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[pxe] Invoke INT 1a,564e when PXE stack is activated 

Invoke INT 1a,564e whenever a PXE stack is activated, passing the
address of the PXENV+ structure in %es:%bx.  This is designed to allow
a BIOS to be notified when a PXE stack has been installed, providing
an opportunity for start-of-day commands such as setting the MAC
address according to a policy chosen by the BIOS.

PXE defines INT 1a,5650 as a means of locating the PXENV+ structure:
this call returns %ax=0x564e and the address of the PXENV+ structure
in %es:%bx.  We choose INT 1a,564e as a fairly natural notification
call, using the parameters as would be returned by INT 1a,5650.

The full calling convention (documented as per section 3.1 of the PXE
specification) is:

  INT 1a,564e - PXE installation notification
  Enter:
    %ax = 0x564e
    %es = 16-bit segment address of the PXENV+ structure
    %bx = 16-bit offset of the PXENV+ structure
  Exit:
    %edx may be trashed (as is the case for INT 1a,5650)
    All other register contents must be preserved
    CF is cleared
    IF is preserved
    All other flags are undefined

Signed-off-by: Michael Brown <mcb30@ipxe.org>
This commit is contained in:
Michael Brown 2015-09-15 13:20:17 +01:00
parent fdad22a1ed
commit 3b586c8e29
1 changed files with 12 additions and 0 deletions
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12
src/arch/i386/interface/pxe/pxe_call.c
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@ -265,6 +265,9 @@ struct init_fn pxe_init_fn __init_fn ( INIT_NORMAL ) = {
* @v netdev Net device to use as PXE net device
*/
void pxe_activate ( struct net_device *netdev ) {
uint32_t discard_a;
uint32_t discard_b;
uint32_t discard_d;
/* Ensure INT 1A is hooked */
if ( ! int_1a_hooked ) {
@ -276,6 +279,15 @@ void pxe_activate ( struct net_device *netdev ) {
/* Set PXE network device */
pxe_set_netdev ( netdev );
/* Notify BIOS of installation */
__asm__ __volatile__ ( REAL_CODE ( "pushw %%cs\n\t"
"popw %%es\n\t"
"int $0x1a\n\t" )
: "=a" ( discard_a ), "=b" ( discard_b ),
"=d" ( discard_d )
: "0" ( 0x564e ),
"1" ( __from_text16 ( &pxenv ) ) );
}
/**