On 6/10/19 8:22 AM, Yu-cheng Yu wrote: >> How does glibc know the linear address space size? We don’t want LA64 to >> break old binaries because the address calculation changed. > When an application starts, its highest stack address is determined. > It uses that as the maximum the bitmap needs to cover. Huh, I didn't think we ran code from the stack. ;) Especially given the way that we implemented the new 5-level-paging address space, I don't think that expecting code to be below the stack is a good universal expectation.