From 3b586c8e29d471553a0e206de875923ef4deb6b8 Mon Sep 17 00:00:00 2001 From: Michael Brown Date: Tue, 15 Sep 2015 13:20:17 +0100 Subject: [PATCH] [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 --- src/arch/i386/interface/pxe/pxe_call.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/src/arch/i386/interface/pxe/pxe_call.c b/src/arch/i386/interface/pxe/pxe_call.c index 10431366..2d89cc4d 100644 --- a/src/arch/i386/interface/pxe/pxe_call.c +++ b/src/arch/i386/interface/pxe/pxe_call.c @@ -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 ) ) ); } /**