linux-kernel - [PATCH 4/5] MIPS: Support R_MIPS

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Date:	Wed, 3 Feb 2016 03:44:44 +0000
From:	Paul Burton <paul.burton@...tec.com>
To:	<linux-mips@...ux-mips.org>, Ralf Baechle <ralf@...ux-mips.org>
CC:	Paul Burton <paul.burton@...tec.com>,
	Andrey Konovalov <adech.fo@...il.com>,
	Andrey Ryabinin <ryabinin.a.a@...il.com>,
	<linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH 4/5] MIPS: Support R_MIPS_PC16 rel-style reloc

MIPS32 code uses rel-style relocs, and MIPS32r6 modules may include the
R_MIPS_PC16 relocation. We thus need to support R_MIPS_PC16 rel-style
relocations in order to load MIPS32r6 kernel modules. This patch adds
such support, which is similar to the rela-style R_MIPS_PC16 support but
making use of the implicit addend from the instruction encoding.

Signed-off-by: Paul Burton <paul.burton@...tec.com>
---

 arch/mips/kernel/module.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/arch/mips/kernel/module.c b/arch/mips/kernel/module.c
index 2adf572..f2de9b8 100644
--- a/arch/mips/kernel/module.c
+++ b/arch/mips/kernel/module.c
@@ -183,13 +183,25 @@ out_danger:
 	return -ENOEXEC;
 }
 
+static int apply_r_mips_pc16_rel(struct module *me, u32 *location, Elf_Addr v)
+{
+	u16 val;
+
+	val = *location;
+	val += (v - (Elf_Addr)location) >> 2;
+	*location = (*location & 0xffff0000) | val;
+
+	return 0;
+}
+
 static int (*reloc_handlers_rel[]) (struct module *me, u32 *location,
 				Elf_Addr v) = {
 	[R_MIPS_NONE]		= apply_r_mips_none,
 	[R_MIPS_32]		= apply_r_mips_32_rel,
 	[R_MIPS_26]		= apply_r_mips_26_rel,
 	[R_MIPS_HI16]		= apply_r_mips_hi16_rel,
-	[R_MIPS_LO16]		= apply_r_mips_lo16_rel
+	[R_MIPS_LO16]		= apply_r_mips_lo16_rel,
+	[R_MIPS_PC16]		= apply_r_mips_pc16_rel,
 };
 
 int apply_relocate(Elf_Shdr *sechdrs, const char *strtab,
-- 
2.7.0