ftrace, kprobes: Support IPMODIFY flag to find IP modify conflict
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
Steven Rostedt
Родитель
a017784f1b
Коммит
f8b8be8a31
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@ -234,6 +234,11 @@ of ftrace. Here is a list of some of the key files:
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will be displayed on the same line as the function that
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is returning registers.
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If the callback registered to be traced by a function with
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the "ip modify" attribute (thus the regs->ip can be changed),
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an 'I' will be displayed on the same line as the function that
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can be overridden.
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function_profile_enabled:
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When set it will enable all functions with either the function
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@ -61,6 +61,11 @@ ftrace_func_t ftrace_ops_get_func(struct ftrace_ops *ops);
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/*
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* FTRACE_OPS_FL_* bits denote the state of ftrace_ops struct and are
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* set in the flags member.
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* CONTROL, SAVE_REGS, SAVE_REGS_IF_SUPPORTED, RECURSION_SAFE, STUB and
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* IPMODIFY are a kind of attribute flags which can be set only before
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* registering the ftrace_ops, and can not be modified while registered.
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* Changing those attribute flags after regsitering ftrace_ops will
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* cause unexpected results.
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*
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* ENABLED - set/unset when ftrace_ops is registered/unregistered
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* DYNAMIC - set when ftrace_ops is registered to denote dynamically
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@ -101,6 +106,10 @@ ftrace_func_t ftrace_ops_get_func(struct ftrace_ops *ops);
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* The ftrace_ops trampoline can be set by the ftrace users, and
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* in such cases the arch must not modify it. Only the arch ftrace
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* core code should set this flag.
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* IPMODIFY - The ops can modify the IP register. This can only be set with
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* SAVE_REGS. If another ops with this flag set is already registered
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* for any of the functions that this ops will be registered for, then
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* this ops will fail to register or set_filter_ip.
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*/
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enum {
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FTRACE_OPS_FL_ENABLED = 1 << 0,
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@ -116,6 +125,7 @@ enum {
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FTRACE_OPS_FL_REMOVING = 1 << 10,
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FTRACE_OPS_FL_MODIFYING = 1 << 11,
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FTRACE_OPS_FL_ALLOC_TRAMP = 1 << 12,
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FTRACE_OPS_FL_IPMODIFY = 1 << 13,
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};
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#ifdef CONFIG_DYNAMIC_FTRACE
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@ -310,6 +320,7 @@ bool is_ftrace_trampoline(unsigned long addr);
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* ENABLED - the function is being traced
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* REGS - the record wants the function to save regs
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* REGS_EN - the function is set up to save regs.
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* IPMODIFY - the record allows for the IP address to be changed.
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*
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* When a new ftrace_ops is registered and wants a function to save
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* pt_regs, the rec->flag REGS is set. When the function has been
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@ -323,10 +334,11 @@ enum {
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FTRACE_FL_REGS_EN = (1UL << 29),
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FTRACE_FL_TRAMP = (1UL << 28),
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FTRACE_FL_TRAMP_EN = (1UL << 27),
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FTRACE_FL_IPMODIFY = (1UL << 26),
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};
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#define FTRACE_REF_MAX_SHIFT 27
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#define FTRACE_FL_BITS 5
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#define FTRACE_REF_MAX_SHIFT 26
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#define FTRACE_FL_BITS 6
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#define FTRACE_FL_MASKED_BITS ((1UL << FTRACE_FL_BITS) - 1)
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#define FTRACE_FL_MASK (FTRACE_FL_MASKED_BITS << FTRACE_REF_MAX_SHIFT)
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#define FTRACE_REF_MAX ((1UL << FTRACE_REF_MAX_SHIFT) - 1)
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@ -1358,6 +1358,9 @@ ftrace_hash_rec_disable_modify(struct ftrace_ops *ops, int filter_hash);
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static void
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ftrace_hash_rec_enable_modify(struct ftrace_ops *ops, int filter_hash);
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static int ftrace_hash_ipmodify_update(struct ftrace_ops *ops,
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struct ftrace_hash *new_hash);
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static int
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ftrace_hash_move(struct ftrace_ops *ops, int enable,
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struct ftrace_hash **dst, struct ftrace_hash *src)
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@ -1368,8 +1371,13 @@ ftrace_hash_move(struct ftrace_ops *ops, int enable,
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struct ftrace_hash *new_hash;
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int size = src->count;
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int bits = 0;
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int ret;
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int i;
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/* Reject setting notrace hash on IPMODIFY ftrace_ops */
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if (ops->flags & FTRACE_OPS_FL_IPMODIFY && !enable)
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return -EINVAL;
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/*
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* If the new source is empty, just free dst and assign it
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* the empty_hash.
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@ -1403,6 +1411,16 @@ ftrace_hash_move(struct ftrace_ops *ops, int enable,
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}
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update:
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/* Make sure this can be applied if it is IPMODIFY ftrace_ops */
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if (enable) {
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/* IPMODIFY should be updated only when filter_hash updating */
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ret = ftrace_hash_ipmodify_update(ops, new_hash);
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if (ret < 0) {
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free_ftrace_hash(new_hash);
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return ret;
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}
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}
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/*
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* Remove the current set, update the hash and add
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* them back.
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@ -1767,6 +1785,114 @@ static void ftrace_hash_rec_enable_modify(struct ftrace_ops *ops,
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ftrace_hash_rec_update_modify(ops, filter_hash, 1);
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}
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/*
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* Try to update IPMODIFY flag on each ftrace_rec. Return 0 if it is OK
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* or no-needed to update, -EBUSY if it detects a conflict of the flag
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* on a ftrace_rec, and -EINVAL if the new_hash tries to trace all recs.
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* Note that old_hash and new_hash has below meanings
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* - If the hash is NULL, it hits all recs (if IPMODIFY is set, this is rejected)
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* - If the hash is EMPTY_HASH, it hits nothing
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* - Anything else hits the recs which match the hash entries.
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*/
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static int __ftrace_hash_update_ipmodify(struct ftrace_ops *ops,
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struct ftrace_hash *old_hash,
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struct ftrace_hash *new_hash)
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{
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struct ftrace_page *pg;
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struct dyn_ftrace *rec, *end = NULL;
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int in_old, in_new;
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/* Only update if the ops has been registered */
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if (!(ops->flags & FTRACE_OPS_FL_ENABLED))
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return 0;
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if (!(ops->flags & FTRACE_OPS_FL_IPMODIFY))
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return 0;
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/*
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* Since the IPMODIFY is a very address sensitive action, we do not
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* allow ftrace_ops to set all functions to new hash.
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*/
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if (!new_hash || !old_hash)
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return -EINVAL;
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/* Update rec->flags */
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do_for_each_ftrace_rec(pg, rec) {
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/* We need to update only differences of filter_hash */
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in_old = !!ftrace_lookup_ip(old_hash, rec->ip);
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in_new = !!ftrace_lookup_ip(new_hash, rec->ip);
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if (in_old == in_new)
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continue;
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if (in_new) {
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/* New entries must ensure no others are using it */
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if (rec->flags & FTRACE_FL_IPMODIFY)
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goto rollback;
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rec->flags |= FTRACE_FL_IPMODIFY;
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} else /* Removed entry */
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rec->flags &= ~FTRACE_FL_IPMODIFY;
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} while_for_each_ftrace_rec();
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return 0;
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rollback:
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end = rec;
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/* Roll back what we did above */
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do_for_each_ftrace_rec(pg, rec) {
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if (rec == end)
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goto err_out;
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in_old = !!ftrace_lookup_ip(old_hash, rec->ip);
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in_new = !!ftrace_lookup_ip(new_hash, rec->ip);
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if (in_old == in_new)
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continue;
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if (in_new)
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rec->flags &= ~FTRACE_FL_IPMODIFY;
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else
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rec->flags |= FTRACE_FL_IPMODIFY;
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} while_for_each_ftrace_rec();
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err_out:
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return -EBUSY;
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}
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static int ftrace_hash_ipmodify_enable(struct ftrace_ops *ops)
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{
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struct ftrace_hash *hash = ops->func_hash->filter_hash;
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if (ftrace_hash_empty(hash))
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hash = NULL;
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return __ftrace_hash_update_ipmodify(ops, EMPTY_HASH, hash);
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}
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/* Disabling always succeeds */
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static void ftrace_hash_ipmodify_disable(struct ftrace_ops *ops)
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{
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struct ftrace_hash *hash = ops->func_hash->filter_hash;
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if (ftrace_hash_empty(hash))
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hash = NULL;
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__ftrace_hash_update_ipmodify(ops, hash, EMPTY_HASH);
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}
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static int ftrace_hash_ipmodify_update(struct ftrace_ops *ops,
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struct ftrace_hash *new_hash)
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{
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struct ftrace_hash *old_hash = ops->func_hash->filter_hash;
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if (ftrace_hash_empty(old_hash))
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old_hash = NULL;
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if (ftrace_hash_empty(new_hash))
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new_hash = NULL;
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return __ftrace_hash_update_ipmodify(ops, old_hash, new_hash);
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}
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static void print_ip_ins(const char *fmt, unsigned char *p)
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{
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int i;
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@ -2436,6 +2562,15 @@ static int ftrace_startup(struct ftrace_ops *ops, int command)
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*/
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ops->flags |= FTRACE_OPS_FL_ENABLED | FTRACE_OPS_FL_ADDING;
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ret = ftrace_hash_ipmodify_enable(ops);
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if (ret < 0) {
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/* Rollback registration process */
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__unregister_ftrace_function(ops);
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ftrace_start_up--;
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ops->flags &= ~FTRACE_OPS_FL_ENABLED;
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return ret;
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}
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ftrace_hash_rec_enable(ops, 1);
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ftrace_startup_enable(command);
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@ -2464,6 +2599,8 @@ static int ftrace_shutdown(struct ftrace_ops *ops, int command)
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*/
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WARN_ON_ONCE(ftrace_start_up < 0);
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/* Disabling ipmodify never fails */
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ftrace_hash_ipmodify_disable(ops);
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ftrace_hash_rec_disable(ops, 1);
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ops->flags &= ~FTRACE_OPS_FL_ENABLED;
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@ -3058,9 +3195,10 @@ static int t_show(struct seq_file *m, void *v)
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if (iter->flags & FTRACE_ITER_ENABLED) {
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struct ftrace_ops *ops = NULL;
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seq_printf(m, " (%ld)%s",
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seq_printf(m, " (%ld)%s%s",
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ftrace_rec_count(rec),
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rec->flags & FTRACE_FL_REGS ? " R" : " ");
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rec->flags & FTRACE_FL_REGS ? " R" : " ",
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rec->flags & FTRACE_FL_IPMODIFY ? " I" : " ");
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if (rec->flags & FTRACE_FL_TRAMP_EN) {
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ops = ftrace_find_tramp_ops_any(rec);
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if (ops)
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