[LTP] [PATCH] cve: Fix kernel symbol finding for meltdown case

[Jan Stancek]

----- Original Message -----
> From: He Zhe <zhe.he@windriver.com>
> 
> meltdown case failed as below.
> safe_file_ops.c:219: BROK: Expected 3 conversions got 2 at meltdown.c:272

What line doesn't match current pattern?
I'm not seeing any changes in kallsyms output:

kernel: "%px %c %s\n"
        "%px %c %s\t[%s]\n"
LTP:    "%lx %c SYMBOL%c"

> 
> The case used SAFE_FILE_LINES_SCANF which is a wrapper of vsscanf which
> cannot
> extract the symbol name from the following line pattern of kernel symbol
> table.

Did you mean "extract symbol address"?

> 
> 01234567 T SYMBOL_NAME
> 
> Also the original format pattern is not correct.
> 
> This patch re-writes the symbol extraction process and adds a NULL pointer
> check.
> 
> Signed-off-by: He Zhe <zhe.he@windriver.com>
> ---
>  testcases/cve/meltdown.c | 38 +++++++++++++++++++++++++++++++-------
>  1 file changed, 31 insertions(+), 7 deletions(-)
> 
> diff --git a/testcases/cve/meltdown.c b/testcases/cve/meltdown.c
> index f78c38b..4c3f3b2 100644
> --- a/testcases/cve/meltdown.c
> +++ b/testcases/cve/meltdown.c
> @@ -248,15 +248,34 @@ set_cache_hit_threshold(void)
>  static unsigned long
>  find_symbol_in_file(const char *filename, const char *symname)
>  {
> -	unsigned long addr;
> -	char type;
> -	int ret, read;
> -	char fmt[strlen(symname) + 64];
> +	unsigned long addr = 0;
> +	int found = 0;
> +	char line[BUFSIZ] = {0};
> +	FILE *fp = NULL;
> +	char *p = NULL;
> +
> +	fp = fopen(filename, "r");
> +	if (fp == NULL) {
> +		tst_res(TBROK | TERRNO,
> +			"Failed to open file:%s for symbol:%s",
> +			filename, symname);
> +		return 0;
> +	}
>  
> -	sprintf(fmt, "%%lx %%c %s%%c", symname);
> +	while (fgets(line, BUFSIZ, fp) != NULL) {
> +		p = strstr(line, symname);
> +		/* Make sure this line is exactly for this symbol.
> +		 * Substract the EOL added by fgets for each line.
> +		 */
> +		if (p && ((strlen(p) - 1) == strlen(symname))) {
> +			found = sscanf(line, "%lx", &addr);
> +			if (found == 1)
> +				break;
> +		}
> +	}
> +	fclose(fp);
>  
> -	ret = SAFE_FILE_LINES_SCANF(filename, fmt, &addr, &type, &read);
> -	if (ret)
> +	if (found != 1)
>  		return 0;
>  
>  	return addr;
> @@ -322,6 +341,11 @@ static void run(void)
>  
>  	/* read address of saved_cmdline_addr */
>  	addr = saved_cmdline_addr;
> +	if (!addr) {
> +		tst_res(TBROK | TERRNO, "saved_cmdline_addr is 0\n");
> +		return;
> +	}
> +
>  	size = sizeof(addr);
>  	for (i = 0; i < size; i++) {
>  		ret = readbyte(spec_fd, addr);
> --
> 2.7.4
> 
> 
> --
> Mailing list info: https://lists.linux.it/listinfo/ltp
>