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

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Date:   Sun, 28 May 2023 14:56:38 +0100
From:   Conor Dooley <conor@...nel.org>
To:     Alexandre Ghiti <alex@...ti.fr>
Cc:     Alexandre Ghiti <alexghiti@...osinc.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Andreas Schwab <schwab@...ux-m68k.org>,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH -fixes] riscv: Fix relocatable kernels with early
 alternatives using -fno-pie

On Sun, May 28, 2023 at 03:42:59PM +0200, Alexandre Ghiti wrote:
> Hmmm, it still works for me with both clang and gcc-9.

gcc-9 is a bit of a relic, do you have more recent compilers lying
around? If not, I can try some older compilers at some point.

> 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!

What do you mean by "sha1"? It falls with v6.4-rc1 which is a stable
hash, if that's what you're looking for.

Otherwise,
https://github.com/ConchuOD/riscv-env/releases/download/v2022.03/vmlinux.bin
(ignore the release crap haha, too lazy to find a proper hosting
mechanism)

| git show
| commit 3bd124485ed55d8ee6c1ff3532c8f617b24aa6ef (HEAD)
| Author: Alexandre Ghiti <alexghiti@...osinc.com>
| Date:   Fri May 26 17:46:30 2023 +0200
| 
|     riscv: Fix relocatable kernels with early alternatives using -fno-pie
|     
|     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@...osinc.com>
|     Signed-off-by: Conor Dooley <conor.dooley@...rochip.com>
| 
| diff --git a/arch/riscv/errata/Makefile b/arch/riscv/errata/Makefile
| index a1055965fbee..7b2637c8c332 100644
| --- a/arch/riscv/errata/Makefile
| +++ b/arch/riscv/errata/Makefile
| @@ -1,2 +1,6 @@
| +ifdef CONFIG_RELOCATABLE
| +KBUILD_CFLAGS += -fno-pie
| +endif
| +
|  obj-$(CONFIG_ERRATA_SIFIVE) += sifive/
|  obj-$(CONFIG_ERRATA_THEAD) += thead/
| diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile
| index fbdccc21418a..153864e4f399 100644
| --- a/arch/riscv/kernel/Makefile
| +++ b/arch/riscv/kernel/Makefile
| @@ -23,6 +23,10 @@ ifdef CONFIG_FTRACE
|  CFLAGS_REMOVE_alternative.o = $(CC_FLAGS_FTRACE)
|  CFLAGS_REMOVE_cpufeature.o = $(CC_FLAGS_FTRACE)
|  endif
| +ifdef CONFIG_RELOCATABLE
| +CFLAGS_alternative.o += -fno-pie
| +CFLAGS_cpufeature.o += -fno-pie
| +endif
|  ifdef CONFIG_KASAN
|  KASAN_SANITIZE_alternative.o := n
|  KASAN_SANITIZE_cpufeature.o := n


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