223 lines
6 KiB
ArmAsm
223 lines
6 KiB
ArmAsm
/*
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* arch/arm64/kernel/entry-ftrace.S
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*
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* Copyright (C) 2013 Linaro Limited
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* Author: AKASHI Takahiro <takahiro.akashi@linaro.org>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#include <linux/linkage.h>
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#include <asm/assembler.h>
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#include <asm/ftrace.h>
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#include <asm/insn.h>
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/*
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* Gcc with -pg will put the following code in the beginning of each function:
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* mov x0, x30
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* bl _mcount
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* [function's body ...]
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* "bl _mcount" may be replaced to "bl ftrace_caller" or NOP if dynamic
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* ftrace is enabled.
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*
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* Please note that x0 as an argument will not be used here because we can
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* get lr(x30) of instrumented function at any time by winding up call stack
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* as long as the kernel is compiled without -fomit-frame-pointer.
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* (or CONFIG_FRAME_POINTER, this is forced on arm64)
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*
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* stack layout after mcount_enter in _mcount():
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*
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* current sp/fp => 0:+-----+
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* in _mcount() | x29 | -> instrumented function's fp
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* +-----+
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* | x30 | -> _mcount()'s lr (= instrumented function's pc)
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* old sp => +16:+-----+
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* when instrumented | |
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* function calls | ... |
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* _mcount() | |
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* | |
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* instrumented => +xx:+-----+
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* function's fp | x29 | -> parent's fp
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* +-----+
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* | x30 | -> instrumented function's lr (= parent's pc)
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* +-----+
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* | ... |
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*/
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.macro mcount_enter
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stp x29, x30, [sp, #-16]!
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mov x29, sp
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.endm
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.macro mcount_exit
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ldp x29, x30, [sp], #16
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ret
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.endm
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.macro mcount_adjust_addr rd, rn
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sub \rd, \rn, #AARCH64_INSN_SIZE
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.endm
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/* for instrumented function's parent */
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.macro mcount_get_parent_fp reg
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ldr \reg, [x29]
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ldr \reg, [\reg]
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.endm
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/* for instrumented function */
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.macro mcount_get_pc0 reg
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mcount_adjust_addr \reg, x30
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.endm
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.macro mcount_get_pc reg
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ldr \reg, [x29, #8]
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mcount_adjust_addr \reg, \reg
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.endm
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.macro mcount_get_lr reg
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ldr \reg, [x29]
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ldr \reg, [\reg, #8]
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.endm
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.macro mcount_get_lr_addr reg
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ldr \reg, [x29]
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add \reg, \reg, #8
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.endm
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#ifndef CONFIG_DYNAMIC_FTRACE
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/*
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* void _mcount(unsigned long return_address)
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* @return_address: return address to instrumented function
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*
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* This function makes calls, if enabled, to:
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* - tracer function to probe instrumented function's entry,
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* - ftrace_graph_caller to set up an exit hook
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*/
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ENTRY(_mcount)
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mcount_enter
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ldr_l x2, ftrace_trace_function
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adr x0, ftrace_stub
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cmp x0, x2 // if (ftrace_trace_function
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b.eq skip_ftrace_call // != ftrace_stub) {
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mcount_get_pc x0 // function's pc
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mcount_get_lr x1 // function's lr (= parent's pc)
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blr x2 // (*ftrace_trace_function)(pc, lr);
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skip_ftrace_call: // }
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#ifdef CONFIG_FUNCTION_GRAPH_TRACER
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ldr_l x2, ftrace_graph_return
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cmp x0, x2 // if ((ftrace_graph_return
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b.ne ftrace_graph_caller // != ftrace_stub)
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ldr_l x2, ftrace_graph_entry // || (ftrace_graph_entry
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adr_l x0, ftrace_graph_entry_stub // != ftrace_graph_entry_stub))
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cmp x0, x2
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b.ne ftrace_graph_caller // ftrace_graph_caller();
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#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
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mcount_exit
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ENDPROC(_mcount)
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#else /* CONFIG_DYNAMIC_FTRACE */
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/*
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* _mcount() is used to build the kernel with -pg option, but all the branch
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* instructions to _mcount() are replaced to NOP initially at kernel start up,
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* and later on, NOP to branch to ftrace_caller() when enabled or branch to
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* NOP when disabled per-function base.
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*/
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ENTRY(_mcount)
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ret
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ENDPROC(_mcount)
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/*
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* void ftrace_caller(unsigned long return_address)
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* @return_address: return address to instrumented function
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*
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* This function is a counterpart of _mcount() in 'static' ftrace, and
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* makes calls to:
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* - tracer function to probe instrumented function's entry,
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* - ftrace_graph_caller to set up an exit hook
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*/
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ENTRY(ftrace_caller)
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mcount_enter
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mcount_get_pc0 x0 // function's pc
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mcount_get_lr x1 // function's lr
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.global ftrace_call
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ftrace_call: // tracer(pc, lr);
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nop // This will be replaced with "bl xxx"
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// where xxx can be any kind of tracer.
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#ifdef CONFIG_FUNCTION_GRAPH_TRACER
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.global ftrace_graph_call
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ftrace_graph_call: // ftrace_graph_caller();
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nop // If enabled, this will be replaced
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// "b ftrace_graph_caller"
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#endif
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mcount_exit
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ENDPROC(ftrace_caller)
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#endif /* CONFIG_DYNAMIC_FTRACE */
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ENTRY(ftrace_stub)
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ret
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ENDPROC(ftrace_stub)
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#ifdef CONFIG_FUNCTION_GRAPH_TRACER
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/* save return value regs*/
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.macro save_return_regs
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sub sp, sp, #64
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stp x0, x1, [sp]
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stp x2, x3, [sp, #16]
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stp x4, x5, [sp, #32]
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stp x6, x7, [sp, #48]
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.endm
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/* restore return value regs*/
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.macro restore_return_regs
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ldp x0, x1, [sp]
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ldp x2, x3, [sp, #16]
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ldp x4, x5, [sp, #32]
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ldp x6, x7, [sp, #48]
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add sp, sp, #64
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.endm
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/*
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* void ftrace_graph_caller(void)
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*
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* Called from _mcount() or ftrace_caller() when function_graph tracer is
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* selected.
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* This function w/ prepare_ftrace_return() fakes link register's value on
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* the call stack in order to intercept instrumented function's return path
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* and run return_to_handler() later on its exit.
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*/
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ENTRY(ftrace_graph_caller)
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mcount_get_lr_addr x0 // pointer to function's saved lr
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mcount_get_pc x1 // function's pc
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mcount_get_parent_fp x2 // parent's fp
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bl prepare_ftrace_return // prepare_ftrace_return(&lr, pc, fp)
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mcount_exit
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ENDPROC(ftrace_graph_caller)
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/*
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* void return_to_handler(void)
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*
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* Run ftrace_return_to_handler() before going back to parent.
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* @fp is checked against the value passed by ftrace_graph_caller()
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* only when HAVE_FUNCTION_GRAPH_FP_TEST is enabled.
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*/
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ENTRY(return_to_handler)
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save_return_regs
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mov x0, x29 // parent's fp
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bl ftrace_return_to_handler// addr = ftrace_return_to_hander(fp);
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mov x30, x0 // restore the original return address
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restore_return_regs
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ret
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END(return_to_handler)
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#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
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