MIPS32 code uses rel-style relocs, and MIPS32r6 modules may include
R_MIPS_PC16, R_MIPS_PC21 & R_MIPS_PC26 relocations. We thus need to
support these relocations in order to load MIPS32r6 kernel modules. This
patch adds such support, which is similar to the rela-style support in
module-rela.c but making use of the implicit addend from the instruction
encoding.
Signed-off-by: Paul Burton <paul.burton@xxxxxxxxxx>
---
Changes in v2:
- Unify PC{16,21,26} implementation.
arch/mips/kernel/module.c | 51 ++++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 50 insertions(+), 1 deletion(-)
diff --git a/arch/mips/kernel/module.c b/arch/mips/kernel/module.c
index e16624f..ff5d97d 100644
--- a/arch/mips/kernel/module.c
+++ b/arch/mips/kernel/module.c
@@ -182,13 +182,62 @@ out_danger:
return -ENOEXEC;
}
+static int apply_r_mips_pc_rel(struct module *me, u32 *location, Elf_Addr v,
+ unsigned bits)
+{
+ unsigned long mask = GENMASK(bits - 1, 0);
+ unsigned long se_bits;
+ long offset;
+
+ if (v % 4) {
+ pr_err("module %s: dangerous R_MIPS_PC%u REL relocation\n",
+ me->name, bits);
+ return -ENOEXEC;
+ }
+
+ /* retrieve & sign extend implicit addend */
+ offset = *location & mask;
+ offset |= (offset & BIT(bits - 1)) ? ~mask : 0;
+
+ offset += ((long)v - (long)location) >> 2;
+
+ /* check the sign bit onwards are identical - ie. we didn't overflow */
+ se_bits = (offset & BIT(bits - 1)) ? ~0ul : 0;
+ if ((offset & ~mask) != (se_bits & ~mask)) {
+ pr_err("module %s: relocation overflow\n", me->name);
+ return -ENOEXEC;
+ }
+
+ *location = (*location & ~mask) | (offset & mask);
+
+ return 0;
+}
+
+static int apply_r_mips_pc16_rel(struct module *me, u32 *location, Elf_Addr v)
+{
+ return apply_r_mips_pc_rel(me, location, v, 16);
+}
+
+static int apply_r_mips_pc21_rel(struct module *me, u32 *location, Elf_Addr v)
+{
+ return apply_r_mips_pc_rel(me, location, v, 21);
+}
+
+static int apply_r_mips_pc26_rel(struct module *me, u32 *location, Elf_Addr v)
+{
+ return apply_r_mips_pc_rel(me, location, v, 26);
+}
+
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,
+ [R_MIPS_PC21_S2] = apply_r_mips_pc21_rel,
+ [R_MIPS_PC26_S2] = apply_r_mips_pc26_rel,
};
int apply_relocate(Elf_Shdr *sechdrs, const char *strtab,
--
2.7.0
