startup context (physical address) */
+unsigned long __boot_ctx;
+
+/*
+ * Main starter
+ * This is the C function that runs first.
+ */
+static void start_main(void)
+{
+    int retval;
+
+    /* Save startup context, so we can refer to it later.
+     * We have to keep it in physical address since we will relocate. */
+    __boot_ctx = virt_to_phys(__context);
+
+    init_exceptions();
+
+    /* Set up client context */
+    client_ctx = init_context(image_stack, sizeof image_stack, 1);
+    __context = client_ctx;
+
+    /* Start the real fun */
+    retval = openbios();
+
+    /* Pass return value to startup context. Bootloader may see it. */
+    boot_ctx->eax = retval;
+
+    /* Returning from here should jump to __exit_context */
+    __context = boot_ctx;
+}
+
+/* Setup a new context using the given stack.
+ */
+struct context *
+init_context(uint8_t *stack, uint32_t stack_size, int num_params)
+{
+    struct context *ctx;
+
+    ctx = (struct context *)
+	(stack + stack_size - (sizeof(*ctx) + num_params*sizeof(uint32_t)));
+    memset(ctx, 0, sizeof(*ctx));
+
+    return ctx;
+}
+
+/* init-program */
+int
+arch_init_program(void)
+{
+    struct context volatile *ctx = __context;
+    ucell type, entry, param;
+    
+    /* Fill in reasonable default for flat memory model */
+    ctx->gdt_base = virt_to_phys(gdt);
+    ctx->gdt_limit = GDT_LIMIT;
+    ctx->cs = FLAT_CS;
+    ctx->ds = FLAT_DS;
+    ctx->es = FLAT_DS;
+    ctx->fs = FLAT_DS;
+    ctx->gs = FLAT_DS;
+    ctx->ss = FLAT_DS;
+    ctx->esp = virt_to_phys(ESP_LOC(ctx));
+    ctx->return_addr = virt_to_phys(__exit_context);
+    
+    /* Set param */
+    feval("load-state >ls.param @");
+    param = POP();
+    ctx->param[0] = param;
+
+    /* Only elf-boot type has a param */
+    feval("load-state >ls.file-type @");
+    type = POP();
+    if (type == 0) {
+        ctx->eax = 0xe1fb007;
+        ctx->ebx = param;
+    }
+
+    /* Set entry point */
+    feval("load-state >ls.entry @");
+    entry = POP();
+    ctx->eip = entry;
+
+    return 0;
+}
+
+/* Switch to another context. */
+struct context *switch_to(struct context *ctx)
+{
+    struct context *save, *ret;
+
+    debug("switching to new context:\n");
+    save = __context;
+    __context = ctx;
+    asm ("pushl %cs; call __switch_context");
+    ret = __context;
+    __context = save;
+    return ret;
+}
+
+/* Start ELF Boot image */
+unsigned int start_elf(void)
+{
+    volatile struct context *ctx = __context;
+
+    ctx = switch_to((struct context *)ctx);
+    return ctx->eax;
+}