forked from luck/tmp_suning_uos_patched
538f19526e
With dynamic function tracer, by default, _mcount is defined as an
"empty" function, it returns directly without any more action . When
enabling it in user-space, it will jump to a real tracing
function(ftrace_caller), and do the real job for us.
Differ from the static function tracer, dynamic function tracer provides
two functions ftrace_make_call()/ftrace_make_nop() to enable/disable the
tracing of some indicated kernel functions(set_ftrace_filter).
In the -v4 version, the implementation of this support is basically the same as
X86 version does: _mcount is implemented as an empty function and ftrace_caller
is implemented as a real tracing function respectively.
But in this version, to support module tracing with the help of
-mlong-calls in arch/mips/Makefile:
MODFLAGS += -mlong-calls.
The stuff becomes a little more complex. We need to cope with two
different type of calling to _mcount.
For the kernel part, the calling to _mcount(result of "objdump -hdr
vmlinux"). is like this:
108: 03e0082d move at,ra
10c: 0c000000 jal 0 <fpcsr_pending>
10c: R_MIPS_26 _mcount
10c: R_MIPS_NONE *ABS*
10c: R_MIPS_NONE *ABS*
110: 00020021 nop
For the module with -mlong-calls, it looks like this:
c: 3c030000 lui v1,0x0
c: R_MIPS_HI16 _mcount
c: R_MIPS_NONE *ABS*
c: R_MIPS_NONE *ABS*
10: 64630000 daddiu v1,v1,0
10: R_MIPS_LO16 _mcount
10: R_MIPS_NONE *ABS*
10: R_MIPS_NONE *ABS*
14: 03e0082d move at,ra
18: 0060f809 jalr v1
In the kernel version, there is only one "_mcount" string for every
kernel function, so, we just need to match this one in mcount_regex of
scripts/recordmcount.pl, but in the module version, we need to choose
one of the two to match. Herein, I choose the first one with
"R_MIPS_HI16 _mcount".
and In the kernel verion, without module tracing support, we just need
to replace "jal _mcount" by "jal ftrace_caller" to do real tracing, and
filter the tracing of some kernel functions via replacing it by a nop
instruction.
but as we have described before, the instruction "jal ftrace_caller" only left
32bit length for the address of ftrace_caller, it will fail when calling from
the module space. so, herein, we must replace something else.
the basic idea is loading the address of ftrace_caller to v1 via changing these
two instructions:
lui v1,0x0
addiu v1,v1,0
If we want to enable the tracing, we need to replace the above instructions to:
lui v1, HI_16BIT_ftrace_caller
addiu v1, v1, LOW_16BIT_ftrace_caller
If we want to stop the tracing of the indicated kernel functions, we
just need to replace the "jalr v1" to a nop instruction. but we need to
replace two instructions and encode the above two instructions
oursevles.
Is there a simpler solution? Yes! Here it is, in this version, we put _mcount
and ftrace_caller together, which means the address of _mcount and
ftrace_caller is the same:
_mcount:
ftrace_caller:
j ftrace_stub
nop
...(do real tracing here)...
ftrace_stub:
jr ra
move ra, at
By default, the kernel functions call _mcount, and then jump to ftrace_stub and
return. and when we want to do real tracing, we just need to remove that "j
ftrace_stub", and it will run through the two "nop" instructions and then do
the real tracing job.
what about filtering job? we just need to do this:
lui v1, hi_16bit_of_mcount <--> b 1f (0x10000004)
addiu v1, v1, low_16bit_of_mcount
move at, ra
jalr v1
nop
1f: (rec->ip + 12)
In linux-mips64, there will be some local symbols, whose name are
prefixed by $L, which need to be filtered. thanks goes to Steven for
writing the mips64-specific function_regex.
In a conclusion, with RISC, things becomes easier with such a "stupid"
trick, RISC is something like K.I.S.S, and also, there are lots of
"simple" tricks in the whole ftrace support, thanks goes to Steven and
the other folks for providing such a wonderful tracing framework!
Signed-off-by: Wu Zhangjin <wuzhangjin@gmail.com>
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/675/
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
106 lines
3.6 KiB
Makefile
106 lines
3.6 KiB
Makefile
#
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# Makefile for the Linux/MIPS kernel.
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#
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CPPFLAGS_vmlinux.lds := $(KBUILD_CFLAGS)
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extra-y := head.o init_task.o vmlinux.lds
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obj-y += cpu-probe.o branch.o entry.o genex.o irq.o process.o \
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ptrace.o reset.o setup.o signal.o syscall.o \
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time.o topology.o traps.o unaligned.o watch.o
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ifdef CONFIG_FUNCTION_TRACER
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CFLAGS_REMOVE_ftrace.o = -pg
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CFLAGS_REMOVE_early_printk.o = -pg
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endif
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obj-$(CONFIG_CEVT_BCM1480) += cevt-bcm1480.o
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obj-$(CONFIG_CEVT_R4K_LIB) += cevt-r4k.o
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obj-$(CONFIG_MIPS_MT_SMTC) += cevt-smtc.o
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obj-$(CONFIG_CEVT_DS1287) += cevt-ds1287.o
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obj-$(CONFIG_CEVT_GT641XX) += cevt-gt641xx.o
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obj-$(CONFIG_CEVT_SB1250) += cevt-sb1250.o
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obj-$(CONFIG_CEVT_TXX9) += cevt-txx9.o
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obj-$(CONFIG_CSRC_BCM1480) += csrc-bcm1480.o
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obj-$(CONFIG_CSRC_IOASIC) += csrc-ioasic.o
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obj-$(CONFIG_CSRC_POWERTV) += csrc-powertv.o
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obj-$(CONFIG_CSRC_R4K_LIB) += csrc-r4k.o
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obj-$(CONFIG_CSRC_SB1250) += csrc-sb1250.o
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obj-$(CONFIG_SYNC_R4K) += sync-r4k.o
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obj-$(CONFIG_STACKTRACE) += stacktrace.o
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obj-$(CONFIG_MODULES) += mips_ksyms.o module.o
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obj-$(CONFIG_FUNCTION_TRACER) += mcount.o ftrace.o
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obj-$(CONFIG_CPU_LOONGSON2) += r4k_fpu.o r4k_switch.o
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obj-$(CONFIG_CPU_MIPS32) += r4k_fpu.o r4k_switch.o
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obj-$(CONFIG_CPU_MIPS64) += r4k_fpu.o r4k_switch.o
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obj-$(CONFIG_CPU_R3000) += r2300_fpu.o r2300_switch.o
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obj-$(CONFIG_CPU_R4300) += r4k_fpu.o r4k_switch.o
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obj-$(CONFIG_CPU_R4X00) += r4k_fpu.o r4k_switch.o
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obj-$(CONFIG_CPU_R5000) += r4k_fpu.o r4k_switch.o
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obj-$(CONFIG_CPU_R6000) += r6000_fpu.o r4k_switch.o
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obj-$(CONFIG_CPU_R5432) += r4k_fpu.o r4k_switch.o
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obj-$(CONFIG_CPU_R5500) += r4k_fpu.o r4k_switch.o
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obj-$(CONFIG_CPU_R8000) += r4k_fpu.o r4k_switch.o
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obj-$(CONFIG_CPU_RM7000) += r4k_fpu.o r4k_switch.o
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obj-$(CONFIG_CPU_RM9000) += r4k_fpu.o r4k_switch.o
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obj-$(CONFIG_CPU_NEVADA) += r4k_fpu.o r4k_switch.o
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obj-$(CONFIG_CPU_R10000) += r4k_fpu.o r4k_switch.o
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obj-$(CONFIG_CPU_SB1) += r4k_fpu.o r4k_switch.o
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obj-$(CONFIG_CPU_TX39XX) += r2300_fpu.o r2300_switch.o
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obj-$(CONFIG_CPU_TX49XX) += r4k_fpu.o r4k_switch.o
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obj-$(CONFIG_CPU_VR41XX) += r4k_fpu.o r4k_switch.o
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obj-$(CONFIG_CPU_CAVIUM_OCTEON) += octeon_switch.o
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obj-$(CONFIG_SMP) += smp.o
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obj-$(CONFIG_SMP_UP) += smp-up.o
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obj-$(CONFIG_MIPS_MT) += mips-mt.o
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obj-$(CONFIG_MIPS_MT_FPAFF) += mips-mt-fpaff.o
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obj-$(CONFIG_MIPS_MT_SMTC) += smtc.o smtc-asm.o smtc-proc.o
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obj-$(CONFIG_MIPS_MT_SMP) += smp-mt.o
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obj-$(CONFIG_MIPS_CMP) += smp-cmp.o
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obj-$(CONFIG_CPU_MIPSR2) += spram.o
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obj-$(CONFIG_MIPS_VPE_LOADER) += vpe.o
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obj-$(CONFIG_MIPS_VPE_APSP_API) += rtlx.o
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obj-$(CONFIG_MIPS_APSP_KSPD) += kspd.o
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obj-$(CONFIG_I8259) += i8259.o
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obj-$(CONFIG_IRQ_CPU) += irq_cpu.o
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obj-$(CONFIG_IRQ_CPU_RM7K) += irq-rm7000.o
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obj-$(CONFIG_IRQ_CPU_RM9K) += irq-rm9000.o
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obj-$(CONFIG_MIPS_MSC) += irq-msc01.o
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obj-$(CONFIG_IRQ_TXX9) += irq_txx9.o
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obj-$(CONFIG_IRQ_GT641XX) += irq-gt641xx.o
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obj-$(CONFIG_IRQ_GIC) += irq-gic.o
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obj-$(CONFIG_32BIT) += scall32-o32.o
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obj-$(CONFIG_64BIT) += scall64-64.o
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obj-$(CONFIG_MIPS32_COMPAT) += linux32.o ptrace32.o signal32.o
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obj-$(CONFIG_MIPS32_N32) += binfmt_elfn32.o scall64-n32.o signal_n32.o
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obj-$(CONFIG_MIPS32_O32) += binfmt_elfo32.o scall64-o32.o
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obj-$(CONFIG_KGDB) += kgdb.o
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obj-$(CONFIG_PROC_FS) += proc.o
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obj-$(CONFIG_64BIT) += cpu-bugs64.o
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obj-$(CONFIG_I8253) += i8253.o
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obj-$(CONFIG_GPIO_TXX9) += gpio_txx9.o
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obj-$(CONFIG_KEXEC) += machine_kexec.o relocate_kernel.o
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obj-$(CONFIG_EARLY_PRINTK) += early_printk.o
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CFLAGS_cpu-bugs64.o = $(shell if $(CC) $(KBUILD_CFLAGS) -Wa,-mdaddi -c -o /dev/null -xc /dev/null >/dev/null 2>&1; then echo "-DHAVE_AS_SET_DADDI"; fi)
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obj-$(CONFIG_HAVE_STD_PC_SERIAL_PORT) += 8250-platform.o
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obj-$(CONFIG_MIPS_CPUFREQ) += cpufreq/
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EXTRA_CFLAGS += -Werror
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