ARM: Allow SMP kernels to boot on UP systems

UP systems do not implement all the instructions that SMP systems have,
so in order to boot a SMP kernel on a UP system, we need to rewrite
parts of the kernel.

Do this using an 'alternatives' scheme, where the kernel code and data
is modified prior to initialization to replace the SMP instructions,
thereby rendering the problematical code ineffectual.  We use the linker
to generate a list of 32-bit word locations and their replacement values,
and run through these replacements when we detect a UP system.

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

1 files changed, 21 insertions, 25 deletions

diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
index 6a3a2d0cd6db..e2335811c02e 100644
--- a/arch/arm/mm/mmu.c
+++ b/arch/arm/mm/mmu.c
@@ -310,9 +310,8 @@ static void __init build_mem_type_table(void)
                         cachepolicy = CPOLICY_WRITEBACK;
                 ecc_mask = 0;
         }
-#ifdef CONFIG_SMP
-        cachepolicy = CPOLICY_WRITEALLOC;
-#endif
+        if (is_smp())
+                cachepolicy = CPOLICY_WRITEALLOC;
 
         /*
          * Strip out features not present on earlier architectures.
@@ -406,13 +405,11 @@ static void __init build_mem_type_table(void)
         cp = &cache_policies[cachepolicy];
         vecs_pgprot = kern_pgprot = user_pgprot = cp->pte;
 
-#ifndef CONFIG_SMP
         /*
          * Only use write-through for non-SMP systems
          */
-        if (cpu_arch >= CPU_ARCH_ARMv5 && cachepolicy > CPOLICY_WRITETHROUGH)
+        if (!is_smp() && cpu_arch >= CPU_ARCH_ARMv5 && cachepolicy > CPOLICY_WRITETHROUGH)
                 vecs_pgprot = cache_policies[CPOLICY_WRITETHROUGH].pte;
-#endif
 
         /*
          * Enable CPU-specific coherency if supported.
@@ -436,22 +433,23 @@ static void __init build_mem_type_table(void)
                 mem_types[MT_MINICLEAN].prot_sect |= PMD_SECT_APX|PMD_SECT_AP_WRITE;
                 mem_types[MT_CACHECLEAN].prot_sect |= PMD_SECT_APX|PMD_SECT_AP_WRITE;
 
-#ifdef CONFIG_SMP
-                /*
-                 * Mark memory with the "shared" attribute for SMP systems
-                 */
-                user_pgprot |= L_PTE_SHARED;
-                kern_pgprot |= L_PTE_SHARED;
-                vecs_pgprot |= L_PTE_SHARED;
-                mem_types[MT_DEVICE_WC].prot_sect |= PMD_SECT_S;
-                mem_types[MT_DEVICE_WC].prot_pte |= L_PTE_SHARED;
-                mem_types[MT_DEVICE_CACHED].prot_sect |= PMD_SECT_S;
-                mem_types[MT_DEVICE_CACHED].prot_pte |= L_PTE_SHARED;
-                mem_types[MT_MEMORY].prot_sect |= PMD_SECT_S;
-                mem_types[MT_MEMORY].prot_pte |= L_PTE_SHARED;
-                mem_types[MT_MEMORY_NONCACHED].prot_sect |= PMD_SECT_S;
-                mem_types[MT_MEMORY_NONCACHED].prot_pte |= L_PTE_SHARED;
-#endif
+                if (is_smp()) {
+                        /*
+                         * Mark memory with the "shared" attribute
+                         * for SMP systems
+                         */
+                        user_pgprot |= L_PTE_SHARED;
+                        kern_pgprot |= L_PTE_SHARED;
+                        vecs_pgprot |= L_PTE_SHARED;
+                        mem_types[MT_DEVICE_WC].prot_sect |= PMD_SECT_S;
+                        mem_types[MT_DEVICE_WC].prot_pte |= L_PTE_SHARED;
+                        mem_types[MT_DEVICE_CACHED].prot_sect |= PMD_SECT_S;
+                        mem_types[MT_DEVICE_CACHED].prot_pte |= L_PTE_SHARED;
+                        mem_types[MT_MEMORY].prot_sect |= PMD_SECT_S;
+                        mem_types[MT_MEMORY].prot_pte |= L_PTE_SHARED;
+                        mem_types[MT_MEMORY_NONCACHED].prot_sect |= PMD_SECT_S;
+                        mem_types[MT_MEMORY_NONCACHED].prot_pte |= L_PTE_SHARED;
+                }
         }
 
         /*
@@ -829,8 +827,7 @@ static void __init sanity_check_meminfo(void)
                          * rather difficult.
                          */
                         reason = "with VIPT aliasing cache";
-#ifdef CONFIG_SMP
-                } else if (tlb_ops_need_broadcast()) {
+                } else if (is_smp() && tlb_ops_need_broadcast()) {
                         /*
                          * kmap_high needs to occasionally flush TLB entries,
                          * however, if the TLB entries need to be broadcast
@@ -840,7 +837,6 @@ static void __init sanity_check_meminfo(void)
                          *   (must not be called with irqs off)
                          */
                         reason = "without hardware TLB ops broadcasting";
-#endif
                 }
                 if (reason) {
                         printk(KERN_CRIT "HIGHMEM is not supported %s, ignoring high memory\n",