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There are two logic bugs breaking RestrictMemoryToMaxAddress. 1. adding left_padding within MapDynamicShadow. - RoundUpTo((uptr)free_begin + left_padding, alignment) already adjusts for left padding. Adding this additionally within MapDynamicShadow causes us to allocate a page larger than necessary. - This incorrect calculation also means RestrictMemoryToMaxAddress will never find a big enough gap. 2. There is also an issue with the expectation of hitting KERN_INVALID_ADDRESS when we are beyond the addressable regions. - For most embedded scenarios, we exceed vm_max_address without getting KREN_INVALID_ADDRESS so we setting max_occupied_address to a memory region the process doesn't have access to, beyond the max address, and that space is never marked as available so we never find a valid gap in those regions. - At some point previous it seems the assumption was once we were beyond the Max address we could expect KREN_INVALID_ADDRESS, which is no longer true up through the extended space not given to most processes. - Because of this, the check` if (new_max_vm < max_occupied_addr)` will always fail and we will never restrict the address on smaller devices. - Additionally because of the extra page added by adding left_padding, and how we only minimally restrict the vm, there's a chance we restrict the vm only enough for the correctly calculated size of shadow. In these cases, restricting the vm max address and will always fail due to the extra page added to space size. credit to @delcypher for the left_padding diagnosis, remembered his old radar and PR when investigating this. https://reviews.llvm.org/D85389 Will monitor closely for fall out. rdar://66603866
Compiler-RT ================================ This directory and its subdirectories contain source code for the compiler support routines. Compiler-RT is open source software. You may freely distribute it under the terms of the license agreement found in LICENSE.txt. ================================