s390/ftrace: add HAVE_DYNAMIC_FTRACE_WITH_REGS support

This code is based on a patch from Vojtech Pavlik.
http://marc.info/?l=linux-s390&m=140438885114413&w=2

The actual implementation now differs significantly:
Instead of adding a second function "ftrace_regs_caller" which would be nearly
identical to the existing ftrace_caller function, the current ftrace_caller
function is now an alias to ftrace_regs_caller and always passes the needed
pt_regs structure and function_trace_op parameters unconditionally.

Besides that also use asm offsets to correctly allocate and access the new
struct pt_regs on the stack.

While at it we can make use of new instruction to get rid of some indirect
loads if compiled for new machines.

The passed struct pt_regs can be changed by the called function and it's new
contents will replace the current contents.

Note: to change the return address the embedded psw member of the pt_regs
structure must be changed. The psw member is right now incomplete, since
the mask part is missing. For all current use cases this should be sufficent.
Providing and restoring a sane mask would mean we need to add an epsw/lpswe
pair to the mcount code. Only these two instruction would cost us ~120 cycles
which currently seems not necessary.

Cc: Vojtech Pavlik <vojtech@suse.cz>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

2 files changed, 38 insertions, 12 deletions

diff --git a/arch/s390/kernel/ftrace.c b/arch/s390/kernel/ftrace.c
index de55efa5b64e..14b61954d5a8 100644
--- a/arch/s390/kernel/ftrace.c
+++ b/arch/s390/kernel/ftrace.c
@@ -107,6 +107,13 @@ asm(
 
 #endif /* CONFIG_64BIT */
 
+#ifdef CONFIG_64BIT
+int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
+		       unsigned long addr)
+{
+	return 0;
+}
+#endif
 
 int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
 		    unsigned long addr)
diff --git a/arch/s390/kernel/mcount64.S b/arch/s390/kernel/mcount64.S
index 5b33c83adde9..4a65dabae851 100644
--- a/arch/s390/kernel/mcount64.S
+++ b/arch/s390/kernel/mcount64.S
@@ -8,28 +8,47 @@
 #include <linux/linkage.h>
 #include <asm/asm-offsets.h>
 #include <asm/ftrace.h>
+#include <asm/ptrace.h>
 
 	.section .kprobes.text, "ax"
 
 ENTRY(ftrace_stub)
 	br	%r14
 
+#define STACK_FRAME_SIZE  (STACK_FRAME_OVERHEAD + __PT_SIZE)
+#define STACK_PARENT_IP   (STACK_FRAME_SIZE + 8)
+#define STACK_PTREGS	  (STACK_FRAME_OVERHEAD)
+#define STACK_PTREGS_GPRS (STACK_PTREGS + __PT_GPRS)
+#define STACK_PTREGS_PSW  (STACK_PTREGS + __PT_PSW)
+
 ENTRY(_mcount)
 #ifdef CONFIG_DYNAMIC_FTRACE
 	br	%r14
 
 ENTRY(ftrace_caller)
+	.globl	ftrace_regs_caller
+	.set	ftrace_regs_caller,ftrace_caller
 #endif
-	stmg	%r2,%r5,32(%r15)
-	stg	%r14,112(%r15)
 	lgr	%r1,%r15
-	aghi	%r15,-160
+	aghi	%r15,-STACK_FRAME_SIZE
 	stg	%r1,__SF_BACKCHAIN(%r15)
+	stg	%r1,(STACK_PTREGS_GPRS+15*8)(%r15)
+	stmg	%r0,%r13,STACK_PTREGS_GPRS(%r15)
+	stg	%r14,(STACK_PTREGS_PSW+8)(%r15)
+#ifdef CONFIG_HAVE_MARCH_Z196_FEATURES
+	aghik	%r2,%r14,-MCOUNT_INSN_SIZE
+	lgrl	%r4,function_trace_op
+	lgrl	%r14,ftrace_trace_function
+#else
 	lgr	%r2,%r14
-	lg	%r3,168(%r15)
 	aghi	%r2,-MCOUNT_INSN_SIZE
+	larl	%r4,function_trace_op
+	lg	%r4,0(%r4)
 	larl	%r14,ftrace_trace_function
 	lg	%r14,0(%r14)
+#endif
+	lg	%r3,STACK_PARENT_IP(%r15)
+	la	%r5,STACK_PTREGS(%r15)
 	basr	%r14,%r14
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 # The j instruction gets runtime patched to a nop instruction.
@@ -37,16 +56,16 @@ ENTRY(ftrace_caller)
 #	j	.+4
 ENTRY(ftrace_graph_caller)
 	j	ftrace_graph_caller_end
-	lg	%r2,168(%r15)
-	lg	%r3,272(%r15)
+	lg	%r2,STACK_PARENT_IP(%r15)
+	lg	%r3,(STACK_PTREGS_PSW+8)(%r15)
 	brasl	%r14,prepare_ftrace_return
-	stg	%r2,168(%r15)
+	stg	%r2,STACK_PARENT_IP(%r15)
 ftrace_graph_caller_end:
 	.globl	ftrace_graph_caller_end
 #endif
-	aghi	%r15,160
-	lmg	%r2,%r5,32(%r15)
-	lg	%r14,112(%r15)
+	lmg	%r0,%r13,STACK_PTREGS_GPRS(%r15)
+	lg	%r14,(STACK_PTREGS_PSW+8)(%r15)
+	aghi	%r15,STACK_FRAME_SIZE
 	br	%r14
 
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
@@ -54,10 +73,10 @@ ftrace_graph_caller_end:
 ENTRY(return_to_handler)
 	stmg	%r2,%r5,32(%r15)
 	lgr	%r1,%r15
-	aghi	%r15,-160
+	aghi	%r15,-STACK_FRAME_OVERHEAD
 	stg	%r1,__SF_BACKCHAIN(%r15)
 	brasl	%r14,ftrace_return_to_handler
-	aghi	%r15,160
+	aghi	%r15,STACK_FRAME_OVERHEAD
 	lgr	%r14,%r2
 	lmg	%r2,%r5,32(%r15)
 	br	%r14