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SubjectRe: [PATCH v3] mm, slub: change run-time assertion in kmalloc_index() to compile-time
Hello Vlastimil, recently kbuild-all test bot reported compile error on
clang 10.0.1, with defconfig.

Nathan Chancellor wrote:
> I think this happens because arch_prepare_optimized_kprobe() calls kzalloc()
> with a size of MAX_OPTINSN_SIZE, which is
> #define MAX_OPTINSN_SIZE \
> (((unsigned long)optprobe_template_end - \
> (unsigned long)optprobe_template_entry) + \

> and the optprobe_template_{end,entry} are not evaluated as constants.
> I am not sure what the solution is. There seem to be a growing list of issues
> with LLVM 10 that were fixed in LLVM 11, which might necessitate requiring
> LLVM 11 and newer to build the kernel, given this affects a defconfig.
> Cheers,
> Nathan

I think it's because kmalloc compiles successfully when size is constant,
and kmalloc_index isn't. so I think compiler seems to be confused.

currently if size is non-constant, kmalloc calls dummy function __kmalloc,
which always returns NULL.

so what about changing kmalloc to do compile-time assertion too, and track
all callers that are calling kmalloc with non-constant argument.

How do you think? If you think it is the solution, I'll do that work.

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