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authorH. Peter Anvin <hpa@zytor.com>2009-03-16 19:17:57 -0700
committerH. Peter Anvin <hpa@zytor.com>2009-03-16 19:17:57 -0700
commit505039558c70d8ff66ff7af6119dcf1a74b00d0a (patch)
tree0bd96c025812b829fc795b90db9f2875fbb6cad7 /memdisk
parent6ab875d0d2316c8d6649f137b3e28405d5244f95 (diff)
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memdisk: zero the .bss section
It is just too confusing to have a .bss section that isn't zeroed, to explicitly zero it.
Diffstat (limited to 'memdisk')
-rw-r--r--memdisk/Makefile4
-rw-r--r--memdisk/memdisk.ld128
-rw-r--r--memdisk/start32.S10
3 files changed, 139 insertions, 3 deletions
diff --git a/memdisk/Makefile b/memdisk/Makefile
index 37767310..ba35b5c7 100644
--- a/memdisk/Makefile
+++ b/memdisk/Makefile
@@ -95,8 +95,8 @@ spotless: clean
memdisk16.elf: $(OBJS16)
$(LD) -Ttext 0 -o $@ $^
-memdisk32.elf: $(OBJS32)
- $(LD) -Ttext 0x100000 -o $@ $^
+memdisk32.elf: memdisk.ld $(OBJS32)
+ $(LD) -o $@ -T $^
%.bin: %.elf
$(OBJCOPY) -O binary $< $@
diff --git a/memdisk/memdisk.ld b/memdisk/memdisk.ld
new file mode 100644
index 00000000..10d8a929
--- /dev/null
+++ b/memdisk/memdisk.ld
@@ -0,0 +1,128 @@
+/*
+ * Linker script for MEMDISK
+ */
+
+/* Script for -z combreloc: combine and sort reloc sections */
+OUTPUT_FORMAT("elf32-i386", "elf32-i386", "elf32-i386")
+OUTPUT_ARCH(i386)
+EXTERN(_start)
+ENTRY(_start)
+SECTIONS
+{
+ /* Read-only sections, merged into text segment: */
+ . = 0x100000;
+ PROVIDE (__executable_start = .);
+
+ .init :
+ {
+ KEEP (*(.init))
+ } =0x90909090
+ .text :
+ {
+ *(.text .stub .text.* .gnu.linkonce.t.*)
+ /* .gnu.warning sections are handled specially by elf32.em. */
+ *(.gnu.warning)
+ } =0x90909090
+ .fini :
+ {
+ KEEP (*(.fini))
+ } =0x90909090
+ PROVIDE (__etext = .);
+ PROVIDE (_etext = .);
+ PROVIDE (etext = .);
+ .rodata : { *(.rodata .rodata.* .gnu.linkonce.r.*) }
+ .rodata1 : { *(.rodata1) }
+
+ /* Ensure the __preinit_array_start label is properly aligned. We
+ could instead move the label definition inside the section, but
+ the linker would then create the section even if it turns out to
+ be empty, which isn't pretty. */
+ . = ALIGN(4);
+ PROVIDE (__preinit_array_start = .);
+ .preinit_array : { *(.preinit_array) }
+ PROVIDE (__preinit_array_end = .);
+ PROVIDE (__init_array_start = .);
+ .init_array : { *(.init_array) }
+ PROVIDE (__init_array_end = .);
+ PROVIDE (__fini_array_start = .);
+ .fini_array : { *(.fini_array) }
+ PROVIDE (__fini_array_end = .);
+ PROVIDE (__ctors_start = .);
+ .ctors :
+ {
+ KEEP (*(SORT(.ctors.*)))
+ KEEP (*(.ctors))
+ }
+ PROVIDE (__ctors_end = .);
+ PROVIDE (__dtors_start = .);
+ .dtors :
+ {
+ KEEP (*(SORT(.dtors.*)))
+ KEEP (*(.dtors))
+ }
+ PROVIDE (__dtors_end = .);
+
+ /* Adjust the address for the data segment. Avoid mixing code and
+ data within same 128-byte chunk. */
+ . = ALIGN(128);
+
+ .data :
+ {
+ *(.data .data.* .gnu.linkonce.d.*)
+ SORT(CONSTRUCTORS)
+ }
+ .data1 : { *(.data1) }
+ _edata = .;
+ PROVIDE (edata = .);
+ .bss :
+ {
+ __bss_start = .;
+ *(.dynbss)
+ *(.bss .bss.* .gnu.linkonce.b.*)
+ *(COMMON)
+ /* Align here to ensure that the .bss section occupies space up to
+ _end. Align after .bss to ensure correct alignment even if the
+ .bss section disappears because there are no input sections. */
+ . = ALIGN(32 / 8);
+ __bss_end = .;
+ }
+ . = ALIGN(32 / 8);
+ _end = .;
+ PROVIDE (end = .);
+
+
+ /* 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) }
+ /* 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_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) }
+ /DISCARD/ : { *(.note.GNU-stack) }
+}
diff --git a/memdisk/start32.S b/memdisk/start32.S
index ee89b71d..073d049c 100644
--- a/memdisk/start32.S
+++ b/memdisk/start32.S
@@ -2,7 +2,15 @@
# Simple stub to get us to the right point in the 32-bit code;
# this module must be linked first
#
- .text
+ .section ".init", "ax"
.globl _start
_start:
+ /* Zero the bss */
+ cld
+ movl $__bss_start, %edi
+ movl $__bss_end, %ecx
+ subl %edi, %ecx
+ xorl %eax, %eax
+ shrl $2, %ecx
+ rep ; stosl
jmp setup