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ftrace, kprobes: Support IPMODIFY flag to find IP modify conflict

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Introduce FTRACE_OPS_FL_IPMODIFY to avoid conflict among
ftrace users who may modify regs->ip to change the execution
path. If two or more users modify the regs->ip on the same
function entry, one of them will be broken. So they must add
IPMODIFY flag and make sure that ftrace_set_filter_ip() succeeds.

Note that ftrace doesn't allow ftrace_ops which has IPMODIFY
flag to have notrace hash, and the ftrace_ops must have a
filter hash (so that the ftrace_ops can hook only specific
entries), because it strongly depends on the address and
must be allowed for only few selected functions.

Link: http://lkml.kernel.org/r/20141121102516.11844.27829.stgit@localhost.localdomain

Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Petr Mladek <pmladek@suse.cz>
Cc: Vojtech Pavlik <vojtech@suse.cz>
Cc: Miroslav Benes <mbenes@suse.cz>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
[ fixed up some of the comments ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This commit is contained in:
Masami Hiramatsu
2014-11-21 05:25:16 -05:00
committed by Steven Rostedt
parent a017784f1b
commit f8b8be8a31
3 changed files with 159 additions and 4 deletions
Download Patch File Download Diff File Expand all files Collapse all files

142
kernel/trace/ftrace.c
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@@ -1358,6 +1358,9 @@ ftrace_hash_rec_disable_modify(struct ftrace_ops *ops, int filter_hash);
static void
ftrace_hash_rec_enable_modify(struct ftrace_ops *ops, int filter_hash);
static int ftrace_hash_ipmodify_update(struct ftrace_ops *ops,
struct ftrace_hash *new_hash);
static int
ftrace_hash_move(struct ftrace_ops *ops, int enable,
struct ftrace_hash **dst, struct ftrace_hash *src)
@@ -1368,8 +1371,13 @@ ftrace_hash_move(struct ftrace_ops *ops, int enable,
struct ftrace_hash *new_hash;
int size = src->count;
int bits = 0;
int ret;
int i;
/* Reject setting notrace hash on IPMODIFY ftrace_ops */
if (ops->flags & FTRACE_OPS_FL_IPMODIFY && !enable)
return -EINVAL;
/*
* If the new source is empty, just free dst and assign it
* the empty_hash.
@@ -1403,6 +1411,16 @@ ftrace_hash_move(struct ftrace_ops *ops, int enable,
}
update:
/* Make sure this can be applied if it is IPMODIFY ftrace_ops */
if (enable) {
/* IPMODIFY should be updated only when filter_hash updating */
ret = ftrace_hash_ipmodify_update(ops, new_hash);
if (ret < 0) {
free_ftrace_hash(new_hash);
return ret;
}
}
/*
* Remove the current set, update the hash and add
* them back.
@@ -1767,6 +1785,114 @@ static void ftrace_hash_rec_enable_modify(struct ftrace_ops *ops,
ftrace_hash_rec_update_modify(ops, filter_hash, 1);
}
/*
* Try to update IPMODIFY flag on each ftrace_rec. Return 0 if it is OK
* or no-needed to update, -EBUSY if it detects a conflict of the flag
* on a ftrace_rec, and -EINVAL if the new_hash tries to trace all recs.
* Note that old_hash and new_hash has below meanings
* - If the hash is NULL, it hits all recs (if IPMODIFY is set, this is rejected)
* - If the hash is EMPTY_HASH, it hits nothing
* - Anything else hits the recs which match the hash entries.
*/
static int __ftrace_hash_update_ipmodify(struct ftrace_ops *ops,
struct ftrace_hash *old_hash,
struct ftrace_hash *new_hash)
{
struct ftrace_page *pg;
struct dyn_ftrace *rec, *end = NULL;
int in_old, in_new;
/* Only update if the ops has been registered */
if (!(ops->flags & FTRACE_OPS_FL_ENABLED))
return 0;
if (!(ops->flags & FTRACE_OPS_FL_IPMODIFY))
return 0;
/*
* Since the IPMODIFY is a very address sensitive action, we do not
* allow ftrace_ops to set all functions to new hash.
*/
if (!new_hash || !old_hash)
return -EINVAL;
/* Update rec->flags */
do_for_each_ftrace_rec(pg, rec) {
/* We need to update only differences of filter_hash */
in_old = !!ftrace_lookup_ip(old_hash, rec->ip);
in_new = !!ftrace_lookup_ip(new_hash, rec->ip);
if (in_old == in_new)
continue;
if (in_new) {
/* New entries must ensure no others are using it */
if (rec->flags & FTRACE_FL_IPMODIFY)
goto rollback;
rec->flags |= FTRACE_FL_IPMODIFY;
} else /* Removed entry */
rec->flags &= ~FTRACE_FL_IPMODIFY;
} while_for_each_ftrace_rec();
return 0;
rollback:
end = rec;
/* Roll back what we did above */
do_for_each_ftrace_rec(pg, rec) {
if (rec == end)
goto err_out;
in_old = !!ftrace_lookup_ip(old_hash, rec->ip);
in_new = !!ftrace_lookup_ip(new_hash, rec->ip);
if (in_old == in_new)
continue;
if (in_new)
rec->flags &= ~FTRACE_FL_IPMODIFY;
else
rec->flags |= FTRACE_FL_IPMODIFY;
} while_for_each_ftrace_rec();
err_out:
return -EBUSY;
}
static int ftrace_hash_ipmodify_enable(struct ftrace_ops *ops)
{
struct ftrace_hash *hash = ops->func_hash->filter_hash;
if (ftrace_hash_empty(hash))
hash = NULL;
return __ftrace_hash_update_ipmodify(ops, EMPTY_HASH, hash);
}
/* Disabling always succeeds */
static void ftrace_hash_ipmodify_disable(struct ftrace_ops *ops)
{
struct ftrace_hash *hash = ops->func_hash->filter_hash;
if (ftrace_hash_empty(hash))
hash = NULL;
__ftrace_hash_update_ipmodify(ops, hash, EMPTY_HASH);
}
static int ftrace_hash_ipmodify_update(struct ftrace_ops *ops,
struct ftrace_hash *new_hash)
{
struct ftrace_hash *old_hash = ops->func_hash->filter_hash;
if (ftrace_hash_empty(old_hash))
old_hash = NULL;
if (ftrace_hash_empty(new_hash))
new_hash = NULL;
return __ftrace_hash_update_ipmodify(ops, old_hash, new_hash);
}
static void print_ip_ins(const char *fmt, unsigned char *p)
{
int i;
@@ -2436,6 +2562,15 @@ static int ftrace_startup(struct ftrace_ops *ops, int command)
*/
ops->flags |= FTRACE_OPS_FL_ENABLED | FTRACE_OPS_FL_ADDING;
ret = ftrace_hash_ipmodify_enable(ops);
if (ret < 0) {
/* Rollback registration process */
__unregister_ftrace_function(ops);
ftrace_start_up--;
ops->flags &= ~FTRACE_OPS_FL_ENABLED;
return ret;
}
ftrace_hash_rec_enable(ops, 1);
ftrace_startup_enable(command);
@@ -2464,6 +2599,8 @@ static int ftrace_shutdown(struct ftrace_ops *ops, int command)
*/
WARN_ON_ONCE(ftrace_start_up < 0);
/* Disabling ipmodify never fails */
ftrace_hash_ipmodify_disable(ops);
ftrace_hash_rec_disable(ops, 1);
ops->flags &= ~FTRACE_OPS_FL_ENABLED;
@@ -3058,9 +3195,10 @@ static int t_show(struct seq_file *m, void *v)
if (iter->flags & FTRACE_ITER_ENABLED) {
struct ftrace_ops *ops = NULL;
seq_printf(m, " (%ld)%s",
seq_printf(m, " (%ld)%s%s",
ftrace_rec_count(rec),
rec->flags & FTRACE_FL_REGS ? " R" : " ");
rec->flags & FTRACE_FL_REGS ? " R" : " ",
rec->flags & FTRACE_FL_IPMODIFY ? " I" : " ");
if (rec->flags & FTRACE_FL_TRAMP_EN) {
ops = ftrace_find_tramp_ops_any(rec);
if (ops)