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

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Message-ID: <20250326051445.55131-2-ziyao@disroot.org>
Date: Wed, 26 Mar 2025 05:14:46 +0000
From: Yao Zi <ziyao@...root.org>
To: 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: [PATCH] riscv/kexec_file: Handle R_RISCV_64 in purgatory relocator

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.

Fixes: 58ff537109ac ("riscv: Omit optimized string routines when using KASAN")
Signed-off-by: Yao Zi <ziyao@...root.org>
---

I noticed RISC-V support hasn't been merged into kexec-tools, so this
patch is tested with this dowmstream branch[1].

Thanks for your time and review.

[1]: https://github.com/ziyao233/kexec-tools/tree/rv-Image

 arch/riscv/kernel/elf_kexec.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/riscv/kernel/elf_kexec.c b/arch/riscv/kernel/elf_kexec.c
index 3c37661801f9..e783a72d051f 100644
--- a/arch/riscv/kernel/elf_kexec.c
+++ b/arch/riscv/kernel/elf_kexec.c
@@ -468,6 +468,9 @@ int arch_kexec_apply_relocations_add(struct purgatory_info *pi,
 		case R_RISCV_ALIGN:
 		case R_RISCV_RELAX:
 			break;
+		case R_RISCV_64:
+			*(u64 *)loc = val;
+			break;
 		default:
 			pr_err("Unknown rela relocation: %d\n", r_type);
 			return -ENOEXEC;
-- 
2.49.0