3 files changed, 27 insertions, 8 deletions

diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c
index 8a16ee5d8a95..84db893dedc2 100644
--- a/arch/arm/kernel/setup.c
+++ b/arch/arm/kernel/setup.c
@@ -393,19 +393,34 @@ static void __init cpuid_init_hwcaps(void)
                 elf_hwcap |= HWCAP_LPAE;
 }
 
-static void __init feat_v6_fixup(void)
+static void __init elf_hwcap_fixup(void)
 {
-        int id = read_cpuid_id();
-
-        if ((id & 0xff0f0000) != 0x41070000)
-                return;
+        unsigned id = read_cpuid_id();
+        unsigned sync_prim;
 
         /*
          * HWCAP_TLS is available only on 1136 r1p0 and later,
          * see also kuser_get_tls_init.
          */
-        if ((((id >> 4) & 0xfff) == 0xb36) && (((id >> 20) & 3) == 0))
+        if (read_cpuid_part() == ARM_CPU_PART_ARM1136 &&
+            ((id >> 20) & 3) == 0) {
                 elf_hwcap &= ~HWCAP_TLS;
+                return;
+        }
+
+        /* Verify if CPUID scheme is implemented */
+        if ((id & 0x000f0000) != 0x000f0000)
+                return;
+
+        /*
+         * If the CPU supports LDREX/STREX and LDREXB/STREXB,
+         * avoid advertising SWP; it may not be atomic with
+         * multiprocessing cores.
+         */
+        sync_prim = ((read_cpuid_ext(CPUID_EXT_ISAR3) >> 8) & 0xf0) |
+                    ((read_cpuid_ext(CPUID_EXT_ISAR4) >> 20) & 0x0f);
+        if (sync_prim >= 0x13)
+                elf_hwcap &= ~HWCAP_SWP;
 }
 
 /*
@@ -609,7 +624,7 @@ static void __init setup_processor(void)
 #endif
         erratum_a15_798181_init();
 
-        feat_v6_fixup();
+        elf_hwcap_fixup();
 
         cacheid_init();
         cpu_init();
diff --git a/arch/arm/kernel/swp_emulate.c b/arch/arm/kernel/swp_emulate.c
index b1b89882b113..67ca8578c6d8 100644
--- a/arch/arm/kernel/swp_emulate.c
+++ b/arch/arm/kernel/swp_emulate.c
@@ -27,6 +27,7 @@
 #include <linux/perf_event.h>
 
 #include <asm/opcodes.h>
+#include <asm/system_info.h>
 #include <asm/traps.h>
 #include <asm/uaccess.h>
 
@@ -266,6 +267,9 @@ static struct undef_hook swp_hook = {
  */
 static int __init swp_emulation_init(void)
 {
+        if (cpu_architecture() < CPU_ARCH_ARMv7)
+                return 0;
+
 #ifdef CONFIG_PROC_FS
         if (!proc_create("cpu/swp_emulation", S_IRUGO, NULL, &proc_status_fops))
                 return -ENOMEM;
diff --git a/arch/arm/mm/Kconfig b/arch/arm/mm/Kconfig
index df46620206af..577039a3f6e5 100644
--- a/arch/arm/mm/Kconfig
+++ b/arch/arm/mm/Kconfig
@@ -669,7 +669,7 @@ config ARM_VIRT_EXT
           details.
 
 config SWP_EMULATE
-        bool "Emulate SWP/SWPB instructions"
+        bool "Emulate SWP/SWPB instructions" if !SMP
         depends on CPU_V7
         default y if SMP
         select HAVE_PROC_CPU if PROC_FS