linux-kernel - [PATCH v2] RISC-V: Support 32_PCREL relocation type in kernel module

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Message-Id: <20230615072302.25638-1-nylon.chen@sifive.com>
Date:   Thu, 15 Jun 2023 15:23:02 +0800
From:   Nylon Chen <nylon.chen@...ive.com>
To:     linux-kernel@...r.kernel.org
Cc:     linux-riscv@...ts.infradead.org, jszhang@...nel.org,
        ajones@...tanamicro.com, conor.dooley@...rochip.com,
        aou@...s.berkeley.edu, palmer@...belt.com,
        paul.walmsley@...ive.com, greentime.hu@...ive.com,
        zong.li@...ive.com, nylon7717@...il.com,
        Nylon Chen <nylon.chen@...ive.com>
Subject: [PATCH v2] RISC-V: Support 32_PCREL relocation type in kernel module

Fix the 'unsupported relocation type' error caused by
enabling the -fasynchronous-unwind-tables flag,
which generates relocation types that are not supported.

Signed-off-by: Nylon Chen <nylon.chen@...ive.com>
Reviewed-by: Zong Li <zong.li@...ive.com>
---
Changed in v2:
- add commit message.

 arch/riscv/kernel/module.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/arch/riscv/kernel/module.c b/arch/riscv/kernel/module.c
index 7c651d55fcbd..65be0360a494 100644
--- a/arch/riscv/kernel/module.c
+++ b/arch/riscv/kernel/module.c
@@ -310,6 +310,15 @@ static int apply_r_riscv_sub64_rela(struct module *me, u32 *location,
 	return 0;
 }
 
+static int apply_r_riscv_pcrel_32_rela(struct module *me, u32 *location,
+				       Elf_Addr v)
+{
+	ptrdiff_t offset = (void *)v - (void *)location;
+
+	*location = (*location & 0xffff0000) | (offset & 0xffff);
+	return 0;
+}
+
 static int (*reloc_handlers_rela[]) (struct module *me, u32 *location,
 				Elf_Addr v) = {
 	[R_RISCV_32]			= apply_r_riscv_32_rela,
@@ -335,6 +344,7 @@ static int (*reloc_handlers_rela[]) (struct module *me, u32 *location,
 	[R_RISCV_SUB16]			= apply_r_riscv_sub16_rela,
 	[R_RISCV_SUB32]			= apply_r_riscv_sub32_rela,
 	[R_RISCV_SUB64]			= apply_r_riscv_sub64_rela,
+	[R_RISCV_32_PCREL]		= apply_r_riscv_pcrel_32_rela,
 };
 
 int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
-- 
2.40.1