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tracing: Use linker magic instead of recasting ftrace_ops_list_func() 

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@gmx.com>
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt (VMware) 2020-06-17 16:56:16 -04:00
parent affc659246
commit 34cdd18b8d
3 changed files with 28 additions and 17 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
include/asm-generic/vmlinux.lds.h
View File

@ -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

12
include/linux/ftrace.h
View File

@ -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 {

23
kernel/trace/ftrace.c
View File

@ -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 @@ out:
* 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