1 files changed, 22 insertions, 14 deletions

diff --git a/arch/arm64/kernel/armv8_deprecated.c b/arch/arm64/kernel/armv8_deprecated.c
index 42ffdb54e162..b0988bb1bf64 100644
--- a/arch/arm64/kernel/armv8_deprecated.c
+++ b/arch/arm64/kernel/armv8_deprecated.c
@@ -280,35 +280,43 @@ static void __init register_insn_emulation_sysctl(struct ctl_table *table)
 /*
  * Error-checking SWP macros implemented using ldxr{b}/stxr{b}
  */
-#define __user_swpX_asm(data, addr, res, temp, B)               \
+
+/* Arbitrary constant to ensure forward-progress of the LL/SC loop */
+#define __SWP_LL_SC_LOOPS       4
+
+#define __user_swpX_asm(data, addr, res, temp, temp2, B)        \
         __asm__ __volatile__(                                   \
+        "       mov             %w3, %w7\n"                     \
         ALTERNATIVE("nop", SET_PSTATE_PAN(0), ARM64_HAS_PAN,    \
                     CONFIG_ARM64_PAN)                           \
-        "0:     ldxr"B"         %w2, [%3]\n"                    \
-        "1:     stxr"B"         %w0, %w1, [%3]\n"               \
+        "0:     ldxr"B"         %w2, [%4]\n"                    \
+        "1:     stxr"B"         %w0, %w1, [%4]\n"               \
         "       cbz             %w0, 2f\n"                      \
-        "       mov             %w0, %w4\n"                     \
+        "       sub             %w3, %w3, #1\n"                 \
+        "       cbnz            %w3, 0b\n"                      \
+        "       mov             %w0, %w5\n"                     \
         "       b               3f\n"                           \
         "2:\n"                                                  \
         "       mov             %w1, %w2\n"                     \
         "3:\n"                                                  \
         "       .pushsection     .fixup,\"ax\"\n"               \
         "       .align          2\n"                            \
-        "4:     mov             %w0, %w5\n"                     \
+        "4:     mov             %w0, %w6\n"                     \
         "       b               3b\n"                           \
         "       .popsection"                                    \
         _ASM_EXTABLE(0b, 4b)                                    \
         _ASM_EXTABLE(1b, 4b)                                    \
         ALTERNATIVE("nop", SET_PSTATE_PAN(1), ARM64_HAS_PAN,    \
                 CONFIG_ARM64_PAN)                               \
-        : "=&r" (res), "+r" (data), "=&r" (temp)                \
-        : "r" (addr), "i" (-EAGAIN), "i" (-EFAULT)              \
+        : "=&r" (res), "+r" (data), "=&r" (temp), "=&r" (temp2) \
+        : "r" (addr), "i" (-EAGAIN), "i" (-EFAULT),             \
+          "i" (__SWP_LL_SC_LOOPS)                               \
         : "memory")
 
-#define __user_swp_asm(data, addr, res, temp) \
-        __user_swpX_asm(data, addr, res, temp, "")
-#define __user_swpb_asm(data, addr, res, temp) \
-        __user_swpX_asm(data, addr, res, temp, "b")
+#define __user_swp_asm(data, addr, res, temp, temp2) \
+        __user_swpX_asm(data, addr, res, temp, temp2, "")
+#define __user_swpb_asm(data, addr, res, temp, temp2) \
+        __user_swpX_asm(data, addr, res, temp, temp2, "b")
 
 /*
  * Bit 22 of the instruction encoding distinguishes between
@@ -328,12 +336,12 @@ static int emulate_swpX(unsigned int address, unsigned int *data,
         }
 
         while (1) {
-                unsigned long temp;
+                unsigned long temp, temp2;
 
                 if (type == TYPE_SWPB)
-                        __user_swpb_asm(*data, address, res, temp);
+                        __user_swpb_asm(*data, address, res, temp, temp2);
                 else
-                        __user_swp_asm(*data, address, res, temp);
+                        __user_swp_asm(*data, address, res, temp, temp2);
 
                 if (likely(res != -EAGAIN) || signal_pending(current))
                         break;