linux-kernel - Re: [PATCH v6 4/4] risc/purgatory: Add linker script

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Message-ID: <CANiDSCufbm80g4AqukpiuER17OXhD-yRNmTZRz7s_x-Xi9BDCw@mail.gmail.com>
Date:   Mon, 1 May 2023 21:54:43 +0200
From:   Ricardo Ribalda <ribalda@...omium.org>
To:     Conor Dooley <conor@...nel.org>
Cc:     Eric Biederman <ebiederm@...ssion.com>,
        Philipp Rudo <prudo@...ux.vnet.ibm.com>,
        Dave Young <dyoung@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>,
        Nathan Chancellor <nathan@...nel.org>,
        Tom Rix <trix@...hat.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Nicholas Piggin <npiggin@...il.com>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>, Baoquan He <bhe@...hat.com>,
        Philipp Rudo <prudo@...hat.com>, kexec@...ts.infradead.org,
        linux-kernel@...r.kernel.org, Ross Zwisler <zwisler@...gle.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Simon Horman <horms@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        llvm@...ts.linux.dev, linuxppc-dev@...ts.ozlabs.org,
        linux-riscv@...ts.infradead.org, stable@...r.kernel.org
Subject: Re: [PATCH v6 4/4] risc/purgatory: Add linker script

Hi Conor

On Mon, 1 May 2023 at 19:41, Conor Dooley <conor@...nel.org> wrote:
>
> Hey Ricardo,
>
> 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@...r.kernel.org
> > Fixes: 930457057abe ("kernel/kexec_file.c: split up __kexec_load_puragory")
> > Signed-off-by: Ricardo Ribalda <ribalda@...omium.org>
> > ---
> >  arch/riscv/purgatory/Makefile | 5 +++++
> >  1 file changed, 5 insertions(+)
> >
> > diff --git a/arch/riscv/purgatory/Makefile b/arch/riscv/purgatory/Makefile
> > index 5730797a6b40..cf3a44121a90 100644
> > --- a/arch/riscv/purgatory/Makefile
> > +++ b/arch/riscv/purgatory/Makefile
> > @@ -35,6 +35,11 @@ CFLAGS_sha256.o := -D__DISABLE_EXPORTS
> >  CFLAGS_string.o := -D__DISABLE_EXPORTS
> >  CFLAGS_ctype.o := -D__DISABLE_EXPORTS
> >
> > +# When profile optimization is enabled, llvm emits two different overlapping
> > +# text sections, which is not supported by kexec. Remove profile optimization
> > +# flags.
> > +KBUILD_CFLAGS := $(filter-out -fprofile-sample-use=% -fprofile-use=%,$(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?

Definitely, not a Makefile expert here, but when I tried this:

@@ -35,6 +40,7 @@ PURGATORY_CFLAGS_REMOVE := -mcmodel=kernel
 PURGATORY_CFLAGS := -mcmodel=large -ffreestanding
-fno-zero-initialized-in-bss -g0
 PURGATORY_CFLAGS += $(DISABLE_STACKLEAK_PLUGIN) -DDISABLE_BRANCH_PROFILING
 PURGATORY_CFLAGS += -fno-stack-protector
+PURGATORY_CFLAGS := $(filter-out -fprofile-sample-use=%
-fprofile-use=%,$(KBUILD_CFLAGS))

It did not work.

Fixes: bde971a83bbf ("KVM: arm64: nvhe: Fix build with profile optimization")

does this approach, so this is what I tried and worked.

Thanks!
>
> Cheers,
> Conor.
>
> > +
> >  # When linking purgatory.ro with -r unresolved symbols are not checked,
> >  # also link a purgatory.chk binary without -r to check for unresolved symbols.
> >  PURGATORY_LDFLAGS := -e purgatory_start -z nodefaultlib
> >
> > --
> > 2.40.1.495.gc816e09b53d-goog
> >
> >
> > _______________________________________________
> > linux-riscv mailing list
> > linux-riscv@...ts.infradead.org
> > http://lists.infradead.org/mailman/listinfo/linux-riscv



-- 
Ricardo Ribalda


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