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2023-12-08 01573e231f18eb2d99162747186f59511f56b64d

 kernel/arch/arm64/kernel/entry-ftrace.S
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@@ -1,18 +1,148 @@
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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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- * 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/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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+
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+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
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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	<entry>
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+ *
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+ * ... where <entry> is either ftrace_caller or ftrace_regs_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 pt_regs before invoking any ftrace
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+ * callbacks. So that we can get a sensible backtrace, we create a stack record
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+ * for the callsite and the ftrace entry assembly. This is not sufficient for
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+ * reliable stacktrace: until we create the callsite stack record, its caller
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+ * is missing from the LR and existing chain of frame records.
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+ */
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+	.macro  ftrace_regs_entry, allregs=0
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+	/* Make room for pt_regs, plus a callee frame */
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+	sub	sp, sp, #(S_FRAME_SIZE + 16)
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+
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+	/* Save function arguments (and x9 for simplicity) */
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+	stp	x0, x1, [sp, #S_X0]
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+	stp	x2, x3, [sp, #S_X2]
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+	stp	x4, x5, [sp, #S_X4]
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+	stp	x6, x7, [sp, #S_X6]
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+	stp	x8, x9, [sp, #S_X8]
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+
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+	/* Optionally save the callee-saved registers, always save the FP */
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+	.if \allregs == 1
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+	stp	x10, x11, [sp, #S_X10]
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+	stp	x12, x13, [sp, #S_X12]
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+	stp	x14, x15, [sp, #S_X14]
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+	stp	x16, x17, [sp, #S_X16]
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+	stp	x18, x19, [sp, #S_X18]
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+	stp	x20, x21, [sp, #S_X20]
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+	stp	x22, x23, [sp, #S_X22]
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+	stp	x24, x25, [sp, #S_X24]
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+	stp	x26, x27, [sp, #S_X26]
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+	stp	x28, x29, [sp, #S_X28]
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+	.else
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+	str	x29, [sp, #S_FP]
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+	.endif
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+
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+	/* Save the callsite's SP and LR */
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+	add	x10, sp, #(S_FRAME_SIZE + 16)
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+	stp	x9, x10, [sp, #S_LR]
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+
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+	/* Save the PC after the ftrace callsite */
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+	str	x30, [sp, #S_PC]
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+
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+	/* Create a frame record for the callsite above pt_regs */
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+	stp	x29, x9, [sp, #S_FRAME_SIZE]
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+	add	x29, sp, #S_FRAME_SIZE
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+
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+	/* Create our frame record within pt_regs. */
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+	stp	x29, x30, [sp, #S_STACKFRAME]
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+	add	x29, sp, #S_STACKFRAME
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+	.endm
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+
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+SYM_CODE_START(ftrace_regs_caller)
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+#ifdef BTI_C
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+	BTI_C
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+#endif
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+	ftrace_regs_entry	1
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+	b	ftrace_common
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+SYM_CODE_END(ftrace_regs_caller)
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+
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+SYM_CODE_START(ftrace_caller)
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+#ifdef BTI_C
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+	BTI_C
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+#endif
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+	ftrace_regs_entry	0
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+	b	ftrace_common
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+SYM_CODE_END(ftrace_caller)
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+
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+SYM_CODE_START(ftrace_common)
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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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+	ldr_l	x2, function_trace_op		// op
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+	mov	x3, sp				// regs
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+
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+SYM_INNER_LABEL(ftrace_call, SYM_L_GLOBAL)
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+	bl	ftrace_stub
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+
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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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+
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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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+ftrace_common_return:
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+	/* Restore function arguments */
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+	ldp	x0, x1, [sp]
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+	ldp	x2, x3, [sp, #S_X2]
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+	ldp	x4, x5, [sp, #S_X4]
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+	ldp	x6, x7, [sp, #S_X6]
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+	ldr	x8, [sp, #S_X8]
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+
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+	/* Restore the callsite's FP, LR, PC */
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+	ldr	x29, [sp, #S_FP]
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+	ldr	x30, [sp, #S_LR]
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+	ldr	x9, [sp, #S_PC]
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+
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+	/* Restore the callsite's SP */
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+	add	sp, sp, #S_FRAME_SIZE + 16
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+
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+	ret	x9
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+SYM_CODE_END(ftrace_common)
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+
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+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
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+SYM_CODE_START(ftrace_graph_caller)
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+	ldr	x0, [sp, #S_PC]
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+	sub	x0, x0, #AARCH64_INSN_SIZE	// ip (callsite's BL insn)
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+	add	x1, sp, #S_LR			// parent_ip (callsite's LR)
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+	ldr	x2, [sp, #S_FRAME_SIZE]	   	// parent fp (callsite's FP)
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+	bl	prepare_ftrace_return
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+	b	ftrace_common_return
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+SYM_CODE_END(ftrace_graph_caller)
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+#endif
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+
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+#else /* CONFIG_DYNAMIC_FTRACE_WITH_REGS */
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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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@@ -95,7 +225,7 @@
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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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+SYM_FUNC_START(_mcount)
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 	mcount_enter
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 	ldr_l	x2, ftrace_trace_function
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@@ -119,7 +249,9 @@
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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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+SYM_FUNC_END(_mcount)
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+EXPORT_SYMBOL(_mcount)
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+NOKPROBE(_mcount)
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 #else /* CONFIG_DYNAMIC_FTRACE */
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 /*
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@@ -128,9 +260,11 @@
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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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+SYM_FUNC_START(_mcount)
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 	ret
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-ENDPROC(_mcount)
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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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@@ -141,51 +275,27 @@
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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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+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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-	.global ftrace_call
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-ftrace_call:				// tracer(pc, 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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-	.global ftrace_graph_call
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-ftrace_graph_call:			// ftrace_graph_caller();
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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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-ENDPROC(ftrace_caller)
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+SYM_FUNC_END(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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-
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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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-
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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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 /*
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  * void ftrace_graph_caller(void)
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  *
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@@ -195,28 +305,47 @@
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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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+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(&lr, pc, 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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-ENDPROC(ftrace_graph_caller)
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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_REGS */
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+SYM_FUNC_START(ftrace_stub)
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+	ret
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+SYM_FUNC_END(ftrace_stub)
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+
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+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
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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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+ * @fp is checked against the value passed by ftrace_graph_caller().
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  */
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-ENTRY(return_to_handler)
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-	save_return_regs
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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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+
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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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+
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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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+
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 	ret
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-END(return_to_handler)
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+SYM_CODE_END(return_to_handler)
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 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */