From 54d3d93a92b7bea849f4a59c544173a2538c6bb1 Mon Sep 17 00:00:00 2001
From: Ivaylo Ivanov <ivo.ivanov@null.net>
Date: Tue, 6 Aug 2024 19:21:46 +0300
Subject: [PATCH] arch: aarch64: Set up Stack Pointer

Introduce stack and bss memory regions, rename Start.S to start.S
This commit should allow jumping out of assembly code for certain
SoCs that had issues with SP like MTK and QCOM.

Signed-off-by: Ivaylo Ivanov <ivo.ivanov.ivanov1@gmail.com>
---
 Makefile                      |  4 ++--
 arch/Makefile                 |  2 +-
 arch/aarch64/Start.S          | 12 ------------
 arch/aarch64/linker.lds.S     | 21 ++++++++++++++++++---
 arch/aarch64/macros.h         | 15 +++++++++++++++
 arch/aarch64/start.S          | 22 ++++++++++++++++++++++
 arch/arm/linker.lds.S         |  2 +-
 arch/arm/{Start.S => start.S} |  0
 8 files changed, 59 insertions(+), 19 deletions(-)
 delete mode 100644 arch/aarch64/Start.S
 create mode 100644 arch/aarch64/macros.h
 create mode 100644 arch/aarch64/start.S
 rename arch/arm/{Start.S => start.S} (100%)

diff --git a/Makefile b/Makefile
index cffd1b8..a5a6d8c 100644
--- a/Makefile
+++ b/Makefile
@@ -340,8 +340,8 @@ endif # $(dot-config)
 all: arch/$(ARCH)/linker.lds uniLoader
 
 # List of main executables
-main-y		:= main/main.o
-main-y		+= arch/$(ARCH)/Start.o
+main-y		:= arch/$(ARCH)/start.o \
+		   main/main.o
 
 # Object directories
 objs-y		:= main
diff --git a/arch/Makefile b/arch/Makefile
index e403bdc..e3ece6d 100644
--- a/arch/Makefile
+++ b/arch/Makefile
@@ -1 +1 @@
-obj-y += $(ARCH)/Start.o
+obj-y += $(ARCH)/start.o
diff --git a/arch/aarch64/Start.S b/arch/aarch64/Start.S
deleted file mode 100644
index 316d0a6..0000000
--- a/arch/aarch64/Start.S
+++ /dev/null
@@ -1,12 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0 */
-/*
- * Copyright (c) 2022, Ivaylo Ivanov <ivo.ivanov.ivanov1@gmail.com>
- */
-
-    adr	x0, dtb
-    adr	x1, kernel
-    b main
-
-.global load_kernel
-load_kernel:
-    br	x4
diff --git a/arch/aarch64/linker.lds.S b/arch/aarch64/linker.lds.S
index e145266..80aee3f 100644
--- a/arch/aarch64/linker.lds.S
+++ b/arch/aarch64/linker.lds.S
@@ -13,15 +13,30 @@ INPUT(DTB_PATH)
 SECTIONS
 {
 	.boot : {
-		arch/aarch64/Start.o
+		arch/aarch64/start.o
 	}
 
-	.dtb ALIGN(0x1000) : {
+	.text : {
+		*(.text)
+	}
+
+	.bss ALIGN(4096) : {
+		_bss_start = .;
+		. = . + 4096;
+		_bss_end = .;
+	}
+
+	.stack ALIGN(4096) : {
+		. = . + 4096;
+		_stack_end = .;
+	}
+
+	.dtb ALIGN(4096) : {
 		dtb = .;
 		DTB_PATH
 	}
 
-	.kernel ALIGN(0x1000) : {
+	.kernel ALIGN(4096) : {
 		kernel = .;
 		KERNEL_PATH
 	}
diff --git a/arch/aarch64/macros.h b/arch/aarch64/macros.h
new file mode 100644
index 0000000..cfe341a
--- /dev/null
+++ b/arch/aarch64/macros.h
@@ -0,0 +1,15 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (c) 2022, Ivaylo Ivanov <ivo.ivanov.ivanov1@gmail.com>
+ */
+
+.macro ENTRY name
+	.globl \name
+	.type \name, %function
+	.align 2
+	\name:
+.endm
+
+.macro ENDPROC name
+	.size \name, . - \name
+.endm
diff --git a/arch/aarch64/start.S b/arch/aarch64/start.S
new file mode 100644
index 0000000..d63f3fe
--- /dev/null
+++ b/arch/aarch64/start.S
@@ -0,0 +1,22 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (c) 2022, Ivaylo Ivanov <ivo.ivanov.ivanov1@gmail.com>
+ */
+.include "arch/aarch64/macros.h"
+
+.section .text
+ENTRY _start
+	/* Set up the base address for the stack */
+	adr x0, _stack_end
+
+	/* Set up the stack pointer (SP) */
+	mov sp, x0
+
+	/* Fall through */
+	adr	x0, dtb
+	adr	x1, kernel
+	b main
+
+ENTRY load_kernel
+	br	x4
+ENDPROC load_kernel
diff --git a/arch/arm/linker.lds.S b/arch/arm/linker.lds.S
index 90d2b76..fe7cea2 100644
--- a/arch/arm/linker.lds.S
+++ b/arch/arm/linker.lds.S
@@ -14,7 +14,7 @@ SECTIONS
         . = __start_address;
 	
         .boot : {
-                arch/arm/Start.o
+                arch/arm/start.o
         }
 
         .dtb ALIGN(0x1000) : {
diff --git a/arch/arm/Start.S b/arch/arm/start.S
similarity index 100%
rename from arch/arm/Start.S
rename to arch/arm/start.S