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Re: Intel XNU bug report


On Aug 8, 2006, at 12:22 PM, email@hidden wrote:

Now that the source is released, we might as well get to work.
That's the point of releasing the source in the first place, right?

File: xnu-792.10.96/osfmk/i386/acpi.c
Line: 151

if (cpu_mode_is64bit()) {
cpu_IA32e_enable(current_cpu_datap());
cpu_desc_load64(current_cpu_datap());
kprintf("acpi_sleep_kernel 64-bit mode re-enabled\n");
fast_syscall_init64();
} else {
fast_syscall_init()
}

Bug: The 64 bit mode should be restored if the cpu is *NOT* currently
in 64 bit mode.

Without double-checking the source, I think you are making an erroneous assumption here.

The first line should read:
if (!cpu_mode_is64bit()) {

I believe the applicable logic is that, returning from sleep the CPU will either be in 32-bit mode
on a 32-bit system, or 64-bit mode on a 64-bit system.

In the former case, nothing need be done as that is the mode in which the kernel operates. On
non-64-bit systems, attempting to restore 64-bit mode operation would be fatal.

In the latter case, however, the kernel is run in IA32e mode and thus it's necessary to change.

The diagnostic there is perhaps confusing the matter.

 = Mike

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