On 27.07.2020 20:11, Anthony Yznaga wrote: > 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, So, the goal is an update of QEMU binary without a stopping of virtual machine? > 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(-) >
