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9.2. Context at the probe point

The following functions provide ways to access the current task context at a probe point. Note that these may not return correct values when a probe is hit in interrupt context.

9.2.1. backtrace
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General syntax: 
backtrace:string ()
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Returns a string of hex addresses that are a backtrace of the stack. The output is truncated to MAXSTRINGLEN.

9.2.2. caller
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General syntax: 
caller:string()
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Returns the address and name of the calling function. It works only for return probes.

9.2.3. caller_addr
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General syntax: 
caller_addr:long ()
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Returns the address of the calling function. It works only for return probes.

9.2.4. cpu
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General syntax: 
cpu:long ()
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Returns the current cpu number.

9.2.5. egid
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General syntax: 
egid:long ()
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Returns the effective group ID of the current process.

9.2.6. euid
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General syntax: 
euid:long ()
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Returns the effective user ID of the current process.

9.2.7. execname
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General syntax: 
execname:string ()
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Returns the name of the current process.

9.2.8. gid
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General syntax: 
gid:long ()
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Returns the group ID of the current process.

9.2.9. is_return
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General syntax: 
is_return:long ()
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Returns 1 if the probe point is a return probe, else it returns zero.
Deprecated.

9.2.10. pexecname
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General syntax: 
pexecname:string ()
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Returns the name of the parent process.

9.2.11. pid
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General syntax: 
pid:long ()
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Returns the process ID of the current process.

9.2.12. ppid
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General syntax: 
ppid:long ()
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Returns the process ID of the parent process.

9.2.13. tid
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General syntax: 
tid:long ()
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Returns the ID of the current thread.

9.2.14. uid
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General syntax: 
uid:long ()
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Returns the user ID of the current task.

9.2.15. print_backtrace
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General syntax: 
print_backtrace:unknown ()
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This function is equivalent to print_stack(backtrace()), except that deeper stack nesting is supported. The function does not return a value.

9.2.16. print_regs
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General syntax: 
print_regs:unknown ()
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This function prints a register dump.

9.2.17. print_stack
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General syntax: 
print_stack:unknown (stk:string)
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This function performs a symbolic lookup of the addresses in the given string, which is assumed to be the result of a prior call to backtrace(). It prints one line per address. Each printed line includes the address, the name of the function containing the address, and an estimate of its position within that function. The function does not return a value.

9.2.18. stack_size
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General syntax: 
stack_size:long ()
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Returns the size of the stack.

9.2.19. stack_unused
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General syntax: 
stack_unused:long ()
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Returns how many bytes are currently unused in the stack.

9.2.20. stack_used
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General syntax: 
stack_used:long ()
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Returns how many bytes are currently used in the stack.

9.2.21. stp_pid
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stp_pid:long ()
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Returns the process ID of the of the staprun process.

9.2.22. target
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General syntax: 
target:long ()
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Returns the process ID of the target process. This is useful in conjunction with the -x PID or -c CMD command-line options to stap. An example of its use is to create scripts that filter on a specific process. 
-x <pid>
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target() returns the pid specified by -x 
-c <command>
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target() returns the pid for the executed command specified by -c.
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