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From: "maennich at android dot com" <sourceware-bugzilla@sourceware.org>
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Subject: [Bug default/28954] add Linux Kernel symbol namespace support
Date: Fri, 11 Mar 2022 12:20:44 +0000
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https://sourceware.org/bugzilla/show_bug.cgi?id=3D28954

Matthias Maennich <maennich at android dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |maennich at android dot com

--- Comment #4 from Matthias Maennich <maennich at android dot com> ---
The namespaces are not part of the linkage name as that would confuse linke=
rs,
loaders and external tools (and would also break some).

Instead the namespace is embedded in the ksymtab along with a MODVERSION CR=
C.
The ksymtab is basically an array of structs (struct kernel_symbol) that is
referred to from the symtab by the __ksymtab__<symbol> entries.

At module load time, every required symbol of a module is looked up in the =
list
of existing symbols (largely coming from vmlinux, and possibly from another
module) and loading is denied if the symbol has an attached namespace AND t=
he
module does not declare the namespace as imported. (similarly loading is de=
nied
upon a mismatch of the CRCs).=20

Hence, the ABI breakage happens if the exported symbol newly has a namespace
attached while the consuming module does not (yet) declare the import of sa=
id
namespace.

--=20
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