The current ELF loading mechancism provides page-aligned mappings. This can lead to the program being loaded in a way unsuitable for file-backed, transparent huge pages when handling PIE executables. While specifying -z,max-page-size=0x200000 to the linker will generate suitably aligned segments for huge pages on x86_64, the executable needs to be loaded at a suitably aligned address as well. This alignment requires the binary's cooperation, as distinct segments need to be appropriately paddded to be eligible for THP. For binaries built with increased alignment, this limits the number of bits usable for ASLR, but provides some randomization over using fixed load addresses/non-PIE binaries. Changes V2 -> V3: * Minor code tweaks based on off-thread feedback Changes V1 -> V2: * Added test Chris Kennelly (2): fs/binfmt_elf: Use PT_LOAD p_align values for suitable start address. Add self-test for verifying load alignment. fs/binfmt_elf.c | 23 +++++++ tools/testing/selftests/exec/.gitignore | 1 + tools/testing/selftests/exec/Makefile | 9 ++- tools/testing/selftests/exec/load_address.c | 68 +++++++++++++++++++++ 4 files changed, 99 insertions(+), 2 deletions(-) create mode 100644 tools/testing/selftests/exec/load_address.c -- 2.28.0.297.g1956fa8f8d-goog
