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https://gitlab.com/qemu-project/openbios.git
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e9c1365d32
The existing 8K stack used when switching context to run the executable payload was not enough. Increasing the stack to 16K solves the issue, preventing the payload from clobbering memory within OpenBIOS as it runs. Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@siriusit.co.uk> git-svn-id: svn://coreboot.org/openbios/trunk/openbios-devel@873 f158a5a8-5612-0410-a976-696ce0be7e32
135 lines
3.3 KiB
C
135 lines
3.3 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 "context.h"
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#include "libopenbios/sys_info.h"
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#include "boot.h"
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#include "openbios.h"
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#define MAIN_STACK_SIZE 16384
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#define IMAGE_STACK_SIZE 4096*4
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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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static struct context main_ctx = {
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.regs[REG_SP] = (uint64_t) &_estack - STACK_BIAS - 96,
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.pc = (uint64_t) start_main,
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.npc = (uint64_t) start_main + 4,
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.return_addr = (uint64_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 * volatile __context = &main_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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/* 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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/* 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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static uint64_t ALIGN_SIZE(uint64_t x, uint64_t a)
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{
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return (x + a - 1) & ~(a-1);
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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, uint64_t stack_size, int num_params)
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{
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struct context *ctx;
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uint8_t *stack_top = stack + stack_size;
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ctx = (struct context *)
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(stack_top - ALIGN_SIZE(sizeof(*ctx) + num_params*sizeof(uint64_t), sizeof(uint64_t)));
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memset(ctx, 0, sizeof(*ctx));
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/* Fill in reasonable default for flat memory model */
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ctx->regs[REG_SP] = virt_to_phys(stack_top - STACK_BIAS - 192);
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ctx->return_addr = virt_to_phys(__exit_context);
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return ctx;
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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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struct context *save, *ret;
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debug("switching to new context: entry point %#llx stack 0x%016llx\n", ctx->pc, ctx->regs[REG_SP]);
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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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asm ("call __switch_context_nosave; nop");
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ret = __context;
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__context = save;
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return ret;
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}
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/* Start ELF Boot image */
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uint64_t start_elf(uint64_t entry_point, uint64_t param)
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{
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struct context *ctx;
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ctx = init_context(image_stack, sizeof image_stack, 1);
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ctx->pc = entry_point;
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ctx->param[0] = param;
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//ctx->eax = 0xe1fb007;
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//ctx->ebx = param;
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ctx = switch_to(ctx);
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//return ctx->eax;
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return 0;
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}
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/* Start client image */
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uint64_t start_client_image(uint64_t entry_point, uint64_t cif_handler)
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{
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struct context *ctx;
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ctx = init_context(image_stack, sizeof image_stack, 0);
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ctx->pc = entry_point;
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ctx->npc = entry_point+4;
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ctx->regs[REG_O0] = 0;
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ctx->regs[REG_O0+4] = cif_handler;
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ctx = switch_to(ctx);
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return 0;
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}
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