[Bug translator/18075] New: Add a return-probe variant of .callee

[Bug translator/18075] New: Add a return-probe variant of .callee

[jistone at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=18075

            Bug ID: 18075
           Summary: Add a return-probe variant of .callee
           Product: systemtap
           Version: unspecified
            Status: NEW
          Severity: enhancement
          Priority: P2
         Component: translator
          Assignee: systemtap at sourceware dot org
          Reporter: jistone at redhat dot com

AIUI, callee probes are essentially translated into respective call probes with
a filter to match the caller.  It would also be useful to have return probes of
this sort.  It might even be easier, because I think the registers of a return
probe will already be into the caller's frame.

For example, a fault injection script might wish to tweak the return value of a
function, but only for particular callers, like this glibc article is doing.
https://sourceware.org/glibc/wiki/Testing/WhiteBox

-- 
You are receiving this mail because:
You are the assignee for the bug.

[Bug translator/18075] Add a return-probe variant of .callee

[fche at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=18075

Frank Ch. Eigler <fche at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |fche at redhat dot com

--- Comment #1 from Frank Ch. Eigler <fche at redhat dot com> ---
*** Bug 18415 has been marked as a duplicate of this bug. ***

-- 
You are receiving this mail because:
You are the assignee for the bug.

[Bug translator/18075] Add a return-probe variant of .callee

[flu at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=18075

Felix Lu <flu at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |flu at redhat dot com

--- Comment #2 from Felix Lu <flu at redhat dot com> ---
The _caller_match() function can be used to match the return with caller.

Example:
stap -e 'probe process("stap").function("version").return { print_ubacktrace();
 println(_caller_match(1,1,"/opt/codebase/install/bin/stap", ".absolute",
0x40efff)) }'

 0x428d55 : _ZN17systemtap_session13parse_cmdlineEiPKPc+0x9b5/0x5dc0
[/opt/codebase/install/bin/stap]
 0x40efff : main+0x21f/0x1320 [/opt/codebase/install/bin/stap]
 0x7fe8fca69fe0 [/usr/lib64/libc-2.20.so+0x1ffe0/0x3bd000]
1

-- 
You are receiving this mail because:
You are the assignee for the bug.

[Bug translator/18075] Add a return-probe variant of .callee

[jistone at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=18075

--- Comment #3 from Josh Stone <jistone at redhat dot com> ---
Why are you matching main though?  That's the second-level caller; version() is
actually called by parse_cmdline(), as seen in the first step of your
backtrace.  That's what I meant by the registers of a return probe already
reflecting the caller's frame.

So process.function("parse_cmdline").callee("version").return would be
translated to process.function("version").return, as you wrote, but with a
_caller_match(1,0,...) in this case.

-- 
You are receiving this mail because:
You are the assignee for the bug.

[Bug translator/18075] Add a return-probe variant of .callee

[flu at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=18075

Felix Lu <flu at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Assignee|systemtap at sourceware dot org    |flu at redhat dot com

-- 
You are receiving this mail because:
You are the assignee for the bug.