Thumb-2: Correctly handle undefined instructions in the kernel

VFP instructions in the kernel may trigger undefined exceptions if VFP
hardware is not present. This patch corrects the loading of such Thumb-2
instructions. It also marks the "no_fp" label as a function so that the
linker generate a Thumb address.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

1 files changed, 11 insertions, 1 deletions

diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S
index a332bc7225b..0a2ba51cf35 100644
--- a/arch/arm/kernel/entry-armv.S
+++ b/arch/arm/kernel/entry-armv.S
@@ -272,7 +272,15 @@ __und_svc:
         @
         @  r0 - instruction
         @
+#ifndef CONFIG_THUMB2_KERNEL
         ldr     r0, [r2, #-4]
+#else
+        ldrh    r0, [r2, #-2]                   @ Thumb instruction at LR - 2
+        and     r9, r0, #0xf800
+        cmp     r9, #0xe800                     @ 32-bit instruction if xx >= 0
+        ldrhhs  r9, [r2]                        @ bottom 16 bits
+        orrhs   r0, r9, r0, lsl #16
+#endif
         adr     r9, BSYM(1f)
         bl      call_fpe
 
@@ -678,7 +686,9 @@ ENTRY(fp_enter)
         .word   no_fp
         .previous
 
-no_fp:  mov     pc, lr
+ENTRY(no_fp)
+        mov     pc, lr
+ENDPROC(no_fp)
 
 __und_usr_unknown:
         enable_irq