Messages in this thread | | | Date | Mon, 22 Sep 2014 09:55:09 -0700 | From | David Daney <> | Subject | Re: [PATCH 1/2] MIPS: ftrace.h: Fix the MCOUNT_INSN_SIZE definition |
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On 09/22/2014 06:32 AM, Markos Chandras wrote: > The MCOUNT_INSN_SIZE is meant to be used to denote the overall > size of the mcount() call. Since a jal instruction is used to > call mcount() the delay slot should be taken into consideration > as well. > This also replaces the MCOUNT_INSN_SIZE usage with the real size > of a single MIPS instruction since, as described above, the > MCOUNT_INSN_SIZE is used to denote the total overhead of the > mcount() call.
Are you seeing errors with the existing code? If so please state what they are.
By changing this, we can no longer atomically replace the instruction. So I think shouldn't be changing this stuff unless there is a real bug we are fixing.
In conclusion: NAK unless the patch fixes a bug, in which case the change log *must* state what the bug is, and how the patch addresses the problem.
David Daney
> > Cc: Steven Rostedt <rostedt@goodmis.org> > Cc: Ingo Molnar <mingo@redhat.com> > Cc: linux-kernel@vger.kernel.org > Signed-off-by: Markos Chandras <markos.chandras@imgtec.com> > --- > arch/mips/include/asm/ftrace.h | 2 +- > arch/mips/kernel/ftrace.c | 4 +++- > 2 files changed, 4 insertions(+), 2 deletions(-) > > diff --git a/arch/mips/include/asm/ftrace.h b/arch/mips/include/asm/ftrace.h > index 992aaba603b5..70d4a35fb560 100644 > --- a/arch/mips/include/asm/ftrace.h > +++ b/arch/mips/include/asm/ftrace.h > @@ -13,7 +13,7 @@ > #ifdef CONFIG_FUNCTION_TRACER > > #define MCOUNT_ADDR ((unsigned long)(_mcount)) > -#define MCOUNT_INSN_SIZE 4 /* sizeof mcount call */ > +#define MCOUNT_INSN_SIZE 8 /* sizeof mcount call + delay slot */ > > #ifndef __ASSEMBLY__ > extern void _mcount(void); > diff --git a/arch/mips/kernel/ftrace.c b/arch/mips/kernel/ftrace.c > index 937c54bc8ccc..211460d4617d 100644 > --- a/arch/mips/kernel/ftrace.c > +++ b/arch/mips/kernel/ftrace.c > @@ -28,6 +28,8 @@ > #define MCOUNT_OFFSET_INSNS 4 > #endif > > +#define FTRACE_MIPS_INSN_SIZE 4 /* Size of single MIPS instruction */ > + > #ifdef CONFIG_DYNAMIC_FTRACE > > /* Arch override because MIPS doesn't need to run this from stop_machine() */ > @@ -395,7 +397,7 @@ void prepare_ftrace_return(unsigned long *parent_ra_addr, unsigned long self_ra, > */ > > insns = in_kernel_space(self_ra) ? 2 : MCOUNT_OFFSET_INSNS + 1; > - trace.func = self_ra - (MCOUNT_INSN_SIZE * insns); > + trace.func = self_ra - (FTRACE_MIPS_INSN_SIZE * insns); > > /* Only trace if the calling function expects to */ > if (!ftrace_graph_entry(&trace)) { >
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