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From: Fangrui Song <maskray@google.com>
To: Nick Desaulniers <ndesaulniers@google.com>
Cc: "Björn Töpel" <bjorn@kernel.org>,
	"Alexandre Ghiti" <alex@ghiti.fr>,
	"Alexandre Ghiti" <alexghiti@rivosinc.com>,
	"Michael Ellerman" <mpe@ellerman.id.au>,
	"Nicholas Piggin" <npiggin@gmail.com>,
	"Christophe Leroy" <christophe.leroy@csgroup.eu>,
	"Paul Walmsley" <paul.walmsley@sifive.com>,
	"Palmer Dabbelt" <palmer@dabbelt.com>,
	"Albert Ou" <aou@eecs.berkeley.edu>,
	linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org,
	linux-riscv@lists.infradead.org, nathan@kernel.org,
	linux-kbuild@vger.kernel.org, llvm@lists.linux.dev
Subject: Re: [PATCH v8 1/3] riscv: Introduce CONFIG_RELOCATABLE
Date: Thu, 23 Mar 2023 13:01:15 -0700	[thread overview]
Message-ID: <CAFP8O3+UO0x9aETSnOkL7=473mX0wrt+ueuB9UgOJaf+N0p7gw@mail.gmail.com> (raw)
In-Reply-To: <CAKwvOdk0Lr-9gt0xAKvkcwA53+Wy8oeYQo1RJ7XH-LKCCURQCQ@mail.gmail.com>

On Wed, Mar 22, 2023 at 11:26 AM Nick Desaulniers
<ndesaulniers@google.com> wrote:
>
> On Fri, Feb 24, 2023 at 7:58 AM Björn Töpel <bjorn@kernel.org> wrote:
> >
> > Alexandre Ghiti <alex@ghiti.fr> writes:
> >
> > > +cc linux-kbuild, llvm, Nathan, Nick
> > >
> > > On 2/15/23 15:36, Alexandre Ghiti wrote:
> > >> From: Alexandre Ghiti <alex@ghiti.fr>
> > >>
> > > I tried a lot of things, but I struggle to understand, does anyone have
> > > any idea? FYI, the same problem happens with LLVM.
>
> Off the top of my head, no idea.
>
> (Maybe as a follow up to this series, I wonder if pursuing
> ARCH_HAS_RELR for ARCH=riscv is worthwhile?)

(I had thought about this for my own fun, but the currently only
implementation arch/arm64/kernel/head.S uses assembly.
Every port needs to write some assembly for the same task, which is a pity.
In FreeBSD rtld, glibc, and musl, DT_RELR code is target-independent.)


> >
> > Don't ask me *why*, but adding --emit-relocs to your linker flags solves
> > "the NULL .rela.dyn" both for GCC and LLVM.
> >
> > The downside is that you end up with a bunch of .rela cruft in your
> > vmlinux.
>
> There was a patch just this week to use $(OBJCOPY) to strip these from
> vmlinux (for x86). Looks like x86 uses --emit-relocs for KASLR:
> https://lore.kernel.org/lkml/20230320121006.4863-1-petr.pavlu@suse.com/
> --
> Thanks,
> ~Nick Desaulniers
>


-- 
宋方睿

WARNING: multiple messages have this Message-ID (diff)
From: Fangrui Song <maskray@google.com>
To: Nick Desaulniers <ndesaulniers@google.com>
Cc: "Björn Töpel" <bjorn@kernel.org>,
	"Alexandre Ghiti" <alex@ghiti.fr>,
	"Alexandre Ghiti" <alexghiti@rivosinc.com>,
	"Michael Ellerman" <mpe@ellerman.id.au>,
	"Nicholas Piggin" <npiggin@gmail.com>,
	"Christophe Leroy" <christophe.leroy@csgroup.eu>,
	"Paul Walmsley" <paul.walmsley@sifive.com>,
	"Palmer Dabbelt" <palmer@dabbelt.com>,
	"Albert Ou" <aou@eecs.berkeley.edu>,
	linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org,
	linux-riscv@lists.infradead.org, nathan@kernel.org,
	linux-kbuild@vger.kernel.org, llvm@lists.linux.dev
Subject: Re: [PATCH v8 1/3] riscv: Introduce CONFIG_RELOCATABLE
Date: Thu, 23 Mar 2023 13:01:15 -0700	[thread overview]
Message-ID: <CAFP8O3+UO0x9aETSnOkL7=473mX0wrt+ueuB9UgOJaf+N0p7gw@mail.gmail.com> (raw)
In-Reply-To: <CAKwvOdk0Lr-9gt0xAKvkcwA53+Wy8oeYQo1RJ7XH-LKCCURQCQ@mail.gmail.com>

On Wed, Mar 22, 2023 at 11:26 AM Nick Desaulniers
<ndesaulniers@google.com> wrote:
>
> On Fri, Feb 24, 2023 at 7:58 AM Björn Töpel <bjorn@kernel.org> wrote:
> >
> > Alexandre Ghiti <alex@ghiti.fr> writes:
> >
> > > +cc linux-kbuild, llvm, Nathan, Nick
> > >
> > > On 2/15/23 15:36, Alexandre Ghiti wrote:
> > >> From: Alexandre Ghiti <alex@ghiti.fr>
> > >>
> > > I tried a lot of things, but I struggle to understand, does anyone have
> > > any idea? FYI, the same problem happens with LLVM.
>
> Off the top of my head, no idea.
>
> (Maybe as a follow up to this series, I wonder if pursuing
> ARCH_HAS_RELR for ARCH=riscv is worthwhile?)

(I had thought about this for my own fun, but the currently only
implementation arch/arm64/kernel/head.S uses assembly.
Every port needs to write some assembly for the same task, which is a pity.
In FreeBSD rtld, glibc, and musl, DT_RELR code is target-independent.)


> >
> > Don't ask me *why*, but adding --emit-relocs to your linker flags solves
> > "the NULL .rela.dyn" both for GCC and LLVM.
> >
> > The downside is that you end up with a bunch of .rela cruft in your
> > vmlinux.
>
> There was a patch just this week to use $(OBJCOPY) to strip these from
> vmlinux (for x86). Looks like x86 uses --emit-relocs for KASLR:
> https://lore.kernel.org/lkml/20230320121006.4863-1-petr.pavlu@suse.com/
> --
> Thanks,
> ~Nick Desaulniers
>


-- 
宋方睿

_______________________________________________
linux-riscv mailing list
linux-riscv@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-riscv

WARNING: multiple messages have this Message-ID (diff)
From: Fangrui Song <maskray@google.com>
To: Nick Desaulniers <ndesaulniers@google.com>
Cc: "Albert Ou" <aou@eecs.berkeley.edu>,
	"Alexandre Ghiti" <alexghiti@rivosinc.com>,
	"Alexandre Ghiti" <alex@ghiti.fr>,
	linux-kbuild@vger.kernel.org, llvm@lists.linux.dev,
	linux-kernel@vger.kernel.org, nathan@kernel.org,
	"Björn Töpel" <bjorn@kernel.org>,
	"Palmer Dabbelt" <palmer@dabbelt.com>,
	"Nicholas Piggin" <npiggin@gmail.com>,
	"Paul Walmsley" <paul.walmsley@sifive.com>,
	linux-riscv@lists.infradead.org, linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH v8 1/3] riscv: Introduce CONFIG_RELOCATABLE
Date: Thu, 23 Mar 2023 13:01:15 -0700	[thread overview]
Message-ID: <CAFP8O3+UO0x9aETSnOkL7=473mX0wrt+ueuB9UgOJaf+N0p7gw@mail.gmail.com> (raw)
In-Reply-To: <CAKwvOdk0Lr-9gt0xAKvkcwA53+Wy8oeYQo1RJ7XH-LKCCURQCQ@mail.gmail.com>

On Wed, Mar 22, 2023 at 11:26 AM Nick Desaulniers
<ndesaulniers@google.com> wrote:
>
> On Fri, Feb 24, 2023 at 7:58 AM Björn Töpel <bjorn@kernel.org> wrote:
> >
> > Alexandre Ghiti <alex@ghiti.fr> writes:
> >
> > > +cc linux-kbuild, llvm, Nathan, Nick
> > >
> > > On 2/15/23 15:36, Alexandre Ghiti wrote:
> > >> From: Alexandre Ghiti <alex@ghiti.fr>
> > >>
> > > I tried a lot of things, but I struggle to understand, does anyone have
> > > any idea? FYI, the same problem happens with LLVM.
>
> Off the top of my head, no idea.
>
> (Maybe as a follow up to this series, I wonder if pursuing
> ARCH_HAS_RELR for ARCH=riscv is worthwhile?)

(I had thought about this for my own fun, but the currently only
implementation arch/arm64/kernel/head.S uses assembly.
Every port needs to write some assembly for the same task, which is a pity.
In FreeBSD rtld, glibc, and musl, DT_RELR code is target-independent.)


> >
> > Don't ask me *why*, but adding --emit-relocs to your linker flags solves
> > "the NULL .rela.dyn" both for GCC and LLVM.
> >
> > The downside is that you end up with a bunch of .rela cruft in your
> > vmlinux.
>
> There was a patch just this week to use $(OBJCOPY) to strip these from
> vmlinux (for x86). Looks like x86 uses --emit-relocs for KASLR:
> https://lore.kernel.org/lkml/20230320121006.4863-1-petr.pavlu@suse.com/
> --
> Thanks,
> ~Nick Desaulniers
>


-- 
宋方睿

  reply	other threads:[~2023-03-23 20:01 UTC|newest]

Thread overview: 51+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-02-15 14:36 [PATCH v8 0/3] Introduce 64b relocatable kernel Alexandre Ghiti
2023-02-15 14:36 ` Alexandre Ghiti
2023-02-15 14:36 ` [PATCH v8 1/3] riscv: Introduce CONFIG_RELOCATABLE Alexandre Ghiti
2023-02-15 14:36   ` Alexandre Ghiti
2023-02-22 12:29   ` Alexandre Ghiti
2023-02-22 12:29     ` Alexandre Ghiti
2023-02-24 15:58     ` Björn Töpel
2023-02-24 15:58       ` Björn Töpel
2023-03-22 18:25       ` Nick Desaulniers
2023-03-22 18:25         ` Nick Desaulniers
2023-03-22 18:25         ` Nick Desaulniers
2023-03-23 20:01         ` Fangrui Song [this message]
2023-03-23 20:01           ` Fangrui Song
2023-03-23 20:01           ` Fangrui Song
2023-03-24 10:34         ` Alexandre Ghiti
2023-03-24 10:34           ` Alexandre Ghiti
2023-03-24 10:34           ` Alexandre Ghiti
2023-03-22 13:38     ` Alexandre Ghiti
2023-03-22 13:38       ` Alexandre Ghiti
2023-05-09 19:07   ` Andreas Schwab
2023-05-09 19:07     ` Andreas Schwab
2023-05-09 19:07     ` Andreas Schwab
2023-05-09 19:55     ` Alexandre Ghiti
2023-05-09 19:55       ` Alexandre Ghiti
2023-05-09 19:55       ` Alexandre Ghiti
2023-05-11 18:18       ` Andreas Schwab
2023-05-11 18:18         ` Andreas Schwab
2023-05-11 18:18         ` Andreas Schwab
2023-05-12 18:41         ` Palmer Dabbelt
2023-05-12 18:41           ` Palmer Dabbelt
2023-05-12 18:41           ` Palmer Dabbelt
2023-05-19 11:08         ` Alexandre Ghiti
2023-05-19 11:08           ` Alexandre Ghiti
2023-05-19 11:08           ` Alexandre Ghiti
2023-05-19 21:48           ` Andreas Schwab
2023-05-19 21:48             ` Andreas Schwab
2023-05-19 21:48             ` Andreas Schwab
2023-05-19 21:55             ` Palmer Dabbelt
2023-05-19 21:55               ` Palmer Dabbelt
2023-05-19 21:55               ` Palmer Dabbelt
2023-05-22 10:48               ` Alexandre Ghiti
2023-05-22 10:48                 ` Alexandre Ghiti
2023-05-22 10:48                 ` Alexandre Ghiti
2023-02-15 14:36 ` [PATCH v8 2/3] powerpc: Move script to check relocations at compile time in scripts/ Alexandre Ghiti
2023-02-15 14:36   ` Alexandre Ghiti
2023-02-15 14:36   ` Alexandre Ghiti
2023-02-15 14:36 ` [PATCH v8 3/3] riscv: Check relocations at compile time Alexandre Ghiti
2023-02-15 14:36   ` Alexandre Ghiti
2023-02-15 14:36   ` Alexandre Ghiti
2023-02-20  9:14 ` [PATCH v8 0/3] Introduce 64b relocatable kernel Björn Töpel
2023-02-20  9:14   ` Björn Töpel

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