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>
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 7b2616f..ed50195 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -61,6 +61,11 @@
/*
* FTRACE_OPS_FL_* bits denote the state of ftrace_ops struct and are
* set in the flags member.
+ * CONTROL, SAVE_REGS, SAVE_REGS_IF_SUPPORTED, RECURSION_SAFE, STUB and
+ * IPMODIFY are a kind of attribute flags which can be set only before
+ * registering the ftrace_ops, and can not be modified while registered.
+ * Changing those attribute flags after regsitering ftrace_ops will
+ * cause unexpected results.
*
* ENABLED - set/unset when ftrace_ops is registered/unregistered
* DYNAMIC - set when ftrace_ops is registered to denote dynamically
@@ -101,6 +106,10 @@
* The ftrace_ops trampoline can be set by the ftrace users, and
* in such cases the arch must not modify it. Only the arch ftrace
* core code should set this flag.
+ * IPMODIFY - The ops can modify the IP register. This can only be set with
+ * SAVE_REGS. If another ops with this flag set is already registered
+ * for any of the functions that this ops will be registered for, then
+ * this ops will fail to register or set_filter_ip.
*/
enum {
FTRACE_OPS_FL_ENABLED = 1 << 0,
@@ -116,6 +125,7 @@
FTRACE_OPS_FL_REMOVING = 1 << 10,
FTRACE_OPS_FL_MODIFYING = 1 << 11,
FTRACE_OPS_FL_ALLOC_TRAMP = 1 << 12,
+ FTRACE_OPS_FL_IPMODIFY = 1 << 13,
};
#ifdef CONFIG_DYNAMIC_FTRACE
@@ -310,6 +320,7 @@
* ENABLED - the function is being traced
* REGS - the record wants the function to save regs
* REGS_EN - the function is set up to save regs.
+ * IPMODIFY - the record allows for the IP address to be changed.
*
* When a new ftrace_ops is registered and wants a function to save
* pt_regs, the rec->flag REGS is set. When the function has been
@@ -323,10 +334,11 @@
FTRACE_FL_REGS_EN = (1UL << 29),
FTRACE_FL_TRAMP = (1UL << 28),
FTRACE_FL_TRAMP_EN = (1UL << 27),
+ FTRACE_FL_IPMODIFY = (1UL << 26),
};
-#define FTRACE_REF_MAX_SHIFT 27
-#define FTRACE_FL_BITS 5
+#define FTRACE_REF_MAX_SHIFT 26
+#define FTRACE_FL_BITS 6
#define FTRACE_FL_MASKED_BITS ((1UL << FTRACE_FL_BITS) - 1)
#define FTRACE_FL_MASK (FTRACE_FL_MASKED_BITS << FTRACE_REF_MAX_SHIFT)
#define FTRACE_REF_MAX ((1UL << FTRACE_REF_MAX_SHIFT) - 1)