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Date:   Fri, 5 May 2023 13:30:15 +0100
From:   Conor Dooley <conor.dooley@microchip.com>
To:     Ricardo Ribalda <ribalda@chromium.org>
CC:     Conor Dooley <conor@kernel.org>,
        Eric Biederman <ebiederm@xmission.com>,
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        "H. Peter Anvin" <hpa@zytor.com>,
        Nathan Chancellor <nathan@kernel.org>,
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Subject: Re: [PATCH v6 4/4] risc/purgatory: Add linker script
Message-ID: <20230505-subsidy-shininess-46a8be31b267@wendy>
References: <20230321-kexec_clang16-v6-0-a2255e81ab45@chromium.org>
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On Mon, May 01, 2023 at 09:54:43PM +0200, Ricardo Ribalda wrote:
> On Mon, 1 May 2023 at 19:41, Conor Dooley <conor@kernel.org> wrote:
> > On Mon, May 01, 2023 at 02:38:22PM +0200, Ricardo Ribalda wrote:
> > > If PGO is enabled, the purgatory ends up with multiple .text sections.
> > > This is not supported by kexec and crashes the system.
> > >
> > > Cc: stable@vger.kernel.org
> > > Fixes: 930457057abe ("kernel/kexec_file.c: split up __kexec_load_pura=
gory")
> > > Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
> > > ---
> > >  arch/riscv/purgatory/Makefile | 5 +++++
> > >  1 file changed, 5 insertions(+)
> > >
> > > diff --git a/arch/riscv/purgatory/Makefile b/arch/riscv/purgatory/Mak=
efile
> > > index 5730797a6b40..cf3a44121a90 100644
> > > --- a/arch/riscv/purgatory/Makefile
> > > +++ b/arch/riscv/purgatory/Makefile
> > > @@ -35,6 +35,11 @@ CFLAGS_sha256.o :=3D -D__DISABLE_EXPORTS
> > >  CFLAGS_string.o :=3D -D__DISABLE_EXPORTS
> > >  CFLAGS_ctype.o :=3D -D__DISABLE_EXPORTS
> > >
> > > +# When profile optimization is enabled, llvm emits two different ove=
rlapping
> > > +# text sections, which is not supported by kexec. Remove profile opt=
imization
> > > +# flags.
> > > +KBUILD_CFLAGS :=3D $(filter-out -fprofile-sample-use=3D% -fprofile-u=
se=3D%,$(KBUILD_CFLAGS))
> >
> > With the caveat of not being au fait with the workings of either PGO or
> > of purgatory, how come you modify KBUILD_CFLAGS here rather than the
> > purgatory specific PURGATORY_CFLAGS that are used later in the file?
>=20
> Definitely, not a Makefile expert here, but when I tried this:
>=20
> @@ -35,6 +40,7 @@ PURGATORY_CFLAGS_REMOVE :=3D -mcmodel=3Dkernel
>  PURGATORY_CFLAGS :=3D -mcmodel=3Dlarge -ffreestanding
> -fno-zero-initialized-in-bss -g0
>  PURGATORY_CFLAGS +=3D $(DISABLE_STACKLEAK_PLUGIN) -DDISABLE_BRANCH_PROFI=
LING
>  PURGATORY_CFLAGS +=3D -fno-stack-protector
> +PURGATORY_CFLAGS :=3D $(filter-out -fprofile-sample-use=3D%
> -fprofile-use=3D%,$(KBUILD_CFLAGS))
>=20
> It did not work.

Unfortunately I am oh-so-far from an expert on this kind of thing, but I
had thought that PURGATORY_CFLAGS_REMOVE was intended for this sort of
purpose.

> Fixes: bde971a83bbf ("KVM: arm64: nvhe: Fix build with profile optimizati=
on")
>=20
> does this approach, so this is what I tried and worked.

That doesn't have a specific CFLAGS though afaict.
Perhaps Nick etc have a more informed opinion here than I do, sorry.

Thanks,
Conor.

> > > +
> > >  # When linking purgatory.ro with -r unresolved symbols are not check=
ed,
> > >  # also link a purgatory.chk binary without -r to check for unresolve=
d symbols.
> > >  PURGATORY_LDFLAGS :=3D -e purgatory_start -z nodefaultlib
> > >
> > > --
> > > 2.40.1.495.gc816e09b53d-goog
> > >
> > >
> > > _______________________________________________
> > > linux-riscv mailing list
> > > linux-riscv@lists.infradead.org
> > > http://lists.infradead.org/mailman/listinfo/linux-riscv
>=20
>=20
>=20
> --=20
> Ricardo Ribalda

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