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| author | Jeff Mahoney <jeffm@suse.com> | 2010-02-24 13:59:23 -0500 |
|---|---|---|
| committer | Steven Rostedt <rostedt@goodmis.org> | 2010-02-25 09:38:11 -0500 |
| commit | 86c38a31aa7f2dd6e74a262710bf8ebf7455acc5 (patch) | |
| tree | 167d2c46917233373e597cc5f82d3f9132170e65 /kernel/trace | |
| parent | 0c54dd341fb701928b8e5dca91ced1870c55b05b (diff) | |
| download | linux-86c38a31aa7f2dd6e74a262710bf8ebf7455acc5.tar.bz2 | |
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>
Diffstat (limited to 'kernel/trace')
| -rw-r--r-- | kernel/trace/trace.h | 3 |
1 files changed, 2 insertions, 1 deletions
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)) |