https://sourceware.org/bugzilla/show_bug.cgi?id=26391
Bug ID: 26391
Summary: Question regarding duplicate symbols
Product: binutils
Version: unspecified
Status: UNCONFIRMED
Severity: normal
Priority: P2
Component: binutils
Assignee: unassigned at sourceware dot org
Reporter: kaccardi at gmail dot com
Target Milestone: ---
I am implementing "function granular kernel address space layout randomization"
for Linux, and am trying to solve a problem that I am really hoping there is a
compiler or linker option for. My implementation uses gcc's -ffunction-sections
to break apart the kernel .text section by function. At kernel boot time, just
after decompression, I shuffle all the function sections randomly and re-layout
the kernel. Surprisingly, this works pretty well, but I am having a problem
with a niche condition that is important to resolve for the live-patching use
case. In order to live-patch the kernel, the live-patching code will request
the address of symbols by name from the kernel. This works great after
randomization because it always receives the current address at runtime rather
than relying on any kind of buildtime address. The issue with with the
live-patching code's algorithm for resolving duplicate symbol names. If they
request a symbol by name from the kernel and there are 3 symbols with the same
name, they use the symbol's position in the built binary image to select the
correct symbol. This is obviously invalid when the layout has been shuffled
randomly. I was hoping there was some kind of compiler or linker option that
would add some kind of uniqueness to the symbols to make sure their were never
any duplicates, but I am not finding such a thing. Is there something like this
already available? Thanks very much!
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