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Date: Mon, 13 May 2013 15:03:13 +0200
From: Heiko Carstens <heiko.carstens@...ibm.com>
To: Tony Jones <tonyj@...e.com>, Steven Rostedt <rostedt@...dmis.org>,
Ralf Baechle <ralf@...ux-mips.org>,
Wu Zhangjin <wuzhangjin@...il.com>,
David Daney <david.daney@...ium.com>
Cc: linux-kernel@...r.kernel.org
Subject: [PATCH] s390/ftrace: fix mcount adjustment
Hi,
Tony Jones reported a bug which _seems_ to be present on MIPS64 as
well: http://lkml.indiana.edu/hypermail/linux/kernel/1301.1/02107.html
(don't know if it was fixed in the meantime, the asm code wasn't changed
recently though).
So just for reference here the s390 fix:
>From 6a07176c14b6318667f1ebd8c09c7bb4c30d78a0 Mon Sep 17 00:00:00 2001
From: Heiko Carstens <heiko.carstens@...ibm.com>
Date: Mon, 13 May 2013 14:48:52 +0200
Subject: [PATCH] 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@...e.com>
Signed-off-by: Heiko Carstens <heiko.carstens@...ibm.com>
---
arch/s390/include/asm/ftrace.h | 12 +++++++-----
arch/s390/kernel/mcount.S | 2 ++
arch/s390/kernel/mcount64.S | 2 ++
3 files changed, 11 insertions(+), 5 deletions(-)
diff --git a/arch/s390/include/asm/ftrace.h b/arch/s390/include/asm/ftrace.h
index b7931fa..bf246da 100644
--- a/arch/s390/include/asm/ftrace.h
+++ b/arch/s390/include/asm/ftrace.h
@@ -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 */
diff --git a/arch/s390/kernel/mcount.S b/arch/s390/kernel/mcount.S
index 4567ce2..08dcf21 100644
--- a/arch/s390/kernel/mcount.S
+++ b/arch/s390/kernel/mcount.S
@@ -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
diff --git a/arch/s390/kernel/mcount64.S b/arch/s390/kernel/mcount64.S
index 1133219..1c52eae 100644
--- a/arch/s390/kernel/mcount64.S
+++ b/arch/s390/kernel/mcount64.S
@@ -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
--
1.8.1.6
--
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