1 files changed, 265 insertions, 0 deletions
diff --git a/arch/arm/kernel/entry-ftrace.S b/arch/arm/kernel/entry-ftrace.S
new file mode 100644
index 000000000..5f1b1ce10
--- /dev/null
+++ b/arch/arm/kernel/entry-ftrace.S
@@ -0,0 +1,265 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#include <asm/assembler.h>
+#include <asm/ftrace.h>
+#include <asm/unwind.h>
+
+#include "entry-header.S"
+
+/*
+ * When compiling with -pg, gcc inserts a call to the mcount routine at the
+ * start of every function.  In mcount, apart from the function's address (in
+ * lr), we need to get hold of the function's caller's address.
+ *
+ * Newer GCCs (4.4+) solve this problem by using a version of mcount with call
+ * sites like:
+ *
+ *	push	{lr}
+ *	bl	__gnu_mcount_nc
+ *
+ * With these compilers, frame pointers are not necessary.
+ *
+ * mcount can be thought of as a function called in the middle of a subroutine
+ * call.  As such, it needs to be transparent for both the caller and the
+ * callee: the original lr needs to be restored when leaving mcount, and no
+ * registers should be clobbered.
+ *
+ * When using dynamic ftrace, we patch out the mcount call by a "pop {lr}"
+ * instead of the __gnu_mcount_nc call (see arch/arm/kernel/ftrace.c).
+ */
+
+.macro mcount_adjust_addr rd, rn
+	bic	\rd, \rn, #1		@ clear the Thumb bit if present
+	sub	\rd, \rd, #MCOUNT_INSN_SIZE
+.endm
+
+.macro __mcount suffix
+	mcount_enter
+	ldr	r0, =ftrace_trace_function
+	ldr	r2, [r0]
+	adr	r0, .Lftrace_stub
+	cmp	r0, r2
+	bne	1f
+
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+	ldr     r1, =ftrace_graph_return
+	ldr     r2, [r1]
+	cmp     r0, r2
+	bne     ftrace_graph_caller\suffix
+
+	ldr     r1, =ftrace_graph_entry
+	ldr     r2, [r1]
+	ldr     r0, =ftrace_graph_entry_stub
+	cmp     r0, r2
+	bne     ftrace_graph_caller\suffix
+#endif
+
+	mcount_exit
+
+1: 	mcount_get_lr	r1			@ lr of instrumented func
+	mcount_adjust_addr	r0, lr		@ instrumented function
+	badr	lr, 2f
+	mov	pc, r2
+2:	mcount_exit
+.endm
+
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
+
+.macro __ftrace_regs_caller
+
+	str	lr, [sp, #-8]!	@ store LR as PC and make space for CPSR/OLD_R0,
+				@ OLD_R0 will overwrite previous LR
+
+	ldr	lr, [sp, #8]    @ get previous LR
+
+	str	r0, [sp, #8]	@ write r0 as OLD_R0 over previous LR
+
+	str	lr, [sp, #-4]!	@ store previous LR as LR
+
+	add 	lr, sp, #16	@ move in LR the value of SP as it was
+				@ before the push {lr} of the mcount mechanism
+
+	push	{r0-r11, ip, lr}
+
+	@ stack content at this point:
+	@ 0  4          48   52       56            60   64    68       72
+	@ R0 | R1 | ... | IP | SP + 4 | previous LR | LR | PSR | OLD_R0 |
+
+	mov	r3, sp				@ struct pt_regs*
+
+	ldr r2, =function_trace_op
+	ldr r2, [r2]				@ pointer to the current
+						@ function tracing op
+
+	ldr	r1, [sp, #S_LR]			@ lr of instrumented func
+
+	ldr	lr, [sp, #S_PC]			@ get LR
+
+	mcount_adjust_addr	r0, lr		@ instrumented function
+
+	.globl ftrace_regs_call
+ftrace_regs_call:
+	bl	ftrace_stub
+
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+	.globl ftrace_graph_regs_call
+ftrace_graph_regs_call:
+	mov	r0, r0
+#endif
+
+	@ pop saved regs
+	pop	{r0-r11, ip, lr}		@ restore r0 through r12
+	ldr	lr, [sp], #4			@ restore LR
+	ldr	pc, [sp], #12
+.endm
+
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+.macro __ftrace_graph_regs_caller
+
+	sub     r0, fp, #4              @ lr of instrumented routine (parent)
+
+	@ called from __ftrace_regs_caller
+	ldr     r1, [sp, #S_PC]		@ instrumented routine (func)
+	mcount_adjust_addr	r1, r1
+
+	mov	r2, fp			@ frame pointer
+	bl	prepare_ftrace_return
+
+	@ pop registers saved in ftrace_regs_caller
+	pop	{r0-r11, ip, lr}		@ restore r0 through r12
+	ldr	lr, [sp], #4			@ restore LR
+	ldr	pc, [sp], #12
+
+.endm
+#endif
+#endif
+
+.macro __ftrace_caller suffix
+	mcount_enter
+
+	mcount_get_lr	r1			@ lr of instrumented func
+	mcount_adjust_addr	r0, lr		@ instrumented function
+
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
+	ldr r2, =function_trace_op
+	ldr r2, [r2]				@ pointer to the current
+						@ function tracing op
+	mov r3, #0				@ regs is NULL
+#endif
+
+	.globl ftrace_call\suffix
+ftrace_call\suffix:
+	bl	ftrace_stub
+
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+	.globl ftrace_graph_call\suffix
+ftrace_graph_call\suffix:
+	mov	r0, r0
+#endif
+
+	mcount_exit
+.endm
+
+.macro __ftrace_graph_caller
+	sub	r0, fp, #4		@ &lr of instrumented routine (&parent)
+#ifdef CONFIG_DYNAMIC_FTRACE
+	@ called from __ftrace_caller, saved in mcount_enter
+	ldr	r1, [sp, #16]		@ instrumented routine (func)
+	mcount_adjust_addr	r1, r1
+#else
+	@ called from __mcount, untouched in lr
+	mcount_adjust_addr	r1, lr	@ instrumented routine (func)
+#endif
+	mov	r2, fp			@ frame pointer
+	bl	prepare_ftrace_return
+	mcount_exit
+.endm
+
+/*
+ * __gnu_mcount_nc
+ */
+
+.macro mcount_enter
+/*
+ * This pad compensates for the push {lr} at the call site.  Note that we are
+ * unable to unwind through a function which does not otherwise save its lr.
+ */
+ UNWIND(.pad	#4)
+	stmdb	sp!, {r0-r3, lr}
+ UNWIND(.save	{r0-r3, lr})
+.endm
+
+.macro mcount_get_lr reg
+	ldr	\reg, [sp, #20]
+.endm
+
+.macro mcount_exit
+	ldmia	sp!, {r0-r3}
+	ldr	lr, [sp, #4]
+	ldr	pc, [sp], #8
+.endm
+
+ENTRY(__gnu_mcount_nc)
+UNWIND(.fnstart)
+#ifdef CONFIG_DYNAMIC_FTRACE
+	push	{lr}
+	ldr	lr, [sp, #4]
+	ldr	pc, [sp], #8
+#else
+	__mcount
+#endif
+UNWIND(.fnend)
+ENDPROC(__gnu_mcount_nc)
+
+#ifdef CONFIG_DYNAMIC_FTRACE
+ENTRY(ftrace_caller)
+UNWIND(.fnstart)
+	__ftrace_caller
+UNWIND(.fnend)
+ENDPROC(ftrace_caller)
+
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
+ENTRY(ftrace_regs_caller)
+UNWIND(.fnstart)
+	__ftrace_regs_caller
+UNWIND(.fnend)
+ENDPROC(ftrace_regs_caller)
+#endif
+
+#endif
+
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+ENTRY(ftrace_graph_caller)
+UNWIND(.fnstart)
+	__ftrace_graph_caller
+UNWIND(.fnend)
+ENDPROC(ftrace_graph_caller)
+
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
+ENTRY(ftrace_graph_regs_caller)
+UNWIND(.fnstart)
+	__ftrace_graph_regs_caller
+UNWIND(.fnend)
+ENDPROC(ftrace_graph_regs_caller)
+#endif
+#endif
+
+.purgem mcount_enter
+.purgem mcount_get_lr
+.purgem mcount_exit
+
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+	.globl return_to_handler
+return_to_handler:
+	stmdb	sp!, {r0-r3}
+	mov	r0, fp			@ frame pointer
+	bl	ftrace_return_to_handler
+	mov	lr, r0			@ r0 has real ret addr
+	ldmia	sp!, {r0-r3}
+	ret	lr
+#endif
+
+ENTRY(ftrace_stub)
+.Lftrace_stub:
+	ret	lr
+ENDPROC(ftrace_stub)