Unable to access function parameters

[Frank Ch. Eigler]

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