ARM: BUG if jumping to usermode address in kernel mode

Detect if we are returning to usermode via the normal kernel exit paths
but the saved PSR value indicates that we are in kernel mode.  This
could occur due to corrupted stack state, which has been observed with
"ftracetest".

This ensures that we catch the problem case before we get to user code.

Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>

1 files changed, 18 insertions, 0 deletions

diff --git a/arch/arm/include/asm/assembler.h b/arch/arm/include/asm/assembler.h
index ad301f107dd2..bc8d4bbd82e2 100644
--- a/arch/arm/include/asm/assembler.h
+++ b/arch/arm/include/asm/assembler.h
@@ -518,4 +518,22 @@ THUMB(	orr	\reg , \reg , #PSR_T_BIT	)
 #endif
         .endm
 
+        .macro  bug, msg, line
+#ifdef CONFIG_THUMB2_KERNEL
+1:      .inst   0xde02
+#else
+1:      .inst   0xe7f001f2
+#endif
+#ifdef CONFIG_DEBUG_BUGVERBOSE
+        .pushsection .rodata.str, "aMS", %progbits, 1
+2:      .asciz  "\msg"
+        .popsection
+        .pushsection __bug_table, "aw"
+        .align  2
+        .word   1b, 2b
+        .hword  \line
+        .popsection
+#endif
+        .endm
+
 #endif /* __ASM_ASSEMBLER_H__ */