From 3a48e2bfd774d88e51f5bb32e5dfc68d748458db Mon Sep 17 00:00:00 2001
From: Zack Buhman <zack@buhman.org>
Date: Sat, 23 Dec 2023 22:03:15 +0800
Subject: [PATCH] improve linker scripts

Previously, due to the ordering of .text.p2ram and .bss, the linker
was forced to allocate .bss in the output file, increasing the size
of the final binary unnecessarily.

The linker scripts now preserve debugging symbols during linking.
---
 alt.lds   | 30 ++++++++++++------------------
 debug.lds | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
 main.lds  | 36 ++++++++++++++++--------------------
 3 files changed, 76 insertions(+), 38 deletions(-)
 create mode 100644 debug.lds

diff --git a/alt.lds b/alt.lds
index bce99eb..86a8dc7 100644
--- a/alt.lds
+++ b/alt.lds
@@ -33,35 +33,29 @@ SECTIONS
     KEEP(*(.ctors.*))
   } > p1ram
 
-  .bss ALIGN(4) (NOLOAD) : SUBALIGN(4)
-  {
-    *(.bss)
-    *(.bss.*)
-  } > p1ram
-
   .text.p2ram ALIGN(4) : SUBALIGN(4)
   {
     *(.p2ram)
     *(.p2ram.*)
   } > p1ram
 
-  __p1ram_end = .;
-
-  /DISCARD/ :
+  .bss ALIGN(4) (NOLOAD) : SUBALIGN(4)
   {
-    *(.debug*)
-    *(.comment*)
-    *(.rela*)
-  }
+    *(.bss)
+    *(.bss.*)
+    *(COMMON)
+  } > p1ram
 
-  __bss_link_start = ADDR(.bss);
-  __bss_link_end = ADDR(.bss) + SIZEOF(.bss);
-
-  __ctors_link_start = ADDR(.ctors);
-  __ctors_link_end = ADDR(.ctors) + SIZEOF(.ctors);
+  INCLUDE "debug.lds"
 }
 
 __p1ram_start = ORIGIN(p1ram);
 __p1ram_end = ORIGIN(p1ram) + LENGTH(p1ram);
 
+__bss_link_start = ADDR(.bss);
+__bss_link_end = ADDR(.bss) + SIZEOF(.bss);
+
+__ctors_link_start = ADDR(.ctors);
+__ctors_link_end = ADDR(.ctors) + SIZEOF(.ctors);
+
 INCLUDE "addresses.lds"
diff --git a/debug.lds b/debug.lds
new file mode 100644
index 0000000..71b5eb2
--- /dev/null
+++ b/debug.lds
@@ -0,0 +1,48 @@
+  /* Stabs debugging sections.  */
+  .stab          0 : { *(.stab) }
+  .stabstr       0 : { *(.stabstr) }
+  .stab.excl     0 : { *(.stab.excl) }
+  .stab.exclstr  0 : { *(.stab.exclstr) }
+  .stab.index    0 : { *(.stab.index) }
+  .stab.indexstr 0 : { *(.stab.indexstr) }
+  .comment       0 : { *(.comment) }
+  .gnu.build.attributes : { *(.gnu.build.attributes .gnu.build.attributes.*) }
+  /* DWARF debug sections.
+     Symbols in the DWARF debugging sections are relative to the beginning
+     of the section so we begin them at 0.  */
+  /* DWARF 1.  */
+  .debug          0 : { *(.debug) }
+  .line           0 : { *(.line) }
+  /* GNU DWARF 1 extensions.  */
+  .debug_srcinfo  0 : { *(.debug_srcinfo) }
+  .debug_sfnames  0 : { *(.debug_sfnames) }
+  /* DWARF 1.1 and DWARF 2.  */
+  .debug_aranges  0 : { *(.debug_aranges) }
+  .debug_pubnames 0 : { *(.debug_pubnames) }
+  /* DWARF 2.  */
+  .debug_info     0 : { *(.debug_info .gnu.linkonce.wi.*) }
+  .debug_abbrev   0 : { *(.debug_abbrev) }
+  .debug_line     0 : { *(.debug_line .debug_line.* .debug_line_end) }
+  .debug_frame    0 : { *(.debug_frame) }
+  .debug_str      0 : { *(.debug_str) }
+  .debug_loc      0 : { *(.debug_loc) }
+  .debug_macinfo  0 : { *(.debug_macinfo) }
+  /* SGI/MIPS DWARF 2 extensions.  */
+  .debug_weaknames 0 : { *(.debug_weaknames) }
+  .debug_funcnames 0 : { *(.debug_funcnames) }
+  .debug_typenames 0 : { *(.debug_typenames) }
+  .debug_varnames  0 : { *(.debug_varnames) }
+  /* DWARF 3.  */
+  .debug_pubtypes 0 : { *(.debug_pubtypes) }
+  .debug_ranges   0 : { *(.debug_ranges) }
+  /* DWARF 5.  */
+  .debug_addr     0 : { *(.debug_addr) }
+  .debug_line_str 0 : { *(.debug_line_str) }
+  .debug_loclists 0 : { *(.debug_loclists) }
+  .debug_macro    0 : { *(.debug_macro) }
+  .debug_names    0 : { *(.debug_names) }
+  .debug_rnglists 0 : { *(.debug_rnglists) }
+  .debug_str_offsets 0 : { *(.debug_str_offsets) }
+  .debug_sup      0 : { *(.debug_sup) }
+  .gnu.attributes 0 : { KEEP (*(.gnu.attributes)) }
+  /DISCARD/ : { *(.note.GNU-stack) *(.gnu_debuglink) *(.gnu.lto_*) *(.rela.*) }
diff --git a/main.lds b/main.lds
index c744c77..91159a2 100644
--- a/main.lds
+++ b/main.lds
@@ -6,7 +6,7 @@ MEMORY
 }
 SECTIONS
 {
-  . = 0x8c010000;
+  . = ORIGIN(p1ram);
 
   .text ALIGN(4) : SUBALIGN(4)
   {
@@ -34,15 +34,7 @@ SECTIONS
     KEEP(*(.ctors.*))
   } > p1ram
 
-  .bss ALIGN(4) (NOLOAD) : SUBALIGN(4)
-  {
-    *(.bss)
-    *(.bss.*)
-  } > p1ram
-
-  __p1ram_end = .;
-
-  . = 0xac010000 + __p1ram_end - __p1ram_start;
+  . = ORIGIN(p2ram) + (. - ORIGIN(p1ram));
 
   .text.p2ram ALIGN(4) : SUBALIGN(4)
   {
@@ -50,21 +42,25 @@ SECTIONS
     *(.p2ram.*)
   } > p2ram AT>p1ram
 
-  /DISCARD/ :
+  . = ORIGIN(p1ram) + (. - ORIGIN(p2ram));
+
+  .bss ALIGN(4) (NOLOAD) : SUBALIGN(4)
   {
-    *(.debug*)
-    *(.comment*)
-    *(.rela*)
-  }
+    *(.bss)
+    *(.bss.*)
+    *(COMMON)
+  } > p1ram
 
-  __bss_link_start = ADDR(.bss);
-  __bss_link_end = ADDR(.bss) + SIZEOF(.bss);
-
-  __ctors_link_start = ADDR(.ctors);
-  __ctors_link_end = ADDR(.ctors) + SIZEOF(.ctors);
+  INCLUDE "debug.ld"
 }
 
 __p1ram_start = ORIGIN(p1ram);
 __p1ram_end = ORIGIN(p1ram) + LENGTH(p1ram);
 
+__bss_link_start = ADDR(.bss);
+__bss_link_end = ADDR(.bss) + SIZEOF(.bss);
+
+__ctors_link_start = ADDR(.ctors);
+__ctors_link_end = ADDR(.ctors) + SIZEOF(.ctors);
+
 INCLUDE "addresses.lds"