293 lines
8.1 KiB
ArmAsm
293 lines
8.1 KiB
ArmAsm
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/* SPDX-License-Identifier: GPL-2.0-only */
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/*
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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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#include <linux/linkage.h>
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#include <linux/cfi_types.h>
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#include <asm/asm-offsets.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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#ifdef CONFIG_DYNAMIC_FTRACE_WITH_ARGS
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/*
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* Due to -fpatchable-function-entry=2, the compiler has placed two NOPs before
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* the regular function prologue. For an enabled callsite, ftrace_init_nop() and
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* ftrace_make_call() have patched those NOPs to:
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*
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* MOV X9, LR
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* BL ftrace_caller
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*
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* Each instrumented function follows the AAPCS, so here x0-x8 and x18-x30 are
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* live (x18 holds the Shadow Call Stack pointer), and x9-x17 are safe to
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* clobber.
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*
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* We save the callsite's context into a struct ftrace_regs before invoking any
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* ftrace callbacks. So that we can get a sensible backtrace, we create frame
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* records for the callsite and the ftrace entry assembly. This is not
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* sufficient for reliable stacktrace: until we create the callsite stack
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* record, its caller is missing from the LR and existing chain of frame
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* records.
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*/
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SYM_CODE_START(ftrace_caller)
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bti c
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/* Save original SP */
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mov x10, sp
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/* Make room for ftrace regs, plus two frame records */
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sub sp, sp, #(FREGS_SIZE + 32)
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/* Save function arguments */
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stp x0, x1, [sp, #FREGS_X0]
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stp x2, x3, [sp, #FREGS_X2]
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stp x4, x5, [sp, #FREGS_X4]
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stp x6, x7, [sp, #FREGS_X6]
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str x8, [sp, #FREGS_X8]
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/* Save the callsite's FP, LR, SP */
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str x29, [sp, #FREGS_FP]
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str x9, [sp, #FREGS_LR]
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str x10, [sp, #FREGS_SP]
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/* Save the PC after the ftrace callsite */
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str x30, [sp, #FREGS_PC]
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/* Create a frame record for the callsite above the ftrace regs */
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stp x29, x9, [sp, #FREGS_SIZE + 16]
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add x29, sp, #FREGS_SIZE + 16
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/* Create our frame record above the ftrace regs */
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stp x29, x30, [sp, #FREGS_SIZE]
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add x29, sp, #FREGS_SIZE
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/* Prepare arguments for the the tracer func */
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sub x0, x30, #AARCH64_INSN_SIZE // ip (callsite's BL insn)
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mov x1, x9 // parent_ip (callsite's LR)
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mov x3, sp // regs
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#ifdef CONFIG_DYNAMIC_FTRACE_WITH_CALL_OPS
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/*
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* The literal pointer to the ops is at an 8-byte aligned boundary
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* which is either 12 or 16 bytes before the BL instruction in the call
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* site. See ftrace_call_adjust() for details.
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*
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* Therefore here the LR points at `literal + 16` or `literal + 20`,
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* and we can find the address of the literal in either case by
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* aligning to an 8-byte boundary and subtracting 16. We do the
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* alignment first as this allows us to fold the subtraction into the
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* LDR.
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*/
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bic x2, x30, 0x7
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ldr x2, [x2, #-16] // op
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ldr x4, [x2, #FTRACE_OPS_FUNC] // op->func
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blr x4 // op->func(ip, parent_ip, op, regs)
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#else
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ldr_l x2, function_trace_op // op
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SYM_INNER_LABEL(ftrace_call, SYM_L_GLOBAL)
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bl ftrace_stub // func(ip, parent_ip, op, regs)
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#endif
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/*
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* At the callsite x0-x8 and x19-x30 were live. Any C code will have preserved
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* x19-x29 per the AAPCS, and we created frame records upon entry, so we need
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* to restore x0-x8, x29, and x30.
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*/
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/* Restore function arguments */
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ldp x0, x1, [sp, #FREGS_X0]
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ldp x2, x3, [sp, #FREGS_X2]
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ldp x4, x5, [sp, #FREGS_X4]
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ldp x6, x7, [sp, #FREGS_X6]
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ldr x8, [sp, #FREGS_X8]
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/* Restore the callsite's FP, LR, PC */
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ldr x29, [sp, #FREGS_FP]
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ldr x30, [sp, #FREGS_LR]
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ldr x9, [sp, #FREGS_PC]
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/* Restore the callsite's SP */
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add sp, sp, #FREGS_SIZE + 32
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ret x9
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SYM_CODE_END(ftrace_caller)
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#else /* CONFIG_DYNAMIC_FTRACE_WITH_ARGS */
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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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/*
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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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SYM_FUNC_START(_mcount)
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ret
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SYM_FUNC_END(_mcount)
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EXPORT_SYMBOL(_mcount)
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NOKPROBE(_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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SYM_FUNC_START(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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SYM_INNER_LABEL(ftrace_call, SYM_L_GLOBAL) // 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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SYM_INNER_LABEL(ftrace_graph_call, SYM_L_GLOBAL) // 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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SYM_FUNC_END(ftrace_caller)
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#ifdef CONFIG_FUNCTION_GRAPH_TRACER
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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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SYM_FUNC_START(ftrace_graph_caller)
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mcount_get_pc x0 // function's pc
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mcount_get_lr_addr x1 // pointer to function's saved lr
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mcount_get_parent_fp x2 // parent's fp
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bl prepare_ftrace_return // prepare_ftrace_return(pc, &lr, fp)
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mcount_exit
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SYM_FUNC_END(ftrace_graph_caller)
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#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
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#endif /* CONFIG_DYNAMIC_FTRACE_WITH_ARGS */
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SYM_TYPED_FUNC_START(ftrace_stub)
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ret
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SYM_FUNC_END(ftrace_stub)
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#ifdef CONFIG_FUNCTION_GRAPH_TRACER
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SYM_TYPED_FUNC_START(ftrace_stub_graph)
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ret
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SYM_FUNC_END(ftrace_stub_graph)
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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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*/
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SYM_CODE_START(return_to_handler)
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/* save return value 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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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 value 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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ret
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SYM_CODE_END(return_to_handler)
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#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
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