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Message-ID: <20211022204841.027696836@goodmis.org>
Date: Fri, 22 Oct 2021 16:48:12 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: linux-kernel@...r.kernel.org
Cc: Ingo Molnar <mingo@...nel.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Oscar Carter <oscar.carter@....com>,
kernel test robot <lkp@...el.com>
Subject: [for-next][PATCH 16/40] tracing: Use linker magic instead of recasting ftrace_ops_list_func()
From: "Steven Rostedt (VMware)" <rostedt@...dmis.org>
In an effort to enable -Wcast-function-type in the top-level Makefile to
support Control Flow Integrity builds, all function casts need to be
removed.
This means that 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
ftrace_ops_list_func() has four parameters.
Instead of a typecast, use vmlinux.lds.h to define ftrace_ops_list_func() to
arch_ftrace_ops_list_func() that will define the proper set of parameters.
Link: https://lore.kernel.org/r/20200614070154.6039-1-oscar.carter@gmx.com
Link: https://lkml.kernel.org/r/20200617165616.52241bde@oasis.local.home
Link: https://lore.kernel.org/all/20211005053922.GA702049@embeddedor/
Requested-by: Oscar Carter <oscar.carter@....com>
Reported-by: kernel test robot <lkp@...el.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
---
include/asm-generic/vmlinux.lds.h | 10 ++++++++--
include/linux/ftrace.h | 12 ++++++++++--
kernel/trace/ftrace.c | 23 ++++++++++-------------
3 files changed, 28 insertions(+), 17 deletions(-)
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index f2984af2b85b..8771c435f34b 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -164,16 +164,22 @@
* Need to also make ftrace_stub_graph point to ftrace_stub
* so that the same stub location may have different protocols
* and not mess up with C verifiers.
+ *
+ * ftrace_ops_list_func will be defined as arch_ftrace_ops_list_func
+ * as some archs will have a different prototype for that function
+ * but ftrace_ops_list_func() will have a single prototype.
*/
#define MCOUNT_REC() . = ALIGN(8); \
__start_mcount_loc = .; \
KEEP(*(__mcount_loc)) \
KEEP(*(__patchable_function_entries)) \
__stop_mcount_loc = .; \
- ftrace_stub_graph = ftrace_stub;
+ ftrace_stub_graph = ftrace_stub; \
+ ftrace_ops_list_func = arch_ftrace_ops_list_func;
#else
# ifdef CONFIG_FUNCTION_TRACER
-# define MCOUNT_REC() ftrace_stub_graph = ftrace_stub;
+# define MCOUNT_REC() ftrace_stub_graph = ftrace_stub; \
+ ftrace_ops_list_func = arch_ftrace_ops_list_func;
# else
# define MCOUNT_REC()
# endif
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 832e65f06754..12fcfa2d23ea 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -30,16 +30,26 @@
#define ARCH_SUPPORTS_FTRACE_OPS 0
#endif
+#ifdef CONFIG_FUNCTION_TRACER
+struct ftrace_ops;
+struct ftrace_regs;
/*
* If the arch's mcount caller does not support all of ftrace's
* features, then it must call an indirect function that
* does. Or at least does enough to prevent any unwelcome side effects.
+ *
+ * Also define the function prototype that these architectures use
+ * to call the ftrace_ops_list_func().
*/
#if !ARCH_SUPPORTS_FTRACE_OPS
# define FTRACE_FORCE_LIST_FUNC 1
+void arch_ftrace_ops_list_func(unsigned long ip, unsigned long parent_ip);
#else
# define FTRACE_FORCE_LIST_FUNC 0
+void arch_ftrace_ops_list_func(unsigned long ip, unsigned long parent_ip,
+ struct ftrace_ops *op, struct ftrace_regs *fregs);
#endif
+#endif /* CONFIG_FUNCTION_TRACER */
/* Main tracing buffer and events set up */
#ifdef CONFIG_TRACING
@@ -88,8 +98,6 @@ extern int
ftrace_enable_sysctl(struct ctl_table *table, int write,
void *buffer, size_t *lenp, loff_t *ppos);
-struct ftrace_ops;
-
#ifndef CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS
struct ftrace_regs {
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 2c3e9760df7f..8b5801881271 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -119,14 +119,9 @@ struct ftrace_ops __rcu *ftrace_ops_list __read_mostly = &ftrace_list_end;
ftrace_func_t ftrace_trace_function __read_mostly = ftrace_stub;
struct ftrace_ops global_ops;
-#if ARCH_SUPPORTS_FTRACE_OPS
-static void ftrace_ops_list_func(unsigned long ip, unsigned long parent_ip,
- struct ftrace_ops *op, struct ftrace_regs *fregs);
-#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)
-#endif
+/* Defined by vmlinux.lds.h see the commment above arch_ftrace_ops_list_func for details */
+void ftrace_ops_list_func(unsigned long ip, unsigned long parent_ip,
+ struct ftrace_ops *op, struct ftrace_regs *fregs);
static inline void ftrace_ops_init(struct ftrace_ops *ops)
{
@@ -7032,21 +7027,23 @@ __ftrace_ops_list_func(unsigned long ip, unsigned long parent_ip,
* Note, CONFIG_DYNAMIC_FTRACE_WITH_REGS expects a full regs to be saved.
* An architecture can pass partial regs with ftrace_ops and still
* set the ARCH_SUPPORTS_FTRACE_OPS.
+ *
+ * In vmlinux.lds.h, ftrace_ops_list_func() is defined to be
+ * arch_ftrace_ops_list_func.
*/
#if ARCH_SUPPORTS_FTRACE_OPS
-static void ftrace_ops_list_func(unsigned long ip, unsigned long parent_ip,
- struct ftrace_ops *op, struct ftrace_regs *fregs)
+void arch_ftrace_ops_list_func(unsigned long ip, unsigned long parent_ip,
+ struct ftrace_ops *op, struct ftrace_regs *fregs)
{
__ftrace_ops_list_func(ip, parent_ip, NULL, fregs);
}
-NOKPROBE_SYMBOL(ftrace_ops_list_func);
#else
-static void ftrace_ops_no_ops(unsigned long ip, unsigned long parent_ip)
+void arch_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(arch_ftrace_ops_list_func);
/*
* If there's only one function registered but it does not support
--
2.33.0
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