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    Subject[PATCH v5 1/3] mm: Create utility function for accessing a tasks commandline value
    Date
    introduce get_cmdline() for retreiving the value of a processes
    proc/self/cmdline value.

    Acked-by: David Rientjes <rientjes@google.com>
    Acked-by: Stephen Smalley <sds@tycho.nsa.gov>

    Signed-off-by: William Roberts <wroberts@tresys.com>
    ---
    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 f28f46e..db89a94 100644
    --- a/include/linux/mm.h
    +++ b/include/linux/mm.h
    @@ -1175,6 +1175,7 @@ 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 a24aa22..8122710 100644
    --- a/mm/util.c
    +++ b/mm/util.c
    @@ -445,6 +445,54 @@ unsigned long vm_commit_limit(void)
    return allowed;
    }

    +/**
    + * 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);
    --
    1.7.9.5


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