| /* SPDX-License-Identifier: GPL-2.0 */ |
| /* |
| * linux/boot/head.S |
| * |
| * Copyright (C) 1991, 1992, 1993 Linus Torvalds |
| */ |
| |
| /* |
| * head.S contains the 32-bit startup code. |
| * |
| * NOTE!!! Startup happens at absolute address 0x00001000, which is also where |
| * the page directory will exist. The startup code will be overwritten by |
| * the page directory. [According to comments etc elsewhere on a compressed |
| * kernel it will end up at 0x1000 + 1Mb I hope so as I assume this. - AC] |
| * |
| * Page 0 is deliberately kept safe, since System Management Mode code in |
| * laptops may need to access the BIOS data stored there. This is also |
| * useful for future device drivers that either access the BIOS via VM86 |
| * mode. |
| */ |
| |
| /* |
| * High loaded stuff by Hans Lermen & Werner Almesberger, Feb. 1996 |
| */ |
| .text |
| |
| #include <linux/init.h> |
| #include <linux/linkage.h> |
| #include <asm/segment.h> |
| #include <asm/page_types.h> |
| #include <asm/boot.h> |
| #include <asm/asm-offsets.h> |
| #include <asm/bootparam.h> |
| |
| /* |
| * The 32-bit x86 assembler in binutils 2.26 will generate R_386_GOT32X |
| * relocation to get the symbol address in PIC. When the compressed x86 |
| * kernel isn't built as PIC, the linker optimizes R_386_GOT32X |
| * relocations to their fixed symbol addresses. However, when the |
| * compressed x86 kernel is loaded at a different address, it leads |
| * to the following load failure: |
| * |
| * Failed to allocate space for phdrs |
| * |
| * during the decompression stage. |
| * |
| * If the compressed x86 kernel is relocatable at run-time, it should be |
| * compiled with -fPIE, instead of -fPIC, if possible and should be built as |
| * Position Independent Executable (PIE) so that linker won't optimize |
| * R_386_GOT32X relocation to its fixed symbol address. Older |
| * linkers generate R_386_32 relocations against locally defined symbols, |
| * _bss, _ebss, _got and _egot, in PIE. It isn't wrong, just less |
| * optimal than R_386_RELATIVE. But the x86 kernel fails to properly handle |
| * R_386_32 relocations when relocating the kernel. To generate |
| * R_386_RELATIVE relocations, we mark _bss, _ebss, _got and _egot as |
| * hidden: |
| */ |
| .hidden _bss |
| .hidden _ebss |
| .hidden _got |
| .hidden _egot |
| |
| __HEAD |
| ENTRY(startup_32) |
| cld |
| /* |
| * Test KEEP_SEGMENTS flag to see if the bootloader is asking |
| * us to not reload segments |
| */ |
| testb $KEEP_SEGMENTS, BP_loadflags(%esi) |
| jnz 1f |
| |
| cli |
| movl $__BOOT_DS, %eax |
| movl %eax, %ds |
| movl %eax, %es |
| movl %eax, %fs |
| movl %eax, %gs |
| movl %eax, %ss |
| 1: |
| |
| /* |
| * Calculate the delta between where we were compiled to run |
| * at and where we were actually loaded at. This can only be done |
| * with a short local call on x86. Nothing else will tell us what |
| * address we are running at. The reserved chunk of the real-mode |
| * data at 0x1e4 (defined as a scratch field) are used as the stack |
| * for this calculation. Only 4 bytes are needed. |
| */ |
| leal (BP_scratch+4)(%esi), %esp |
| call 1f |
| 1: popl %ebp |
| subl $1b, %ebp |
| |
| /* |
| * %ebp contains the address we are loaded at by the boot loader and %ebx |
| * contains the address where we should move the kernel image temporarily |
| * for safe in-place decompression. |
| */ |
| |
| #ifdef CONFIG_RELOCATABLE |
| movl %ebp, %ebx |
| movl BP_kernel_alignment(%esi), %eax |
| decl %eax |
| addl %eax, %ebx |
| notl %eax |
| andl %eax, %ebx |
| cmpl $LOAD_PHYSICAL_ADDR, %ebx |
| jge 1f |
| #endif |
| movl $LOAD_PHYSICAL_ADDR, %ebx |
| 1: |
| |
| /* Target address to relocate to for decompression */ |
| movl BP_init_size(%esi), %eax |
| subl $_end, %eax |
| addl %eax, %ebx |
| |
| /* Set up the stack */ |
| leal boot_stack_end(%ebx), %esp |
| |
| /* Zero EFLAGS */ |
| pushl $0 |
| popfl |
| |
| /* |
| * Copy the compressed kernel to the end of our buffer |
| * where decompression in place becomes safe. |
| */ |
| pushl %esi |
| leal (_bss-4)(%ebp), %esi |
| leal (_bss-4)(%ebx), %edi |
| movl $(_bss - startup_32), %ecx |
| shrl $2, %ecx |
| std |
| rep movsl |
| cld |
| popl %esi |
| |
| /* |
| * Jump to the relocated address. |
| */ |
| leal .Lrelocated(%ebx), %eax |
| jmp *%eax |
| ENDPROC(startup_32) |
| |
| #ifdef CONFIG_EFI_STUB |
| /* |
| * We don't need the return address, so set up the stack so efi_main() can find |
| * its arguments. |
| */ |
| ENTRY(efi_pe_entry) |
| add $0x4, %esp |
| |
| call 1f |
| 1: popl %esi |
| subl $1b, %esi |
| |
| popl %ecx |
| movl %ecx, efi32_config(%esi) /* Handle */ |
| popl %ecx |
| movl %ecx, efi32_config+8(%esi) /* EFI System table pointer */ |
| |
| /* Relocate efi_config->call() */ |
| leal efi32_config(%esi), %eax |
| add %esi, 40(%eax) |
| pushl %eax |
| |
| call make_boot_params |
| cmpl $0, %eax |
| je fail |
| movl %esi, BP_code32_start(%eax) |
| popl %ecx |
| pushl %eax |
| pushl %ecx |
| jmp 2f /* Skip efi_config initialization */ |
| ENDPROC(efi_pe_entry) |
| |
| ENTRY(efi32_stub_entry) |
| add $0x4, %esp |
| popl %ecx |
| popl %edx |
| |
| call 1f |
| 1: popl %esi |
| subl $1b, %esi |
| |
| movl %ecx, efi32_config(%esi) /* Handle */ |
| movl %edx, efi32_config+8(%esi) /* EFI System table pointer */ |
| |
| /* Relocate efi_config->call() */ |
| leal efi32_config(%esi), %eax |
| add %esi, 40(%eax) |
| pushl %eax |
| 2: |
| call efi_main |
| cmpl $0, %eax |
| movl %eax, %esi |
| jne 2f |
| fail: |
| /* EFI init failed, so hang. */ |
| hlt |
| jmp fail |
| 2: |
| movl BP_code32_start(%esi), %eax |
| leal startup_32(%eax), %eax |
| jmp *%eax |
| ENDPROC(efi32_stub_entry) |
| #endif |
| |
| .text |
| .Lrelocated: |
| |
| /* |
| * Clear BSS (stack is currently empty) |
| */ |
| xorl %eax, %eax |
| leal _bss(%ebx), %edi |
| leal _ebss(%ebx), %ecx |
| subl %edi, %ecx |
| shrl $2, %ecx |
| rep stosl |
| |
| /* |
| * Adjust our own GOT |
| */ |
| leal _got(%ebx), %edx |
| leal _egot(%ebx), %ecx |
| 1: |
| cmpl %ecx, %edx |
| jae 2f |
| addl %ebx, (%edx) |
| addl $4, %edx |
| jmp 1b |
| 2: |
| |
| /* |
| * Do the extraction, and jump to the new kernel.. |
| */ |
| /* push arguments for extract_kernel: */ |
| pushl $z_output_len /* decompressed length, end of relocs */ |
| |
| movl BP_init_size(%esi), %eax |
| subl $_end, %eax |
| movl %ebx, %ebp |
| subl %eax, %ebp |
| pushl %ebp /* output address */ |
| |
| pushl $z_input_len /* input_len */ |
| leal input_data(%ebx), %eax |
| pushl %eax /* input_data */ |
| leal boot_heap(%ebx), %eax |
| pushl %eax /* heap area */ |
| pushl %esi /* real mode pointer */ |
| call extract_kernel /* returns kernel location in %eax */ |
| addl $24, %esp |
| |
| /* |
| * Jump to the extracted kernel. |
| */ |
| xorl %ebx, %ebx |
| jmp *%eax |
| |
| #ifdef CONFIG_EFI_STUB |
| .data |
| efi32_config: |
| .fill 5,8,0 |
| .long efi_call_phys |
| .long 0 |
| .byte 0 |
| #endif |
| |
| /* |
| * Stack and heap for uncompression |
| */ |
| .bss |
| .balign 4 |
| boot_heap: |
| .fill BOOT_HEAP_SIZE, 1, 0 |
| boot_stack: |
| .fill BOOT_STACK_SIZE, 1, 0 |
| boot_stack_end: |
