x86/ftrace, x86/asm: Kill ftrace_caller_end label

One of ftrace_caller_end and ftrace_return is redundant so unify them.
Rename ftrace_return to ftrace_epilogue to mean that everything after
that label represents, like an afterword, work which happens *after* the
ftrace call, e.g., the function graph tracer for one.

Steve wants this to rather mean "[a]n event which reflects meaningfully
on a recently ended conflict or struggle." I can imagine that ftrace can
be a struggle sometimes.

Anyway, beef up the comment about the code contents and layout before
ftrace_epilogue label.

Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1455612202-14414-4-git-send-email-bp@alien8.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

2 files changed, 13 insertions, 12 deletions

diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index 29408d6d6626..04f9641e0cb6 100644
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -697,9 +697,8 @@ static inline void tramp_free(void *tramp) { }
 #endif
 
 /* Defined as markers to the end of the ftrace default trampolines */
-extern void ftrace_caller_end(void);
 extern void ftrace_regs_caller_end(void);
-extern void ftrace_return(void);
+extern void ftrace_epilogue(void);
 extern void ftrace_caller_op_ptr(void);
 extern void ftrace_regs_caller_op_ptr(void);
 
@@ -746,7 +745,7 @@ create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size)
                 op_offset = (unsigned long)ftrace_regs_caller_op_ptr;
         } else {
                 start_offset = (unsigned long)ftrace_caller;
-                end_offset = (unsigned long)ftrace_caller_end;
+                end_offset = (unsigned long)ftrace_epilogue;
                 op_offset = (unsigned long)ftrace_caller_op_ptr;
         }
 
@@ -754,7 +753,7 @@ create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size)
 
         /*
          * Allocate enough size to store the ftrace_caller code,
-         * the jmp to ftrace_return, as well as the address of
+         * the jmp to ftrace_epilogue, as well as the address of
          * the ftrace_ops this trampoline is used for.
          */
         trampoline = alloc_tramp(size + MCOUNT_INSN_SIZE + sizeof(void *));
@@ -772,8 +771,8 @@ create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size)
 
         ip = (unsigned long)trampoline + size;
 
-        /* The trampoline ends with a jmp to ftrace_return */
-        jmp = ftrace_jmp_replace(ip, (unsigned long)ftrace_return);
+        /* 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);
 
         /*
diff --git a/arch/x86/kernel/mcount_64.S b/arch/x86/kernel/mcount_64.S
index 87e1762e2bca..ed48a9f465f8 100644
--- a/arch/x86/kernel/mcount_64.S
+++ b/arch/x86/kernel/mcount_64.S
@@ -168,12 +168,14 @@ GLOBAL(ftrace_call)
         restore_mcount_regs
 
         /*
-         * The copied trampoline must call ftrace_return as it
+         * The copied trampoline must call ftrace_epilogue as it
          * still may need to call the function graph tracer.
+         *
+         * The code up to this label is copied into trampolines so
+         * think twice before adding any new code or changing the
+         * layout here.
          */
-GLOBAL(ftrace_caller_end)
-
-GLOBAL(ftrace_return)
+GLOBAL(ftrace_epilogue)
 
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 GLOBAL(ftrace_graph_call)
@@ -244,14 +246,14 @@ GLOBAL(ftrace_regs_call)
         popfq
 
         /*
-         * As this jmp to ftrace_return can be a short jump
+         * As this jmp to ftrace_epilogue can be a short jump
          * it must not be copied into the trampoline.
          * The trampoline will add the code to jump
          * to the return.
          */
 GLOBAL(ftrace_regs_caller_end)
 
-        jmp ftrace_return
+        jmp ftrace_epilogue
 
 END(ftrace_regs_caller)