From 505039558c70d8ff66ff7af6119dcf1a74b00d0a Mon Sep 17 00:00:00 2001 From: "H. Peter Anvin" Date: Mon, 16 Mar 2009 19:17:57 -0700 Subject: [PATCH] memdisk: zero the .bss section It is just too confusing to have a .bss section that isn't zeroed, to explicitly zero it. --- memdisk/Makefile | 4 +- memdisk/memdisk.ld | 128 +++++++++++++++++++++++++++++++++++++++++++++++++++++ memdisk/start32.S | 10 ++++- 3 files changed, 139 insertions(+), 3 deletions(-) create mode 100644 memdisk/memdisk.ld diff --git a/memdisk/Makefile b/memdisk/Makefile index 3776731..ba35b5c 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 0000000..10d8a92 --- /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 ee89b71..073d049 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 -- 2.7.4