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authorJeff Mahoney <jeffm@suse.com>2010-02-24 13:59:23 -0500
committerSteven Rostedt <rostedt@goodmis.org>2010-02-25 09:38:11 -0500
commit86c38a31aa7f2dd6e74a262710bf8ebf7455acc5 (patch)
tree167d2c46917233373e597cc5f82d3f9132170e65
parent0c54dd341fb701928b8e5dca91ced1870c55b05b (diff)
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tracing: Fix ftrace_event_call alignment for use with gcc 4.5
GCC 4.5 introduces behavior that forces the alignment of structures to use the largest possible value. The default value is 32 bytes, so if some structures are defined with a 4-byte alignment and others aren't declared with an alignment constraint at all - it will align at 32-bytes. For things like the ftrace events, this results in a non-standard array. When initializing the ftrace subsystem, we traverse the _ftrace_events section and call the initialization callback for each event. When the structures are misaligned, we could be treating another part of the structure (or the zeroed out space between them) as a function pointer. This patch forces the alignment for all the ftrace_event_call structures to 4 bytes. Without this patch, the kernel fails to boot very early when built with gcc 4.5. It's trivial to check the alignment of the members of the array, so it might be worthwhile to add something to the build system to do that automatically. Unfortunately, that only covers this case. I've asked one of the gcc developers about adding a warning when this condition is seen. Cc: stable@kernel.org Signed-off-by: Jeff Mahoney <jeffm@suse.com> LKML-Reference: <4B85770B.6010901@suse.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
-rw-r--r--include/linux/syscalls.h6
-rw-r--r--include/trace/ftrace.h3
-rw-r--r--kernel/trace/trace.h3
3 files changed, 8 insertions, 4 deletions
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index 7b219696ad24..91bd7d78a07d 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -132,7 +132,8 @@ struct perf_event_attr;
#define SYSCALL_TRACE_ENTER_EVENT(sname) \
static const struct syscall_metadata __syscall_meta_##sname; \
- static struct ftrace_event_call event_enter_##sname; \
+ static struct ftrace_event_call \
+ __attribute__((__aligned__(4))) event_enter_##sname; \
static struct trace_event enter_syscall_print_##sname = { \
.trace = print_syscall_enter, \
}; \
@@ -153,7 +154,8 @@ struct perf_event_attr;
#define SYSCALL_TRACE_EXIT_EVENT(sname) \
static const struct syscall_metadata __syscall_meta_##sname; \
- static struct ftrace_event_call event_exit_##sname; \
+ static struct ftrace_event_call \
+ __attribute__((__aligned__(4))) event_exit_##sname; \
static struct trace_event exit_syscall_print_##sname = { \
.trace = print_syscall_exit, \
}; \
diff --git a/include/trace/ftrace.h b/include/trace/ftrace.h
index 09fd9afc0859..f23a0ca6910a 100644
--- a/include/trace/ftrace.h
+++ b/include/trace/ftrace.h
@@ -65,7 +65,8 @@
};
#undef DEFINE_EVENT
#define DEFINE_EVENT(template, name, proto, args) \
- static struct ftrace_event_call event_##name
+ static struct ftrace_event_call \
+ __attribute__((__aligned__(4))) event_##name
#undef DEFINE_EVENT_PRINT
#define DEFINE_EVENT_PRINT(template, name, proto, args, print) \
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index b477fce41edf..fd05bcaf91b0 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -792,7 +792,8 @@ extern const char *__stop___trace_bprintk_fmt[];
#undef FTRACE_ENTRY
#define FTRACE_ENTRY(call, struct_name, id, tstruct, print) \
- extern struct ftrace_event_call event_##call;
+ extern struct ftrace_event_call \
+ __attribute__((__aligned__(4))) event_##call;
#undef FTRACE_ENTRY_DUP
#define FTRACE_ENTRY_DUP(call, struct_name, id, tstruct, print) \
FTRACE_ENTRY(call, struct_name, id, PARAMS(tstruct), PARAMS(print))