[ARM] 5428/1: Module relocation update for R_ARM_V4BX

It would seem when building kernel modules with modern binutils
(required by modern GCC) for ARM v4T targets (specifically observed
with the Samsung 24xx SoC which is an 920T) R_ARM_V4BX relocations
are emitted for function epilogues.

This manifests at module load time with an "unknown relocation: 40"
error message.

The following patch adds the R_ARM_V4BX relocation to the ARM kernel
module loader. The relocation operation is taken from that within the
binutils bfd library.

Signed-off-by: Simtec Linux Team <linux@simtec.co.uk>
Signed-off-by: Vincent Sanders <vince@simtec.co.uk>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 9 insertions, 0 deletions

diff --git a/arch/arm/kernel/module.c b/arch/arm/kernel/module.c
index dab48f27263f..9f509fd00fda 100644
--- a/arch/arm/kernel/module.c
+++ b/arch/arm/kernel/module.c
@@ -132,6 +132,15 @@ apply_relocate(Elf32_Shdr *sechdrs, const char *strtab, unsigned int symindex,
                         *(u32 *)loc |= offset & 0x00ffffff;
                         break;
 
+               case R_ARM_V4BX:
+                       /* Preserve Rm and the condition code. Alter
+                        * other bits to re-code instruction as
+                        * MOV PC,Rm.
+                        */
+                       *(u32 *)loc &= 0xf000000f;
+                       *(u32 *)loc |= 0x01a0f000;
+                       break;
+
                 default:
                         printk(KERN_ERR "%s: unknown relocation: %u\n",
                                module->name, ELF32_R_TYPE(rel->r_info));