[PATCH 3/5] MIPS: Add support for 64-bit R6 ELF relocations

Paul Burton
2016-02-03T03:45:50Z

From: "Steven J. Hill" <Steven.Hill@imgtec.com>

This patch fixes MIPS64r6 kernel modules by adding new ELF
relocations. Toolchains that compile 64-bit R6 binaries emit
two new ELF relocations R_MIPS_PC21_S2 and R_MIPS_PC26_S2.
The pre-existing R_MIPS_PC16 ELF relocation is also emitted.

Signed-off-by: Steven J. Hill <Steven.Hill@imgtec.com>
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Signed-off-by: Paul Burton <paul.burton@imgtec.com>
---

arch/mips/include/asm/elf.h | 5 +++
arch/mips/kernel/module-rela.c | 69 +++++++++++++++++++++++++++++++++++++++++-
2 files changed, 73 insertions(+), 1 deletion(-)

diff --git a/arch/mips/include/asm/elf.h b/arch/mips/include/asm/elf.h
index cefb7a5..7cec234 100644
--- a/arch/mips/include/asm/elf.h
+++ b/arch/mips/include/asm/elf.h
@@ -111,6 +111,11 @@
#define R_MIPS_CALLHI16 30
#define R_MIPS_CALLLO16 31
/*
+ * Introduced for MIPSr6.
+ */
+#define R_MIPS_PC21_S2 60
+#define R_MIPS_PC26_S2 61
+/*
* This range is reserved for vendor specific relocations.
*/
#define R_MIPS_LOVENDOR 100
diff --git a/arch/mips/kernel/module-rela.c b/arch/mips/kernel/module-rela.c
index f1ff64b..2dbe1b0 100644
--- a/arch/mips/kernel/module-rela.c
+++ b/arch/mips/kernel/module-rela.c
@@ -16,6 +16,7 @@
* Copyright (C) 2001 Rusty Russell.
* Copyright (C) 2003, 2004 Ralf Baechle (ralf@linux-mips.org)
* Copyright (C) 2005 Thiemo Seufer
+ * Copyright (C) 2015 Imagination Technologies Ltd.
*/

#include <linux/elf.h>
@@ -65,6 +66,27 @@ static int apply_r_mips_lo16_rela(struct module *me, u32 *location, Elf_Addr v)
return 0;
}

+static int apply_r_mips_pc16_rela(struct module *me, u32 *location, Elf_Addr v)
+{
+ long offset;
+
+ if (v % 4) {
+ pr_err("module %s: dangerous R_MIPS_PC16 RELA relocation\n",
+ me->name);
+ return -ENOEXEC;
+ }
+
+ offset = ((long)v - (long)location) >> 2;
+ if (offset != (int16_t)offset) {
+ pr_err("module %s: relocation overflow\n", me->name);
+ return -ENOEXEC;
+ }
+
+ *location = (*location & ~0xffff) | (offset & 0xffff);
+
+ return 0;
+}
+
static int apply_r_mips_64_rela(struct module *me, u32 *location, Elf_Addr v)
{
*(Elf_Addr *)location = v;
@@ -90,6 +112,48 @@ static int apply_r_mips_highest_rela(struct module *me, u32 *location,
return 0;
}

+static int apply_r_mips_pc21_rela(struct module *me, u32 *location, Elf_Addr v)
+{
+ long offset;
+
+ if (v % 4) {
+ pr_err("module %s: dangerous R_MIPS_PC21 RELA relocation\n",
+ me->name);
+ return -ENOEXEC;
+ }
+
+ offset = ((long)v - (long)location) >> 2;
+ if ((offset >> 20) > 0 || (offset >> 20) < -1) {
+ pr_err("module %s: relocation overflow\n", me->name);
+ return -ENOEXEC;
+ }
+
+ *location = (*location & ~0x001fffff) | (offset & 0x001fffff);
+
+ return 0;
+}
+
+static int apply_r_mips_pc26_rela(struct module *me, u32 *location, Elf_Addr v)
+{
+ long offset;
+
+ if (v % 4) {
+ pr_err("module %s: dangerous R_MIPS_PC26 RELA relocation\n",
+ me->name);
+ return -ENOEXEC;
+ }
+
+ offset = ((long)v - (long)location) >> 2;
+ if ((offset >> 25) > 0 || (offset >> 25) < -1) {
+ pr_err("module %s: relocation overflow\n", me->name);
+ return -ENOEXEC;
+ }
+
+ *location = (*location & ~0x03ffffff) | (offset & 0x03ffffff);
+
+ return 0;
+}
+
static int (*reloc_handlers_rela[]) (struct module *me, u32 *location,
Elf_Addr v) = {
[R_MIPS_NONE] = apply_r_mips_none,
@@ -97,9 +161,12 @@ static int (*reloc_handlers_rela[]) (struct module *me, u32 *location,
[R_MIPS_26] = apply_r_mips_26_rela,
[R_MIPS_HI16] = apply_r_mips_hi16_rela,
[R_MIPS_LO16] = apply_r_mips_lo16_rela,
+ [R_MIPS_PC16] = apply_r_mips_pc16_rela,
[R_MIPS_64] = apply_r_mips_64_rela,
[R_MIPS_HIGHER] = apply_r_mips_higher_rela,
- [R_MIPS_HIGHEST] = apply_r_mips_highest_rela
+ [R_MIPS_HIGHEST] = apply_r_mips_highest_rela,
+ [R_MIPS_PC21_S2] = apply_r_mips_pc21_rela,
+ [R_MIPS_PC26_S2] = apply_r_mips_pc26_rela,
};

int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
--
2.7.0