[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-changelog] [xen master] x86/boot: fix BIOS memory corruption on certain IBM systems
commit 1ed76797439e384de18fcd6810bd4743d4f38b1e Author: Andrew Cooper <andrew.cooper3@xxxxxxxxxx> AuthorDate: Fri Dec 6 11:28:00 2013 +0100 Commit: Jan Beulich <jbeulich@xxxxxxxx> CommitDate: Fri Dec 6 11:28:00 2013 +0100 x86/boot: fix BIOS memory corruption on certain IBM systems IBM System x3530 M4 BIOSes (including the latest available at the time of this patch) will corrupt a byte at physical address 0x105ff1 to the value of 0x86 if %esp has the value 0x00080000 when issuing an `int $0x15 (ax=0xec00)` to inform the system about our intended operating mode. Xen gets unhappy when the bootloader has placed it's .text section in over this specific region of RAM. After dropping into 16bit mode, clear all 32 bits of %esp, and for the BIOS call already documented to be affected by BIOS bugs clear all GPRs. Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx> Acked-by: Keir Fraser <keir@xxxxxxx> Release-acked-by: George Dunlap <george.dunlap@xxxxxxxxxxxxx> Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx> --- xen/arch/x86/boot/trampoline.S | 7 ++++++- 1 files changed, 6 insertions(+), 1 deletions(-) diff --git a/xen/arch/x86/boot/trampoline.S b/xen/arch/x86/boot/trampoline.S index 827f412..4f5f8d7 100644 --- a/xen/arch/x86/boot/trampoline.S +++ b/xen/arch/x86/boot/trampoline.S @@ -143,7 +143,7 @@ trampoline_boot_cpu_entry: mov %ax,%ss /* Initialise stack pointer and IDT, and enable irqs. */ - xor %sp,%sp + xor %esp,%esp lidt bootsym(rm_idt) sti @@ -151,6 +151,11 @@ trampoline_boot_cpu_entry: * Declare that our target operating mode is long mode. * Initialise 32-bit registers since some buggy BIOSes depend on it. */ + xor %ecx,%ecx + xor %edx,%edx + xor %esi,%esi + xor %edi,%edi + xor %ebp,%ebp movl $0xec00,%eax # declare target operating mode movl $0x0002,%ebx # long mode int $0x15 -- generated by git-patchbot for /home/xen/git/xen.git#master _______________________________________________ Xen-changelog mailing list Xen-changelog@xxxxxxxxxxxxx http://lists.xensource.com/xen-changelog
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