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Long time ago we had a config item called STRICT_MM_TYPECHECKS to build the kernel with pte_t defined as a structure in order to perform additional build checks or build it with pte_t defined as a simple type in order to get simpler generated code. Commit670eea9241("powerpc/mm: Always use STRICT_MM_TYPECHECKS") made the struct based definition the only one, considering that the generated code was similar in both cases. That's right on ppc64 because the ABI is such that the content of a struct having a single simple type element is passed as register, but on ppc32 such a structure is passed via the stack like any structure. Simple test function: pte_t test(pte_t pte) { return pte; } Before this patch we get c00108ec <test>: c00108ec: 81 24 00 00 lwz r9,0(r4) c00108f0: 91 23 00 00 stw r9,0(r3) c00108f4: 4e 80 00 20 blr So, for PPC32, restore the simple type behaviour we got before commit670eea9241, but instead of adding a config option to activate type check, do it when __CHECKER__ is set so that type checking is performed by 'sparse' and provides feedback like: arch/powerpc/mm/pgtable.c:466:16: warning: incorrect type in return expression (different base types) arch/powerpc/mm/pgtable.c:466:16: expected unsigned long arch/powerpc/mm/pgtable.c:466:16: got struct pte_t [usertype] x With this patch we now get c0010890 <test>: c0010890: 4e 80 00 20 blr Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> [mpe: Define STRICT_MM_TYPECHECKS rather than repeating the condition] Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/c904599f33aaf6bb7ee2836a9ff8368509e0d78d.1631887042.git.christophe.leroy@csgroup.eu
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.