ARM kprobes: don't let a single-stepped stmdb corrupt the exception stack

[pandora-kernel.git] / arch / arm / kernel / entry-armv.S

diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S
index 29dec08..12ecc81 100644 (file)
--- a/arch/arm/kernel/entry-armv.S
+++ b/arch/arm/kernel/entry-armv.S
@@ -112,8 +112,8 @@ common_invalid:
 #define SPFIX(code...)
 #endif
 
-       .macro  svc_entry
-       sub     sp, sp, #S_FRAME_SIZE
+       .macro  svc_entry, stack_hole=0
+       sub     sp, sp, #(S_FRAME_SIZE + \stack_hole)
  SPFIX(        tst     sp, #4          )
  SPFIX(        bicne   sp, sp, #4      )
        stmib   sp, {r1 - r12}
@@ -121,7 +121,7 @@ common_invalid:
        ldmia   r0, {r1 - r3}
        add     r5, sp, #S_SP           @ here for interlock avoidance
        mov     r4, #-1                 @  ""  ""      ""       ""
-       add     r0, sp, #S_FRAME_SIZE   @  ""  ""      ""       ""
+       add     r0, sp, #(S_FRAME_SIZE + \stack_hole)
  SPFIX(        addne   r0, r0, #4      )
        str     r1, [sp]                @ save the "real" r0 copied
                                        @ from the exception stack
@@ -242,7 +242,14 @@ svc_preempt:
 
        .align  5
 __und_svc:
+#ifdef CONFIG_KPROBES
+       @ If a kprobe is about to simulate a "stmdb sp..." instruction,
+       @ it obviously needs free stack space which then will belong to
+       @ the saved context.
+       svc_entry 64
+#else
        svc_entry
+#endif
 
        @
        @ call emulation code, which returns using r9 if it has emulated