Re: [llvmlinux] percpu | bitmap issue? (Cannot boot on bare metal due to a kernel NULL pointer dereference)

[Sedat Dilek]

On Wed, Sep 9, 2015 at 4:29 AM, Baoquan He <bhe@xxxxxxxxxx> wrote:
>
> Seems it happened when call num_possible_cpus() which is a inline
> function to call __bitmap_weight(). So did you check
> lib/bitmap.c:__bitmap_weight() by objdump?
>
> setup_percpu: NR_CPUS:256 nr_cpumask_bits:256 nr_cpu_ids:1 nr_node_ids:1
>

[ CC->TO Denys ]

Hi Boaquan,

Thanks for your reply.

I tried a lot in the meantime :-).

For example I applied a patch from Denys Vlasenko <dvlasenk@xxxxxxxxxx>...

commit 1a1d48a4a8fde49aedc045d894efe67173d59fe0
"linux/bitmap: Force inlining of bitmap weight functions"

...on top of Linux v4.2.

This resulted in the same call-trace in QEMU.

I hacked around to only re-build mm/percpu.c with GCC (rest with
CLANG) with some guidance from Linus (compiler warapper-script) etc.

What do you need for outputs?
objdump of lib/bitmap.o?
>From both builds - with GCC and CLANG?

Please give me clear instructions, Thanks!

Regards,
- Sedat -

[1] http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=1a1d48a4a8fde49aedc045d894efe67173d59fe0
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