Re: [LTP] [PATCH] fix readv01 testcase for parisc architecture

[Jan Stancek <jstancek@redhat.com>]

----- Original Message -----
> From: "Helge Deller" <deller@gmx.de>
> To: ltp-list@lists.sourceforge.net
> Sent: Tuesday, 19 November, 2013 10:46:12 PM
> Subject: [LTP] [PATCH] fix readv01 testcase for parisc architecture
> 
> In the second test of readv01 the rd_iovec[] array was not defined or
> zero-initialized for vectors which will be accessed by the readv() syscall.
> This leads to the fact that on the parisc platform the readv syscall accessed
> random memory which is located behind the array.  Fix this problem by adding
> two more vectors with address NULL and length 0.

Hi,

It shouldn't be behind, since rd_iovec array has size of MAX_IOVEC == 16.

It's partially initialized, and looking at C99 6.7.8.21, I'd expect the
rest to be zero-initialized as well:
"If there are fewer initializers in a brace-enclosed list than there are elements or members
of an aggregate, or fewer characters in a string literal used to initialize an array of known
size than there are elements in the array, the remainder of the aggregate shall be
initialized implicitly the same as objects that have static storage duration."

If you add 'static' to rd_iovec array, does the problem go away?
What compiler are you using?

> 
> Furthermore, in the test2 itself we tell readv() to read 4 vecors, while
> the error message behind it says that it has read CHUNK bytes "followed
> by *two* NULL vectors", which then sums up to a total of 3 vectors
> instead of 4.
> Fix this by calling readv() with only 3 vectors instead of 4.

Agreed.

Regards,
Jan

> 
> Signed-off-by: Helge Deller <deller@gmx.de>
> 
> diff --git a/testcases/kernel/syscalls/readv/readv01.c
> b/testcases/kernel/syscalls/readv/readv01.c
> index d92c1be..ca83310 100644
> --- a/testcases/kernel/syscalls/readv/readv01.c
> +++ b/testcases/kernel/syscalls/readv/readv01.c
> @@ -66,7 +66,9 @@ struct iovec rd_iovec[MAX_IOVEC] = {
>  	{(buf2 + CHUNK * 10), CHUNK},
>  
>  	/* Test case #2 */
> -	{(buf2 + CHUNK * 11), CHUNK}
> +	{(buf2 + CHUNK * 11), CHUNK},
> +	{NULL, 0},
> +	{NULL, 0}
>  };
>  
>  char f_name[K_1];
> @@ -112,7 +114,7 @@ int main(int ac, char **av)
>  
>  //test2:
>  		l_seek(fd, CHUNK * 12, 0);
> -		if (readv(fd, (rd_iovec + 1), 4) != CHUNK) {
> +		if (readv(fd, (rd_iovec + 1), 3) != CHUNK) {
>  			tst_resm(TFAIL, "readv failed reading %d bytes, "
>  				 "followed by two NULL vectors", CHUNK);
>  		} else {
> 
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