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Date: Sun, 19 Jul 2020 17:50:33 +0200
From: Oscar Carter <oscar.carter@....com>
To: Steven Rostedt <rostedt@...dmis.org>,
Ingo Molnar <mingo@...hat.com>,
Kees Cook <keescook@...omium.org>
Cc: Oscar Carter <oscar.carter@....com>,
linux-kernel@...r.kernel.org,
kernel-hardening@...ts.openwall.com,
Jann Horn <jannh@...gle.com>
Subject: [PATCH v2 2/2] kernel/trace: Remove function callback casts
In an effort to enable -Wcast-function-type in the top-level Makefile to
support Control Flow Integrity builds, there are the need to remove all
the function callback casts.
ftrace_ops_list_func() can no longer be defined as ftrace_ops_no_ops().
The reason for ftrace_ops_no_ops() is to use that when an architecture
calls ftrace_ops_list_func() with only two parameters (called from
assembly). And to make sure there's no C side-effects, those archs call
ftrace_ops_no_ops() which only has two parameters, as the function
ftrace_ops_list_func() has four parameters.
This patch removes the no longer needed function ftrace_ops_no_ops() and
all the function callback casts using the previous defined ftrace_func
union and the two function helpers called ftrace_set_ufunc() and
ftrace_same_address_ufunc().
Signed-off-by: Oscar Carter <oscar.carter@....com>
---
kernel/trace/ftrace.c | 48 ++++++++++++++++++++++++++-----------------
1 file changed, 29 insertions(+), 19 deletions(-)
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index fd8fbb422860..124ccf914657 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -143,9 +143,7 @@ static inline bool ftrace_same_address_ufunc(union ftrace_func *ufunc,
return (ufunc->ops == func);
}
#else
-/* See comment below, where ftrace_ops_list_func is defined */
-static void ftrace_ops_no_ops(unsigned long ip, unsigned long parent_ip);
-#define ftrace_ops_list_func ((ftrace_func_t)ftrace_ops_no_ops)
+static void ftrace_ops_list_func(unsigned long ip, unsigned long parent_ip);
static inline void ftrace_set_ufunc(union ftrace_func *ufunc,
ftrace_func_no_ops_t func)
@@ -198,22 +196,29 @@ static void ftrace_sync_ipi(void *data)
smp_rmb();
}
-static ftrace_func_t ftrace_ops_get_list_func(struct ftrace_ops *ops)
+static union ftrace_func ftrace_ops_get_list_func(struct ftrace_ops *ops)
{
+ union ftrace_func list_func;
+
/*
* If this is a dynamic, RCU, or per CPU ops, or we force list func,
* then it needs to call the list anyway.
*/
if (ops->flags & (FTRACE_OPS_FL_DYNAMIC | FTRACE_OPS_FL_RCU) ||
FTRACE_FORCE_LIST_FUNC)
- return ftrace_ops_list_func;
+ ftrace_set_ufunc(&list_func, ftrace_ops_list_func);
+ else
+ list_func.ops = ftrace_ops_get_func(ops);
- return ftrace_ops_get_func(ops);
+ return list_func;
}
static void update_ftrace_function(void)
{
- ftrace_func_t func;
+ union ftrace_func func;
+#ifndef CONFIG_DYNAMIC_FTRACE
+ union ftrace_func tmp;
+#endif
/*
* Prepare the ftrace_ops that the arch callback will use.
@@ -225,7 +230,7 @@ static void update_ftrace_function(void)
/* If there's no ftrace_ops registered, just call the stub function */
if (set_function_trace_op == &ftrace_list_end) {
- func = ftrace_stub;
+ func.ops = ftrace_stub;
/*
* If we are at the end of the list and this ops is
@@ -239,21 +244,21 @@ static void update_ftrace_function(void)
} else {
/* Just use the default ftrace_ops */
set_function_trace_op = &ftrace_list_end;
- func = ftrace_ops_list_func;
+ ftrace_set_ufunc(&func, ftrace_ops_list_func);
}
update_function_graph_func();
/* If there's no change, then do nothing more here */
- if (ftrace_trace_function == func)
+ if (ftrace_trace_function == func.ops)
return;
/*
* If we are using the list function, it doesn't care
* about the function_trace_ops.
*/
- if (func == ftrace_ops_list_func) {
- ftrace_trace_function = func;
+ if (ftrace_same_address_ufunc(&func, ftrace_ops_list_func)) {
+ ftrace_trace_function = func.ops;
/*
* Don't even bother setting function_trace_ops,
* it would be racy to do so anyway.
@@ -272,7 +277,9 @@ static void update_ftrace_function(void)
* function we want, albeit indirectly, but it handles the
* ftrace_ops and doesn't depend on function_trace_op.
*/
- ftrace_trace_function = ftrace_ops_list_func;
+ ftrace_set_ufunc(&tmp, ftrace_ops_list_func);
+ ftrace_trace_function = tmp.ops;
+
/*
* Make sure all CPUs see this. Yes this is slow, but static
* tracing is slow and nasty to have enabled.
@@ -287,7 +294,7 @@ static void update_ftrace_function(void)
/* OK, we are all set to update the ftrace_trace_function now! */
#endif /* !CONFIG_DYNAMIC_FTRACE */
- ftrace_trace_function = func;
+ ftrace_trace_function = func.ops;
}
static void add_ftrace_ops(struct ftrace_ops __rcu **list,
@@ -2680,6 +2687,7 @@ void ftrace_modify_all_code(int command)
int update = command & FTRACE_UPDATE_TRACE_FUNC;
int mod_flags = 0;
int err = 0;
+ union ftrace_func func;
if (command & FTRACE_MAY_SLEEP)
mod_flags = FTRACE_MODIFY_MAY_SLEEP_FL;
@@ -2695,7 +2703,8 @@ void ftrace_modify_all_code(int command)
* traced.
*/
if (update) {
- err = ftrace_update_ftrace_func(ftrace_ops_list_func);
+ ftrace_set_ufunc(&func, ftrace_ops_list_func);
+ err = ftrace_update_ftrace_func(func.ops);
if (FTRACE_WARN_ON(err))
return;
}
@@ -2705,7 +2714,9 @@ void ftrace_modify_all_code(int command)
else if (command & FTRACE_DISABLE_CALLS)
ftrace_replace_code(mod_flags);
- if (update && ftrace_trace_function != ftrace_ops_list_func) {
+ ftrace_set_ufunc(&func, ftrace_ops_list_func);
+
+ if (update && ftrace_trace_function != func.ops) {
function_trace_op = set_function_trace_op;
smp_wmb();
/* If irqs are disabled, we are in stop machine */
@@ -6890,14 +6901,13 @@ static void ftrace_ops_list_func(unsigned long ip, unsigned long parent_ip,
{
__ftrace_ops_list_func(ip, parent_ip, NULL, regs);
}
-NOKPROBE_SYMBOL(ftrace_ops_list_func);
#else
-static void ftrace_ops_no_ops(unsigned long ip, unsigned long parent_ip)
+static void ftrace_ops_list_func(unsigned long ip, unsigned long parent_ip)
{
__ftrace_ops_list_func(ip, parent_ip, NULL, NULL);
}
-NOKPROBE_SYMBOL(ftrace_ops_no_ops);
#endif
+NOKPROBE_SYMBOL(ftrace_ops_list_func);
/*
* If there's only one function registered but it does not support
--
2.20.1
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