From 033c55fe2e326bea022c3cc5178ecf3e0e459b82 Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Wed, 4 Feb 2026 11:36:28 -0500 Subject: [PATCH] tracing: Fix ftrace event field alignments The fields of ftrace specific events (events used to save ftrace internal events like function traces and trace_printk) are generated similarly to how normal trace event fields are generated. That is, the fields are added to a trace_events_fields array that saves the name, offset, size, alignment and signness of the field. It is used to produce the output in the format file in tracefs so that tooling knows how to parse the binary data of the trace events. The issue is that some of the ftrace event structures are packed. The function graph exit event structures are one of them. The 64 bit calltime and rettime fields end up 4 byte aligned, but the algorithm to show to userspace shows them as 8 byte aligned. The macros that create the ftrace events has one for embedded structure fields. There's two macros for theses fields: __field_desc() and __field_packed() The difference of the latter macro is that it treats the field as packed. Rename that field to __field_desc_packed() and create replace the __field_packed() to be a normal field that is packed and have the calltime and rettime use those. This showed up on 32bit architectures for function graph time fields. It had: ~# cat /sys/kernel/tracing/events/ftrace/funcgraph_exit/format [..] field:unsigned long func; offset:8; size:4; signed:0; field:unsigned int depth; offset:12; size:4; signed:0; field:unsigned int overrun; offset:16; size:4; signed:0; field:unsigned long long calltime; offset:24; size:8; signed:0; field:unsigned long long rettime; offset:32; size:8; signed:0; Notice that overrun is at offset 16 with size 4, where in the structure calltime is at offset 20 (16 + 4), but it shows the offset at 24. That's because it used the alignment of unsigned long long when used as a declaration and not as a member of a structure where it would be aligned by word size (in this case 4). By using the proper structure alignment, the format has it at the correct offset: ~# cat /sys/kernel/tracing/events/ftrace/funcgraph_exit/format [..] field:unsigned long func; offset:8; size:4; signed:0; field:unsigned int depth; offset:12; size:4; signed:0; field:unsigned int overrun; offset:16; size:4; signed:0; field:unsigned long long calltime; offset:20; size:8; signed:0; field:unsigned long long rettime; offset:28; size:8; signed:0; Cc: stable@vger.kernel.org Cc: Mathieu Desnoyers Cc: Mark Rutland Acked-by: Masami Hiramatsu (Google) Reported-by: "jempty.liang" Link: https://patch.msgid.link/20260204113628.53faec78@gandalf.local.home Fixes: 04ae87a52074e ("ftrace: Rework event_create_dir()") Closes: https://lore.kernel.org/all/20260130015740.212343-1-imntjempty@163.com/ Closes: https://lore.kernel.org/all/20260202123342.2544795-1-imntjempty@163.com/ Signed-off-by: Steven Rostedt (Google) --- kernel/trace/trace.h | 7 +++++-- kernel/trace/trace_entries.h | 32 ++++++++++++++++---------------- kernel/trace/trace_export.c | 21 +++++++++++++++------ 3 files changed, 36 insertions(+), 24 deletions(-) diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h index b6d42fe06115..c11edec5d8f5 100644 --- a/kernel/trace/trace.h +++ b/kernel/trace/trace.h @@ -68,14 +68,17 @@ enum trace_type { #undef __field_fn #define __field_fn(type, item) type item; +#undef __field_packed +#define __field_packed(type, item) type item; + #undef __field_struct #define __field_struct(type, item) __field(type, item) #undef __field_desc #define __field_desc(type, container, item) -#undef __field_packed -#define __field_packed(type, container, item) +#undef __field_desc_packed +#define __field_desc_packed(type, container, item) #undef __array #define __array(type, item, size) type item[size]; diff --git a/kernel/trace/trace_entries.h b/kernel/trace/trace_entries.h index f6a8d29c0d76..54417468fdeb 100644 --- a/kernel/trace/trace_entries.h +++ b/kernel/trace/trace_entries.h @@ -79,8 +79,8 @@ FTRACE_ENTRY(funcgraph_entry, ftrace_graph_ent_entry, F_STRUCT( __field_struct( struct ftrace_graph_ent, graph_ent ) - __field_packed( unsigned long, graph_ent, func ) - __field_packed( unsigned long, graph_ent, depth ) + __field_desc_packed(unsigned long, graph_ent, func ) + __field_desc_packed(unsigned long, graph_ent, depth ) __dynamic_array(unsigned long, args ) ), @@ -96,9 +96,9 @@ FTRACE_ENTRY_PACKED(fgraph_retaddr_entry, fgraph_retaddr_ent_entry, F_STRUCT( __field_struct( struct fgraph_retaddr_ent, graph_rent ) - __field_packed( unsigned long, graph_rent.ent, func ) - __field_packed( unsigned long, graph_rent.ent, depth ) - __field_packed( unsigned long, graph_rent, retaddr ) + __field_desc_packed( unsigned long, graph_rent.ent, func ) + __field_desc_packed( unsigned long, graph_rent.ent, depth ) + __field_desc_packed( unsigned long, graph_rent, retaddr ) __dynamic_array(unsigned long, args ) ), @@ -123,12 +123,12 @@ FTRACE_ENTRY_PACKED(funcgraph_exit, ftrace_graph_ret_entry, F_STRUCT( __field_struct( struct ftrace_graph_ret, ret ) - __field_packed( unsigned long, ret, func ) - __field_packed( unsigned long, ret, retval ) - __field_packed( unsigned int, ret, depth ) - __field_packed( unsigned int, ret, overrun ) - __field(unsigned long long, calltime ) - __field(unsigned long long, rettime ) + __field_desc_packed( unsigned long, ret, func ) + __field_desc_packed( unsigned long, ret, retval ) + __field_desc_packed( unsigned int, ret, depth ) + __field_desc_packed( unsigned int, ret, overrun ) + __field_packed(unsigned long long, calltime) + __field_packed(unsigned long long, rettime ) ), F_printk("<-- %ps (%u) (start: %llx end: %llx) over: %u retval: %lx", @@ -146,11 +146,11 @@ FTRACE_ENTRY_PACKED(funcgraph_exit, ftrace_graph_ret_entry, F_STRUCT( __field_struct( struct ftrace_graph_ret, ret ) - __field_packed( unsigned long, ret, func ) - __field_packed( unsigned int, ret, depth ) - __field_packed( unsigned int, ret, overrun ) - __field(unsigned long long, calltime ) - __field(unsigned long long, rettime ) + __field_desc_packed( unsigned long, ret, func ) + __field_desc_packed( unsigned int, ret, depth ) + __field_desc_packed( unsigned int, ret, overrun ) + __field_packed(unsigned long long, calltime ) + __field_packed(unsigned long long, rettime ) ), F_printk("<-- %ps (%u) (start: %llx end: %llx) over: %u", diff --git a/kernel/trace/trace_export.c b/kernel/trace/trace_export.c index 1698fc22afa0..32a42ef31855 100644 --- a/kernel/trace/trace_export.c +++ b/kernel/trace/trace_export.c @@ -42,11 +42,14 @@ static int ftrace_event_register(struct trace_event_call *call, #undef __field_fn #define __field_fn(type, item) type item; +#undef __field_packed +#define __field_packed(type, item) type item; + #undef __field_desc #define __field_desc(type, container, item) type item; -#undef __field_packed -#define __field_packed(type, container, item) type item; +#undef __field_desc_packed +#define __field_desc_packed(type, container, item) type item; #undef __array #define __array(type, item, size) type item[size]; @@ -104,11 +107,14 @@ static void __always_unused ____ftrace_check_##name(void) \ #undef __field_fn #define __field_fn(_type, _item) __field_ext(_type, _item, FILTER_TRACE_FN) +#undef __field_packed +#define __field_packed(_type, _item) __field_ext_packed(_type, _item, FILTER_OTHER) + #undef __field_desc #define __field_desc(_type, _container, _item) __field_ext(_type, _item, FILTER_OTHER) -#undef __field_packed -#define __field_packed(_type, _container, _item) __field_ext_packed(_type, _item, FILTER_OTHER) +#undef __field_desc_packed +#define __field_desc_packed(_type, _container, _item) __field_ext_packed(_type, _item, FILTER_OTHER) #undef __array #define __array(_type, _item, _len) { \ @@ -146,11 +152,14 @@ static struct trace_event_fields ftrace_event_fields_##name[] = { \ #undef __field_fn #define __field_fn(type, item) +#undef __field_packed +#define __field_packed(type, item) + #undef __field_desc #define __field_desc(type, container, item) -#undef __field_packed -#define __field_packed(type, container, item) +#undef __field_desc_packed +#define __field_desc_packed(type, container, item) #undef __array #define __array(type, item, len) -- 2.47.3