Re: [PATCH v3 00/11] arm64: BTI kernel and vDSO support

Mark Brown
2020-05-07T16:47:53Z

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On Thu, May 07, 2020 at 05:36:58PM +0100, Will Deacon wrote:
> On Thu, May 07, 2020 at 05:30:45PM +0100, Mark Brown wrote:

> > GCC does emit some helper functions wrapping GCOV stuff but they have
> > appropriate annotations, eg:

> > 00000000000000ac <_sub_D_00100_1>:
> > ac: d503245f bti c

> Hmm, where have the PAC/AUT instructions gone?

I was testing with -mbranch-protection=bti while trying to narrow down
the issue when I pasted that example in, if PAC is enabled then you get
the PAC/AUT instructions instead.

> > It does seem it's a straight compiler issue, if the compiler is emitting
> > runtime then the compiler ought to be ensuring that it agrees with the
> > build options the compiler was given and I can't think how this would be
> > fixable or avoidable outside of the compiler other than "don't do that"
> > which is what my Kconfig bodge did. I'm talking to the toolchain people
> > internally about this.

> Thanks. I'll apply your 'depends on ...' line locally and push that out
> if I don't run into any more issues.

Thanks, hopefully it'll be fine.

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