Commit 10dec7db authored by Heiko Carstens's avatar Heiko Carstens Committed by Martin Schwidefsky
Browse files

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: default avatarHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
parent 2481a87b

arch/s390/Kconfig

+1 −0
Original line number Diff line number Diff line
@@ -114,6 +114,7 @@ config S390 
	select HAVE_C_RECORDMCOUNT

	select HAVE_DEBUG_KMEMLEAK

	select HAVE_DYNAMIC_FTRACE

	select HAVE_DYNAMIC_FTRACE_WITH_REGS if 64BIT

	select HAVE_FTRACE_MCOUNT_RECORD

	select HAVE_FUNCTION_GRAPH_TRACER

	select HAVE_FUNCTION_TRACER

arch/s390/include/asm/ftrace.h

+4 −0
Original line number Diff line number Diff line
@@ -24,4 +24,8 @@ static inline unsigned long ftrace_call_adjust(unsigned long addr) 
#define MCOUNT_INSN_SIZE  22

#endif



#ifdef CONFIG_64BIT

#define ARCH_SUPPORTS_FTRACE_OPS 1

#endif



#endif /* _ASM_S390_FTRACE_H */

arch/s390/kernel/ftrace.c

+7 −0
Original line number Diff line number Diff line
@@ -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)

arch/s390/kernel/mcount64.S

+31 −12
Original line number Diff line number Diff line
@@ -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

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