Re: [RFC][PATCH v2 1/3] mm: Create utility function for accessing a tasks commandline value

introduce get_cmdline() for retreiving the value of a processes proc/self/cmdline value. Signed-off-by: William Roberts <wroberts(a)tresys.com&gt;

--- 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);