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[prefix] Call decompressor in flat real mode when DEBUG=libprefix is enabled 

Allow the decompressor the option of generating debugging output via
the BIOS console by calling it in flat real mode (rather than 16-bit
protected mode) when libprefix.S is built with debugging enabled.

Signed-off-by: Michael Brown <mcb30@ipxe.org>
pull/34/head
Michael Brown 2015-02-26 12:56:07 +00:00
parent 9cdf68a219
commit 93178adb98
1 changed files with 16 additions and 0 deletions
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16
src/arch/i386/prefix/libprefix.S
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@ -394,8 +394,10 @@ process_bytes:
movw %ax, %fs movw %ax, %fs
movw %ax, %gs movw %ax, %gs
#ifdef NDEBUG
/* Call memcpy()-like function */ /* Call memcpy()-like function */
call *%bx call *%bx
#endif
/* Return to (flat) real mode */ /* Return to (flat) real mode */
movl %cr0, %eax movl %cr0, %eax
@ -409,6 +411,20 @@ process_bytes:
popw %fs popw %fs
popw %gs popw %gs
#ifndef NDEBUG
/* Call memcpy()-like function in flat real mode (to allow for
* debug output via INT 10).
*/
pushw %ds
pushw %es
xorw %ax, %ax
movw %ax, %ds
movw %ax, %es
call *%bx
popw %es
popw %ds
#endif
/* Restore GDT */ /* Restore GDT */
data32 lgdt -8(%bp) data32 lgdt -8(%bp)
addw $( 8 /* saved GDT */ + ( PM_DS + 8 ) /* GDT on stack */ ), %sp addw $( 8 /* saved GDT */ + ( PM_DS + 8 ) /* GDT on stack */ ), %sp