From: Will Deacon <will@kernel.org>
To: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>,
Szabolcs Nagy <szabolcs.nagy@arm.com>,
Tamas Zsoldos <tamas.zsoldos@arm.com>,
linux-arm-kernel@lists.infradead.org,
Catalin Marinas <catalin.marinas@arm.com>
Subject: Re: arm64 vdso might miss .eh_frame
Date: Tue, 28 Apr 2020 12:58:36 +0100 [thread overview]
Message-ID: <20200428115835.GA6791@willie-the-truck> (raw)
In-Reply-To: <d6b501ef-c587-8d5a-48ff-93188b78458a@arm.com>
On Tue, Apr 28, 2020 at 12:15:46PM +0100, Vincenzo Frascino wrote:
> On 4/28/20 12:11 PM, Mark Rutland wrote:
> > On Tue, Apr 28, 2020 at 11:54:25AM +0100, Vincenzo Frascino wrote:
> >> On 4/28/20 8:34 AM, Will Deacon wrote:
> >>> On Wed, Apr 15, 2020 at 10:23:36AM +0100, Szabolcs Nagy wrote:
> >>>> On aarch64 linux gcc uses -fasynchronous-unwind-tables -funwind-tables
> >>>> by default since gcc-8, so now the de facto platform ABI is to allow
> >>>> unwinding from async signal handlers.
> >>>>
> >>>> However on bare metal targets (aarch64-none-elf), and on old gcc,
> >>>> async and sync unwind tables are not enabled by default to avoid
> >>>> runtime memory costs.
> >>>>
> >>>> This means if linux is built with a baremetal toolchain the vdso.so
> >>>> may not have unwind tables which breaks our (undocumented) platform
> >>>> ABI guarantee in userspace. So adding -fasynchronous-unwind-tables
> >>>> explicitly to the vgettimeofday.o cflags would be nice (the other
> >>>> objects in the vdso seem to be asm).
> >>>>
> >>>> There was also a report that android clang built linux vdso.so lacks
> >>>> .eh_frame completely, that may be a missing --eh-frame-hdr or different
> >>>> platform ABI on android, Tamas on cc may be able to verify this.
> >>>
> >>> Vincenzo? Looks like this is a regression caused by the move to C -- please
> >>> can you take a look?
> >>
> >> I have already, locally, a patch that addresses the problem presented in this
> >> email, based on Szabolcs comment. I did not post it yet because I was waiting
> >> for Tamas' comment and address everything in one go.
> >
> > Can I suggest that you post the patch as-is here, even if it's not
> > complete, so that we can all review/test in parallel?
> >
>
> Sure, I will write a sensible comment and send it out.
Thanks!
Will
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next prev parent reply other threads:[~2020-04-28 11:58 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-15 9:23 arm64 vdso might miss .eh_frame Szabolcs Nagy
2020-04-28 7:34 ` Will Deacon
2020-04-28 10:54 ` Vincenzo Frascino
2020-04-28 11:11 ` Mark Rutland
2020-04-28 11:15 ` Vincenzo Frascino
2020-04-28 11:58 ` Will Deacon [this message]
2020-04-28 13:40 ` Vincenzo Frascino
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