On 17/01/2022 14:54, Catalin Marinas via Libc-alpha wrote: > On Fri, Jan 07, 2022 at 12:01:17PM +0000, Catalin Marinas wrote: >> I think we can look at this from two angles: >> >> 1. Ignoring MDWE, should whoever does the original mmap() also honour >> PROT_BTI? We do this for static binaries but, for consistency, should >> we extend it to dynamic executable? >> >> 2. A 'simple' fix to allow MDWE together with BTI. > > Thinking about it, (1) is not that different from the kernel setting > PROT_EXEC on the main executable when the dynamic loader could've done > it as well. There is a case for making this more consistent: whoever > does the mmap() should use the full attributes. > > Question for the toolchain people: would the compiler ever generate > relocations in the main executable that the linker needs to resolve via > an mprotect(READ|WRITE) followed by mprotect(READ|EXEC)? If yes, we'd > better go for a proper MDWE implementation in the kernel. > Yes, text relocations. However these are deprecated (some libcs even do not support it) and have a lot of drawbacks.
