[lttng-dev] [PATCH] A minimal rewrite of lttctl
David Goulet
david.goulet at polymtl.ca
Thu Dec 8 11:59:09 EST 2011
You do realize that the code below will return ENOMEM if the malloc *succeeds*... :P
Funny boy!
David
P.S : It might be me, I did not had my second coffee.
On 11-12-08 11:53 AM, Matthew Khouzam wrote:
> wow! sorry about that last post
>
> if (opt_head = (struct lttctl_option *)malloc(sizeof(struct lttctl_option))
> {
> return enomem;
> }
>
> I would be lost without a compiler.
>
>
> On 11-12-08 10:29 AM, Matthew Khouzam wrote:
>> Please correct me if I'm wrong, but shouldn't the failure to malloc
>> return an enomem like :
>> if opt_head = (struct lttctl_option *)malloc(sizeof(struct lttctl_option));
>> {
>> return enomem;
>> }
>> because it is hiding a larger more system destabilizing problem.
>>
>> please others comment.
>> On 11-12-07 03:27 PM, Thibault, Daniel wrote:
>>> ------------------------------
>>>> Date: Tue, 6 Dec 2011 12:04:26 -0500
>>>> From: Mathieu Desnoyers <compudj at krystal.dyndns.org>
>>>>
>>>> If you can split out the obvious bugfixes from the refactoring/rewrite,
>>>> I would gladly accept the bugfixes.
>>> ------------------------------
>>>
>>> All right, here is a minimal patch for lttctl.c:
>>>
>>> ------------------------------
>>> --- ../ltt-control-0.89-792f03c/lttctl/lttctl.c 2011-05-12 08:44:27.000000000 -0400
>>> +++ ../ltt-control-0.89-792f03c.minimalchanges/lttctl/lttctl.c 2011-12-07 15:18:28.000000000 -0500
>>> @@ -64,7 +64,7 @@
>>> struct lttctl_option *next;
>>> };
>>>
>>> -struct lttctl_option *opt_head, *last_opt;
>>> +static struct lttctl_option *opt_head, *last_opt;
>>>
>>> static int opt_create;
>>> static int opt_destroy;
>>> @@ -236,9 +236,11 @@
>>>
>>> if (!opt_head) {
>>> opt_head = (struct lttctl_option *)malloc(sizeof(struct lttctl_option));
>>> + if (opthead) {
>>> init_channel_opt(&opt_head->opt_mode.chan_opt, opt_name);
>>> opt_head->type = CHANNEL;
>>> opt_head->next = NULL;
>>> + }
>>> last_opt = opt_head;
>>> return opt_head;
>>> }
>>> @@ -251,15 +253,17 @@
>>> }
>>>
>>> new_opt = (struct lttctl_option *)malloc(sizeof(struct lttctl_option));
>>> + if (new_opt) {
>>> init_channel_opt(&new_opt->opt_mode.chan_opt, opt_name);
>>> new_opt->type = CHANNEL;
>>> new_opt->next = NULL;
>>> last_opt->next = new_opt;
>>> last_opt = new_opt;
>>> + }
>>> return new_opt;
>>> }
>>>
>>> -int set_channel_opt(struct channel_option *opt, char *opt_name, char *opt_valstr)
>>> +static int set_channel_opt(struct channel_option *opt, char *opt_name, char *opt_valstr)
>>> {
>>> int opt_val, ret;
>>> ------------------------------
>>>
>>> It makes opt_head and last_opt private.
>>> In find_insert_channel_opt, it handles malloc() failure; previously, if malloc() failed while creating a new lttctl_option list node, one immediately got a segmentation fault.
>>> It makes set_channel_opt() private (there is no reason why it should be exportable, and all the other functions in this unit are private).
>>>
>>> Here is a minimal patch for liblttctl.c:
>>>
>>> ------------------------------
>>> --- ../ltt-control-0.89-792f03c/liblttctl/liblttctl.c 2011-05-12 08:44:27.000000000 -0400
>>> +++ ../ltt-control-0.89-792f03c.minimalchanges/liblttctl/liblttctl.c 2011-12-07 15:03:31.000000000 -0500
>>> @@ -35,7 +35,7 @@
>>> #include <fcntl.h>
>>> #include <stdlib.h>
>>>
>>> -#define MAX_CHANNEL (256)
>>> +//#define MAX_CHANNEL (256)
>>>
>>> static char debugfsmntdir[PATH_MAX];
>>>
>>> @@ -107,11 +107,6 @@
>>> {
>>> int fd;
>>>
>>> - if (!fname) {
>>> - fprintf(stderr, "%s: args invalid\n", __func__);
>>> - return 1;
>>> - }
>>> -
>>> fd = open(fname, O_WRONLY);
>>> if (fd == -1) {
>>> fprintf(stderr, "%s: open %s failed: %s\n", __func__, fname,
>>> @@ -227,6 +222,10 @@
>>> continue;
>>> old_list = list;
>>> list = malloc(sizeof(char *) * ++nr_chan);
>>> + if (!list) {
>>> + nr_chan = -ENOMEM;
>>> + break;
>>> + }
>>> memcpy(list, old_list, sizeof(*list) * (nr_chan - 1));
>>> free(old_list);
>>> list[nr_chan - 1] = strdup(dirent->d_name);
>>> @@ -405,7 +404,7 @@
>>> int ret;
>>> char ctlfname[PATH_MAX];
>>>
>>> - if (!name) {
>>> + if (!name || !trans) {
>>> fprintf(stderr, "%s: args invalid\n", __func__);
>>> ret = -EINVAL;
>>> goto arg_error;
>>> @@ -477,9 +476,10 @@
>>> goto op_err;
>>> }
>>>
>>> - for (; n_channel > 0; n_channel--) {
>>> + int ch = 0;
>>> + for ( ; ch < n_channel; ch++) {
>>> ret = __lttctl_set_channel_enable(name,
>>> - channellist[n_channel - 1], enable);
>>> + channellist[ch], enable);
>>> if (ret)
>>> goto op_err_clean;
>>> }
>>> @@ -541,9 +541,10 @@
>>> goto op_err;
>>> }
>>>
>>> - for (; n_channel > 0; n_channel--) {
>>> + int ch = 0;
>>> + for ( ; ch < n_channel; ch++) {
>>> ret = __lttctl_set_channel_overwrite(name,
>>> - channellist[n_channel - 1], overwrite);
>>> + channellist[ch], overwrite);
>>> if (ret)
>>> goto op_err_clean;
>>> }
>>> @@ -609,9 +610,10 @@
>>> goto op_err;
>>> }
>>>
>>> - for (; n_channel > 0; n_channel--) {
>>> + int ch = 0;
>>> + for ( ; ch < n_channel; ch++) {
>>> ret = __lttctl_set_channel_subbuf_num(name,
>>> - channellist[n_channel - 1], subbuf_num);
>>> + channellist[ch], subbuf_num);
>>> if (ret)
>>> goto op_err_clean;
>>> }
>>> @@ -677,9 +679,10 @@
>>> goto op_err;
>>> }
>>>
>>> - for (; n_channel > 0; n_channel--) {
>>> + int ch = 0;
>>> + for ( ; ch < n_channel; ch++) {
>>> ret = __lttctl_set_channel_subbuf_size(name,
>>> - channellist[n_channel - 1], subbuf_size);
>>> + channellist[ch], subbuf_size);
>>> if (ret)
>>> goto op_err_clean;
>>> }
>>> @@ -745,9 +748,10 @@
>>> goto op_err;
>>> }
>>>
>>> - for (; n_channel > 0; n_channel--) {
>>> + int ch = 0;
>>> + for ( ; ch < n_channel; ch++) {
>>> ret = __lttctl_set_channel_switch_timer(name,
>>> - channellist[n_channel - 1], switch_timer);
>>> + channellist[ch], switch_timer);
>>> if (ret)
>>> goto op_err_clean;
>>> }
>>> @@ -769,6 +773,9 @@
>>> char mnt_type[PATH_MAX];
>>> int trymount_done = 0;
>>>
>>> + if (!mntdir)
>>> + return -EINVAL;
>>> +
>>> FILE *fp = fopen("/proc/mounts", "r");
>>> if (!fp)
>>> return -EINVAL;
>>> @@ -779,14 +786,19 @@
>>> break;
>>>
>>> if (!strcmp(mnt_type, "debugfs")) {
>>> + // 4 for the LTT_PATH "/ltt", 9 for the LTT_CONTROL_PATH "/control/"
>>> + // 9 for the LTT_CHANNEL_PATH "/channel/", 13 for the LTT_BUFFERS_TIMER_PATH "/switch_timer"
>>> + // NAME_MAX for the trace name and the channel name
>>> + if (strlen(mnt_dir) >= (PATH_MAX - (4 + 9 + 9 + 13 + 2*NAME_MAX)))
>>> + return -ENOENT;
>>> strcpy(mntdir, mnt_dir);
>>> return 0;
>>> }
>>> }
>>>
>>> if (!trymount_done) {
>>> - mount("debugfs", "/sys/kernel/debug/", "debugfs", 0, NULL);
>>> trymount_done = 1;
>>> + if (!mount("debugfs", "/sys/kernel/debug/", "debugfs", 0, NULL))
>>> goto find_again;
>>> }
>>> ------------------------------
>>>
>>> It comments out the MAX_CHANNEL define, which is unused.
>>> It removes the lttctl_sendop() parameter check, which is unnecessary (this private function will always get valid arguments).
>>> It handles malloc() failure in lttctl_get_channellist(); previously, if malloc() failed while growing the channellist, one immediately got a segmentation fault.
>>> It fixes the missing parameter check in lttctl_set_trans().
>>> In each of the lttctl_set_channel_*() functions, it fixes a memory leak: the original code would count n_channel down to zero before passing it to lttctl_free_channellist(), so that none of the strings stored in the channellist array were freed.
>>> It fixes the missing parameter check in getdebugfsmntdir().
>>> It limits the length of the debugfs mounting point path, based on the longest sub-path possible (generously using PATH_MAX for the channel name, which in practice is limited to 13 characters). Otherwise, whenever sprintf is used to build a debugfs path string, the string buffer could be overrun.
>>> Finally, it prevents getdebugfsmntdir() from scanning /proc/mounts uselessly when the mount command fails.
>>>
>>> I've also written (but omitted from this patch) the following:
>>>
>>> * A version of lttctl_sendop that handles the case where the write() is incomplete. This can potentially occur, but is so rare (I think it happens only if a signal interrupts the write) that it may not be worthwhile to fix it.
>>>
>>> * A version of lttctl_get_channellist that uses readdir_r for thread safety. Is this worthwhile?
>>>
>>> Daniel U. Thibault
>>> R & D pour la défense Canada - Valcartier (RDDC Valcartier) / Defence R&D Canada - Valcartier (DRDC Valcartier)
>>> Système de systèmes (SdS) / System of Systems (SoS)
>>> Solutions informatiques et expérimentations (SIE) / Computing Solutions and Experimentations (CSE)
>>> 2459 Boul. Pie XI Nord
>>> Québec, QC G3J 1X5
>>> CANADA
>>> Vox : (418) 844-4000 x4245
>>> Fax : (418) 844-4538
>>> NAC: 918V QSDJ
>>> Gouvernement du Canada / Government of Canada
>>> <http://www.valcartier.drdc-rddc.gc.ca/>
>>>
>>> _______________________________________________
>>> lttng-dev mailing list
>>> lttng-dev at lists.lttng.org
>>> http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
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