ARM: make cr_alignment read-only #ifndef CONFIG_CPU_CP15

This makes cr_alignment a constant 0 to break code that tries to modify
the value as it's likely that it's built on wrong assumption when
CONFIG_CPU_CP15 isn't defined. For code that is only reading the value 0
is more or less a fine value to report.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Message-Id: 1358413196-5609-2-git-send-email-u.kleine-koenig@pengutronix.de (v8)

4 files changed, 41 insertions, 3 deletions

diff --git a/arch/arm/include/asm/cp15.h b/arch/arm/include/asm/cp15.h
index 5ef4d8015a60..1f3262e99d81 100644
--- a/arch/arm/include/asm/cp15.h
+++ b/arch/arm/include/asm/cp15.h
@@ -42,6 +42,8 @@
 #define vectors_high()  (0)
 #endif
 
+#ifdef CONFIG_CPU_CP15
+
 extern unsigned long cr_no_alignment;   /* defined in entry-armv.S */
 extern unsigned long cr_alignment;      /* defined in entry-armv.S */
 
@@ -82,6 +84,18 @@ static inline void set_copro_access(unsigned int val)
         isb();
 }
 
-#endif
+#else /* ifdef CONFIG_CPU_CP15 */
+
+/*
+ * cr_alignment and cr_no_alignment are tightly coupled to cp15 (at least in the
+ * minds of the developers). Yielding 0 for machines without a cp15 (and making
+ * it read-only) is fine for most cases and saves quite some #ifdeffery.
+ */
+#define cr_no_alignment UL(0)
+#define cr_alignment    UL(0)
+
+#endif /* ifdef CONFIG_CPU_CP15 / else */
+
+#endif /* ifndef __ASSEMBLY__ */
 
 #endif
diff --git a/arch/arm/kernel/head-common.S b/arch/arm/kernel/head-common.S
index 854bd22380d3..5b391a689b47 100644
--- a/arch/arm/kernel/head-common.S
+++ b/arch/arm/kernel/head-common.S
@@ -98,8 +98,9 @@ __mmap_switched:
         str     r9, [r4]                        @ Save processor ID
         str     r1, [r5]                        @ Save machine type
         str     r2, [r6]                        @ Save atags pointer
-        bic     r4, r0, #CR_A                   @ Clear 'A' bit
-        stmia   r7, {r0, r4}                    @ Save control register values
+        cmp     r7, #0
+        bicne   r4, r0, #CR_A                   @ Clear 'A' bit
+        stmneia r7, {r0, r4}                    @ Save control register values
         b       start_kernel
 ENDPROC(__mmap_switched)
 
@@ -113,7 +114,11 @@ __mmap_switched_data:
         .long   processor_id                    @ r4
         .long   __machine_arch_type             @ r5
         .long   __atags_pointer                 @ r6
+#ifdef CONFIG_CPU_CP15
         .long   cr_alignment                    @ r7
+#else
+        .long   0                               @ r7
+#endif
         .long   init_thread_union + THREAD_START_SP @ sp
         .size   __mmap_switched_data, . - __mmap_switched_data
 
diff --git a/arch/arm/mm/alignment.c b/arch/arm/mm/alignment.c
index b820edaf3184..feeb3eaccb1c 100644
--- a/arch/arm/mm/alignment.c
+++ b/arch/arm/mm/alignment.c
@@ -964,12 +964,14 @@ static int __init alignment_init(void)
                 return -ENOMEM;
 #endif
 
+#ifdef CONFIG_CPU_CP15
         if (cpu_is_v6_unaligned()) {
                 cr_alignment &= ~CR_A;
                 cr_no_alignment &= ~CR_A;
                 set_cr(cr_alignment);
                 ai_usermode = safe_usermode(ai_usermode, false);
         }
+#endif
 
         hook_fault_code(FAULT_CODE_ALIGNMENT, do_alignment, SIGBUS, BUS_ADRALN,
                         "alignment exception");
diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
index ce328c7f5c94..7c347bcc9421 100644
--- a/arch/arm/mm/mmu.c
+++ b/arch/arm/mm/mmu.c
@@ -97,6 +97,7 @@ static struct cachepolicy cache_policies[] __initdata = {
         }
 };
 
+#ifdef CONFIG_CPU_CP15
 /*
  * These are useful for identifying cache coherency
  * problems by allowing the cache or the cache and
@@ -195,6 +196,22 @@ void adjust_cr(unsigned long mask, unsigned long set)
 }
 #endif
 
+#else /* ifdef CONFIG_CPU_CP15 */
+
+static int __init early_cachepolicy(char *p)
+{
+        pr_warning("cachepolicy kernel parameter not supported without cp15\n");
+}
+early_param("cachepolicy", early_cachepolicy);
+
+static int __init noalign_setup(char *__unused)
+{
+        pr_warning("noalign kernel parameter not supported without cp15\n");
+}
+__setup("noalign", noalign_setup);
+
+#endif /* ifdef CONFIG_CPU_CP15 / else */
+
 #define PROT_PTE_DEVICE         L_PTE_PRESENT|L_PTE_YOUNG|L_PTE_DIRTY|L_PTE_XN
 #define PROT_SECT_DEVICE        PMD_TYPE_SECT|PMD_SECT_AP_WRITE