diff options
Diffstat (limited to 'arch/x86/boot/header.S')
| -rw-r--r-- | arch/x86/boot/header.S | 41 |
1 files changed, 16 insertions, 25 deletions
diff --git a/arch/x86/boot/header.S b/arch/x86/boot/header.S index 6ef5a060fa11..4cc5b0411db5 100644 --- a/arch/x86/boot/header.S +++ b/arch/x86/boot/header.S @@ -236,39 +236,30 @@ start_of_setup: movw %ax, %es cld -# Apparently some ancient versions of LILO invoked the kernel -# with %ss != %ds, which happened to work by accident for the -# old code. If the CAN_USE_HEAP flag is set in loadflags, or -# %ss != %ds, then adjust the stack pointer. +# Apparently some ancient versions of LILO invoked the kernel with %ss != %ds, +# which happened to work by accident for the old code. Recalculate the stack +# pointer if %ss is invalid. Otherwise leave it alone, LOADLIN sets up the +# stack behind its own code, so we can't blindly put it directly past the heap. - # Smallest possible stack we can tolerate - movw $(_end+STACK_SIZE), %cx - - movw heap_end_ptr, %dx - addw $512, %dx - jnc 1f - xorw %dx, %dx # Wraparound - whole segment available -1: testb $CAN_USE_HEAP, loadflags - jnz 2f - - # No CAN_USE_HEAP movw %ss, %dx cmpw %ax, %dx # %ds == %ss? movw %sp, %dx - # If so, assume %sp is reasonably set, otherwise use - # the smallest possible stack. - jne 4f # -> Smallest possible stack... + je 2f # -> assume %sp is reasonably set + + # Invalid %ss, make up a new stack + movw $_end, %dx + testb $CAN_USE_HEAP, loadflags + jz 1f + movw heap_end_ptr, %dx +1: addw $STACK_SIZE, %dx + jnc 2f + xorw %dx, %dx # Prevent wraparound - # Make sure the stack is at least minimum size. Take a value - # of zero to mean "full segment." -2: +2: # Now %dx should point to the end of our stack space andw $~3, %dx # dword align (might as well...) jnz 3f movw $0xfffc, %dx # Make sure we're not zero -3: cmpw %cx, %dx - jnb 5f -4: movw %cx, %dx # Minimum value we can possibly use -5: movw %ax, %ss +3: movw %ax, %ss movzwl %dx, %esp # Clear upper half of %esp sti # Now we should have a working stack |