linux-kernel - Re: [PATCH v8 1/3] riscv: Introduce CONFIG

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Message-ID: <6fc7f0e1-0dde-9b41-0d60-6b0bd65bb630@ghiti.fr>
Date:   Fri, 19 May 2023 13:08:12 +0200
From:   Alexandre Ghiti <alex@...ti.fr>
To:     Andreas Schwab <schwab@...ux-m68k.org>
Cc:     Alexandre Ghiti <alexghiti@...osinc.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>,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        linux-riscv@...ts.infradead.org
Subject: Re: [PATCH v8 1/3] riscv: Introduce CONFIG_RELOCATABLE

On 5/11/23 20:18, Andreas Schwab wrote:
> On Mai 09 2023, Alexandre Ghiti wrote:
>
>> On 5/9/23 21:07, Andreas Schwab wrote:
>>> That does not work with UEFI booting:
>>>
>>> Loading Linux 6.4.0-rc1-1.g668187d-default ...
>>> Loading initial ramdisk ...
>>> Unhandled exception: Instruction access fault
>>> EPC: ffffffff80016d56 RA: 000000008020334e TVAL: 0000007f80016d56
>>> EPC: ffffffff002d1d56 RA: 00000000004be34e reloc adjusted
>>> Unhandled exception: Load access fault
>>> EPC: 00000000fff462d4 RA: 00000000fff462d0 TVAL: ffffffff80016d56
>>> EPC: 00000000802012d4 RA: 00000000802012d0 reloc adjusted
>>>
>>> Code: c825 8e0d 05b3 40b4 d0ef 0636 7493 ffe4 (d783 0004)
>>> UEFI image [0x00000000fe65e000:0x00000000fe6e3fff] '/efi\boot\bootriscv64.efi'
>>> UEFI image [0x00000000daa82000:0x00000000dcc2afff]
>>>
>> I need more details please, as I have a UEFI bootflow and it works great
>> (KASLR is based on a relocatable kernel and works fine in UEFI too).
> It also crashes without UEFI.  Disabling CONFIG_RELOCATABLE fixes that.
> This was tested on the HiFive Unmatched board.
> The kernel image I tested is available from
> <https://download.opensuse.org/repositories/Kernel:/HEAD/RISCV/>.  The
> same kernel with CONFIG_RELOCATABLE disabled is available from
> <https://download.opensuse.org/repositories/home:/Andreas_Schwab:/riscv:/kernel/standard/>.
>

I have tested the following patch successfully, can you give it a try 
while I make sure this is the only place I forgot to add the -fno-pie flag?

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

Thanks

Alex