/proc/kallsyms and symbol size

From: Stephane Eranian
Date: Mon Sep 24 2007 - 16:55:29 EST


Many monitoring tools use /proc/kallsyms to build a symbol table for the kernel.
This technique has the advantage that it does not require root privileges, nor
an up-to-date /boot/System.map, nor a decompressed kernel in /boot.

The problem is that /proc/kallsyms does not report the size of the symbols.
Yet, the information is available in the kernel as it is used by functions such
as __print_symbol(). Having the size is useful to correlate the address obtained
is a sample with a symbol name. Most tools use an approximation which assumes
symbols are contiguous to estimate the size.

Apart from the backward compatbility problem for the output of kallsyms, what
would be the major issue with exposing this information?


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