From 35d1a6ef41fa716503925226837cf0f0b8894a90 Mon Sep 17 00:00:00 2001
From: Tianhao Wang <shrik3@mailbox.org>
Date: Thu, 18 Apr 2024 03:03:27 +0200
Subject: linker: "optimize" section arrangements

1. throw vectors in a custom ".reserved" section
2. throw idt in a NOLOAD ".reserved_0" section: save some binary size
   (like .bss) since we don't care for its initial value.
3. squash all ".data.*" sections from rust into ".data"
---
 defs/x86_64-linker.ld         | 18 ++++++++++++++++--
 src/arch/x86_64/asm/vectors.s |  5 +++--
 2 files changed, 19 insertions(+), 4 deletions(-)

diff --git a/defs/x86_64-linker.ld b/defs/x86_64-linker.ld
index aee69aa..3d54187 100644
--- a/defs/x86_64-linker.ld
+++ b/defs/x86_64-linker.ld
@@ -12,12 +12,26 @@ SECTIONS
 
     .data :
     {
-		*(".data.idt")
-		*(".data.vectors")
         *(".data")
+        *(".data.*")
         *(".data$")
     }
 
+	.reserved : {
+		*(".reserved")
+		*(".reserved.*")
+	}
+
+	/*
+	 * basically the same as BSS, but I want some flexibility and I don't care
+	 * for zeroing because it's explicitly overwritten anyways. I KNOW WHAT I'M
+	 * DOING! An example is the idt.
+	 */
+	.reserved_0 (NOLOAD) : {
+		*(".reserved_0")
+		*(".reserved_0.*")
+	}
+
     .rodata :
     {
         *(".rodata")
diff --git a/src/arch/x86_64/asm/vectors.s b/src/arch/x86_64/asm/vectors.s
index ba5fb87..2798032 100644
--- a/src/arch/x86_64/asm/vectors.s
+++ b/src/arch/x86_64/asm/vectors.s
@@ -5,7 +5,7 @@
 [GLOBAL vectors_start]
 [EXTERN interrupt_gate]
 
-[SECTION .data.idt]
+[SECTION .reserved_0.idt]
 ;
 ; Interrupt descriptor table with 256 entries
 ; TODO: use a interrupt stack instead of the current stack.
@@ -14,6 +14,7 @@ idt:
 ; reserve space for 256x idt entries (16 bytes each)
 resb 16 * 256
 
+[SECTION .reserved]
 idt_descr:
 	dw	256*8 - 1	 ; 256 entries
 	dq idt
@@ -22,6 +23,7 @@ idt_descr:
 ; bytes. DO NOT modify the wrapper, instead change the wrapper_body if needed.
 ; if the vector has to be modified into more than 16 bytes,
 ; arch::x86_64:: interrupt::_idt_init() must be modified accordingly
+[SECTION .reserved.vectors]
 %macro wrapper 1
 align 16
 wrapper_%1:
@@ -34,7 +36,6 @@ wrapper_%1:
 
 ; automatic generation of 256 interrupt-handling routines, based on above macro
 
-[SECTION .data.vectors]
 vectors_start:
 %assign i 0
 %rep 256
-- 
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