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Diffstat (limited to 'Documentation/trace/ftrace.rst')
| -rw-r--r-- | Documentation/trace/ftrace.rst | 33 |
1 files changed, 32 insertions, 1 deletions
diff --git a/Documentation/trace/ftrace.rst b/Documentation/trace/ftrace.rst index b927fb2b94dc..027437b745a0 100644 --- a/Documentation/trace/ftrace.rst +++ b/Documentation/trace/ftrace.rst @@ -350,6 +350,19 @@ of ftrace. Here is a list of some of the key files: an 'I' will be displayed on the same line as the function that can be overridden. + If a non ftrace trampoline is attached (BPF) a 'D' will be displayed. + Note, normal ftrace trampolines can also be attached, but only one + "direct" trampoline can be attached to a given function at a time. + + Some architectures can not call direct trampolines, but instead have + the ftrace ops function located above the function entry point. In + such cases an 'O' will be displayed. + + If a function had either the "ip modify" or a "direct" call attached to + it in the past, a 'M' will be shown. This flag is never cleared. It is + used to know if a function was every modified by the ftrace infrastructure, + and can be used for debugging. + If the architecture supports it, it will also show what callback is being directly called by the function. If the count is greater than 1 it most likely will be ftrace_ops_list_func(). @@ -359,6 +372,18 @@ of ftrace. Here is a list of some of the key files: its address will be printed as well as the function that the trampoline calls. + touched_functions: + + This file contains all the functions that ever had a function callback + to it via the ftrace infrastructure. It has the same format as + enabled_functions but shows all functions that have every been + traced. + + To see any function that has every been modified by "ip modify" or a + direct trampoline, one can perform the following command: + + grep ' M ' /sys/kernel/tracing/touched_functions + function_profile_enabled: When set it will enable all functions with either the function @@ -1027,6 +1052,7 @@ To see what is available, simply cat the file:: nohex nobin noblock + nofields trace_printk annotate nouserstacktrace @@ -1110,6 +1136,11 @@ Here are the available options: block When set, reading trace_pipe will not block when polled. + fields + Print the fields as described by their types. This is a better + option than using hex, bin or raw, as it gives a better parsing + of the content of the event. + trace_printk Can disable trace_printk() from writing into the buffer. @@ -3510,7 +3541,7 @@ directories, the rmdir will fail with EBUSY. Stack trace ----------- Since the kernel has a fixed sized stack, it is important not to -waste it in functions. A kernel developer must be conscience of +waste it in functions. A kernel developer must be conscious of what they allocate on the stack. If they add too much, the system can be in danger of a stack overflow, and corruption will occur, usually leading to a system panic. |