On 01/25/2017 03:00 PM, Rob Gardner wrote:
On 01/25/2017 12:57 PM, Khalid Aziz wrote:@@ -157,6 +158,24 @@ int __get_user_pages_fast(unsigned long start, int nr_pages, int write, pgd_t *pgdp; int nr = 0; +#ifdef CONFIG_SPARC64 + if (adi_capable()) { + long addr = start; + + /* If userspace has passed a versioned address, kernel + * will not find it in the VMAs since it does not store + * the version tags in the list of VMAs. Storing version + * tags in list of VMAs is impractical since they can be + * changed any time from userspace without dropping into + * kernel. Any address search in VMAs will be done with + * non-versioned addresses. Ensure the ADI version bits + * are dropped here by sign extending the last bit before + * ADI bits. IOMMU does not implement version tags. + */ + addr = (addr << (long)adi_nbits()) >> (long)adi_nbits();So you are depending on the sign extension to clear the ADI bits... but this only happens if there is a zero in that "last bit before ADI bits". If the last bit is a 1, then the ADI bits will be set instead of cleared. That seems like an unintended consequence given the comment. I am aware of the value of adi_nbits() and of the number of valid bits in a virtual address on the M7 processor, but wouldn't using 'unsigned long' for everything here guarantee the ADI bits get cleared regardless of the state of the last non-adi bit?
Sign extension is the right thing to do. MMU considers values of 0 and 15 for bits 63-60 to be untagged addresses and expects bit 59 to be sign-extended for untagged virtual addresses. The code I added is explicitly meant to sign-extend, not zero out the top 4 bits.
-- Khalid
