linux/arch/s390/kernel/mcount.S
Heiko Carstens aca9120977 s390/ftrace: fix mcount adjustment
Tony Jones reported that the ftrace self tests on s390 do not work:

<6>Testing dynamic ftrace ops : (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: Tony Jones <tonyj@suse.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2013-05-15 13:09:09 +02:00

74 lines
1.3 KiB
ArmAsm

/*
* Copyright IBM Corp. 2008, 2009
*
* Author(s): Heiko Carstens <heiko.carstens@de.ibm.com>,
*
*/
#include <linux/linkage.h>
#include <asm/asm-offsets.h>
#include <asm/ftrace.h>
.section .kprobes.text, "ax"
ENTRY(ftrace_stub)
br %r14
ENTRY(_mcount)
#ifdef CONFIG_DYNAMIC_FTRACE
br %r14
ENTRY(ftrace_caller)
#endif
stm %r2,%r5,16(%r15)
bras %r1,2f
0: .long ftrace_trace_function
1: .long function_trace_stop
2: l %r2,1b-0b(%r1)
icm %r2,0xf,0(%r2)
jnz 3f
st %r14,56(%r15)
lr %r0,%r15
ahi %r15,-96
l %r3,100(%r15)
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
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
l %r2,100(%r15)
l %r3,152(%r15)
ENTRY(ftrace_graph_caller)
# The bras instruction gets runtime patched to call prepare_ftrace_return.
# See ftrace_enable_ftrace_graph_caller. The patched instruction is:
# bras %r14,prepare_ftrace_return
bras %r14,0f
0: st %r2,100(%r15)
#endif
ahi %r15,96
l %r14,56(%r15)
3: lm %r2,%r5,16(%r15)
br %r14
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
ENTRY(return_to_handler)
stm %r2,%r5,16(%r15)
st %r14,56(%r15)
lr %r0,%r15
ahi %r15,-96
st %r0,__SF_BACKCHAIN(%r15)
bras %r1,0f
.long ftrace_return_to_handler
0: l %r2,0b-0b(%r1)
basr %r14,%r2
lr %r14,%r2
ahi %r15,96
lm %r2,%r5,16(%r15)
br %r14
#endif