From: "Steven Rostedt (Google)" rostedt@goodmis.org

alignof() gives an alignment of types as they would be as standalone variables. But alignment in structures might be different, and when building the fields of events, the alignment must be the actual alignment otherwise the field offsets may not match what they actually are.

This caused trace-cmd to crash, as libtraceevent did not check if the field offset was bigger than the event. The write_msr and read_msr events on 32 bit had their fields incorrect, because it had a u64 field between two ints. alignof(u64) would give 8, but the u64 field was at a 4 byte alignment.

Define a macro as:

ALIGN_STRUCTFIELD(type) ((int)(offsetof(struct {char a; type b;}, b)))

which gives the actual alignment of types in a structure.

Link: https://lkml.kernel.org/r/20220731015928.7ab3a154@rorschach.local.home

Cc: Ingo Molnar mingo@kernel.org Cc: Andrew Morton akpm@linux-foundation.org Cc: Peter Zijlstra peterz@infradead.org Cc: Thomas Gleixner tglx@linutronix.de Cc: Masami Hiramatsu mhiramat@kernel.org Cc: stable@vger.kernel.org Fixes: 04ae87a52074e ("ftrace: Rework event_create_dir()") Signed-off-by: Steven Rostedt (Google) rostedt@goodmis.org --- include/trace/stages/stage4_event_fields.h | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/include/trace/stages/stage4_event_fields.h b/include/trace/stages/stage4_event_fields.h index c3790ec7a453..80d34f396555 100644 --- a/include/trace/stages/stage4_event_fields.h +++ b/include/trace/stages/stage4_event_fields.h @@ -2,16 +2,18 @@

/* Stage 4 definitions for creating trace events */

+#define ALIGN_STRUCTFIELD(type) ((int)(offsetof(struct {char a; type b;}, b))) + #undef __field_ext #define __field_ext(_type, _item, _filter_type) { \ .type = #_type, .name = #_item, \ - .size = sizeof(_type), .align = __alignof__(_type), \ + .size = sizeof(_type), .align = ALIGN_STRUCTFIELD(_type), \ .is_signed = is_signed_type(_type), .filter_type = _filter_type },

#undef __field_struct_ext #define __field_struct_ext(_type, _item, _filter_type) { \ .type = #_type, .name = #_item, \ - .size = sizeof(_type), .align = __alignof__(_type), \ + .size = sizeof(_type), .align = ALIGN_STRUCTFIELD(_type), \ 0, .filter_type = _filter_type },

#undef __field @@ -23,7 +25,7 @@ #undef __array #define __array(_type, _item, _len) { \ .type = #_type"["__stringify(_len)"]", .name = #_item, \ - .size = sizeof(_type[_len]), .align = __alignof__(_type), \ + .size = sizeof(_type[_len]), .align = ALIGN_STRUCTFIELD(_type), \ .is_signed = is_signed_type(_type), .filter_type = FILTER_OTHER },

#undef __dynamic_array