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    SubjectRe: [RFC][PATCH v2 1/3] mm: Create utility function for accessing a tasks commandline value
    On 01/13/2014 12:02 PM, William Roberts wrote:
    > introduce get_cmdline() for retreiving the value of a processes
    > proc/self/cmdline value.
    >
    > Signed-off-by: William Roberts <wroberts@tresys.com>

    Acked-by: Stephen Smalley <sds@tycho.nsa.gov>

    > ---
    > include/linux/mm.h | 1 +
    > mm/util.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
    > 2 files changed, 49 insertions(+)
    >
    > diff --git a/include/linux/mm.h b/include/linux/mm.h
    > index 3552717..01e7970 100644
    > --- a/include/linux/mm.h
    > +++ b/include/linux/mm.h
    > @@ -1134,6 +1134,7 @@ void account_page_writeback(struct page *page);
    > int set_page_dirty(struct page *page);
    > int set_page_dirty_lock(struct page *page);
    > int clear_page_dirty_for_io(struct page *page);
    > +int get_cmdline(struct task_struct *task, char *buffer, int buflen);
    >
    > /* Is the vma a continuation of the stack vma above it? */
    > static inline int vma_growsdown(struct vm_area_struct *vma, unsigned long addr)
    > diff --git a/mm/util.c b/mm/util.c
    > index f7bc209..5285ff0 100644
    > --- a/mm/util.c
    > +++ b/mm/util.c
    > @@ -410,6 +410,54 @@ unsigned long vm_commit_limit(void)
    > * sysctl_overcommit_ratio / 100) + total_swap_pages;
    > }
    >
    > +/**
    > + * get_cmdline() - copy the cmdline value to a buffer.
    > + * @task: the task whose cmdline value to copy.
    > + * @buffer: the buffer to copy to.
    > + * @buflen: the length of the buffer. Larger cmdline values are truncated
    > + * to this length.
    > + * Returns the size of the cmdline field copied. Note that the copy does
    > + * not guarantee an ending NULL byte.
    > + */
    > +int get_cmdline(struct task_struct *task, char *buffer, int buflen)
    > +{
    > + int res = 0;
    > + unsigned int len;
    > + struct mm_struct *mm = get_task_mm(task);
    > + if (!mm)
    > + goto out;
    > + if (!mm->arg_end)
    > + goto out_mm; /* Shh! No looking before we're done */
    > +
    > + len = mm->arg_end - mm->arg_start;
    > +
    > + if (len > buflen)
    > + len = buflen;
    > +
    > + res = access_process_vm(task, mm->arg_start, buffer, len, 0);
    > +
    > + /*
    > + * If the nul at the end of args has been overwritten, then
    > + * assume application is using setproctitle(3).
    > + */
    > + if (res > 0 && buffer[res-1] != '\0' && len < buflen) {
    > + len = strnlen(buffer, res);
    > + if (len < res) {
    > + res = len;
    > + } else {
    > + len = mm->env_end - mm->env_start;
    > + if (len > buflen - res)
    > + len = buflen - res;
    > + res += access_process_vm(task, mm->env_start,
    > + buffer+res, len, 0);
    > + res = strnlen(buffer, res);
    > + }
    > + }
    > +out_mm:
    > + mmput(mm);
    > +out:
    > + return res;
    > +}
    >
    > /* Tracepoints definitions. */
    > EXPORT_TRACEPOINT_SYMBOL(kmalloc);
    >



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