linux-kernel - Re: [PATCH] riscv/kexec_file: Handle R_RISCV

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Message-ID: <877c4bg1us.fsf@all.your.base.are.belong.to.us>
Date: Wed, 26 Mar 2025 18:04:27 +0100
From: Björn Töpel <bjorn@...nel.org>
To: Yao Zi <ziyao@...root.org>, Paul Walmsley <paul.walmsley@...ive.com>,
 Palmer Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>,
 Alexandre Ghiti <alex@...ti.fr>, Pasha Tatashin
 <pasha.tatashin@...een.com>, Kent Overstreet <kent.overstreet@...ux.dev>,
 Petr Tesarik <petr@...arici.cz>, Ying Sun <sunying@...c.iscas.ac.cn>,
 Samuel Holland <samuel.holland@...ive.com>
Cc: linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org, Han Gao
 <rabenda.cn@...il.com>, Yao Zi <ziyao@...root.org>
Subject: Re: [PATCH] riscv/kexec_file: Handle R_RISCV_64 in purgatory relocator

Yao Zi <ziyao@...root.org> writes:

> Commit 58ff537109ac ("riscv: Omit optimized string routines when
> using KASAN") introduced calls to EXPORT_SYMBOL() in assembly string
> routines, which result in R_RISCV_64 relocations against
> .export_symbol section. As these rountines are reused by RISC-V
> purgatory and our relocator doesn't recognize these relocations, this
> fails kexec-file-load with dmesg like
>
> 	[   11.344251] kexec_image: Unknown rela relocation: 2
> 	[   11.345972] kexec_image: Error loading purgatory ret=-8
>
> Let's support R_RISCV_64 relocation to fix kexec on 64-bit RISC-V.
> 32-bit variant isn't covered since KEXEC_FILE and KEXEC_PURGATORY isn't
> available.

Hi!

This patch does fix the vmlinux loading for kexec-file -- very nice!
However, I haven't been able to get kexec to successfully boot a kernel
from qemu, i.e.:

  kexec -s -l /path/to/vmlinux # fixed w/ your patch
  kexec -e # hangs after "Bye..."

Same when I try vanilla kexec (kexec -c -l /path/to/vmlinux). kexec with
an Image works for me in qemu.

Before I start to bisect too much; What config/qemu did you use to test
this?


Thanks,
Björn