284 lines
6.2 KiB
ArmAsm
284 lines
6.2 KiB
ArmAsm
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/* SPDX-License-Identifier: GPL-2.0 */
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/*
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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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#include <asm/bootparam.h>
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/*
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* The 32-bit x86 assembler in binutils 2.26 will generate R_386_GOT32X
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* relocation to get the symbol address in PIC. When the compressed x86
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* kernel isn't built as PIC, the linker optimizes R_386_GOT32X
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* relocations to their fixed symbol addresses. However, when the
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* compressed x86 kernel is loaded at a different address, it leads
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* to the following load failure:
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*
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* Failed to allocate space for phdrs
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*
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* during the decompression stage.
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*
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* If the compressed x86 kernel is relocatable at run-time, it should be
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* compiled with -fPIE, instead of -fPIC, if possible and should be built as
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* Position Independent Executable (PIE) so that linker won't optimize
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* R_386_GOT32X relocation to its fixed symbol address. Older
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* linkers generate R_386_32 relocations against locally defined symbols,
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* _bss, _ebss, _got, _egot and _end, in PIE. It isn't wrong, just less
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* optimal than R_386_RELATIVE. But the x86 kernel fails to properly handle
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* R_386_32 relocations when relocating the kernel. To generate
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* R_386_RELATIVE relocations, we mark _bss, _ebss, _got, _egot and _end as
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* hidden:
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*/
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.hidden _bss
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.hidden _ebss
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.hidden _got
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.hidden _egot
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.hidden _end
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__HEAD
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ENTRY(startup_32)
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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 $KEEP_SEGMENTS, 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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cmpl $LOAD_PHYSICAL_ADDR, %ebx
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jae 1f
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#endif
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movl $LOAD_PHYSICAL_ADDR, %ebx
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1:
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/* Target address to relocate to for decompression */
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movl BP_init_size(%esi), %eax
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subl $_end, %eax
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addl %eax, %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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#ifdef CONFIG_EFI_STUB
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/*
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* We don't need the return address, so set up the stack so efi_main() can find
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* 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 1f
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1: popl %esi
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subl $1b, %esi
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popl %ecx
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movl %ecx, efi32_config(%esi) /* Handle */
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popl %ecx
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movl %ecx, efi32_config+8(%esi) /* EFI System table pointer */
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/* Relocate efi_config->call() */
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leal efi32_config(%esi), %eax
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add %esi, 40(%eax)
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pushl %eax
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call make_boot_params
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cmpl $0, %eax
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je fail
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movl %esi, BP_code32_start(%eax)
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popl %ecx
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pushl %eax
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pushl %ecx
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jmp 2f /* Skip efi_config initialization */
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ENDPROC(efi_pe_entry)
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ENTRY(efi32_stub_entry)
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add $0x4, %esp
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popl %ecx
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popl %edx
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call 1f
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1: popl %esi
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subl $1b, %esi
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movl %ecx, efi32_config(%esi) /* Handle */
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movl %edx, efi32_config+8(%esi) /* EFI System table pointer */
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/* Relocate efi_config->call() */
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leal efi32_config(%esi), %eax
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add %esi, 40(%eax)
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pushl %eax
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2:
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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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fail:
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/* EFI init failed, so hang. */
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hlt
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jmp fail
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2:
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movl BP_code32_start(%esi), %eax
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leal startup_32(%eax), %eax
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jmp *%eax
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ENDPROC(efi32_stub_entry)
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#endif
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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 extraction, and jump to the new kernel..
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*/
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/* push arguments for extract_kernel: */
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pushl $z_output_len /* decompressed length, end of relocs */
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movl BP_init_size(%esi), %eax
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subl $_end, %eax
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movl %ebx, %ebp
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subl %eax, %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 extract_kernel /* returns kernel location in %eax */
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addl $24, %esp
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/*
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* Jump to the extracted kernel.
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*/
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xorl %ebx, %ebx
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jmp *%eax
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#ifdef CONFIG_EFI_STUB
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.data
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efi32_config:
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.fill 5,8,0
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.long efi_call_phys
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.long 0
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.byte 0
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#endif
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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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