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From:   Petr Tesarik <petrtesarik@huaweicloud.com>
To:     Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        Conor Dooley <conor.dooley@microchip.com>,
        Li Huafei <lihuafei1@huawei.com>,
        Liao Chang <liaochang1@huawei.com>,
        Masahiro Yamada <masahiroy@kernel.org>,
        Alyssa Ross <hi@alyssa.is>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Ricardo Ribalda <ribalda@chromium.org>,
        Kees Cook <keescook@chromium.org>,
        Heiko Stuebner <heiko@sntech.de>,
        Li Zhengyu <lizhengyu3@huawei.com>,
        linux-riscv@lists.infradead.org (open list:RISC-V ARCHITECTURE),
        linux-kernel@vger.kernel.org (open list)
Cc:     Roberto Sassu <roberto.sassu@huaweicloud.com>, petr@tesarici.cz
Subject: [PATCH v1 2/3] riscv/kexec: handle R_RISCV_ADD16 and R_RISCV_SUB16 relocation types
Date:   Tue, 25 Jul 2023 10:44:26 +0200
Message-Id: <f75c763d86529a47eb23d46c5ef9bcbaaf118200.1690274483.git.petr.tesarik.ext@huawei.com>
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From: Petr Tesarik <petr.tesarik.ext@huawei.com>

16-bit add and subtract relocation types are used by the purgatory code
when the kernel is built with CONFIG_RISCV_ALTERNATIVES. If they are not
handled, kexec_file_load(2) fails with:

 Unknown rela relocation: 34
 kexec_image: Error loading purgatory ret=-8

or later with:

 Unknown rela relocation: 38
 kexec_image: Error loading purgatory ret=-8

Note that alternatives are not yet handled in purgatory code; this patch
merely allows to load it.

Fixes: 838b3e28488f ("RISC-V: Load purgatory in kexec_file")
Signed-off-by: Petr Tesarik <petr.tesarik.ext@huawei.com>
Cc: Li Zhengyu <lizhengyu3@huawei.com>
Cc: stable@vger.kernel.org
---
 arch/riscv/kernel/elf_kexec.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/riscv/kernel/elf_kexec.c b/arch/riscv/kernel/elf_kexec.c
index 38390d3bdcac..f23fd419c402 100644
--- a/arch/riscv/kernel/elf_kexec.c
+++ b/arch/riscv/kernel/elf_kexec.c
@@ -444,6 +444,12 @@ int arch_kexec_apply_relocations_add(struct purgatory_info *pi,
 		case R_RISCV_SUB32:
 			*(u32 *)loc -= val;
 			break;
+		case R_RISCV_ADD16:
+			*(u16 *)loc += val;
+			break;
+		case R_RISCV_SUB16:
+			*(u16 *)loc -= val;
+			break;
 		/* It has been applied by R_RISCV_PCREL_HI20 sym */
 		case R_RISCV_PCREL_LO12_I:
 		case R_RISCV_ALIGN:
-- 
2.25.1