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    SubjectRe: [PATCH -v4 4/9] tracing: add static function tracer support for MIPS
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    On Wed, 2009-10-21 at 11:24 -0400, Steven Rostedt wrote:
    > On Wed, 2009-10-21 at 22:34 +0800, Wu Zhangjin wrote:
    >
    > > +++ b/arch/mips/kernel/mcount.S
    > > @@ -0,0 +1,94 @@
    > > +/*
    > > + * the mips-specific _mcount implementation
    > > + *
    > > + * This file is subject to the terms and conditions of the GNU General Public
    > > + * License. See the file "COPYING" in the main directory of this archive for
    > > + * more details.
    > > + *
    > > + * Copyright (C) 2009 DSLab, Lanzhou University, China
    > > + * Author: Wu Zhangjin <wuzj@lemote.com>
    > > + */
    > > +
    > > +#include <asm/regdef.h>
    > > +#include <asm/stackframe.h>
    > > +#include <asm/ftrace.h>
    > > +
    > > + .text
    > > + .set noreorder
    > > + .set noat
    > > +
    > > + /* since there is a "addiu sp,sp,-8" before "jal _mcount" in 32bit */
    > > + .macro RESTORE_SP_FOR_32BIT
    > > +#ifdef CONFIG_32BIT
    > > + PTR_ADDIU sp, 8
    > > +#endif
    > > + .endm
    > > +
    > > + .macro MCOUNT_SAVE_REGS
    > > + PTR_SUBU sp, PT_SIZE
    > > + PTR_S ra, PT_R31(sp)
    > > + PTR_S AT, PT_R1(sp)
    > > + PTR_S a0, PT_R4(sp)
    > > + PTR_S a1, PT_R5(sp)
    > > + PTR_S a2, PT_R6(sp)
    > > + PTR_S a3, PT_R7(sp)
    > > +#ifdef CONFIG_64BIT
    > > + PTR_S a4, PT_R8(sp)
    > > + PTR_S a5, PT_R9(sp)
    > > + PTR_S a6, PT_R10(sp)
    > > + PTR_S a7, PT_R11(sp)
    > > +#endif
    > > + .endm
    > > +
    > > + .macro MCOUNT_RESTORE_REGS
    > > + PTR_L ra, PT_R31(sp)
    > > + PTR_L AT, PT_R1(sp)
    > > + PTR_L a0, PT_R4(sp)
    > > + PTR_L a1, PT_R5(sp)
    > > + PTR_L a2, PT_R6(sp)
    > > + PTR_L a3, PT_R7(sp)
    > > +#ifdef CONFIG_64BIT
    > > + PTR_L a4, PT_R8(sp)
    > > + PTR_L a5, PT_R9(sp)
    > > + PTR_L a6, PT_R10(sp)
    > > + PTR_L a7, PT_R11(sp)
    > > +#endif
    > > + PTR_ADDIU sp, PT_SIZE
    > > +.endm
    > > +
    > > + .macro MCOUNT_SET_ARGS
    > > + move a0, ra /* arg1: next ip, selfaddr */
    > > + move a1, AT /* arg2: the caller's next ip, parent */
    > > + PTR_SUBU a0, MCOUNT_INSN_SIZE
    > > + .endm
    > > +
    > > + .macro RETURN_BACK
    > > + jr ra
    > > + move ra, AT
    > > + .endm
    > > +
    > > +NESTED(_mcount, PT_SIZE, ra)
    > > + RESTORE_SP_FOR_32BIT
    > > + PTR_LA t0, ftrace_stub
    > > + PTR_L t1, ftrace_trace_function /* please don't use t1 later, safe? */
    >
    > Is t0 and t1 safe for mcount to use? Remember, mcount does not follow
    > the dynamics of C function ABI.

    So, perhaps we can use the saved registers(a0,a1...) instead.

    Regards!



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