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
