From 63499e9cfd5331e90a88a6d92d370bfe6f1874f3 Mon Sep 17 00:00:00 2001 From: Michael Brown Date: Sat, 13 May 2006 11:44:11 +0000 Subject: [PATCH] Allow re-entrancy and provide a global counter of the number of interrupts hooked. --- src/arch/i386/interface/pcbios/biosint.c | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+) diff --git a/src/arch/i386/interface/pcbios/biosint.c b/src/arch/i386/interface/pcbios/biosint.c index 345961ac..6028998a 100644 --- a/src/arch/i386/interface/pcbios/biosint.c +++ b/src/arch/i386/interface/pcbios/biosint.c @@ -7,6 +7,17 @@ * */ +/** + * Hooked interrupt count + * + * At exit, after unhooking all possible interrupts, this counter + * should be examined. If it is non-zero, it means that we failed to + * unhook at least one interrupt vector, and so must not free up the + * memory we are using. (Note that this also implies that we should + * re-hook INT 15 in order to hide ourselves from the memory map). + */ +int hooked_bios_interrupts = 0; + /** * Hook INT vector * @@ -26,9 +37,15 @@ void hook_bios_interrupt ( unsigned int interrupt, unsigned int handler, .offset = handler, }; + if ( ( chain_vector->segment != 0 ) || + ( chain_vector->offset != 0 ) ) { + /* Already hooked; do nothing */ + return; + } copy_from_real ( chain_vector, 0, ( interrupt * 4 ), sizeof ( *chain_vector ) ); copy_to_real ( 0, ( interrupt * 4 ), &vector, sizeof ( vector ) ); + hooked_bios_interrupts++; } /** @@ -53,5 +70,8 @@ int unhook_bios_interrupt ( unsigned int interrupt, unsigned int handler, return -EBUSY; copy_to_real ( 0, ( interrupt * 4 ), chain_vector, sizeof ( *chain_vector ) ); + chain_vector->segment = 0; + chain_vector->offset = 0; + hooked_bios_interrupts--; return 0; }