156 lines
3.6 KiB
C
156 lines
3.6 KiB
C
/*
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* context switching
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* 2003-10 by SONE Takeshi
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*/
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#include "config.h"
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#include "kernel/kernel.h"
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#include "libopenbios/bindings.h"
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#include "libopenbios/initprogram.h"
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#include "segment.h"
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#include "context.h"
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#define MAIN_STACK_SIZE 16384
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#define IMAGE_STACK_SIZE 4096
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#define debug printk
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static void start_main(void); /* forward decl. */
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void __exit_context(void); /* assembly routine */
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/*
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* Main context structure
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* It is placed at the bottom of our stack, and loaded by assembly routine
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* to start us up.
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*/
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struct context main_ctx __attribute__((section (".initctx"))) = {
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.gdt_base = (uint64_t) gdt,
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.gdt_limit = GDT_LIMIT,
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.cs = FLAT_CS,
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.ds = FLAT_DS,
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.es = FLAT_DS,
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.fs = FLAT_DS,
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.gs = FLAT_DS,
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.ss = FLAT_DS,
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.esp = (uint32_t) ESP_LOC(&main_ctx),
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.eip = (uint32_t) start_main,
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.return_addr = (uint32_t) __exit_context,
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};
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/* This is used by assembly routine to load/store the context which
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* it is to switch/switched. */
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struct context *__context = &main_ctx;
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/* Client program context */
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static struct context *client_ctx;
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/* Stack for loaded ELF image */
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static uint8_t image_stack[IMAGE_STACK_SIZE];
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/* Pointer to startup context (physical address) */
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unsigned long __boot_ctx;
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/*
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* Main starter
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* This is the C function that runs first.
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*/
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static void start_main(void)
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{
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int retval;
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extern int openbios(void);
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/* Save startup context, so we can refer to it later.
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* We have to keep it in physical address since we will relocate. */
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__boot_ctx = virt_to_phys(__context);
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/* Set up client context */
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client_ctx = init_context(image_stack, sizeof image_stack, 1);
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__context = client_ctx;
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/* Start the real fun */
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retval = openbios();
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/* Pass return value to startup context. Bootloader may see it. */
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boot_ctx->eax = retval;
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/* Returning from here should jump to __exit_context */
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__context = boot_ctx;
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}
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/* Setup a new context using the given stack.
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*/
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struct context *
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init_context(uint8_t *stack, uint32_t stack_size, int num_params)
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{
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struct context *ctx;
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ctx = (struct context *)
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(stack + stack_size - (sizeof(*ctx) + num_params*sizeof(uint32_t)));
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memset(ctx, 0, sizeof(*ctx));
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return ctx;
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}
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/* init-program */
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int
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arch_init_program(void)
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{
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struct context volatile *ctx = __context;
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ucell type, entry, param;
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/* Fill in reasonable default for flat memory model */
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ctx->gdt_base = virt_to_phys(gdt);
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ctx->gdt_limit = GDT_LIMIT;
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ctx->cs = FLAT_CS;
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ctx->ds = FLAT_DS;
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ctx->es = FLAT_DS;
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ctx->fs = FLAT_DS;
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ctx->gs = FLAT_DS;
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ctx->ss = FLAT_DS;
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ctx->esp = virt_to_phys(ESP_LOC(ctx));
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ctx->return_addr = virt_to_phys(__exit_context);
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/* Set param */
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feval("load-state >ls.param @");
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param = POP();
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ctx->param[0] = param;
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/* Only elf-boot type has a param */
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feval("load-state >ls.file-type @");
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type = POP();
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if (type == 0) {
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ctx->eax = 0xe1fb007;
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ctx->ebx = param;
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}
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/* Set entry point */
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feval("load-state >ls.entry @");
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entry = POP();
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ctx->eip = entry;
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return 0;
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}
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/* Switch to another context. */
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struct context *switch_to(struct context *ctx)
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{
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volatile struct context *save;
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struct context *ret;
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debug("switching to new context:\n");
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save = __context;
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__context = ctx;
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asm ("pushl %cs; call __switch_context");
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ret = __context;
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__context = (struct context *)save;
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return ret;
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}
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/* Start ELF image */
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unsigned int start_elf(void)
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{
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volatile struct context *ctx = __context;
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ctx = switch_to((struct context *)ctx);
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return ctx->eax;
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}
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