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Commit aca91209 authored by Heiko Carstens's avatar Heiko Carstens Committed by Martin Schwidefsky
Browse files

s390/ftrace: fix mcount adjustment 



Tony Jones reported that the ftrace self tests on s390 do not work:

<6>Testing dynamic ftrace ops #1: (0 0 0 0 0) FAILED!
<6>Testing tracer irqsoff:
<3>failed to start irqsoff tracer
<4>.. no entries found ..FAILED!
<6>Testing tracer wakeup:
<3>failed to start wakeup tracer
<4>.. no entries found ..FAILED!
<6>Testing tracer function_graph:
<4>Failed to init function_graph tracer, init returned -19
<4>FAILED!

This happens because we forgot to adjust the instruction pointer that gets
passed to the ftrace trace function by MCOUNT_INSN_SIZE.

In addition change MCOUNT_INSN_SIZE to the correct value on 31 bit.
It only worked so far because the to be patched instruction was identical.

Reported-by: default avatarTony Jones <tonyj@suse.com>
Signed-off-by: default avatarHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
parent bb4b42ce

arch/s390/include/asm/ftrace.h

+7 −5
Original line number Diff line number Diff line
@@ -9,11 +9,6 @@ struct dyn_arch_ftrace { }; 


#define MCOUNT_ADDR ((long)_mcount)



#ifdef CONFIG_64BIT

#define MCOUNT_INSN_SIZE  12

#else

#define MCOUNT_INSN_SIZE  20

#endif



static inline unsigned long ftrace_call_adjust(unsigned long addr)

{
@@ -21,4 +16,11 @@ static inline unsigned long ftrace_call_adjust(unsigned long addr) 
}



#endif /* __ASSEMBLY__ */



#ifdef CONFIG_64BIT

#define MCOUNT_INSN_SIZE  12

#else

#define MCOUNT_INSN_SIZE  22

#endif



#endif /* _ASM_S390_FTRACE_H */

arch/s390/kernel/ftrace.c

+2 −7
Original line number Diff line number Diff line
@@ -16,12 +16,6 @@ 
#include <trace/syscall.h>

#include <asm/asm-offsets.h>



#ifdef CONFIG_64BIT

#define MCOUNT_OFFSET_RET 12

#else

#define MCOUNT_OFFSET_RET 22

#endif



#ifdef CONFIG_DYNAMIC_FTRACE



void ftrace_disable_code(void);
@@ -155,9 +149,10 @@ unsigned long __kprobes prepare_ftrace_return(unsigned long parent, 


	if (unlikely(atomic_read(&current->tracing_graph_pause)))

		goto out;

	ip = (ip & PSW_ADDR_INSN) - MCOUNT_INSN_SIZE;

	if (ftrace_push_return_trace(parent, ip, &trace.depth, 0) == -EBUSY)

		goto out;

	trace.func = (ip & PSW_ADDR_INSN) - MCOUNT_OFFSET_RET;

	trace.func = ip;

	/* Only trace if the calling function expects to. */

	if (!ftrace_graph_entry(&trace)) {

		current->curr_ret_stack--;

arch/s390/kernel/mcount.S

+2 −0
Original line number Diff line number Diff line
@@ -7,6 +7,7 @@ 


#include <linux/linkage.h>

#include <asm/asm-offsets.h>

#include <asm/ftrace.h>



	.section .kprobes.text, "ax"
@@ -33,6 +34,7 @@ ENTRY(ftrace_caller) 
	la	%r2,0(%r14)

	st	%r0,__SF_BACKCHAIN(%r15)

	la	%r3,0(%r3)

	ahi	%r2,-MCOUNT_INSN_SIZE

	l	%r14,0b-0b(%r1)

	l	%r14,0(%r14)

	basr	%r14,%r14

arch/s390/kernel/mcount64.S

+2 −0
Original line number Diff line number Diff line
@@ -7,6 +7,7 @@ 


#include <linux/linkage.h>

#include <asm/asm-offsets.h>

#include <asm/ftrace.h>



	.section .kprobes.text, "ax"
@@ -29,6 +30,7 @@ ENTRY(ftrace_caller) 
	stg	%r1,__SF_BACKCHAIN(%r15)

	lgr	%r2,%r14

	lg	%r3,168(%r15)

	aghi	%r2,-MCOUNT_INSN_SIZE

	larl	%r14,ftrace_trace_function

	lg	%r14,0(%r14)

	basr	%r14,%r14