| /* |
| * context switching |
| * 2003-10 by SONE Takeshi |
| */ |
| |
| #include "config.h" |
| #include "kernel/kernel.h" |
| #include "libopenbios/bindings.h" |
| #include "libopenbios/initprogram.h" |
| #include "segment.h" |
| #include "context.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. |
| */ |
| struct context main_ctx __attribute__((section (".initctx"))) = { |
| .gdt_base = (uint64_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; |
| |
| /* 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; |
| extern int openbios(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); |
| |
| /* 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) |
| { |
| volatile struct context *save; |
| struct context *ret; |
| |
| debug("switching to new context:\n"); |
| save = __context; |
| __context = ctx; |
| asm ("pushl %cs; call __switch_context"); |
| ret = __context; |
| __context = (struct context *)save; |
| return ret; |
| } |
| |
| /* Start ELF image */ |
| unsigned int start_elf(void) |
| { |
| volatile struct context *ctx = __context; |
| |
| ctx = switch_to((struct context *)ctx); |
| return ctx->eax; |
| } |