From 26f255646e0ca6fde0e994e2a815ba2b31770dce Mon Sep 17 00:00:00 2001 From: Tom Zanussi Date: Fri, 17 Jan 2014 15:11:44 -0600 Subject: tracing/README: Add event file usage to tracing mini-HOWTO It would be useful to have a cheat-sheet for everything under tracing/events/ alongside the existing text describing the other files in the tracing/ dir. Add short descriptions of the directories and files under events/ along with examples, similar to the existing text for the other files in tracing/. Also clean up a few minor alignment problems noticed when adding the new text. Link: http://lkml.kernel.org/r/1389993104.3040.445.camel@empanada Signed-off-by: Tom Zanussi Signed-off-by: Steven Rostedt diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 20c755e..2ced5e5 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -3523,9 +3523,9 @@ static const char readme_msg[] = #ifdef CONFIG_DYNAMIC_FTRACE "\n available_filter_functions - list of functions that can be filtered on\n" " set_ftrace_filter\t- echo function name in here to only trace these functions\n" - " accepts: func_full_name, *func_end, func_begin*, *func_middle*\n" - " modules: Can select a group via module\n" - " Format: :mod:\n" + " accepts: func_full_name, *func_end, func_begin*, *func_middle*\n" + " modules: Can select a group via module\n" + " Format: :mod:\n" " example: echo :mod:ext3 > set_ftrace_filter\n" " triggers: a command to perform when function is hit\n" " Format: :[:count]\n" @@ -3573,6 +3573,37 @@ static const char readme_msg[] = " stack_trace_filter\t- Like set_ftrace_filter but limits what stack_trace traces\n" #endif #endif /* CONFIG_STACK_TRACER */ + " events/\t\t- Directory containing all trace event subsystems:\n" + " enable\t\t- Write 0/1 to enable/disable tracing of all events\n" + " events//\t- Directory containing all trace events for :\n" + " enable\t\t- Write 0/1 to enable/disable tracing of all events\n" + " filter\t\t- If set, only events passing filter are traced\n" + " events///\t- Directory containing control files for :\n" + " enable\t\t- Write 0/1 to enable/disable tracing of \n" + " filter\t\t- If set, only events passing filter are traced\n" + " trigger\t\t- If set, a command to perform when event is hit\n" + " Format: [:count][if ]\n" + " trigger: traceon, traceoff\n" + " enable_event::\n" + " disable_event::\n" +#ifdef CONFIG_STACKTRACE + " stacktrace\n" +#endif +#ifdef CONFIG_TRACER_SNAPSHOT + " snapshot\n" +#endif + " example: echo traceoff > events/block/block_unplug/trigger\n" + " echo traceoff:3 > events/block/block_unplug/trigger\n" + " echo 'enable_event:kmem:kmalloc:3 if nr_rq > 1' > events/block/block_unplug/trigger\n" + " The first disables tracing every time block_unplug is hit.\n" + " The second disables tracing the first 3 times block_unplug is hit.\n" + " The third enables the kmalloc event the first 3 times block_unplug\n" + " is hit and has value of greater than 1 for the 'nr_rq' event field.\n" + " To remove a trigger without a count:\n" + " echo '! > //trigger\n" + " To remove a trigger with a count:\n" + " echo '!:0 > //trigger\n" + " Filters can be ignored when removing a trigger.\n" ; static ssize_t -- cgit v0.10.2 From 71485c45891b8a0fcc4ce22d87251424ab51e096 Mon Sep 17 00:00:00 2001 From: "Steven Rostedt (Red Hat)" Date: Thu, 23 Jan 2014 00:10:04 -0500 Subject: tracing: Fix formatting of trace README file Fix the formatting of the README file in the trace debugfs to fit in an 80 character window. Also add a comment about the event trigger counter with regards to traceon and traceoff. Signed-off-by: Steven Rostedt diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 2ced5e5..7857ea9 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -3519,91 +3519,103 @@ static const char readme_msg[] = " instances\t\t- Make sub-buffers with: mkdir instances/foo\n" "\t\t\t Remove sub-buffer with rmdir\n" " trace_options\t\t- Set format or modify how tracing happens\n" - "\t\t\t Disable an option by adding a suffix 'no' to the option name\n" + "\t\t\t Disable an option by adding a suffix 'no' to the\n" + "\t\t\t option name\n" #ifdef CONFIG_DYNAMIC_FTRACE "\n available_filter_functions - list of functions that can be filtered on\n" - " set_ftrace_filter\t- echo function name in here to only trace these functions\n" - " accepts: func_full_name, *func_end, func_begin*, *func_middle*\n" - " modules: Can select a group via module\n" - " Format: :mod:\n" - " example: echo :mod:ext3 > set_ftrace_filter\n" - " triggers: a command to perform when function is hit\n" - " Format: :[:count]\n" - " trigger: traceon, traceoff\n" - " enable_event::\n" - " disable_event::\n" + " set_ftrace_filter\t- echo function name in here to only trace these\n" + "\t\t\t functions\n" + "\t accepts: func_full_name, *func_end, func_begin*, *func_middle*\n" + "\t modules: Can select a group via module\n" + "\t Format: :mod:\n" + "\t example: echo :mod:ext3 > set_ftrace_filter\n" + "\t triggers: a command to perform when function is hit\n" + "\t Format: :[:count]\n" + "\t trigger: traceon, traceoff\n" + "\t\t enable_event::\n" + "\t\t disable_event::\n" #ifdef CONFIG_STACKTRACE - " stacktrace\n" + "\t\t stacktrace\n" #endif #ifdef CONFIG_TRACER_SNAPSHOT - " snapshot\n" + "\t\t snapshot\n" #endif - " example: echo do_fault:traceoff > set_ftrace_filter\n" - " echo do_trap:traceoff:3 > set_ftrace_filter\n" - " The first one will disable tracing every time do_fault is hit\n" - " The second will disable tracing at most 3 times when do_trap is hit\n" - " The first time do trap is hit and it disables tracing, the counter\n" - " will decrement to 2. If tracing is already disabled, the counter\n" - " will not decrement. It only decrements when the trigger did work\n" - " To remove trigger without count:\n" - " echo '!: > set_ftrace_filter\n" - " To remove trigger with a count:\n" - " echo '!::0 > set_ftrace_filter\n" + "\t example: echo do_fault:traceoff > set_ftrace_filter\n" + "\t echo do_trap:traceoff:3 > set_ftrace_filter\n" + "\t The first one will disable tracing every time do_fault is hit\n" + "\t The second will disable tracing at most 3 times when do_trap is hit\n" + "\t The first time do trap is hit and it disables tracing, the\n" + "\t counter will decrement to 2. If tracing is already disabled,\n" + "\t the counter will not decrement. It only decrements when the\n" + "\t trigger did work\n" + "\t To remove trigger without count:\n" + "\t echo '!: > set_ftrace_filter\n" + "\t To remove trigger with a count:\n" + "\t echo '!::0 > set_ftrace_filter\n" " set_ftrace_notrace\t- echo function name in here to never trace.\n" - " accepts: func_full_name, *func_end, func_begin*, *func_middle*\n" - " modules: Can select a group via module command :mod:\n" - " Does not accept triggers\n" + "\t accepts: func_full_name, *func_end, func_begin*, *func_middle*\n" + "\t modules: Can select a group via module command :mod:\n" + "\t Does not accept triggers\n" #endif /* CONFIG_DYNAMIC_FTRACE */ #ifdef CONFIG_FUNCTION_TRACER - " set_ftrace_pid\t- Write pid(s) to only function trace those pids (function)\n" + " set_ftrace_pid\t- Write pid(s) to only function trace those pids\n" + "\t\t (function)\n" #endif #ifdef CONFIG_FUNCTION_GRAPH_TRACER " set_graph_function\t- Trace the nested calls of a function (function_graph)\n" " max_graph_depth\t- Trace a limited depth of nested calls (0 is unlimited)\n" #endif #ifdef CONFIG_TRACER_SNAPSHOT - "\n snapshot\t\t- Like 'trace' but shows the content of the static snapshot buffer\n" - "\t\t\t Read the contents for more information\n" + "\n snapshot\t\t- Like 'trace' but shows the content of the static\n" + "\t\t\t snapshot buffer. Read the contents for more\n" + "\t\t\t information\n" #endif #ifdef CONFIG_STACK_TRACER " stack_trace\t\t- Shows the max stack trace when active\n" " stack_max_size\t- Shows current max stack size that was traced\n" - "\t\t\t Write into this file to reset the max size (trigger a new trace)\n" + "\t\t\t Write into this file to reset the max size (trigger a\n" + "\t\t\t new trace)\n" #ifdef CONFIG_DYNAMIC_FTRACE - " stack_trace_filter\t- Like set_ftrace_filter but limits what stack_trace traces\n" + " stack_trace_filter\t- Like set_ftrace_filter but limits what stack_trace\n" + "\t\t\t traces\n" #endif #endif /* CONFIG_STACK_TRACER */ " events/\t\t- Directory containing all trace event subsystems:\n" " enable\t\t- Write 0/1 to enable/disable tracing of all events\n" " events//\t- Directory containing all trace events for :\n" - " enable\t\t- Write 0/1 to enable/disable tracing of all events\n" + " enable\t\t- Write 0/1 to enable/disable tracing of all \n" + "\t\t\t events\n" " filter\t\t- If set, only events passing filter are traced\n" - " events///\t- Directory containing control files for :\n" + " events///\t- Directory containing control files for\n" + "\t\t\t :\n" " enable\t\t- Write 0/1 to enable/disable tracing of \n" " filter\t\t- If set, only events passing filter are traced\n" " trigger\t\t- If set, a command to perform when event is hit\n" - " Format: [:count][if ]\n" - " trigger: traceon, traceoff\n" - " enable_event::\n" - " disable_event::\n" + "\t Format: [:count][if ]\n" + "\t trigger: traceon, traceoff\n" + "\t enable_event::\n" + "\t disable_event::\n" #ifdef CONFIG_STACKTRACE - " stacktrace\n" + "\t\t stacktrace\n" #endif #ifdef CONFIG_TRACER_SNAPSHOT - " snapshot\n" + "\t\t snapshot\n" #endif - " example: echo traceoff > events/block/block_unplug/trigger\n" - " echo traceoff:3 > events/block/block_unplug/trigger\n" - " echo 'enable_event:kmem:kmalloc:3 if nr_rq > 1' > events/block/block_unplug/trigger\n" - " The first disables tracing every time block_unplug is hit.\n" - " The second disables tracing the first 3 times block_unplug is hit.\n" - " The third enables the kmalloc event the first 3 times block_unplug\n" - " is hit and has value of greater than 1 for the 'nr_rq' event field.\n" - " To remove a trigger without a count:\n" - " echo '! > //trigger\n" - " To remove a trigger with a count:\n" - " echo '!:0 > //trigger\n" - " Filters can be ignored when removing a trigger.\n" + "\t example: echo traceoff > events/block/block_unplug/trigger\n" + "\t echo traceoff:3 > events/block/block_unplug/trigger\n" + "\t echo 'enable_event:kmem:kmalloc:3 if nr_rq > 1' > \\\n" + "\t events/block/block_unplug/trigger\n" + "\t The first disables tracing every time block_unplug is hit.\n" + "\t The second disables tracing the first 3 times block_unplug is hit.\n" + "\t The third enables the kmalloc event the first 3 times block_unplug\n" + "\t is hit and has value of greater than 1 for the 'nr_rq' event field.\n" + "\t Like function triggers, the counter is only decremented if it\n" + "\t enabled or disabled tracing.\n" + "\t To remove a trigger without a count:\n" + "\t echo '! > //trigger\n" + "\t To remove a trigger with a count:\n" + "\t echo '!:0 > //trigger\n" + "\t Filters can be ignored when removing a trigger.\n" ; static ssize_t -- cgit v0.10.2 From 3132e107d608f8753240d82d61303c500fd515b4 Mon Sep 17 00:00:00 2001 From: "Steven Rostedt (Red Hat)" Date: Thu, 23 Jan 2014 12:27:59 -0500 Subject: tracing: Check if tracing is enabled in trace_puts() If trace_puts() is used very early in boot up, it can crash the machine if it is called before the ring buffer is allocated. If a trace_printk() is used with no arguments, then it will be converted into a trace_puts() and suffer the same fate. Cc: stable@vger.kernel.org # 3.10+ Fixes: 09ae72348ecc "tracing: Add trace_puts() for even faster trace_printk() tracing" Signed-off-by: Steven Rostedt diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 7857ea9..815c878 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -455,6 +455,9 @@ int __trace_puts(unsigned long ip, const char *str, int size) unsigned long irq_flags; int alloc; + if (unlikely(tracing_selftest_running || tracing_disabled)) + return 0; + alloc = sizeof(*entry) + size + 2; /* possible \n added */ local_save_flags(irq_flags); @@ -495,6 +498,9 @@ int __trace_bputs(unsigned long ip, const char *str) unsigned long irq_flags; int size = sizeof(struct bputs_entry); + if (unlikely(tracing_selftest_running || tracing_disabled)) + return 0; + local_save_flags(irq_flags); buffer = global_trace.trace_buffer.buffer; event = trace_buffer_lock_reserve(buffer, TRACE_BPUTS, size, -- cgit v0.10.2