Runtime check for PAE option on BSD 6+ i386
Philip Soeberg
philip-freebsd1 at soeberg.net
Tue May 3 13:28:41 UTC 2011
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;
}
}
<<<
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?
Thanx,
Phil
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