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authorSteven Rostedt (VMware) <rostedt@goodmis.org>2018-01-22 22:32:51 -0500
committerSteven Rostedt (VMware) <rostedt@goodmis.org>2018-01-23 15:56:55 -0500
commit6be7fa3c74d1e0cd50f2157b5c1524f152bf641e (patch)
tree4ce16d7acac4f57ab60005997ca097faaf216e87 /arch
parente2ac83d74a4d753cea88407e65136c84a0cb60b2 (diff)
downloadlinux-6be7fa3c74d1e0cd50f2157b5c1524f152bf641e.tar.bz2
ftrace, orc, x86: Handle ftrace dynamically allocated trampolines
The function tracer can create a dynamically allocated trampoline that is called by the function mcount or fentry hook that is used to call the function callback that is registered. The problem is that the orc undwinder will bail if it encounters one of these trampolines. This breaks the stack trace of function callbacks, which include the stack tracer and setting the stack trace for individual functions. Since these dynamic trampolines are basically copies of the static ftrace trampolines defined in ftrace_*.S, we do not need to create new orc entries for the dynamic trampolines. Finding the return address on the stack will be identical as the functions that were copied to create the dynamic trampolines. When encountering a ftrace dynamic trampoline, we can just use the orc entry of the ftrace static function that was copied for that trampoline. Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/kernel/unwind_orc.c48
1 files changed, 47 insertions, 1 deletions
diff --git a/arch/x86/kernel/unwind_orc.c b/arch/x86/kernel/unwind_orc.c
index be86a865087a..1f9188f5357c 100644
--- a/arch/x86/kernel/unwind_orc.c
+++ b/arch/x86/kernel/unwind_orc.c
@@ -74,8 +74,50 @@ static struct orc_entry *orc_module_find(unsigned long ip)
}
#endif
+#ifdef CONFIG_DYNAMIC_FTRACE
+static struct orc_entry *orc_find(unsigned long ip);
+
+/*
+ * Ftrace dynamic trampolines do not have orc entries of their own.
+ * But they are copies of the ftrace entries that are static and
+ * defined in ftrace_*.S, which do have orc entries.
+ *
+ * If the undwinder comes across a ftrace trampoline, then find the
+ * ftrace function that was used to create it, and use that ftrace
+ * function's orc entrie, as the placement of the return code in
+ * the stack will be identical.
+ */
+static struct orc_entry *orc_ftrace_find(unsigned long ip)
+{
+ struct ftrace_ops *ops;
+ unsigned long caller;
+
+ ops = ftrace_ops_trampoline(ip);
+ if (!ops)
+ return NULL;
+
+ if (ops->flags & FTRACE_OPS_FL_SAVE_REGS)
+ caller = (unsigned long)ftrace_regs_call;
+ else
+ caller = (unsigned long)ftrace_call;
+
+ /* Prevent unlikely recursion */
+ if (ip == caller)
+ return NULL;
+
+ return orc_find(caller);
+}
+#else
+static struct orc_entry *orc_ftrace_find(unsigned long ip)
+{
+ return NULL;
+}
+#endif
+
static struct orc_entry *orc_find(unsigned long ip)
{
+ static struct orc_entry *orc;
+
if (!orc_init)
return NULL;
@@ -111,7 +153,11 @@ static struct orc_entry *orc_find(unsigned long ip)
__stop_orc_unwind_ip - __start_orc_unwind_ip, ip);
/* Module lookup: */
- return orc_module_find(ip);
+ orc = orc_module_find(ip);
+ if (orc)
+ return orc;
+
+ return orc_ftrace_find(ip);
}
static void orc_sort_swap(void *_a, void *_b, int size)