This patchset adds support for preserving an anonymous memory range across exec(3) using a new madvise MADV_DOEXEC argument. The primary benefit for sharing memory in this manner, as opposed to re-attaching to a named shared memory segment, is to ensure it is mapped at the same virtual address in the new process as it was in the old one. An intended use for this is to preserve guest memory for guests using vfio while qemu exec's an updated version of itself. By ensuring the memory is preserved at a fixed address, vfio mappings and their associated kernel data structures can remain valid. In addition, for the qemu use case, qemu instances that back guest RAM with anonymous memory can be updated. Patches 1 and 2 ensure that loading of ELF load segments does not silently clobber existing VMAS, and remove assumptions that the stack is the only VMA in the mm when the stack is set up. Patch 1 re-introduces the use of MAP_FIXED_NOREPLACE to load ELF binaries that addresses the previous issues and could be considered on its own. Patches 3, 4, and 5 introduce the feature and an opt-in method for its use using an ELF note. Anthony Yznaga (5): elf: reintroduce using MAP_FIXED_NOREPLACE for elf executable mappings mm: do not assume only the stack vma exists in setup_arg_pages() mm: introduce VM_EXEC_KEEP exec, elf: require opt-in for accepting preserved mem mm: introduce MADV_DOEXEC arch/x86/Kconfig | 1 + fs/binfmt_elf.c | 196 +++++++++++++++++++++++++-------- fs/exec.c | 33 +++++- include/linux/binfmts.h | 7 +- include/linux/mm.h | 5 + include/uapi/asm-generic/mman-common.h | 3 + kernel/fork.c | 2 +- mm/madvise.c | 25 +++++ mm/mmap.c | 47 ++++++++ 9 files changed, 266 insertions(+), 53 deletions(-) -- 1.8.3.1
