Re: [PATCH -fixes] riscv: Fix relocatable kernels with early alternatives using -fno-pie

[Alexandre Ghiti]

On 28/05/2023 15:12, Conor Dooley wrote:
> On Sun, May 28, 2023 at 03:00:57PM +0200, Alexandre Ghiti wrote:
> > On Sat, May 27, 2023 at 12:02 PM Conor Dooley <conor@xxxxxxxxxx> wrote:
> > > On Sat, May 27, 2023 at 11:13:18AM +0200, Alexandre Ghiti wrote:
> > > > On 26/05/2023 18:35, Conor Dooley wrote:
> > > > > On Fri, May 26, 2023 at 05:24:41PM +0100, Conor Dooley wrote:
> > > > > > On Fri, May 26, 2023 at 05:46:30PM +0200, Alexandre Ghiti wrote:
> > > > > > > Early alternatives are called with the mmu disabled, and then should not
> > > > > > > access any global symbols through the GOT since it requires relocations,
> > > > > > > relocations that we do before but *virtually*. So only use medany code
> > > > > > > model for this early code.
> > > > > > >
> > > > > > > Signed-off-by: Alexandre Ghiti <alexghiti@xxxxxxxxxxxx>
> > > > > > > ---
> > > > > > >
> > > > > > > Note that I'm not very happy with this fix, I think we need to put more
> > > > > > > effort into "harmonizing" this very early code (ie before the mmu is
> > > > > > > enabled) as it is spread between different locations and compiled
> > > > > > > differently.
> > > > > > Totally & I'll happily spend the time trying to review that work.
> > > > > >
> > > > > > > I'll work on that later, but for now, this fix does what is
> > > > > > > needed to work (from my testing at least). Any Tested-by on the Unmatched
> > > > > > > and T-head boards is welcome!
> > > > > > On 6.4-rc1 & v6.4-rc1 + this patch, with CONFIG_RELOCATABLE added to my
> > > > > > config, my Nezha fails to boot. There is no output whatsoever from the
> > > > > > kernel. Turning off CONFIG_RELOCATABLE boots again.
> > > > > I don't know if this is better or worse news, but same thing happens on
> > > > > an icicle kit. What systems, other than QEMU, has the relocatable
> > > > > eries been tested with, btw?
> > > >
> > > > I tested it on the Unmatched (Andreas did too).
> > > Cool. I cracked out my unmatched and it has the same issue as the
> > > icicle. Ditto my Visionfive v2. Here's my config.
> > > https://raw.githubusercontent.com/ConchuOD/riscv-env/dev/conf/defconfig
> > >
> > > A ~default qemu virt doesn't work either. (-m 2G -smp 5)
> > I can boot with this config using:
> >
> > $ sudo ~/qemu/build/qemu-system-riscv64 -machine virt -cpu
> > rv64,sv48=off -nographic -m 2G -smp 5 -kernel
> > build_conor/arch/riscv/boot/Image -s
> Just in case, that is my normal config that I use for testing random
> stuff on LKML, I added CONFIG_RELOCATABLE in addition to that.
>
> > I noticed when trying to add this to our internal CI that I had local
> > failures that did not happen in the CI because the CI was not using
> > the same toolchain: can you give me the full .config? So that I can
> > see if the compiler added stack guards or some other things I did not
> > think of.
> https://gist.githubusercontent.com/ConchuOD/655f9cc19fb3be63f1c9da7e7e3ab717/raw/a1aad3c0d307609b2062fd3a66705166aede9f9f/.config
>
> 90% of what I test for upstream stuff uses clang, since clang appears to
> be a minority choice - but I could reproduce this with gcc-12 as well,
> using the same defconfig as linked above + CONFIG_RELOCATABLE.


Hmmm, it still works for me with both clang and gcc-9.


You don't have to do that now but is there a way I could get your 
compiled image? With the sha1 used to build it? Sorry, I don't see what 
happens, I need to get my hands dirty in some debug!


Thanks for being so quick Conor!


> Cheers,
> Conor.
>
> _______________________________________________
> linux-riscv mailing list
> linux-riscv@xxxxxxxxxxxxxxxxxxx
> http://lists.infradead.org/mailman/listinfo/linux-riscv