How can I get argv[0] from "struct linux_binprm"?

[Tetsuo Handa <penguin-newbie@xxxxxxxxxxxxxxxxxxx>]

Hello.

I want to get argv[0] from "struct linux_binprm".
But it seems that elements of "struct linux_binprm" has changed at 2.6.23-rc1 .
And I want to know how to follow this change.
The following is the code,
but I'm not sure whether get_user_pages()/put_page() usage is correct.
This code is called from security_bprm_check().
Could somebody please review this code?

Regards.



static char *get_argv0(struct linux_binprm *bprm)
{
	char *arg_ptr = kmalloc(PAGE_SIZE, GFP_KERNEL); /* Initial buffer. */
	int arg_len = 0;
	unsigned long pos = bprm->p;
	int i = pos / PAGE_SIZE, offset = pos % PAGE_SIZE;
	if (!bprm->argc || !arg_ptr) goto out;
	while (1) {
		struct page *page;
#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,23) && defined(CONFIG_MMU)
		if (get_user_pages(current, bprm->mm, pos, 1, 0, 1, &page, NULL) <= 0) goto out;
#else
		page = bprm->page[i];
#endif
		{ /* Map and copy to kernel buffer and unmap. */
			const char *kaddr = kmap(page);
			if (!kaddr) { /* Mapping failed. */
#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,23) && defined(CONFIG_MMU)
				put_page(page);
#endif
				goto out;
			}
			memmove(arg_ptr + arg_len, kaddr + offset, PAGE_SIZE - offset);
			kunmap(page);
		}
#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,23) && defined(CONFIG_MMU)
		put_page(page);
		pos += PAGE_SIZE - offset;
#endif
		arg_len += PAGE_SIZE - offset;
		if (memchr(arg_ptr, '\0', arg_len)) break;
		{ /* Initial buffer was too small for argv[0]. Retry after expanding buffer. */
			char *tmp_arg_ptr = kmalloc(arg_len + PAGE_SIZE, GFP_KERNEL);
			if (!tmp_arg_ptr) goto out;
			memmove(tmp_arg_ptr, arg_ptr, arg_len);
			kfree(arg_ptr);
			arg_ptr = tmp_arg_ptr;
		}
		i++;
		offset = 0;
	}
	return arg_ptr;
 out: /* Release initial buffer. */
	kfree(arg_ptr);
	return NULL;
}

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