linux/arch/s390/kernel/mcount64.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 #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: 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

66 lines
1.2 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
larl %r1,function_trace_stop
icm %r1,0xf,0(%r1)
bnzr %r14
stmg %r2,%r5,32(%r15)
stg %r14,112(%r15)
lgr %r1,%r15
aghi %r15,-160
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
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
lg %r2,168(%r15)
lg %r3,272(%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: stg %r2,168(%r15)
#endif
aghi %r15,160
lmg %r2,%r5,32(%r15)
lg %r14,112(%r15)
br %r14
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
ENTRY(return_to_handler)
stmg %r2,%r5,32(%r15)
lgr %r1,%r15
aghi %r15,-160
stg %r1,__SF_BACKCHAIN(%r15)
brasl %r14,ftrace_return_to_handler
aghi %r15,160
lgr %r14,%r2
lmg %r2,%r5,32(%r15)
br %r14
#endif