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Annotation of qemu/roms/openbios/arch/amd64/context.c, revision 1.1.1.1

1.1       root        1: /*
                      2:  * context switching
                      3:  * 2003-10 by SONE Takeshi
                      4:  */
                      5: 
                      6: #include "config.h"
                      7: #include "kernel/kernel.h"
                      8: #include "segment.h"
                      9: #include "context.h"
                     10: 
                     11: #define MAIN_STACK_SIZE 16384
                     12: #define IMAGE_STACK_SIZE 4096
                     13: 
                     14: #define debug printk
                     15: 
                     16: static void start_main(void); /* forward decl. */
                     17: void __exit_context(void); /* assembly routine */
                     18: 
                     19: /*
                     20:  * Main context structure
                     21:  * It is placed at the bottom of our stack, and loaded by assembly routine
                     22:  * to start us up.
                     23:  */
                     24: struct context main_ctx __attribute__((section (".initctx"))) = {
                     25:     .gdt_base = (uint64_t) gdt,
                     26:     .gdt_limit = GDT_LIMIT,
                     27:     .cs = FLAT_CS,
                     28:     .ds = FLAT_DS,
                     29:     .es = FLAT_DS,
                     30:     .fs = FLAT_DS,
                     31:     .gs = FLAT_DS,
                     32:     .ss = FLAT_DS,
                     33:     .esp = (uint32_t) ESP_LOC(&main_ctx),
                     34:     .eip = (uint32_t) start_main,
                     35:     .return_addr = (uint32_t) __exit_context,
                     36: };
                     37: 
                     38: /* This is used by assembly routine to load/store the context which
                     39:  * it is to switch/switched.  */
                     40: struct context *__context = &main_ctx;
                     41: 
                     42: /* Stack for loaded ELF image */
                     43: static uint8_t image_stack[IMAGE_STACK_SIZE];
                     44: 
                     45: /* Pointer to startup context (physical address) */
                     46: unsigned long __boot_ctx;
                     47: 
                     48: /*
                     49:  * Main starter
                     50:  * This is the C function that runs first.
                     51:  */
                     52: static void start_main(void)
                     53: {
                     54:     int retval;
                     55:     extern int openbios(void);
                     56: 
                     57:     /* Save startup context, so we can refer to it later.
                     58:      * We have to keep it in physical address since we will relocate. */
                     59:     __boot_ctx = virt_to_phys(__context);
                     60: 
                     61:     /* Start the real fun */
                     62:     retval = openbios();
                     63: 
                     64:     /* Pass return value to startup context. Bootloader may see it. */
                     65:     boot_ctx->eax = retval;
                     66: 
                     67:     /* Returning from here should jump to __exit_context */
                     68:     __context = boot_ctx;
                     69: }
                     70: 
                     71: /* Setup a new context using the given stack.
                     72:  */
                     73: struct context *
                     74: init_context(uint8_t *stack, uint32_t stack_size, int num_params)
                     75: {
                     76:     struct context *ctx;
                     77: 
                     78:     ctx = (struct context *)
                     79:        (stack + stack_size - (sizeof(*ctx) + num_params*sizeof(uint32_t)));
                     80:     memset(ctx, 0, sizeof(*ctx));
                     81: 
                     82:     /* Fill in reasonable default for flat memory model */
                     83:     ctx->gdt_base = virt_to_phys(gdt);
                     84:     ctx->gdt_limit = GDT_LIMIT;
                     85:     ctx->cs = FLAT_CS;
                     86:     ctx->ds = FLAT_DS;
                     87:     ctx->es = FLAT_DS;
                     88:     ctx->fs = FLAT_DS;
                     89:     ctx->gs = FLAT_DS;
                     90:     ctx->ss = FLAT_DS;
                     91:     ctx->esp = virt_to_phys(ESP_LOC(ctx));
                     92:     ctx->return_addr = virt_to_phys(__exit_context);
                     93: 
                     94:     return ctx;
                     95: }
                     96: 
                     97: /* Switch to another context. */
                     98: struct context *switch_to(struct context *ctx)
                     99: {
                    100:     struct context *save, *ret;
                    101: 
                    102:     debug("switching to new context:\n");
                    103:     save = __context;
                    104:     __context = ctx;
                    105:     asm ("pushl %cs; call __switch_context");
                    106:     ret = __context;
                    107:     __context = save;
                    108:     return ret;
                    109: }
                    110: 
                    111: /* Start ELF Boot image */
                    112: uint32_t start_elf(uint32_t entry_point, uint32_t param)
                    113: {
                    114:     struct context *ctx;
                    115: 
                    116:     ctx = init_context(image_stack, sizeof image_stack, 1);
                    117:     ctx->eip = entry_point;
                    118:     ctx->param[0] = param;
                    119:     ctx->eax = 0xe1fb007;
                    120:     ctx->ebx = param;
                    121: 
                    122:     ctx = switch_to(ctx);
                    123:     return ctx->eax;
                    124: }

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