From 0a8983119338d7cd917b7827cda92aded027ee22 Mon Sep 17 00:00:00 2001
From: TuxSH <tuxsh@sfr.fr>
Date: Wed, 28 Feb 2018 22:29:17 +0100
Subject: [PATCH] Clear bss at runtime like Nintendo actually does

---
 exosphere/linker.ld           | 31 +++++++++++++++++++------------
 exosphere/src/coldboot_init.c | 18 +++++++++++++-----
 2 files changed, 32 insertions(+), 17 deletions(-)

diff --git a/exosphere/linker.ld b/exosphere/linker.ld
index 9d8123482..d22864ee7 100644
--- a/exosphere/linker.ld
+++ b/exosphere/linker.ld
@@ -68,8 +68,14 @@ SECTIONS
         build/package2.o(.rodata*)
         build/package2.o(.data*)
         . = ALIGN(8);
+    } >pk2ldr AT>fake
+
+    .pk2ldr.bss :
+    {
+        . = ALIGN(8);
+        __pk2ldr_bss_start__ = ABSOLUTE(.);
         build/package2.o(.bss*)
-        . = ALIGN(16);
+        . = ALIGN(8);
         __pk2ldr_end__ = ABSOLUTE(.);
     } >pk2ldr AT>fake
 
@@ -79,7 +85,7 @@ SECTIONS
         __vectors_lma__   = LOADADDR(.vectors);
         __vectors_start__ = ABSOLUTE(.);
         KEEP (*(.vectors*))
-        . = ALIGN(16);
+        . = ALIGN(8);
         __vectors_end__ = ABSOLUTE(.);
     } >evt AT>fake
 
@@ -178,16 +184,6 @@ SECTIONS
         *(.data .data.* .gnu.linkonce.d.*)
         CONSTRUCTORS
         . = ALIGN(8);
-        /*
-            We're too lazy to clear BSS so we integrate it into .data.
-            Nintendo does the same for this main segment's BSS.
-        */
-        __bss_start__ = ABSOLUTE(.);
-        *(.dynbss)
-        *(.bss .bss.* .gnu.linkonce.b.*)
-        *(COMMON)
-        . = ALIGN(8);
-        __bss_end__ = ABSOLUTE(.);
     } >main AT>fake
 
 
@@ -209,6 +205,17 @@ SECTIONS
     .dynstr            : { *(.dynstr) } >main AT>fake
     .rela.dyn          : { *(.rela.*); __main_end__ = ABSOLUTE(.);} >main AT>fake
 
+    .bss :
+    {
+        . = ALIGN(8);
+        __main_bss_start__ = ABSOLUTE(.);
+        *(.dynbss)
+        *(.bss .bss.* .gnu.linkonce.b.*)
+        *(COMMON)
+        . = ALIGN(8);
+        __main_end__ = ABSOLUTE(.);
+    } >main AT>fake
+
     __end__ = ABSOLUTE(.) ;
 
     . = ALIGN(0x1000);
diff --git a/exosphere/src/coldboot_init.c b/exosphere/src/coldboot_init.c
index 86984f6ec..f7c7d431e 100644
--- a/exosphere/src/coldboot_init.c
+++ b/exosphere/src/coldboot_init.c
@@ -1,3 +1,4 @@
+#include <string.h>
 #include "utils.h"
 #include "mmu.h"
 #include "memory_map.h"
@@ -5,8 +6,8 @@
 extern const uint8_t __start_cold[];
 
 extern const uint8_t __warmboot_crt0_start__[], __warmboot_crt0_end__[], __warmboot_crt0_lma__[];
-extern const uint8_t __main_start__[], __main_end__[], __main_lma__[];
-extern const uint8_t __pk2ldr_start__[], __pk2ldr_end__[], __pk2ldr_lma__[];
+extern const uint8_t __main_start__[], __main_bss_start__[], __main_end__[], __main_lma__[];
+extern const uint8_t __pk2ldr_start__[], __pk2ldr_bss_start__[], __pk2ldr_end__[], __pk2ldr_lma__[];
 extern const uint8_t __vectors_start__[], __vectors_end__[], __vectors_lma__[];
 
 /* warmboot_init.c */
@@ -120,10 +121,17 @@ __attribute__((target("cmodel=large"), noinline)) static void copy_other_section
     copy_lma_to_vma(__vectors_start__, __vectors_lma__, __vectors_end__ - __vectors_start__);
 }
 
+__attribute__((target("cmodel=large"), noinline)) static void clear_bss(void) {
+    memset((void *)__pk2ldr_bss_start__, 0, __pk2ldr_end__ - __pk2ldr_bss_start__);
+    memset((void *)__main_bss_start__, 0, __main_end__ - __main_bss_start__);
+}
+
 void coldboot_init(void) {
     /* TODO: Set NX BOOTLOADER clock time field */
+
     copy_warmboot_crt0();
     /* At this point, we can (and will) access functions located in .warm_crt0 */
+
     /* TODO: initialize DMA controllers, etc. */
     configure_ttbls();
     copy_other_sections();
@@ -131,7 +139,7 @@ void coldboot_init(void) {
 
     flush_dcache_all_tzram_pa();
     invalidate_icache_all_inner_shareable_tzram_pa();
-    /* At this point we can access all the mapped segments */
-    /* TODO: zero-initialize the cpu context */
-    /* Nintendo clears the (emtpy) pk2ldr's BSS section here , but we embed it 0-filled in the binary */
+    /* At this point we can access all the mapped segments (all other functions, data...) normally */
+
+    clear_bss();
 }