1 files changed, 125 insertions, 0 deletions
diff --git a/src/filo/i386/context.c b/src/filo/i386/context.c
new file mode 100644
index 0000000..54a15e3
--- /dev/null
+++ b/src/filo/i386/context.c
@@ -0,0 +1,125 @@
+/*
+ * context switching
+ * 2003-10 by SONE Takeshi
+ */
+#include <etherboot.h>
+
+#include "segment.h"
+#include "context.h"
+
+#define MAIN_STACK_SIZE 16384
+#define IMAGE_STACK_SIZE 4096
+
+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.
+ */
+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 *__context = &main_ctx;
+
+#if 0
+/* Stack for loaded ELF image */
+static uint8_t image_stack[IMAGE_STACK_SIZE];
+#endif
+
+/* 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;
+    extern int filo(void);
+
+    /* 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);
+
+    /* Start the real fun */
+    retval = filo();
+
+    /* 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));
+
+    /* 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);
+
+    return ctx;
+}
+
+/* Switch to another context. */
+struct context *switch_to(struct context *ctx)
+{
+    struct context *save, *ret;
+
+    save = __context;
+    __context = ctx;
+    asm ("pushl %cs; call __switch_context");
+    ret = __context;
+    __context = save;
+    return ret;
+}
+
+#if 0
+//We will use elf_start in Etherboot
+/* Start ELF Boot image */
+uint32_t start_elf(uint32_t entry_point, uint32_t param)
+{
+    struct context *ctx;
+
+    ctx = init_context(image_stack, sizeof image_stack, 1);
+    ctx->eip = entry_point;
+    ctx->param[0] = param;
+    ctx->eax = 0xe1fb007;
+    ctx->ebx = param;
+
+    ctx = switch_to(ctx);
+    return ctx->eax;
+}
+#endif