Hello Dave,
So here is (hopefully) a final version of the proccgroup module. I've
fixed the null-terminated subsys array issue as well as an inverted
check for the ss member. Everything works as expected.
Many thanks for providing the coredump files.
Regards,
Nikolay
/*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* Nikolay Borisov <n.borisov.lkml@xxxxxxxxx>
*/
#include <stdbool.h>
#include "defs.h"
#define MAX_CGROUP_PATH 4096
static void showcgrp(void);
char *help_proc_cgroups[];
static bool have_ss_member;
static struct command_table_entry command_table[] = {
{ "showcg", showcgrp, help_proc_cgroups, 0},
{ NULL },
};
void __attribute__((constructor))
proccgroup_init(void)
{
if (!MEMBER_EXISTS("task_struct", "cgroups") ||
(!MEMBER_EXISTS("cgroup", "kn") && !MEMBER_EXISTS("cgroup", "name")))
{
error(FATAL, "Unrecognised or disabled cgroup support\n");
}
if (!MEMBER_OFFSET("cgroup_subsys_state", "ss")) {
have_ss_member = false;
error(WARNING, "pre-3.12 kernel detected, no support for getting subsys name\n");
} else
have_ss_member = true;
register_extension(command_table);
}
void __attribute__((destructor))
proccgroup_finish(void) { }
/* Prepends contents of cgroup_name to buf, using start as a pointer
* index into buf
*/
static void prepend_string(char *buf, char **start, char *cgroup_name) {
int len = strlen(cgroup_name);
*start -= len;
if (*start < buf) {
error(FATAL, "Cgroup too long to parse\n");
}
memcpy(*start, cgroup_name, len);
if (--*start < buf) {
error(FATAL, "Cgroup too long to parse\n");
}
**start = '/';
}
/* For post-3.15 kernels */
static void get_cgroup_name_kn(ulong cgroup, char *buf, int buflen)
{
ulong kernfs_node;
ulong cgroup_name_ptr;
ulong kernfs_parent;
bool slash_prepended = false;
char cgroup_name[BUFSIZE];
char *start = buf + buflen - 1;
*start = '\0'; //null terminate the end
/* Get cgroup->kn */
readmem(cgroup + MEMBER_OFFSET("cgroup", "kn"), KVADDR, &kernfs_node, sizeof(void *),
"cgroup->kn", FAULT_ON_ERROR);
do {
/* Get kn->name */
readmem(kernfs_node + MEMBER_OFFSET("kernfs_node", "name"), KVADDR, &cgroup_name_ptr, sizeof(void *),
"kernfs_node->name", FAULT_ON_ERROR);
/* Get kn->parent */
readmem(kernfs_node + MEMBER_OFFSET("kernfs_node", "parent"), KVADDR, &kernfs_parent, sizeof(void *),
"kernfs_node->parent", FAULT_ON_ERROR);
if (kernfs_parent != 0) {
read_string(cgroup_name_ptr, cgroup_name, BUFSIZE-1);
prepend_string(buf, &start, cgroup_name);
slash_prepended = true;
} else if (!slash_prepended) {
if (--start < buf) {
error(FATAL, "Cgroup too long to parse\n");
}
*start = '/';
}
kernfs_node = kernfs_parent;
} while(kernfs_parent);
memmove(buf, start, buf + buflen - start);
}
/* For pre-3.15 kernels */
static void get_cgroup_name_old(ulong cgroup, char *buf, size_t buflen)
{
ulong cgroup_name_ptr;
ulong cgroup_parent_ptr;
char cgroup_name[BUFSIZE];
char *start = buf + buflen - 1;
*start = '\0'; //null terminate the end
bool slash_prepended = false;
do {
/* Get cgroup->name */
readmem(cgroup + MEMBER_OFFSET("cgroup", "name"), KVADDR, &cgroup_name_ptr, sizeof(void *),
"cgroup->name", FAULT_ON_ERROR);
/* Get cgroup->parent */
readmem(cgroup + MEMBER_OFFSET("cgroup", "parent"), KVADDR, &cgroup_parent_ptr, sizeof(void *),
"cgroup->parent", FAULT_ON_ERROR);
read_string(cgroup_name_ptr + MEMBER_OFFSET("cgroup_name", "name"), cgroup_name, BUFSIZE-1);
if (cgroup_parent_ptr) {
prepend_string(buf, &start, cgroup_name);
slash_prepended = true;
} else if (!slash_prepended) {
if (--start < buf)
break;
*start = '/';
}
cgroup = cgroup_parent_ptr;
} while(cgroup_parent_ptr);
memmove(buf, start, buf + buflen - start);
}
static void get_subsys_name(ulong subsys, char *buf, size_t buflen)
{
ulong subsys_name_ptr;
ulong cgroup_subsys_ptr;
/* Get cgroup->kn */
readmem(subsys + MEMBER_OFFSET("cgroup_subsys_state", "ss"), KVADDR, &cgroup_subsys_ptr, sizeof(void *),
"cgroup_subsys_state->ss", FAULT_ON_ERROR);
readmem(cgroup_subsys_ptr + MEMBER_OFFSET("cgroup_subsys", "name"), KVADDR, &subsys_name_ptr, sizeof(void *),
"cgroup_subsys->name", FAULT_ON_ERROR);
read_string(subsys_name_ptr, buf, buflen-1);
}
static void get_cgroup_name(ulong cgroup, ulong subsys)
{
char *cgroup_path = GETBUF(MAX_CGROUP_PATH);
char subsys_name[BUFSIZE];
/* Handle the 2 cases of cgroup_name and the kernfs one */
if (MEMBER_EXISTS("cgroup", "kn")) {
get_cgroup_name_kn(cgroup, cgroup_path, MAX_CGROUP_PATH);
} else if (MEMBER_EXISTS("cgroup", "name")) {
get_cgroup_name_old(cgroup, cgroup_path, MAX_CGROUP_PATH);
}
/* pre-3.12 cgroup_subsys_state doesn't contain 'ss' member */
if (have_ss_member) {
get_subsys_name(subsys, subsys_name, BUFSIZE);
fprintf(fp, "subsys: %-20s cgroup: %s\n", subsys_name, cgroup_path);
} else {
fprintf(fp, "cgroup: %s\n", cgroup_path);
}
FREEBUF(cgroup_path);
}
void show_proc_cgroups(ulong task_ctx) {
int en_subsys_cnt;
int i;
ulong *cgroup_subsys_arr;
ulong subsys_base_ptr;
ulong cgroups_subsys_ptr = 0;
/* Get address of task_struct->cgroups */
readmem(task_ctx + MEMBER_OFFSET("task_struct", "cgroups"),
KVADDR, &cgroups_subsys_ptr, sizeof(void *),
"task_struct->cgroups", FAULT_ON_ERROR);
subsys_base_ptr = cgroups_subsys_ptr + MEMBER_OFFSET("css_set", "subsys");
en_subsys_cnt = MEMBER_SIZE("css_set", "subsys") / sizeof(void *);
cgroup_subsys_arr = (ulong *)GETBUF(en_subsys_cnt * sizeof(ulong));
/* Get the contents of the css_set->subsys array */
readmem(subsys_base_ptr, KVADDR, cgroup_subsys_arr, sizeof(ulong) * en_subsys_cnt,
"css_set->subsys", FAULT_ON_ERROR);
for (i = 0; i < en_subsys_cnt; i++) {
ulong cgroup;
/* Generally the subsys_array is not NULL-terminated, however
* a particular fedora kernel was NULL-terminated
*/
if (!cgroup_subsys_arr[i])
continue;
/* Get cgroup_subsys_state -> cgroup */
readmem(cgroup_subsys_arr[i] + MEMBER_OFFSET("cgroup_subsys_state", "cgroup"),
KVADDR, &cgroup, sizeof(void *), "cgroup_subsys_state->cgroup", FAULT_ON_ERROR);
get_cgroup_name(cgroup, cgroup_subsys_arr[i]);
}
FREEBUF(cgroup_subsys_arr);
}
static void showcgrp(void) {
ulong value;
struct task_context *tc;
ulong task_struct_ptr = 0;
while (args[++optind]) {
if (IS_A_NUMBER(args[optind])) {
switch (str_to_context(args[optind], &value, &tc))
{
case STR_PID:
task_struct_ptr = tc->task;
++optind;
break;
case STR_TASK:
task_struct_ptr = value;
++optind;
break;
case STR_INVALID:
error(FATAL, "invalid task or pid value: %s\n\n",
args[optind]);
break;
}
} else {
if (argcnt > 1)
error(FATAL, "invalid task or pid value: %s\n",args[optind]);
else
break;
}
}
if (!task_struct_ptr) {
task_struct_ptr = CURRENT_TASK();
}
show_proc_cgroups(task_struct_ptr);
}
char *help_proc_cgroups[] = {
"showcg",
"Show which cgroups is a process member of",
" [task | pid]",
" This command prints the cgroup for each subsys that a process is a member of",
"\nExample",
" Show the cgroup for the currently active process:\n",
" crash> showcg",
" subsys: cpuset cgroup: /user.slice/user-1000.slice/session-c1.scope",
" subsys: cpu cgroup: /user.slice/user-1000.slice/session-c1.scope",
" subsys: cpuacct cgroup: /user.slice/user-1000.slice/session-c1.scope",
" subsys: blkio cgroup: /user.slice/user-1000.slice/session-c1.scope",
" subsys: memory cgroup: /user.slice/user-1000.slice/session-c1.scope",
" subsys: devices cgroup: /user.slice/user-1000.slice/session-c1.scope",
" subsys: freezer cgroup: /user.slice/user-1000.slice/session-c1.scope",
" subsys: net_cls cgroup: /user.slice/user-1000.slice/session-c1.scope",
" subsys: perf_event cgroup: /user.slice/user-1000.slice/session-c1.scope",
" subsys: net_prio cgroup: /user.slice/user-1000.slice/session-c1.scope",
" subsys: hugetlb cgroup: /user.slice/user-1000.slice/session-c1.scope",
"\n Alternatively you can pass either a pid or a task pointer to show the cgroup the",
" respective process is a member of e.g:\n",
" crash> showcg 1064\n OR",
" crash> showcg ffff880405711b80",
NULL
};
--
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