On Tue, Feb 18, 2020 at 5:44 PM Minchan Kim <minchan@xxxxxxxxxx> wrote: > > There is a demand[1] to support pid as well pidfd for process_madvise > to reduce unnecessary syscall to get pidfd if the user has control of > the target process(ie, they could guarantee the process is not gone > or pid is not reused. Or, it might be okay to give a hint to wrong > process). nit: When would "give a hint to wrong process" be ok? I would just remove this part. > > This patch aims for supporting both options like waitid(2). So, the > syscall is currently, > > int process_madvise(int which, pid_t pid, void *addr, > size_t length, int advise, unsigned long flag); > > @which is actually idtype_t for userspace libray and currently, > it supports P_PID and P_PIDFD. > > [1] https://lore.kernel.org/linux-mm/9d849087-3359-c4ab-fbec-859e8186c509@xxxxxxxxxxxxx/ > > Cc: Christian Brauner <christian@xxxxxxxxxx> > Suggested-by: Kirill Tkhai <ktkhai@xxxxxxxxxxxxx> > Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx> > --- > include/linux/syscalls.h | 3 ++- > mm/madvise.c | 34 ++++++++++++++++++++++------------ > 2 files changed, 24 insertions(+), 13 deletions(-) > > diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h > index e4cd2c2f8bb4..f5ada20e2943 100644 > --- a/include/linux/syscalls.h > +++ b/include/linux/syscalls.h > @@ -876,7 +876,8 @@ asmlinkage long sys_munlockall(void); > asmlinkage long sys_mincore(unsigned long start, size_t len, > unsigned char __user * vec); > asmlinkage long sys_madvise(unsigned long start, size_t len, int behavior); > -asmlinkage long sys_process_madvise(int pidfd, unsigned long start, > + > +asmlinkage long sys_process_madvise(int which, pid_t pid, unsigned long start, > size_t len, int behavior, unsigned long flags); > asmlinkage long sys_remap_file_pages(unsigned long start, unsigned long size, > unsigned long prot, unsigned long pgoff, > diff --git a/mm/madvise.c b/mm/madvise.c > index def1507c2030..f6d9b9e66243 100644 > --- a/mm/madvise.c > +++ b/mm/madvise.c > @@ -1182,11 +1182,10 @@ SYSCALL_DEFINE3(madvise, unsigned long, start, size_t, len_in, int, behavior) > return do_madvise(current, current->mm, start, len_in, behavior); > } > > -SYSCALL_DEFINE5(process_madvise, int, pidfd, unsigned long, start, > +SYSCALL_DEFINE6(process_madvise, int, which, pid_t, upid, unsigned long, start, > size_t, len_in, int, behavior, unsigned long, flags) > { > int ret; > - struct fd f; > struct pid *pid; > struct task_struct *task; > struct mm_struct *mm; > @@ -1197,20 +1196,31 @@ SYSCALL_DEFINE5(process_madvise, int, pidfd, unsigned long, start, > if (!process_madvise_behavior_valid(behavior)) > return -EINVAL; > > - f = fdget(pidfd); > - if (!f.file) > - return -EBADF; > + switch (which) { > + case P_PID: > + if (upid <= 0) > + return -EINVAL; > + > + pid = find_get_pid(upid); > + if (!pid) > + return -ESRCH; > + break; > + case P_PIDFD: > + if (upid < 0) > + return -EINVAL; > > - pid = pidfd_pid(f.file); > - if (IS_ERR(pid)) { > - ret = PTR_ERR(pid); > - goto fdput; > + pid = pidfd_get_pid(upid); > + if (IS_ERR(pid)) > + return PTR_ERR(pid); > + break; > + default: > + return -EINVAL; > } > > task = get_pid_task(pid, PIDTYPE_PID); > if (!task) { > ret = -ESRCH; > - goto fdput; > + goto put_pid; > } > > mm = mm_access(task, PTRACE_MODE_ATTACH_FSCREDS); > @@ -1223,7 +1233,7 @@ SYSCALL_DEFINE5(process_madvise, int, pidfd, unsigned long, start, > mmput(mm); > release_task: > put_task_struct(task); > -fdput: > - fdput(f); > +put_pid: > + put_pid(pid); > return ret; > } > -- > 2.25.0.265.gbab2e86ba0-goog > Reviewed-by: Suren Baghdasaryan <surenb@xxxxxxxxxx>
