====== Differences ====== This shows you the differences between two versions of the page.
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soc:2008:dverkamp:notes:start [2008/05/19 16:40] mdc |
soc:2008:dverkamp:notes:start [2008/05/20 08:15] (current) drv |
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| ===== Notes ===== | ===== Notes ===== | ||
| + | |||
| + | ==== COMBOOT ==== | ||
| + | |||
| + | * http://syslinux.zytor.com/wiki/index.php/Comboot_API | ||
| + | * What should happen if/when a COMBOOT executable returns? Do any other image types ever return? | ||
| + | |||
| + | === Basic COMBOOT execution sequence === | ||
| + | |||
| + | * Detect image type (.com/.cbt -> 16-bit COMBOOT; .c32 or magic number B8 FF 4C CD 21 -> COM32) - case-insensitive filenames? | ||
| + | |||
| + | == 16-bit COMBOOT == | ||
| + | |||
| + | - Copy image to offset 0x100 of some segment | ||
| + | - Set up PSP in same segment | ||
| + | - Set up IDT entries to point at COMBOOT API implementation (stubs in lowmem to call actual protected-mode implementation?) | ||
| + | - Change to real mode | ||
| + | - Set segment registers CS = DS = ES = SS to segment containing PSP and code | ||
| + | - Set SP to 0xfffe (end of 64k segment) | ||
| + | - Near call 0x100 (start executing) | ||
| + | |||
| + | == COM32 == | ||
| + | |||
| + | - Copy image to virtual address 0x101000 | ||
| + | - Set DS = ES = SS to the same base as CS (flat address space) | ||
| + | - Set FS = GS = 0 | ||
| + | - Set ESP to end of available memory | ||
| + | - Allocate bounce buffer in lowmem | ||
| + | - Push args onto stack (helper functions, bounce buffer, other args from user) | ||
| + | - Call entry point | ||
| ==== Development and Testing Environment ==== | ==== Development and Testing Environment ==== | ||
