a021506107
Moves the relocation handling into C, after decompression. This requires that the decompressed size is passed to the decompression routine as well so that relocations can be found. Only kernels that need relocation support will use the code (currently just x86_32), but this is laying the ground work for 64-bit using it in support of KASLR. Based on work by Neill Clift and Michael Davidson. Signed-off-by: Kees Cook <keescook@chromium.org> Link: http://lkml.kernel.org/r/20130708161517.GA4832@www.outflux.net Acked-by: Zhang Yanfei <zhangyanfei@cn.fujitsu.com> Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
213 lines
4.1 KiB
ArmAsm
213 lines
4.1 KiB
ArmAsm
/*
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* linux/boot/head.S
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*
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* Copyright (C) 1991, 1992, 1993 Linus Torvalds
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*/
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/*
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* head.S contains the 32-bit startup code.
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*
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* NOTE!!! Startup happens at absolute address 0x00001000, which is also where
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* the page directory will exist. The startup code will be overwritten by
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* the page directory. [According to comments etc elsewhere on a compressed
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* kernel it will end up at 0x1000 + 1Mb I hope so as I assume this. - AC]
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*
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* Page 0 is deliberately kept safe, since System Management Mode code in
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* laptops may need to access the BIOS data stored there. This is also
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* useful for future device drivers that either access the BIOS via VM86
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* mode.
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*/
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/*
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* High loaded stuff by Hans Lermen & Werner Almesberger, Feb. 1996
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*/
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.text
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#include <linux/init.h>
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#include <linux/linkage.h>
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#include <asm/segment.h>
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#include <asm/page_types.h>
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#include <asm/boot.h>
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#include <asm/asm-offsets.h>
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__HEAD
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ENTRY(startup_32)
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#ifdef CONFIG_EFI_STUB
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jmp preferred_addr
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/*
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* We don't need the return address, so set up the stack so
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* efi_main() can find its arguments.
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*/
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ENTRY(efi_pe_entry)
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add $0x4, %esp
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call make_boot_params
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cmpl $0, %eax
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je 1f
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movl 0x4(%esp), %esi
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movl (%esp), %ecx
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pushl %eax
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pushl %esi
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pushl %ecx
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sub $0x4, %esp
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ENTRY(efi_stub_entry)
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add $0x4, %esp
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call efi_main
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cmpl $0, %eax
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movl %eax, %esi
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jne 2f
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1:
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/* EFI init failed, so hang. */
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hlt
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jmp 1b
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2:
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call 3f
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3:
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popl %eax
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subl $3b, %eax
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subl BP_pref_address(%esi), %eax
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add BP_code32_start(%esi), %eax
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leal preferred_addr(%eax), %eax
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jmp *%eax
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preferred_addr:
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#endif
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cld
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/*
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* Test KEEP_SEGMENTS flag to see if the bootloader is asking
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* us to not reload segments
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*/
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testb $(1<<6), BP_loadflags(%esi)
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jnz 1f
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cli
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movl $__BOOT_DS, %eax
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movl %eax, %ds
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movl %eax, %es
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movl %eax, %fs
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movl %eax, %gs
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movl %eax, %ss
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1:
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/*
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* Calculate the delta between where we were compiled to run
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* at and where we were actually loaded at. This can only be done
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* with a short local call on x86. Nothing else will tell us what
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* address we are running at. The reserved chunk of the real-mode
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* data at 0x1e4 (defined as a scratch field) are used as the stack
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* for this calculation. Only 4 bytes are needed.
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*/
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leal (BP_scratch+4)(%esi), %esp
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call 1f
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1: popl %ebp
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subl $1b, %ebp
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/*
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* %ebp contains the address we are loaded at by the boot loader and %ebx
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* contains the address where we should move the kernel image temporarily
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* for safe in-place decompression.
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*/
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#ifdef CONFIG_RELOCATABLE
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movl %ebp, %ebx
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movl BP_kernel_alignment(%esi), %eax
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decl %eax
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addl %eax, %ebx
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notl %eax
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andl %eax, %ebx
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#else
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movl $LOAD_PHYSICAL_ADDR, %ebx
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#endif
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/* Target address to relocate to for decompression */
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addl $z_extract_offset, %ebx
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/* Set up the stack */
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leal boot_stack_end(%ebx), %esp
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/* Zero EFLAGS */
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pushl $0
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popfl
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/*
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* Copy the compressed kernel to the end of our buffer
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* where decompression in place becomes safe.
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*/
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pushl %esi
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leal (_bss-4)(%ebp), %esi
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leal (_bss-4)(%ebx), %edi
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movl $(_bss - startup_32), %ecx
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shrl $2, %ecx
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std
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rep movsl
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cld
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popl %esi
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/*
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* Jump to the relocated address.
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*/
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leal relocated(%ebx), %eax
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jmp *%eax
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ENDPROC(startup_32)
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.text
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relocated:
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/*
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* Clear BSS (stack is currently empty)
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*/
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xorl %eax, %eax
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leal _bss(%ebx), %edi
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leal _ebss(%ebx), %ecx
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subl %edi, %ecx
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shrl $2, %ecx
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rep stosl
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/*
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* Adjust our own GOT
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*/
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leal _got(%ebx), %edx
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leal _egot(%ebx), %ecx
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1:
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cmpl %ecx, %edx
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jae 2f
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addl %ebx, (%edx)
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addl $4, %edx
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jmp 1b
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2:
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/*
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* Do the decompression, and jump to the new kernel..
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*/
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/* push arguments for decompress_kernel: */
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pushl $z_output_len /* decompressed length */
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leal z_extract_offset_negative(%ebx), %ebp
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pushl %ebp /* output address */
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pushl $z_input_len /* input_len */
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leal input_data(%ebx), %eax
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pushl %eax /* input_data */
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leal boot_heap(%ebx), %eax
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pushl %eax /* heap area */
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pushl %esi /* real mode pointer */
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call decompress_kernel
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addl $24, %esp
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/*
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* Jump to the decompressed kernel.
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*/
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xorl %ebx, %ebx
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jmp *%ebp
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/*
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* Stack and heap for uncompression
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*/
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.bss
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.balign 4
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boot_heap:
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.fill BOOT_HEAP_SIZE, 1, 0
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boot_stack:
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.fill BOOT_STACK_SIZE, 1, 0
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boot_stack_end:
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