s390/ftrace: assume -mhotpatch or -mrecord-mcount always available

Currently the kernel minimal compiler requirement is gcc 4.9 or
clang 10.0.1.
* gcc -mhotpatch option is supported since 4.8.
* A combination of -pg -mrecord-mcount -mnop-mcount -mfentry flags is
supported since gcc 9 and since clang 10.

Drop support for old -pg function prologues. Which leaves binary
compatible -mhotpatch / -mnop-mcount -mfentry prologues in a form:
	brcl	0,0
Which are also do not require initial nop optimization / conversion and
presence of _mcount symbol.

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

1 files changed, 10 insertions, 21 deletions

diff --git a/arch/s390/include/asm/ftrace.h b/arch/s390/include/asm/ftrace.h
index 68d362f8d6c1..695c61989f97 100644
--- a/arch/s390/include/asm/ftrace.h
+++ b/arch/s390/include/asm/ftrace.h
@@ -2,16 +2,9 @@
 #ifndef _ASM_S390_FTRACE_H
 #define _ASM_S390_FTRACE_H
 
+#define HAVE_FUNCTION_GRAPH_RET_ADDR_PTR
 #define ARCH_SUPPORTS_FTRACE_OPS 1
-
-#if defined(CC_USING_HOTPATCH) || defined(CC_USING_NOP_MCOUNT)
 #define MCOUNT_INSN_SIZE	6
-#else
-#define MCOUNT_INSN_SIZE	24
-#define MCOUNT_RETURN_FIXUP	18
-#endif
-
-#define HAVE_FUNCTION_GRAPH_RET_ADDR_PTR
 
 #ifndef __ASSEMBLY__
 
@@ -22,7 +15,6 @@
 #define ftrace_return_address(n) __builtin_return_address(n)
 #endif
 
-void _mcount(void);
 void ftrace_caller(void);
 
 extern char ftrace_graph_caller_end;
@@ -30,12 +22,20 @@ extern unsigned long ftrace_plt;
 
 struct dyn_arch_ftrace { };
 
-#define MCOUNT_ADDR ((unsigned long)_mcount)
+#define MCOUNT_ADDR 0
 #define FTRACE_ADDR ((unsigned long)ftrace_caller)
 
 #define KPROBE_ON_FTRACE_NOP	0
 #define KPROBE_ON_FTRACE_CALL	1
 
+struct module;
+struct dyn_ftrace;
+/*
+ * Either -mhotpatch or -mnop-mcount is used - no explicit init is required
+ */
+static inline int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec) { return 0; }
+#define ftrace_init_nop ftrace_init_nop
+
 static inline unsigned long ftrace_call_adjust(unsigned long addr)
 {
 	return addr;
@@ -49,28 +49,17 @@ struct ftrace_insn {
 static inline void ftrace_generate_nop_insn(struct ftrace_insn *insn)
 {
 #ifdef CONFIG_FUNCTION_TRACER
-#if defined(CC_USING_HOTPATCH) || defined(CC_USING_NOP_MCOUNT)
 	/* brcl 0,0 */
 	insn->opc = 0xc004;
 	insn->disp = 0;
-#else
-	/* jg .+24 */
-	insn->opc = 0xc0f4;
-	insn->disp = MCOUNT_INSN_SIZE / 2;
-#endif
 #endif
 }
 
 static inline int is_ftrace_nop(struct ftrace_insn *insn)
 {
 #ifdef CONFIG_FUNCTION_TRACER
-#if defined(CC_USING_HOTPATCH) || defined(CC_USING_NOP_MCOUNT)
 	if (insn->disp == 0)
 		return 1;
-#else
-	if (insn->disp == MCOUNT_INSN_SIZE / 2)
-		return 1;
-#endif
 #endif
 	return 0;
 }