Re: [crash, bisected] Re: [PATCH 3/4] x86_64: Fold pda into per cpu area

[Eric W. Biederman]

"H. Peter Anvin" <hpa@xxxxxxxxx> writes:

> Eric W. Biederman wrote:
>>>
>>> The zero-based PDA mechanism requires the introduction of a new ELF segment
>>> based at vaddr 0 which is sufficiently unusual that it wouldn't surprise me
> if
>>> its triggering some toolchain bug.
>>
>> Agreed.  Given the previous description my hunch is that the bug is occurring
>> during objcopy.  If vmlinux is good and the compressed kernel is bad.
>>
>
> Actually, it's not all that unusual... it's pretty common in various restricted
> environments.  That being said, it's probably uncommon for *64-bit* code.

It is a sensible thing to expect to work.  By unusual I mean it isn't triggered
by normal userspace code.  In general I find that ld features if they aren't used
in userspace and they aren't used in the kernel don't work reliably across versions.

Eric
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