kernel/linux.git/include/linux/trace_seq.h, branch v6.19.11

tracing: Add trace_seq_pop() and seq_buf_pop()

2025-10-29T00:10:59+00:00

In order to allow an interface to remove an added character from the trace_seq and seq_buf descriptors, add helper functions trace_seq_pop() and seq_buf_pop(). Cc: Masami Hiramatsu Cc: Mark Rutland Cc: Mathieu Desnoyers Cc: Andrew Morton Cc: Peter Zijlstra Cc: Namhyung Kim Cc: Takaya Saeki Cc: Tom Zanussi Cc: Thomas Gleixner Cc: Ian Rogers Cc: Douglas Raillard Cc: Arnaldo Carvalho de Melo Cc: Jiri Olsa Cc: Adrian Hunter Cc: Ingo Molnar Link: https://lore.kernel.org/20251028231148.594898736@kernel.org Signed-off-by: Steven Rostedt (Google)

tracing: Move buffer in trace_seq to end of struct

2025-09-23T13:37:31+00:00

TRACE_SEQ_BUFFER_SIZE is dependent on the architecture for its size. on 64-bit systems, it is 8148 bytes. forced 8-byte alignment in size_t and seq_buf means that trace_seq is 8200 bytes on 64-bit systems. moving the buffer to the end of the struct fixes the issue. there shouldn't be any side effects, i.e. pointer arithmetic on trace_seq Cc: Masami Hiramatsu Cc: Mathieu Desnoyers Link: https://lore.kernel.org/20250821053917.23301-1-git@elijahs.space Signed-off-by: Elijah Wright Signed-off-by: Steven Rostedt (Google)

tracing: Mark binary printing functions with __printf() attribute

2025-03-28T12:37:11+00:00

Binary printing functions are using printf() type of format, and compiler is not happy about them as is: kernel/trace/trace.c:3292:9: error: function ‘trace_vbprintk’ might be a candidate for ‘gnu_printf’ format attribute [-Werror=suggest-attribute=format] kernel/trace/trace_seq.c:182:9: error: function ‘trace_seq_bprintf’ might be a candidate for ‘gnu_printf’ format attribute [-Werror=suggest-attribute=format] Fix the compilation errors by adding __printf() attribute. While at it, move existing __printf() attributes from the implementations to the declarations. IT also fixes incorrect attribute parameters that are used for trace_array_printk(). Signed-off-by: Andy Shevchenko Reviewed-by: Kees Cook Reviewed-by: Petr Mladek Link: https://lore.kernel.org/r/20250321144822.324050-4-andriy.shevchenko@linux.intel.com Signed-off-by: Petr Mladek

tracing: Limit trace_seq size to just 8K and not depend on architecture PAGE_SIZE

2024-03-06T18:27:00+00:00

The trace_seq buffer is used to print out entire events. It's typically set to PAGE_SIZE * 2 as there's some events that can be quite large. As a side effect, writes to trace_marker is limited by both the size of the trace_seq buffer as well as the ring buffer's sub-buffer size (which is a power of PAGE_SIZE). By limiting the trace_seq size, it also limits the size of the largest string written to trace_marker. trace_seq does not need to be dependent on PAGE_SIZE like the ring buffer sub-buffers need to be. Hard code it to 8K which is PAGE_SIZE * 2 on most architectures. This will also limit the size of trace_marker on those architectures with greater than 4K PAGE_SIZE. Link: https://lore.kernel.org/all/20240302111244.3a1674be@gandalf.local.home/ Link: https://lore.kernel.org/linux-trace-kernel/20240304191342.56fb1087@gandalf.local.home Cc: Masami Hiramatsu Cc: Mathieu Desnoyers Cc: Linus Torvalds Cc: Sachin Sant Signed-off-by: Steven Rostedt (Google)

trace_seq: Increase the buffer size to almost two pages

2023-12-19T04:14:16+00:00

Now that trace_marker can hold more than 1KB string, and can write as much as the ring buffer can hold, the trace_seq is not big enough to hold writes: ~# a="1234567890" ~# cnt=4080 ~# s="" ~# while [ $cnt -gt 10 ]; do ~# s="${s}${a}" ~# cnt=$((cnt-10)) ~# done ~# echo $s > trace_marker ~# cat trace # tracer: nop # # entries-in-buffer/entries-written: 2/2 #P:8 # # _-----=> irqs-off/BH-disabled # / _----=> need-resched # | / _---=> hardirq/softirq # || / _--=> preempt-depth # ||| / _-=> migrate-disable # |||| / delay # TASK-PID CPU# ||||| TIMESTAMP FUNCTION # | | | ||||| | | <...>-860 [002] ..... 105.543465: tracing_mark_write[LINE TOO BIG] <...>-860 [002] ..... 105.543496: tracing_mark_write: 789012345678901234567890 By increasing the trace_seq buffer to almost two pages, it can now print out the first line. This also subtracts the rest of the trace_seq fields from the buffer, so that the entire trace_seq is now PAGE_SIZE aligned. Link: https://lore.kernel.org/linux-trace-kernel/20231209175220.19867af4@gandalf.local.home Cc: Mark Rutland Cc: Mathieu Desnoyers Reviewed-by: Masami Hiramatsu (Google) Signed-off-by: Steven Rostedt (Google)

tracing: Move readpos from seq_buf to trace_seq

2023-10-20T16:16:10+00:00

To make seq_buf more lightweight as a string buf, move the readpos member from seq_buf to its container, trace_seq. That puts the responsibility of maintaining the readpos entirely in the tracing code. If some future users want to package up the readpos with a seq_buf, we can define a new struct then. Link: https://lore.kernel.org/linux-trace-kernel/20231020033545.2587554-2-willy@infradead.org Cc: Kees Cook Cc: Justin Stitt Cc: Kent Overstreet Cc: Petr Mladek Cc: Andy Shevchenko Cc: Rasmus Villemoes Cc: Sergey Senozhatsky Signed-off-by: Matthew Wilcox (Oracle) Reviewed-by: Christoph Hellwig Acked-by: Greg Kroah-Hartman Signed-off-by: Steven Rostedt (Google)

tracing: Acquire buffer from temparary trace sequence

2023-02-07T17:42:54+00:00

there is one dwc3 trace event declare as below, DECLARE_EVENT_CLASS(dwc3_log_event, TP_PROTO(u32 event, struct dwc3 *dwc), TP_ARGS(event, dwc), TP_STRUCT__entry( __field(u32, event) __field(u32, ep0state) __dynamic_array(char, str, DWC3_MSG_MAX) ), TP_fast_assign( __entry->event = event; __entry->ep0state = dwc->ep0state; ), TP_printk("event (%08x): %s", __entry->event, dwc3_decode_event(__get_str(str), DWC3_MSG_MAX, __entry->event, __entry->ep0state)) ); the problem is when trace function called, it will allocate up to DWC3_MSG_MAX bytes from trace event buffer, but never fill the buffer during fast assignment, it only fill the buffer when output function are called, so this means if output function are not called, the buffer will never used. add __get_buf(len) which acquiree buffer from iter->tmp_seq when trace output function called, it allow user write string to acquired buffer. the mentioned dwc3 trace event will changed as below, DECLARE_EVENT_CLASS(dwc3_log_event, TP_PROTO(u32 event, struct dwc3 *dwc), TP_ARGS(event, dwc), TP_STRUCT__entry( __field(u32, event) __field(u32, ep0state) ), TP_fast_assign( __entry->event = event; __entry->ep0state = dwc->ep0state; ), TP_printk("event (%08x): %s", __entry->event, dwc3_decode_event(__get_buf(DWC3_MSG_MAX), DWC3_MSG_MAX, __entry->event, __entry->ep0state)) );. Link: https://lore.kernel.org/linux-trace-kernel/1675065249-23368-1-git-send-email-quic_linyyuan@quicinc.com Cc: Masami Hiramatsu Signed-off-by: Linyu Yuan Signed-off-by: Steven Rostedt (Google)

tracing: Fix some checker warnings

2022-12-10T18:36:05+00:00

Fix some checker warnings in the trace code by adding __printf attributes to a number of trace functions and their declarations. Changes: ======== ver #2) - Dropped the fix for the unconditional tracing_max_lat_fops decl[1]. Link: https://lore.kernel.org/r/20221205180617.9b9d3971cbe06ee536603523@kernel.org/ [1] Link: https://lore.kernel.org/r/166992525941.1716618.13740663757583361463.stgit@warthog.procyon.org.uk/ # v1 Link: https://lkml.kernel.org/r/167023571258.382307.15314866482834835192.stgit@warthog.procyon.org.uk Signed-off-by: David Howells Signed-off-by: Steven Rostedt (Google)

seq_buf: Avoid type mismatch for seq_buf_init

2020-12-07T23:25:02+00:00

Building with W=2 prints a number of warnings for one function that has a pointer type mismatch: linux/seq_buf.h: In function 'seq_buf_init': linux/seq_buf.h:35:12: warning: pointer targets in assignment from 'unsigned char *' to 'char *' differ in signedness [-Wpointer-sign] Change the type in the function prototype according to the type in the structure. Link: https://lkml.kernel.org/r/20201026161108.3707783-1-arnd@kernel.org Fixes: 9a7777935c34 ("tracing: Convert seq_buf fields to be like seq_file fields") Reviewed-by: Cezary Rojewski Signed-off-by: Arnd Bergmann Signed-off-by: Steven Rostedt (VMware)

tracing: Use seq_buf_hex_dump() to dump buffers

2019-11-14T18:15:12+00:00

Without this, buffers can be printed with __print_array macro that has no formatting options and can be hard to read. The other way is to mimic formatting capability with multiple calls of trace event with one call per row which gives performance impact and different timestamp in each row. Link: http://lkml.kernel.org/r/1573130738-29390-2-git-send-email-piotrx.maziarz@linux.intel.com Signed-off-by: Piotr Maziarz Signed-off-by: Cezary Rojewski Signed-off-by: Steven Rostedt (VMware)