From 388fbaec91f8571ef81c3443487046f3fe9ba0df Mon Sep 17 00:00:00 2001
From: R <rqou@berkeley.edu>
Date: Fri, 12 Apr 2024 18:16:22 +0100
Subject: [PATCH] Strip down linker script

---
 linker.lds | 47 ++++++++++-------------------------------------
 startup.S  | 41 +----------------------------------------
 2 files changed, 11 insertions(+), 77 deletions(-)

diff --git a/linker.lds b/linker.lds
index fc3ea8d..d51d46c 100644
--- a/linker.lds
+++ b/linker.lds
@@ -5,10 +5,14 @@ PROVIDE( _stack_size = __stack_size );
 
 MEMORY
 {
-    /* CH32V20x_D6 -> 10 KB SRAM */
-    /* allow full flash (incl. non-zero-wait) */
-    FLASH (rx) : ORIGIN = 0x00000000, LENGTH = 224K
-    RAM (xrw) : ORIGIN = 0x20000000, LENGTH = 10K
+    /* Try to squeeze down to this target size */
+    FLASH (rx) : ORIGIN = 0x00000000, LENGTH = 2K
+    /* We have a total of 512 bytes here.
+    - Need 256 bytes to buffer a flash page across USB packets
+    - Need space for USB buffers
+    - Tiny tiny amount of free space
+    */
+    USBRAM (rw) : ORIGIN = 0x400060c0, LENGTH = 64
 }
 
 SECTIONS
@@ -29,29 +33,6 @@ SECTIONS
         . = ALIGN(4);
     } >FLASH
 
-    .preinit_array :
-    {
-        PROVIDE_HIDDEN (__preinit_array_start = .);
-        KEEP (*(.preinit_array))
-        PROVIDE_HIDDEN (__preinit_array_end = .);
-    } >FLASH
-
-    .init_array :
-    {
-        PROVIDE_HIDDEN (__init_array_start = .);
-        KEEP (*(SORT_BY_INIT_PRIORITY(.init_array.*) SORT_BY_INIT_PRIORITY(.ctors.*)))
-        KEEP (*(.init_array EXCLUDE_FILE (*crtbegin.o *crtbegin?.o *crtend.o *crtend?.o ) .ctors))
-        PROVIDE_HIDDEN (__init_array_end = .);
-    } >FLASH
-
-    .fini_array :
-    {
-        PROVIDE_HIDDEN (__fini_array_start = .);
-        KEEP (*(SORT_BY_INIT_PRIORITY(.fini_array.*) SORT_BY_INIT_PRIORITY(.dtors.*)))
-        KEEP (*(.fini_array EXCLUDE_FILE (*crtbegin.o *crtbegin?.o *crtend.o *crtend?.o ) .dtors))
-        PROVIDE_HIDDEN (__fini_array_end = .);
-    } >FLASH
-
     PROVIDE(_data_lma = .);
 
     .data :
@@ -73,7 +54,7 @@ SECTIONS
         *(.srodata .srodata.*)
         . = ALIGN(4);
         PROVIDE( _edata = .);
-    } >RAM AT>FLASH
+    } >USBRAM AT>FLASH
 
     .bss :
     {
@@ -85,15 +66,7 @@ SECTIONS
         *(COMMON*)
         . = ALIGN(4);
         PROVIDE( _ebss = .);
-    } >RAM
+    } >USBRAM
 
     PROVIDE( _end = _ebss);
-
-    .stack ORIGIN(RAM) + LENGTH(RAM) - __stack_size :
-    {
-        PROVIDE( _heap_end = . );
-        PROVIDE( _susrstack = . );
-        . = . + __stack_size;
-        PROVIDE( _eusrstack = .);
-    } >RAM 
 }
diff --git a/startup.S b/startup.S
index 4e8a39b..ba82497 100644
--- a/startup.S
+++ b/startup.S
@@ -32,46 +32,7 @@ _start:
     bltu a0, a1, 1b
 2:
 
-    // Call preinit array functions
-    la s0, __preinit_array_start
-    la s1, __preinit_array_end
-    bgeu s0, s1, 2f
-1:
-    lw t0, (s0)
-    jalr t0
-    addi s0, s0, 4
-    bltu s0, s1, 1b
-2:
-
-    // Call init array functions
-    la s0, __init_array_start
-    la s1, __init_array_end
-    bgeu s0, s1, 2f
-1:
-    lw t0, (s0)
-    jalr t0
-    addi s0, s0, 4
-    bltu s0, s1, 1b
-2:
-
-    // Invoke main with a possible mode switch
-    la ra, 1f
+    // Invoke main
     la t0, main
     csrw mepc, t0
     mret
-
-1:
-    // Return from main, call fini array functions
-    la s0, __fini_array_start
-    la s1, __fini_array_end
-    bgeu s0, s1, 2f
-1:
-    lw t0, (s0)
-    jalr t0
-    addi s0, s0, 4
-    bltu s0, s1, 1b
-2:
-
-    // Finally, loop infinitely
-    wfi
-    j 2b