On Tue, Sep 24, 2024 at 12:16:27PM GMT, Lorenzo Stoakes wrote: > process_madvise() was conceived as a useful means for performing a vector > of madvise() operations on a remote process's address space. > > However it's useful to be able to do so on the current process also. It is > currently rather clunky to do this (requiring a pidfd to be opened for the > current process) and introduces unnecessary overhead in incrementing > reference counts for the task and mm. > > Avoid all of this by providing a PR_MADV_SELF flag, which causes > process_madvise() to simply ignore the pidfd parameter and instead apply > the operation to the current process. > How about simply defining a pseudo-fd PIDFD_SELF in the negative int space? There's precedent for it in the fs space (AT_FDCWD). I think it's more ergonomic and if you take out the errno space we have around 2^31 - 4096 available sentinel values. e.g: /* AT_FDCWD = -10, -1 is dangerous, pick a different value */ #define PIDFD_SELF -11 int pidfd = target_pid == getpid() ? PIDFD_SELF : pidfd_open(...); process_madvise(pidfd, ...); What do you think? -- Pedro
