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 <[email protected]> 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 <[email protected]> Signed-off-by: Heiko Carstens <[email protected]> --- 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
