Colin Cross wrote: > On Sat, Jun 22, 2013 at 3:31 AM, Christoph Hellwig <hch@xxxxxxxxxxxxx> > wrote: >> On Fri, Jun 21, 2013 at 04:42:41PM -0700, Colin Cross wrote: >>> ranges, which John Stultz has been implementing. The second is >>> anonymous shareable memory without having a world-writable tmpfs that >>> untrusted apps could fill with files. >> >> I still haven't seen any explanation of what ashmem buys over a shared >> mmap of /dev/zero in that respect, btw. > > I believe the difference is that ashmem ties the memory to an fd, so > it can be passed to another process and mmaped to get to the same > memory, but /dev/zero does not. Passing a /dev/zero fd and mmaping it > would result in a brand new region of zeroed memory. Opening a tmpfs > file would allow sharing memory by passing the fd, but we don't want a > world-writable tmpfs. Couldn't this be done by having a root-only tmpfs, and having a userspace component that creates per-app directories with restrictive permissions on startup/app install? Then each app creates files in its own directory, and can pass the fds around. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>