29c5d3462f
The implementation of function graph tracer for MIPS is a little
different from X86.
in MIPS, gcc(with -pg) only transfer the caller's return address(at) and
the _mcount's return address(ra) to us.
For the kernel part without -mlong-calls:
move at, ra
jal _mcount
For the module part with -mlong-calls:
lui v1, hi16bit_of_mcount
addiu v1, v1, low16bit_of_mcount
move at, ra
jal _mcount
Without -mlong-calls,
if the function is a leaf, it will not save the return address(ra):
ffffffff80101298 <au1k_wait>:
ffffffff80101298: 67bdfff0 daddiu sp,sp,-16
ffffffff8010129c: ffbe0008 sd s8,8(sp)
ffffffff801012a0: 03a0f02d move s8,sp
ffffffff801012a4: 03e0082d move at,ra
ffffffff801012a8: 0c042930 jal ffffffff8010a4c0 <_mcount>
ffffffff801012ac: 00020021 nop
so, we can hijack it directly in _mcount, but if the function is non-leaf, the
return address is saved in the stack.
ffffffff80133030 <copy_process>:
ffffffff80133030: 67bdff50 daddiu sp,sp,-176
ffffffff80133034: ffbe00a0 sd s8,160(sp)
ffffffff80133038: 03a0f02d move s8,sp
ffffffff8013303c: ffbf00a8 sd ra,168(sp)
ffffffff80133040: ffb70098 sd s7,152(sp)
ffffffff80133044: ffb60090 sd s6,144(sp)
ffffffff80133048: ffb50088 sd s5,136(sp)
ffffffff8013304c: ffb40080 sd s4,128(sp)
ffffffff80133050: ffb30078 sd s3,120(sp)
ffffffff80133054: ffb20070 sd s2,112(sp)
ffffffff80133058: ffb10068 sd s1,104(sp)
ffffffff8013305c: ffb00060 sd s0,96(sp)
ffffffff80133060: 03e0082d move at,ra
ffffffff80133064: 0c042930 jal ffffffff8010a4c0 <_mcount>
ffffffff80133068: 00020021 nop
but we can not get the exact stack address(which saved ra) directly in
_mcount, we need to search the content of at register in the stack space
or search the "s{d,w} ra, offset(sp)" instruction in the text. 'Cause we
can not prove there is only a match in the stack space, so, we search
the text instead.
as we can see, if the first instruction above "move at, ra" is not a
store instruction, there should be a leaf function, so we hijack the at
register directly via putting &return_to_handler into it, otherwise, we
search the "s{d,w} ra, offset(sp)" instruction to get the stack offset,
and then the stack address. we use the above copy_process() as an
example, we at last find "ffbf00a8", 0xa8 is the stack offset, we plus
it with s8(fp), that is the stack address, we hijack the content via
writing the &return_to_handler in.
If with -mlong-calls, since there are two more instructions above "move
at, ra", so, we can move the pointer to the position above "lui v1,
hi16bit_of_mcount".
Signed-off-by: Wu Zhangjin <wuzhangjin@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Nicholas Mc Guire <der.herr@hofr.at>
Cc: zhangfx@lemote.com
Cc: Wu Zhangjin <wuzhangjin@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: linux-kernel@vger.kernel.org
Cc: linux-mips@linux-mips.org
Patchwork: http://patchwork.linux-mips.org/patch/677/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
158 lines
3 KiB
ArmAsm
158 lines
3 KiB
ArmAsm
/*
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* MIPS specific _mcount support
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*
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* This file is subject to the terms and conditions of the GNU General Public
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* License. See the file "COPYING" in the main directory of this archive for
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* more details.
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*
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* Copyright (C) 2009 Lemote Inc. & DSLab, Lanzhou University, China
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* Author: Wu Zhangjin <wuzj@lemote.com>
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*/
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#include <asm/regdef.h>
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#include <asm/stackframe.h>
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#include <asm/ftrace.h>
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.text
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.set noreorder
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.set noat
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.macro MCOUNT_SAVE_REGS
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PTR_SUBU sp, PT_SIZE
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PTR_S ra, PT_R31(sp)
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PTR_S AT, PT_R1(sp)
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PTR_S a0, PT_R4(sp)
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PTR_S a1, PT_R5(sp)
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PTR_S a2, PT_R6(sp)
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PTR_S a3, PT_R7(sp)
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#ifdef CONFIG_64BIT
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PTR_S a4, PT_R8(sp)
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PTR_S a5, PT_R9(sp)
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PTR_S a6, PT_R10(sp)
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PTR_S a7, PT_R11(sp)
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#endif
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.endm
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.macro MCOUNT_RESTORE_REGS
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PTR_L ra, PT_R31(sp)
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PTR_L AT, PT_R1(sp)
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PTR_L a0, PT_R4(sp)
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PTR_L a1, PT_R5(sp)
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PTR_L a2, PT_R6(sp)
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PTR_L a3, PT_R7(sp)
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#ifdef CONFIG_64BIT
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PTR_L a4, PT_R8(sp)
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PTR_L a5, PT_R9(sp)
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PTR_L a6, PT_R10(sp)
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PTR_L a7, PT_R11(sp)
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#endif
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#ifdef CONFIG_64BIT
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PTR_ADDIU sp, PT_SIZE
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#else
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PTR_ADDIU sp, (PT_SIZE + 8)
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#endif
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.endm
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.macro RETURN_BACK
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jr ra
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move ra, AT
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.endm
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#ifdef CONFIG_DYNAMIC_FTRACE
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NESTED(ftrace_caller, PT_SIZE, ra)
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.globl _mcount
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_mcount:
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b ftrace_stub
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nop
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lw t0, function_trace_stop
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bnez t0, ftrace_stub
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nop
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MCOUNT_SAVE_REGS
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move a0, ra /* arg1: next ip, selfaddr */
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.globl ftrace_call
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ftrace_call:
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nop /* a placeholder for the call to a real tracing function */
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move a1, AT /* arg2: the caller's next ip, parent */
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MCOUNT_RESTORE_REGS
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.globl ftrace_stub
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ftrace_stub:
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RETURN_BACK
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END(ftrace_caller)
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#else /* ! CONFIG_DYNAMIC_FTRACE */
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NESTED(_mcount, PT_SIZE, ra)
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lw t0, function_trace_stop
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bnez t0, ftrace_stub
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nop
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PTR_LA t0, ftrace_stub
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PTR_L t1, ftrace_trace_function /* Prepare t1 for (1) */
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bne t0, t1, static_trace
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nop
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#ifdef CONFIG_FUNCTION_GRAPH_TRACER
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PTR_L t2, ftrace_graph_return
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bne t0, t2, ftrace_graph_caller
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nop
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PTR_LA t0, ftrace_graph_entry_stub
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PTR_L t2, ftrace_graph_entry
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bne t0, t2, ftrace_graph_caller
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nop
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#endif
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b ftrace_stub
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nop
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static_trace:
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MCOUNT_SAVE_REGS
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move a0, ra /* arg1: next ip, selfaddr */
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jalr t1 /* (1) call *ftrace_trace_function */
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move a1, AT /* arg2: the caller's next ip, parent */
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MCOUNT_RESTORE_REGS
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.globl ftrace_stub
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ftrace_stub:
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RETURN_BACK
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END(_mcount)
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#endif /* ! CONFIG_DYNAMIC_FTRACE */
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#ifdef CONFIG_FUNCTION_GRAPH_TRACER
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NESTED(ftrace_graph_caller, PT_SIZE, ra)
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MCOUNT_SAVE_REGS
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PTR_LA a0, PT_R1(sp) /* arg1: &AT -> a0 */
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move a1, ra /* arg2: next ip, selfaddr */
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jal prepare_ftrace_return
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move a2, fp /* arg3: frame pointer */
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MCOUNT_RESTORE_REGS
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RETURN_BACK
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END(ftrace_graph_caller)
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.align 2
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.globl return_to_handler
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return_to_handler:
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PTR_SUBU sp, PT_SIZE
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PTR_S v0, PT_R2(sp)
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jal ftrace_return_to_handler
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PTR_S v1, PT_R3(sp)
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/* restore the real parent address: v0 -> ra */
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move ra, v0
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PTR_L v0, PT_R2(sp)
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PTR_L v1, PT_R3(sp)
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jr ra
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PTR_ADDIU sp, PT_SIZE
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#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
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.set at
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.set reorder
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