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    SubjectRe: [RFC PATCH 3/6] fork: provide a function for copying init_mm
    On Wed, 29 Aug 2018 01:11:44 -0700
    Nadav Amit <namit@vmware.com> wrote:

    > Provide a function for copying init_mm. This function will be later used
    > for setting a temporary mm.

    This looks good to me :)

    Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>

    Thanks!

    >
    > Cc: Andy Lutomirski <luto@kernel.org>
    > Cc: Masami Hiramatsu <mhiramat@kernel.org>
    > Cc: Kees Cook <keescook@chromium.org>
    > Cc: Peter Zijlstra <peterz@infradead.org>
    > Signed-off-by: Nadav Amit <namit@vmware.com>
    > ---
    > include/linux/sched/task.h | 1 +
    > kernel/fork.c | 24 ++++++++++++++++++------
    > 2 files changed, 19 insertions(+), 6 deletions(-)
    >
    > diff --git a/include/linux/sched/task.h b/include/linux/sched/task.h
    > index 108ede99e533..ac0a675678f5 100644
    > --- a/include/linux/sched/task.h
    > +++ b/include/linux/sched/task.h
    > @@ -74,6 +74,7 @@ extern void exit_itimers(struct signal_struct *);
    > extern long _do_fork(unsigned long, unsigned long, unsigned long, int __user *, int __user *, unsigned long);
    > extern long do_fork(unsigned long, unsigned long, unsigned long, int __user *, int __user *);
    > struct task_struct *fork_idle(int);
    > +struct mm_struct *copy_init_mm(void);
    > extern pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags);
    > extern long kernel_wait4(pid_t, int __user *, int, struct rusage *);
    >
    > diff --git a/kernel/fork.c b/kernel/fork.c
    > index d896e9ca38b0..a1c637b903c1 100644
    > --- a/kernel/fork.c
    > +++ b/kernel/fork.c
    > @@ -1254,13 +1254,20 @@ void mm_release(struct task_struct *tsk, struct mm_struct *mm)
    > complete_vfork_done(tsk);
    > }
    >
    > -/*
    > - * Allocate a new mm structure and copy contents from the
    > - * mm structure of the passed in task structure.
    > +/**
    > + * dup_mm() - duplicates an existing mm structure
    > + * @tsk: the task_struct with which the new mm will be associated.
    > + * @oldmm: the mm to duplicate.
    > + *
    > + * Allocates a new mm structure and copy contents from the provided
    > + * @oldmm structure.
    > + *
    > + * Return: the duplicated mm or NULL on failure.
    > */
    > -static struct mm_struct *dup_mm(struct task_struct *tsk)
    > +static struct mm_struct *dup_mm(struct task_struct *tsk,
    > + struct mm_struct *oldmm)
    > {
    > - struct mm_struct *mm, *oldmm = current->mm;
    > + struct mm_struct *mm;
    > int err;
    >
    > mm = allocate_mm();
    > @@ -1327,7 +1334,7 @@ static int copy_mm(unsigned long clone_flags, struct task_struct *tsk)
    > }
    >
    > retval = -ENOMEM;
    > - mm = dup_mm(tsk);
    > + mm = dup_mm(tsk, current->mm);
    > if (!mm)
    > goto fail_nomem;
    >
    > @@ -2127,6 +2134,11 @@ struct task_struct *fork_idle(int cpu)
    > return task;
    > }
    >
    > +struct mm_struct *copy_init_mm(void)
    > +{
    > + return dup_mm(NULL, &init_mm);
    > +}
    > +
    > /*
    > * Ok, this is the main fork-routine.
    > *
    > --
    > 2.17.1
    >


    --
    Masami Hiramatsu <mhiramat@kernel.org>

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