On Thu, 2013-01-17 at 09:58 -0500, Alan Cooper wrote:
> When the kernel first boots we have to be able to handle the gcc
> generated jalr, addui sequence until ftrace_init gets a chance to run
> and change the sequence. At this point mcount just adjusts the stack
> and returns. When ftrace_init runs, we convert the jalr/addui to nops.
> Then whenever tracing is enabled we convert the first nop to a "jalr
> mcount+8". The mcount+8 entry point skips the stack adjust.
>
I was confused by that too.
>
> On Thu, Jan 17, 2013 at 1:27 AM, Geert Uytterhoeven
> >
> >> @@ -69,7 +68,7 @@ NESTED(ftrace_caller, PT_SIZE, ra)
> >> .globl _mcount
> >> _mcount:
> >> b ftrace_stub
> >> - nop
> >> + addiu sp,sp,8
Can you add a comment here:
/* When tracing is activated, it calls ftrace_caller+8 (aka here) */
> >> lw t1, function_trace_stop
> >> bnez t1, ftrace_stub
> >> nop
> >
-- Steve
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