From 5600955bdd20d95d6509617457cfa9d0d7b464b7 Mon Sep 17 00:00:00 2001 From: Michael Brown Date: Fri, 17 Oct 2008 18:12:24 +0100 Subject: [PATCH] [romprefix] Sanity-check the runtime segment address for PCI 3 Some PCI 3 BIOSes seem to provide a garbage value in %bx, which should contain the runtime segment address. Perform a basic sanity check: we reject the segment if it is below the start of option ROM space. If the sanity check fails, we assume that the BIOS was not expecting us to be a PCI 3 ROM, and we just leave our image in situ. --- src/arch/i386/prefix/romprefix.S | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/src/arch/i386/prefix/romprefix.S b/src/arch/i386/prefix/romprefix.S index ca32a4419..3351494bd 100644 --- a/src/arch/i386/prefix/romprefix.S +++ b/src/arch/i386/prefix/romprefix.S @@ -205,7 +205,16 @@ init: movb %bl, %al call print_hex_byte cmpb $3, %bh + jb 1f + /* PCI >=3.0: leave %gs as-is if sane */ + movw %gs, %ax + cmpw $0xc000, %ax jae 2f + /* PCI 3.0 with insane %gs value: print error and ignore %gs */ + movb $'!', %al + call print_character + movw %gs, %ax + call print_hex_word 1: /* PCI <3.0: set %gs (runtime segment) = %cs (init-time segment) */ pushw %cs popw %gs