[PATCH 2/2] stack trace support: print full instruction pointer in addition to offset

[Masatake YAMATO]

Hi,

...
>  unwind.c |   18 +++++++++++++-----
>  1 files changed, 13 insertions(+), 5 deletions(-)
> 
> Note: I would find it more logical to only show the full instruction pointer,
> instead of both the instruction pointer and the offset. But I'm not sure if
> everyone would agree to that.
> 

In any environment, can we exepct a library or execrable file is mapped to
predictable address?

I conducted a small test on my Fedora 20.
 
    % for x in /proc/[0-9]*/exe; do if [ "$(readlink $x)" = /usr/bin/zsh ]; then echo $x; cat $(dirname $x)/maps | grep zutil.so | grep 'r-xp'; fi; done
    /proc/10783/exe
    7f19a06f0000-7f19a06f7000 r-xp 00000000 fd:02 726402                     /usr/lib64/zsh/5.0.7/zsh/zutil.so
    /proc/14948/exe
    7f3e9fbb2000-7f3e9fbb9000 r-xp 00000000 fd:02 726402                     /usr/lib64/zsh/5.0.7/zsh/zutil.so
    /proc/16628/exe
    7fc3968f9000-7fc396900000 r-xp 00000000 fd:02 726402                     /usr/lib64/zsh/5.0.7/zsh/zutil.so
    /proc/17755/exe
    7f693048c000-7f6930493000 r-xp 00000000 fd:02 726402                     /usr/lib64/zsh/5.0.7/zsh/zutil.so
    /proc/21170/exe
    7f568e5a3000-7f568e5aa000 r-xp 00000000 fd:02 726402                     /usr/lib64/zsh/5.0.7/zsh/zutil.so
    /proc/26202/exe
    7f5722623000-7f572262a000 r-xp 00000000 fd:02 726402                     /usr/lib64/zsh/5.0.7/zsh/zutil.so
    /proc/26493/exe
    7fa92bd2f000-7fa92bd36000 r-xp 00000000 fd:02 726402                     /usr/lib64/zsh/5.0.7/zsh/zutil.so
    /proc/27923/exe
    7fa92bd2f000-7fa92bd36000 r-xp 00000000 fd:02 726402                     /usr/lib64/zsh/5.0.7/zsh/zutil.so
    /proc/30561/exe
    7fc47df8e000-7fc47df95000 r-xp 00000000 fd:02 726402                     /usr/lib64/zsh/5.0.7/zsh/zutil.so
    /proc/6957/exe
    7f578b0bf000-7f578b0c6000 r-xp 00000000 fd:02 726402                     /usr/lib64/zsh/5.0.7/zsh/zutil.so
    /proc/7633/exe
    7f771db8e000-7f771db95000 r-xp 00000000 fd:02 726402                     /usr/lib64/zsh/5.0.7/zsh/zutil.so

zutil.so used in zsh is mapped to different addresses process by process.
That means, the pair of ip and library(or execrable file) name is not enough
for resolving stack trace. Am I wrong?

However, if the address used in the mapping are statically defined, in
other words, predictable, the full instruction pointer is enough.

About the output format, I feel

 > /bin/busybox() [0x10062c60]/[0x62c60]

is a bit verbose in usage of brackets.

How do you think one of following format?

 > /bin/busybox() [0x10062c60|0x62c60]
 > /bin/busybox() [0x10062c60/0x62c60]
 > /bin/busybox() [0x10062c60:0x62c60]

Masatake YAMATO