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[comboot] Allow for tail recursion of COMBOOT images

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Multi-level menus via COMBOOT rely on the COMBOOT program being able
to exit and invoke a new COMBOOT program (the next menu).  This works,
but rapidly (within about five iterations) runs out of space in gPXE's
internal stack, since each new image is executed in a new function
context.

Fix by allowing tail recursion between images; an image can now
specify a replacement image for itself, and image_exec() will perform
the necessary tail recursion.
This commit is contained in:
Michael Brown
2009-02-17 00:47:35 +00:00
parent 349868b8fd
commit 8904cd55f1
8 changed files with 178 additions and 113 deletions
Download Patch File Download Diff File Expand all files Collapse all files

40
src/arch/i386/image/com32.c
View File

@@ -70,20 +70,20 @@ static int com32_exec ( struct image *image ) {
}
DBGC ( image, "COM32 %p: available memory top = 0x%x\n",
image, (int)avail_mem_top );
image, avail_mem_top );
assert ( avail_mem_top != 0 );
com32_external_esp = phys_to_virt ( avail_mem_top );
/* Hook COMBOOT API interrupts */
hook_comboot_interrupts( );
hook_comboot_interrupts();
/* Temporarily de-register image, so that a "boot" command
* doesn't throw us into an execution loop. Hold a reference
* to avoid the image's being freed.
/* Unregister image, so that a "boot" command doesn't
* throw us into an execution loop. We never
* reregister ourselves; COMBOOT images expect to be
* removed on exit.
*/
image_get ( image );
unregister_image ( image );
__asm__ __volatile__ (
@@ -111,25 +111,31 @@ static int com32_exec ( struct image *image ) {
/* %6 */ "r" ( COM32_START_PHYS )
:
"memory" );
DBGC ( image, "COM32 %p: returned\n", image );
break;
case COMBOOT_RETURN_RUN_KERNEL:
DBGC ( image, "COM32 %p: returned to run kernel...\n", image );
comboot_run_kernel ( );
case COMBOOT_EXIT:
DBGC ( image, "COM32 %p: exited\n", image );
break;
case COMBOOT_RETURN_EXIT:
case COMBOOT_EXIT_RUN_KERNEL:
DBGC ( image, "COM32 %p: exited to run kernel %p\n",
image, comboot_replacement_image );
image->replacement = comboot_replacement_image;
image_autoload ( image->replacement );
break;
case COMBOOT_EXIT_COMMAND:
DBGC ( image, "COM32 %p: exited after executing command\n",
image );
break;
default:
assert ( 0 );
break;
}
comboot_force_text_mode ( );
DBGC ( image, "COM32 %p returned\n", image );
/* Re-register image and return */
register_image ( image );
image_put ( image );
comboot_force_text_mode();
return 0;
}

40
src/arch/i386/image/comboot.c
View File

@@ -142,16 +142,16 @@ static int comboot_exec ( struct image *image ) {
comboot_init_psp ( image, seg_userptr );
/* Hook COMBOOT API interrupts */
hook_comboot_interrupts ( );
hook_comboot_interrupts();
DBGC ( image, "executing 16-bit COMBOOT image at %4x:0100\n",
COMBOOT_PSP_SEG );
COMBOOT_PSP_SEG );
/* Temporarily de-register image, so that a "boot" command
* doesn't throw us into an execution loop. Hold a reference
* to avoid the image's being freed.
/* Unregister image, so that a "boot" command doesn't
* throw us into an execution loop. We never
* reregister ourselves; COMBOOT images expect to be
* removed on exit.
*/
image_get ( image );
unregister_image ( image );
/* Store stack segment at 0x38 and stack pointer at 0x3A
@@ -180,26 +180,32 @@ static int comboot_exec ( struct image *image ) {
"xorw %%bp, %%bp\n\t"
"lret\n\t" )
: : "r" ( COMBOOT_PSP_SEG ) : "eax" );
DBGC ( image, "COMBOOT %p: returned\n", image );
break;
case COMBOOT_RETURN_RUN_KERNEL:
DBGC ( image, "COMBOOT %p: returned to run kernel...\n", image );
comboot_run_kernel ( );
case COMBOOT_EXIT:
DBGC ( image, "COMBOOT %p: exited\n", image );
break;
case COMBOOT_RETURN_EXIT:
case COMBOOT_EXIT_RUN_KERNEL:
DBGC ( image, "COMBOOT %p: exited to run kernel %p\n",
image, comboot_replacement_image );
image->replacement = comboot_replacement_image;
image_autoload ( image->replacement );
break;
case COMBOOT_EXIT_COMMAND:
DBGC ( image, "COMBOOT %p: exited after executing command\n",
image );
break;
default:
assert ( 0 );
break;
}
comboot_force_text_mode ( );
comboot_force_text_mode();
DBGC ( image, "COMBOOT %p returned\n", image );
/* Re-register image and return */
register_image ( image );
image_put ( image );
return 0;
}