On Tue, Jan 18, 2022 at 02:19:12PM -0700, Khalid Aziz wrote:
> Example Code
> ============
>
> Snippet of the code that a donor process would run looks like below:
>
> -----------------
> addr = mmap((void *)TB(2), GB(512), PROT_READ | PROT_WRITE,
> MAP_SHARED | MAP_ANONYMOUS, 0, 0);
> if (addr == MAP_FAILED)
> perror("ERROR: mmap failed");
>
> err = syscall(MSHARE_SYSCALL, "testregion", (void *)TB(2),
> GB(512), O_CREAT|O_RDWR|O_EXCL, 600);
> if (err < 0) {
> perror("mshare() syscall failed");
> exit(1);
> }
>
> strncpy(addr, "Some random shared text",
> sizeof("Some random shared text"));
> -----------------
>
> Snippet of code that a consumer process would execute looks like:
>
> -----------------
> fd = open("testregion", O_RDONLY);
> if (fd < 0) {
> perror("open failed");
> exit(1);
> }
>
> if ((count = read(fd, &mshare_info, sizeof(mshare_info)) > 0))
> printf("INFO: %ld bytes shared at addr %lx \n",
> mshare_info[1], mshare_info[0]);
> else
> perror("read failed");
>
> close(fd);
>
> addr = (char *)mshare_info[0];
> err = syscall(MSHARE_SYSCALL, "testregion", (void *)mshare_info[0],
> mshare_info[1], O_RDWR, 600);
> if (err < 0) {
> perror("mshare() syscall failed");
> exit(1);
> }
>
> printf("Guest mmap at %px:\n", addr);
> printf("%s\n", addr);
> printf("\nDone\n");
>
> err = syscall(MSHARE_UNLINK_SYSCALL, "testregion");
> if (err < 0) {
> perror("mshare_unlink() failed");
> exit(1);
> }
> -----------------
I wounder if we can get away with zero-API here: we can transparently
create/use shared page tables for any inode on mmap(MAP_SHARED) as long as
size and alignment is sutiable. Page tables will be linked to the inode
and will be freed when the last of such mapping will go away. I don't see
a need in new syscalls of flags to existing one.
--
Kirill A. Shutemov
