423e4d198a
In a previous patch, we have eliminated GOT entries from the decompressor binary and added an assertion that the .got section is empty. This means that the GOT fixup routines that exist in both the 32-bit and 64-bit startup routines have become dead code, and can be removed. While at it, drop the KEEP() from the linker script, as it has no effect on the contents of output sections that are created by the linker itself. Signed-off-by: Ard Biesheuvel <ardb@kernel.org> Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu> Signed-off-by: Kees Cook <keescook@chromium.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Tested-by: Nick Desaulniers <ndesaulniers@google.com> Tested-by: Sedat Dilek <sedat.dilek@gmail.com> Reviewed-by: Kees Cook <keescook@chromium.org> Acked-by: Arvind Sankar <nivedita@alum.mit.edu> Link: https://lore.kernel.org/r/20200731230820.1742553-4-keescook@chromium.org
241 lines
6.1 KiB
ArmAsm
241 lines
6.1 KiB
ArmAsm
/* 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 and _end, in PIE. It isn't wrong, just less optimal than
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* R_386_RELATIVE. But the x86 kernel fails to properly handle R_386_32
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* relocations when relocating the kernel. To generate R_386_RELATIVE
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* relocations, we mark _bss, _ebss and _end as hidden:
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*/
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.hidden _bss
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.hidden _ebss
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.hidden _end
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__HEAD
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SYM_FUNC_START(startup_32)
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cld
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cli
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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 %edx
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subl $1b, %edx
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/* Load new GDT */
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leal gdt(%edx), %eax
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movl %eax, 2(%eax)
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lgdt (%eax)
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/* Load segment registers with our descriptors */
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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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/*
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* %edx 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. %ebp contains the address that the kernel
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* will be decompressed to.
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*/
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#ifdef CONFIG_RELOCATABLE
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movl %edx, %ebx
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#ifdef CONFIG_EFI_STUB
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/*
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* If we were loaded via the EFI LoadImage service, startup_32() will be at an
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* offset to the start of the space allocated for the image. efi_pe_entry() will
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* set up image_offset to tell us where the image actually starts, so that we
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* can use the full available buffer.
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* image_offset = startup_32 - image_base
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* Otherwise image_offset will be zero and has no effect on the calculations.
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*/
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subl image_offset(%edx), %ebx
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#endif
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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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movl %ebx, %ebp // Save the output address for later
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/* Target address to relocate to for decompression */
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addl BP_init_size(%esi), %ebx
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subl $_end, %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)(%edx), %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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* The GDT may get overwritten either during the copy we just did or
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* during extract_kernel below. To avoid any issues, repoint the GDTR
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* to the new copy of the GDT.
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*/
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leal gdt(%ebx), %eax
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movl %eax, 2(%eax)
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lgdt (%eax)
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/*
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* Jump to the relocated address.
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*/
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leal .Lrelocated(%ebx), %eax
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jmp *%eax
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SYM_FUNC_END(startup_32)
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#ifdef CONFIG_EFI_STUB
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SYM_FUNC_START(efi32_stub_entry)
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SYM_FUNC_START_ALIAS(efi_stub_entry)
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add $0x4, %esp
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movl 8(%esp), %esi /* save boot_params pointer */
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call efi_main
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leal startup_32(%eax), %eax
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jmp *%eax
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SYM_FUNC_END(efi32_stub_entry)
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SYM_FUNC_END_ALIAS(efi_stub_entry)
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#endif
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.text
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SYM_FUNC_START_LOCAL_NOALIGN(.Lrelocated)
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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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* 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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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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SYM_FUNC_END(.Lrelocated)
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.data
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.balign 8
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SYM_DATA_START_LOCAL(gdt)
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.word gdt_end - gdt - 1
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.long 0
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.word 0
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.quad 0x0000000000000000 /* Reserved */
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.quad 0x00cf9a000000ffff /* __KERNEL_CS */
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.quad 0x00cf92000000ffff /* __KERNEL_DS */
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SYM_DATA_END_LABEL(gdt, SYM_L_LOCAL, gdt_end)
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#ifdef CONFIG_EFI_STUB
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SYM_DATA(image_offset, .long 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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