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 <[email protected]> --- 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
