On Tue, Jul 18, 2017 at 8:59 PM, Brian Gerst <brge...@gmail.com> wrote: > On Tue, Jul 18, 2017 at 9:35 PM, H. Peter Anvin <h...@zytor.com> wrote: >> On 07/18/17 15:33, Thomas Garnier wrote: >>> With PIE support and KASLR extended range, the modules may be further >>> away from the kernel than before breaking mcmodel=kernel expectations. >>> >>> Add an option to build modules with mcmodel=large. The modules generated >>> code will make no assumptions on placement in memory. >>> >>> Despite this option, modules still expect kernel functions to be within >>> 2G and generate relative calls. To solve this issue, the PLT arm64 code >>> was adapted for x86_64. When a relative relocation go outside its range, >>> a dynamic PLT entry is used to correctly jump to the destination. >> >> Why large as opposed to medium or medium-PIC? > > Or for that matter, why not small-PIC? We aren't changing the size of > the kernel to be larger than 2G text or data. Small-PIC would still > allow it to be placed anywhere in the address space, and would > generate far better code.
My understanding was that small=PIC and medium=PIC assume that the module code is in the lower 2G of memory. I will do additional testing on the modules to confirm that. > > -- > Brian Gerst -- Thomas _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org https://lists.xen.org/xen-devel
