From dc52da281942aa2c7f009eac1ece4f0f10e451cb Mon Sep 17 00:00:00 2001
From: Michael Scire <SciresM@gmail.com>
Date: Fri, 8 Oct 2021 12:46:23 -0700
Subject: [PATCH] kern: simplify rela-in-bss impl

---
 mesosphere/build_mesosphere.py | 31 +++++--------------------------
 mesosphere/kernel/Makefile     |  2 +-
 mesosphere/kernel/kernel.ld    | 16 +++++++---------
 3 files changed, 13 insertions(+), 36 deletions(-)

diff --git a/mesosphere/build_mesosphere.py b/mesosphere/build_mesosphere.py
index b64fba912..be51da4f0 100644
--- a/mesosphere/build_mesosphere.py
+++ b/mesosphere/build_mesosphere.py
@@ -9,23 +9,6 @@ def align_up(val, algn):
     val += algn - 1
     return val - (val % algn)
 
-def find_rela(kernel, dynamic):
-    rela_offset, rela_size = (None, None)
-    while True:
-        dyn_type, dyn_val = up('<QQ', kernel[dynamic:dynamic+0x10])
-        if dyn_type == 0:
-            break
-        elif dyn_type == 7:
-            assert (rela_offset is None)
-            rela_offset = dyn_val
-        elif dyn_type == 8:
-            assert (rela_size is None)
-            rela_size = dyn_val
-        dynamic += 0x10
-    assert (rela_offset is not None)
-    assert (rela_size is not None)
-    return (rela_offset, rela_size)
-
 def main(argc, argv):
     if argc != 4:
         print('Usage: %s kernel_ldr.bin kernel.bin output.bin' % argv[0])
@@ -37,18 +20,14 @@ def main(argc, argv):
     kernel_metadata_offset = 4
     assert (kernel_metadata_offset <= len(kernel) - 0x40)
     assert (kernel[kernel_metadata_offset:kernel_metadata_offset + 4] == b'MSS0')
-    bss_start, bss_end, kernel_end, dynamic = up('<IIII', kernel[kernel_metadata_offset + 0x30:kernel_metadata_offset + 0x40])
+
+    bss_start, bss_end, kernel_end = up('<III', kernel[kernel_metadata_offset + 0x30:kernel_metadata_offset + 0x3C])
     assert (bss_end >= bss_start)
-    bss_size = bss_end - bss_start
     assert (bss_end == kernel_end)
-    assert (kernel_end <= len(kernel))
 
-    rela_offset, rela_size = find_rela(kernel, dynamic)
-    assert (rela_size == len(kernel) - kernel_end)
-    assert (bss_start <= rela_offset and rela_offset + rela_size <= bss_end)
-    assert (kernel[bss_start:bss_end] == (b'\x00'* bss_size))
-
-    kernel = kernel[:rela_offset] + kernel[bss_end:] + (b'\x00' * (bss_size - (rela_size + (rela_offset - bss_start))))
+    assert (len(kernel) <= kernel_end)
+    if len(kernel) < kernel_end:
+        kernel += b'\x00' * (kernel_end - len(kernel))
     assert (kernel_end == len(kernel))
 
     embedded_ini = b''
diff --git a/mesosphere/kernel/Makefile b/mesosphere/kernel/Makefile
index d5e3deb68..b73a399b9 100644
--- a/mesosphere/kernel/Makefile
+++ b/mesosphere/kernel/Makefile
@@ -102,7 +102,7 @@ DEPENDS	:=	$(OFILES:.o=.d)
 # main targets
 #---------------------------------------------------------------------------------
 $(OUTPUT).bin	:	$(OUTPUT).elf
-	$(OBJCOPY) -S -O binary --set-section-flags .bss=alloc,load,contents $< $@
+	$(OBJCOPY) -S -O binary $< $@
 	@echo built ... $(notdir $@)
 
 $(OUTPUT).elf	:	$(OFILES)
diff --git a/mesosphere/kernel/kernel.ld b/mesosphere/kernel/kernel.ld
index 8d7da0ff0..efbc1c1e9 100644
--- a/mesosphere/kernel/kernel.ld
+++ b/mesosphere/kernel/kernel.ld
@@ -154,16 +154,14 @@ SECTIONS
 
 	__bss_start__ = .;
 
-    OVERLAY : NOCROSSREFS {
-        .bss {
-            *(.dynbss)
-            *(.bss .bss.* .gnu.linkonce.b.*)
-            *(COMMON)
-            . = ALIGN(0x1000);
-        }
-        .rela.dyn { *(.rela.*) }
-    } :data
+    .rela.dyn : { *(.rela.*) } :data
 
+    .bss ADDR(.rela.dyn) (NOLOAD) : {
+        *(.dynbss)
+        *(.bss .bss.* .gnu.linkonce.b.*)
+        *(COMMON)
+        . = ALIGN(0x1000);
+    }
 
 	__bss_end__ = .;