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Re: Unable to access function parameters
- From: fche at redhat dot com (Frank Ch. Eigler)
- To: Sergey Oboguev <oboguev at yahoo dot com>
- Cc: "systemtap at sourceware dot org" <systemtap at sourceware dot org>
- Date: Wed, 06 Nov 2013 14:42:34 -0500
- Subject: Re: Unable to access function parameters
- Authentication-results: sourceware.org; auth=none
- References: <1383764468 dot 67560 dot YahooMailNeo at web184302 dot mail dot ne1 dot yahoo dot com>
Sergey Oboguev <oboguev@yahoo.com> writes:
> [...]
> I am a newbie at SystemTap and just installed it, the latest version from git.
Welcome!
> I seem to be unable to access the values of function parameters, please see examples below. [...]
OK, thanks for the information.
> $ sudo stap -v -e 'probe syscall.open { printf("hit: %s\n", filename); }'
> Pass 1: parsed user script and 157 library script(s) using 102200virt/42448res/2468shr/40872data kb, in 150usr/0sys/159real ms.
> semantic error: not accessible at this address [man error::dwarf] (0xffffffff811f35c0, dieoffset: 0x1c34036): identifier '$filename' at /usr/share/systemtap/tapset/linux/syscalls2.stp:128:32
> source: filename = user_string_quoted($filename)
> ^
This sounds familiar, possibly
https://sourceware.org/bugzilla/show_bug.cgi?id=15123
If you're using that older gcc, and your kernel includes
CONFIG_HAVE_FENTRY, and thus is compiled with CFLAGS+=-mfentry, but
not also -grecord-gcc-switches, then try
# export PR15123_ASSUME_MFENTRY=1
# stap ....
- FChE