1 files changed, 22 insertions, 19 deletions

diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index 7ee8067cbf45..8257a59704ae 100644
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -733,18 +733,20 @@ union ftrace_op_code_union {
         } __attribute__((packed));
 };
 
+#define RET_SIZE                1
+
 static unsigned long
 create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size)
 {
-        unsigned const char *jmp;
         unsigned long start_offset;
         unsigned long end_offset;
         unsigned long op_offset;
         unsigned long offset;
         unsigned long size;
-        unsigned long ip;
+        unsigned long retq;
         unsigned long *ptr;
         void *trampoline;
+        void *ip;
         /* 48 8b 15 <offset> is movq <offset>(%rip), %rdx */
         unsigned const char op_ref[] = { 0x48, 0x8b, 0x15 };
         union ftrace_op_code_union op_ptr;
@@ -764,27 +766,27 @@ create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size)
 
         /*
          * Allocate enough size to store the ftrace_caller code,
-         * the jmp to ftrace_epilogue, as well as the address of
-         * the ftrace_ops this trampoline is used for.
+         * the iret , as well as the address of the ftrace_ops this
+         * trampoline is used for.
          */
-        trampoline = alloc_tramp(size + MCOUNT_INSN_SIZE + sizeof(void *));
+        trampoline = alloc_tramp(size + RET_SIZE + sizeof(void *));
         if (!trampoline)
                 return 0;
 
-        *tramp_size = size + MCOUNT_INSN_SIZE + sizeof(void *);
+        *tramp_size = size + RET_SIZE + sizeof(void *);
 
         /* Copy ftrace_caller onto the trampoline memory */
         ret = probe_kernel_read(trampoline, (void *)start_offset, size);
-        if (WARN_ON(ret < 0)) {
-                tramp_free(trampoline, *tramp_size);
-                return 0;
-        }
+        if (WARN_ON(ret < 0))
+                goto fail;
 
-        ip = (unsigned long)trampoline + size;
+        ip = trampoline + size;
 
-        /* The trampoline ends with a jmp to ftrace_epilogue */
-        jmp = ftrace_jmp_replace(ip, (unsigned long)ftrace_epilogue);
-        memcpy(trampoline + size, jmp, MCOUNT_INSN_SIZE);
+        /* The trampoline ends with ret(q) */
+        retq = (unsigned long)ftrace_stub;
+        ret = probe_kernel_read(ip, (void *)retq, RET_SIZE);
+        if (WARN_ON(ret < 0))
+                goto fail;
 
         /*
          * The address of the ftrace_ops that is used for this trampoline
@@ -794,17 +796,15 @@ create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size)
          * the global function_trace_op variable.
          */
 
-        ptr = (unsigned long *)(trampoline + size + MCOUNT_INSN_SIZE);
+        ptr = (unsigned long *)(trampoline + size + RET_SIZE);
         *ptr = (unsigned long)ops;
 
         op_offset -= start_offset;
         memcpy(&op_ptr, trampoline + op_offset, OP_REF_SIZE);
 
         /* Are we pointing to the reference? */
-        if (WARN_ON(memcmp(op_ptr.op, op_ref, 3) != 0)) {
-                tramp_free(trampoline, *tramp_size);
-                return 0;
-        }
+        if (WARN_ON(memcmp(op_ptr.op, op_ref, 3) != 0))
+                goto fail;
 
         /* Load the contents of ptr into the callback parameter */
         offset = (unsigned long)ptr;
@@ -819,6 +819,9 @@ create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size)
         ops->flags |= FTRACE_OPS_FL_ALLOC_TRAMP;
 
         return (unsigned long)trampoline;
+fail:
+        tramp_free(trampoline, *tramp_size);
+        return 0;
 }
 
 static unsigned long calc_trampoline_call_offset(bool save_regs)