1 files changed, 63 insertions, 0 deletions
diff --git a/arch/arm64/kernel/ftrace.c b/arch/arm64/kernel/ftrace.c
index 570c38be833c..d7c0d023dfe5 100644
--- a/arch/arm64/kernel/ftrace.c
+++ b/arch/arm64/kernel/ftrace.c
@@ -143,6 +143,69 @@ unsigned long ftrace_call_adjust(unsigned long addr)
 	return addr;
 }
 
+/* Convert fentry_ip to the symbol address without kallsyms */
+unsigned long arch_ftrace_get_symaddr(unsigned long fentry_ip)
+{
+	u32 insn;
+
+	/*
+	 * When using patchable-function-entry without pre-function NOPS, ftrace
+	 * entry is the address of the first NOP after the function entry point.
+	 *
+	 * The compiler has either generated:
+	 *
+	 * func+00:	func:	NOP		// To be patched to MOV X9, LR
+	 * func+04:		NOP		// To be patched to BL <caller>
+	 *
+	 * Or:
+	 *
+	 * func-04:		BTI	C
+	 * func+00:	func:	NOP		// To be patched to MOV X9, LR
+	 * func+04:		NOP		// To be patched to BL <caller>
+	 *
+	 * The fentry_ip is the address of `BL <caller>` which is at `func + 4`
+	 * bytes in either case.
+	 */
+	if (!IS_ENABLED(CONFIG_DYNAMIC_FTRACE_WITH_CALL_OPS))
+		return fentry_ip - AARCH64_INSN_SIZE;
+
+	/*
+	 * When using patchable-function-entry with pre-function NOPs, BTI is
+	 * a bit different.
+	 *
+	 * func+00:	func:	NOP		// To be patched to MOV X9, LR
+	 * func+04:		NOP		// To be patched to BL <caller>
+	 *
+	 * Or:
+	 *
+	 * func+00:	func:	BTI	C
+	 * func+04:		NOP		// To be patched to MOV X9, LR
+	 * func+08:		NOP		// To be patched to BL <caller>
+	 *
+	 * The fentry_ip is the address of `BL <caller>` which is at either
+	 * `func + 4` or `func + 8` depends on whether there is a BTI.
+	 */
+
+	/* If there is no BTI, the func address should be one instruction before. */
+	if (!IS_ENABLED(CONFIG_ARM64_BTI_KERNEL))
+		return fentry_ip - AARCH64_INSN_SIZE;
+
+	/* We want to be extra safe in case entry ip is on the page edge,
+	 * but otherwise we need to avoid get_kernel_nofault()'s overhead.
+	 */
+	if ((fentry_ip & ~PAGE_MASK) < AARCH64_INSN_SIZE * 2) {
+		if (get_kernel_nofault(insn, (u32 *)(fentry_ip - AARCH64_INSN_SIZE * 2)))
+			return 0;
+	} else {
+		insn = *(u32 *)(fentry_ip - AARCH64_INSN_SIZE * 2);
+	}
+
+	if (aarch64_insn_is_bti(le32_to_cpu((__le32)insn)))
+		return fentry_ip - AARCH64_INSN_SIZE * 2;
+
+	return fentry_ip - AARCH64_INSN_SIZE;
+}
+
 /*
  * Replace a single instruction, which may be a branch or NOP.
  * If @validate == true, a replaced instruction is checked against 'old'.