Re: [Qemu-devel] libvhost-user: undefined reference to MADV_NOHUGEPAGE

[Sandra Loosemore]

On 8/27/19 9:01 PM, Richard Henderson wrote:
> On 8/27/19 6:42 PM, Sandra Loosemore wrote:
> > Sorry if that was not clear.  The target is aarch64-none-elf with the provided
> > semihosting facilities in QEMU.  The host is x86_64-linux-gnu. We deliberately
> > link against a pretty old glibc sysroot (looks like version 2.11.1), but we did
> > that for last year's 3.0 release as well, and haven't made any other changes in
> > the configure options etc that we use to build QEMU for this target.
>
> Still not clear.
>
> The combination "glibc" and "qemu semihosting" doesn't make sense.  The triplet
> "aarch64-none-elf" is a gcc thing and has no referent in qemu.
>
> Are you building qemu-system-aarch64 for x86_64-linux, using an old x86_64 
> sysroot?

Yes.  We only use this configuration of QEMU as an instruction-set 
simulator so that we can test cross-compilers and gdb for bare-metal 
aarch64-none-elf target, using newlib as the target C library and the 
GDB semihosting support in QEMU for low-level fileio primitives.

BTW, I did not run into this undefined-symbol error when building the 
equivalent configuration for bare-metal nios2-elf target with the same 
sysroot and host setup.  That target does not build libvhost-user at all.

> In any case, glibc 2.11.1 is definitely out of support.  Even CentOS 6 used
> 2.12 and we don't support that anymore either.  Of the current
> long-term-support distros, I believe the oldest version of glibc is CentOS 7
> with 2.17.
>
> As recently mentioned in
>
>    https://lists.gnu.org/archive/html/qemu-devel/2019-08/msg04514.html
>
> we may accept a small patch with a large comment, but there are no guarantees
> how long we will keep such workarounds.

I wouldn't mind just applying a local patch to fix the build.  What I'm 
really trying to do is just get help in understanding what broke this, 
so I can come up with such a patch to un-break it again.

> I encourage you to re-examine why you're carrying around a 10 year old glibc.

We update our host build environment infrequently, and we've still had 
customers requiring CentOS 6 support until quite recently.

-Sandra