On Fri, Feb 17, 2017 at 9:19 AM, Dave Hansen <dave.hansen@xxxxxxxxx> wrote: > On 02/17/2017 06:13 AM, Kirill A. Shutemov wrote: >> +/* >> + * Default maximum virtual address. This is required for >> + * compatibility with applications that assumes 47-bit VA. >> + * The limit can be changed with prctl(PR_SET_MAX_VADDR). >> + */ >> +#define MAX_VADDR_DEFAULT ((1UL << 47) - PAGE_SIZE) > > This is a bit goofy. It's not the largest virtual adddress that can be > accessed, but the beginning of the last page. No, it really is the limit. We don't allow user code to map the last page because ti would be a root hole due to SYSRET. Thanks, Intel. See the comment near TASK_SIZE_MAX IIRC. --Andy
