2 files changed, 39 insertions, 4 deletions

diff --git a/arch/mips/kernel/ftrace.c b/arch/mips/kernel/ftrace.c
index 6a2d758dd8e9..83fa1460e294 100644
--- a/arch/mips/kernel/ftrace.c
+++ b/arch/mips/kernel/ftrace.c
@@ -25,6 +25,12 @@
 #define MCOUNT_OFFSET_INSNS 4
 #endif
 
+/* Arch override because MIPS doesn't need to run this from stop_machine() */
+void arch_ftrace_update_code(int command)
+{
+        ftrace_modify_all_code(command);
+}
+
 /*
  * Check if the address is in kernel space
  *
@@ -89,6 +95,24 @@ static int ftrace_modify_code(unsigned long ip, unsigned int new_code)
         return 0;
 }
 
+#ifndef CONFIG_64BIT
+static int ftrace_modify_code_2(unsigned long ip, unsigned int new_code1,
+                                unsigned int new_code2)
+{
+        int faulted;
+
+        safe_store_code(new_code1, ip, faulted);
+        if (unlikely(faulted))
+                return -EFAULT;
+        ip += 4;
+        safe_store_code(new_code2, ip, faulted);
+        if (unlikely(faulted))
+                return -EFAULT;
+        flush_icache_range(ip, ip + 8); /* original ip + 12 */
+        return 0;
+}
+#endif
+
 /*
  * The details about the calling site of mcount on MIPS
  *
@@ -131,8 +155,18 @@ int ftrace_make_nop(struct module *mod,
          * needed.
          */
         new = in_kernel_space(ip) ? INSN_NOP : INSN_B_1F;
-
+#ifdef CONFIG_64BIT
         return ftrace_modify_code(ip, new);
+#else
+        /*
+         * On 32 bit MIPS platforms, gcc adds a stack adjust
+         * instruction in the delay slot after the branch to
+         * mcount and expects mcount to restore the sp on return.
+         * This is based on a legacy API and does nothing but
+         * waste instructions so it's being removed at runtime.
+         */
+        return ftrace_modify_code_2(ip, new, INSN_NOP);
+#endif
 }
 
 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
diff --git a/arch/mips/kernel/mcount.S b/arch/mips/kernel/mcount.S
index 4c968e7efb74..165867673357 100644
--- a/arch/mips/kernel/mcount.S
+++ b/arch/mips/kernel/mcount.S
@@ -46,9 +46,8 @@
         PTR_L   a5, PT_R9(sp)
         PTR_L   a6, PT_R10(sp)
         PTR_L   a7, PT_R11(sp)
-        PTR_ADDIU       sp, PT_SIZE
 #else
-        PTR_ADDIU       sp, (PT_SIZE + 8)
+        PTR_ADDIU       sp, PT_SIZE
 #endif
 .endm
 
@@ -69,7 +68,9 @@ NESTED(ftrace_caller, PT_SIZE, ra)
         .globl _mcount
 _mcount:
         b       ftrace_stub
-         nop
+        addiu sp,sp,8
+
+        /* When tracing is activated, it calls ftrace_caller+8 (aka here) */
         lw      t1, function_trace_stop
         bnez    t1, ftrace_stub
          nop