s390/ftrace: provide separate ftrace_caller/ftrace_regs_caller implem…

…entations

ftrace_regs_caller is an alias to ftrace_caller - making ftrace_caller
quite heavyweight. Split the function and provide an ftrace_caller
implementation which comes with fewer instructions. Especially getting
rid of 'stosm' on each function entry should help here, e.g. to
have less performance impact on live patched functions.

Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

arch/s390/include/asm/ftrace.h

@@ -17,7 +17,6 @@
 
 void ftrace_caller(void);
 
-extern char ftrace_graph_caller_end;
 extern void *ftrace_func;
 
 struct dyn_arch_ftrace { };

arch/s390/kernel/mcount.S

@@ -33,13 +33,15 @@ ENDPROC(ftrace_stub)
 #define TRACED_FUNC_FRAME_SIZE STACK_FRAME_OVERHEAD
 #endif
 
-ENTRY(ftrace_caller)
- .globl ftrace_regs_caller
- .set ftrace_regs_caller,ftrace_caller
+ .macro ftrace_regs_entry, allregs=0
  stg %r14,(__SF_GPRS+8*8)(%r15) # save traced function caller
+
+ .if \allregs == 1
  lghi %r14,0 # save condition code
  ipm %r14 # don't put any instructions
  sllg %r14,%r14,16 # clobbering CC before this point
+ .endif
+
  lgr %r1,%r15
  # allocate stack frame for ftrace_caller to contain traced function
  aghi %r15,-TRACED_FUNC_FRAME_SIZE
@@ -49,13 +51,30 @@ ENTRY(ftrace_caller)
  # allocate pt_regs and stack frame for ftrace_trace_function
  aghi %r15,-STACK_FRAME_SIZE
  stg %r1,(STACK_PTREGS_GPRS+15*8)(%r15)
+
+ .if \allregs == 1
  stg %r14,(STACK_PTREGS_PSW)(%r15)
- lg %r14,(__SF_GPRS+8*8)(%r1) # restore original return address
  stosm (STACK_PTREGS_PSW)(%r15),0
+ .endif
+
+ lg %r14,(__SF_GPRS+8*8)(%r1) # restore original return address
  aghi %r1,-TRACED_FUNC_FRAME_SIZE
  stg %r1,__SF_BACKCHAIN(%r15)
  stg %r0,(STACK_PTREGS_PSW+8)(%r15)
  stmg %r2,%r14,(STACK_PTREGS_GPRS+2*8)(%r15)
+ .endm
+
+SYM_CODE_START(ftrace_regs_caller)
+ ftrace_regs_entry 1
+ j ftrace_common
+SYM_CODE_END(ftrace_regs_caller)
+
+SYM_CODE_START(ftrace_caller)
+ ftrace_regs_entry 0
+ j ftrace_common
+SYM_CODE_END(ftrace_caller)
+
+SYM_CODE_START(ftrace_common)
 #ifdef CONFIG_HAVE_MARCH_Z196_FEATURES
  aghik %r2,%r0,-MCOUNT_INSN_SIZE
  lgrl %r4,function_trace_op
@@ -74,24 +93,22 @@ ENTRY(ftrace_caller)
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 # The j instruction gets runtime patched to a nop instruction.
 # See ftrace_enable_ftrace_graph_caller.
- .globl ftrace_graph_caller
-ftrace_graph_caller:
- j ftrace_graph_caller_end
+SYM_INNER_LABEL(ftrace_graph_caller, SYM_L_GLOBAL)
+ j .Lftrace_graph_caller_end
  lmg %r2,%r3,(STACK_PTREGS_GPRS+14*8)(%r15)
  lg %r4,(STACK_PTREGS_PSW+8)(%r15)
  brasl %r14,prepare_ftrace_return
  stg %r2,(STACK_PTREGS_GPRS+14*8)(%r15)
-ftrace_graph_caller_end:
- .globl ftrace_graph_caller_end
+.Lftrace_graph_caller_end:
 #endif
  lg %r1,(STACK_PTREGS_PSW+8)(%r15)
  lmg %r2,%r15,(STACK_PTREGS_GPRS+2*8)(%r15)
  BR_EX %r1
-ENDPROC(ftrace_caller)
+SYM_CODE_END(ftrace_common)
 
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 
-ENTRY(return_to_handler)
+SYM_FUNC_START(return_to_handler)
  stmg %r2,%r5,32(%r15)
  lgr %r1,%r15
  aghi %r15,-STACK_FRAME_OVERHEAD
@@ -101,6 +118,6 @@ ENTRY(return_to_handler)
  lgr %r14,%r2
  lmg %r2,%r5,32(%r15)
  BR_EX %r14
-ENDPROC(return_to_handler)
+SYM_FUNC_END(return_to_handler)
 
 #endif