s390/ftrace: remove dead code

ftrace_shared_hotpatch_trampoline() never returns NULL,
therefore quite a bit of code can be removed.
Acked-by: Ilya Leoshkevich <iii@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

arch/s390/kernel/ftrace.c

@@ -80,17 +80,6 @@ asm(
 
 #ifdef CONFIG_MODULES
 static char *ftrace_plt;
-
-asm(
-	"	.data\n"
-	"ftrace_plt_template:\n"
-	"	basr	%r1,%r0\n"
-	"	lg	%r1,0f-.(%r1)\n"
-	"	br	%r1\n"
-	"0:	.quad	ftrace_caller\n"
-	"ftrace_plt_template_end:\n"
-	"	.previous\n"
-);
 #endif /* CONFIG_MODULES */
 
 static const char *ftrace_shared_hotpatch_trampoline(const char **end)
@@ -116,7 +105,7 @@ static const char *ftrace_shared_hotpatch_trampoline(const char **end)
 
 bool ftrace_need_init_nop(void)
 {
-	return ftrace_shared_hotpatch_trampoline(NULL);
+	return true;
 }
 
 int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec)
@@ -175,28 +164,6 @@ int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
 	return 0;
 }
 
-static void ftrace_generate_nop_insn(struct ftrace_insn *insn)
-{
-	/* brcl 0,0 */
-	insn->opc = 0xc004;
-	insn->disp = 0;
-}
-
-static void ftrace_generate_call_insn(struct ftrace_insn *insn,
-				      unsigned long ip)
-{
-	unsigned long target;
-
-	/* brasl r0,ftrace_caller */
-	target = FTRACE_ADDR;
-#ifdef CONFIG_MODULES
-	if (is_module_addr((void *)ip))
-		target = (unsigned long)ftrace_plt;
-#endif /* CONFIG_MODULES */
-	insn->opc = 0xc005;
-	insn->disp = (target - ip) / 2;
-}
-
 static void brcl_disable(void *brcl)
 {
 	u8 op = 0x04; /* set mask field to zero */
@@ -207,23 +174,7 @@ static void brcl_disable(void *brcl)
 int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
 		    unsigned long addr)
 {
-	struct ftrace_insn orig, new, old;
-
-	if (ftrace_shared_hotpatch_trampoline(NULL)) {
-		brcl_disable((void *)rec->ip);
-		return 0;
-	}
-
-	if (copy_from_kernel_nofault(&old, (void *) rec->ip, sizeof(old)))
-		return -EFAULT;
-	/* Replace ftrace call with a nop. */
-	ftrace_generate_call_insn(&orig, rec->ip);
-	ftrace_generate_nop_insn(&new);
-
-	/* Verify that the to be replaced code matches what we expect. */
-	if (memcmp(&orig, &old, sizeof(old)))
-		return -EINVAL;
-	s390_kernel_write((void *) rec->ip, &new, sizeof(new));
+	brcl_disable((void *)rec->ip);
 	return 0;
 }
 
@@ -236,23 +187,7 @@ static void brcl_enable(void *brcl)
 
 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
 {
-	struct ftrace_insn orig, new, old;
-
-	if (ftrace_shared_hotpatch_trampoline(NULL)) {
-		brcl_enable((void *)rec->ip);
-		return 0;
-	}
-
-	if (copy_from_kernel_nofault(&old, (void *) rec->ip, sizeof(old)))
-		return -EFAULT;
-	/* Replace nop with an ftrace call. */
-	ftrace_generate_nop_insn(&orig);
-	ftrace_generate_call_insn(&new, rec->ip);
-
-	/* Verify that the to be replaced code matches what we expect. */
-	if (memcmp(&orig, &old, sizeof(old)))
-		return -EINVAL;
-	s390_kernel_write((void *) rec->ip, &new, sizeof(new));
+	brcl_enable((void *)rec->ip);
 	return 0;
 }
 
@@ -269,10 +204,7 @@ int __init ftrace_dyn_arch_init(void)
 
 void arch_ftrace_update_code(int command)
 {
-	if (ftrace_shared_hotpatch_trampoline(NULL))
-		ftrace_modify_all_code(command);
-	else
-		ftrace_run_stop_machine(command);
+	ftrace_modify_all_code(command);
 }
 
 static void __ftrace_sync(void *dummy)
@@ -281,10 +213,8 @@ static void __ftrace_sync(void *dummy)
 
 int ftrace_arch_code_modify_post_process(void)
 {
-	if (ftrace_shared_hotpatch_trampoline(NULL)) {
-		/* Send SIGP to the other CPUs, so they see the new code. */
-		smp_call_function(__ftrace_sync, NULL, 1);
-	}
+	/* Send SIGP to the other CPUs, so they see the new code. */
+	smp_call_function(__ftrace_sync, NULL, 1);
 	return 0;
 }
 
@@ -299,10 +229,6 @@ static int __init ftrace_plt_init(void)
 		panic("cannot allocate ftrace plt\n");
 
 	start = ftrace_shared_hotpatch_trampoline(&end);
-	if (!start) {
-		start = ftrace_plt_template;
-		end = ftrace_plt_template_end;
-	}
 	memcpy(ftrace_plt, start, end - start);
 	set_memory_ro((unsigned long)ftrace_plt, 1);
 	return 0;