On 03-05-2011 19:43, Kostik Belousov wrote:
On Tue, May 03, 2011 at 11:44:32AM -0400, John Baldwin wrote:
On Tuesday, May 03, 2011 9:10:26 am Philip Soeberg wrote:
Hi fellow FreeBSD hackers,
I've been using the following poor-man's approach in my driver init for
ages in an attempt at detecting PAE option on BSD 6 (or greater) i386
kernels, as I depend on dmabus(9) but provide a loadable kernel module only.
>>>
if (sizeof(void*) == 4) {
if (((uint64_t)(cnt.v_page_count * cnt.v_page_size) / 1073741824)
>= 4) {
printf("FreeBSD i386 detected with PAE option enabled. FreeBSD
PAE type\n");
printf("kernels does not support loadable modules which use DMA.
Please\n");
printf("reconfigure your kernel for non-PAE or switch to amd64
kernel.\n");
return EFAULT;
}
}
<<<
Hmmm, even this isn't really accurate as some folks may choose to enable PAE
even with< 4GB to get PG_NX functionality.
afaik there's a sysctl method of checking this per BSD7 (or is it 8?),
but what about BSD6? Any hints on how I can runtime detect the above?
Definitely a kern.features.pae sysctl in 7. I don't see anything similar in
6.
Read %cr4 and test the bit there.
Ha, as always there exist a simple elegant solution.. thanks, that
method had escaped me.
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