From ace9429bb58fd418f0c81d4c2835699bddf6bde6 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Thu, 11 Apr 2024 10:27:49 +0200 Subject: Adding upstream version 6.6.15. Signed-off-by: Daniel Baumann --- arch/x86/boot/compressed/head_32.S | 188 +++++++++++++++++++++++++++++++++++++ 1 file changed, 188 insertions(+) create mode 100644 arch/x86/boot/compressed/head_32.S (limited to 'arch/x86/boot/compressed/head_32.S') diff --git a/arch/x86/boot/compressed/head_32.S b/arch/x86/boot/compressed/head_32.S new file mode 100644 index 0000000000..1cfe9802a4 --- /dev/null +++ b/arch/x86/boot/compressed/head_32.S @@ -0,0 +1,188 @@ +/* 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 +#include +#include +#include +#include +#include +#include + +/* + * These symbols needed to be marked as .hidden to prevent the BFD linker from + * generating R_386_32 (rather than R_386_RELATIVE) relocations for them when + * the 32-bit compressed kernel is linked as PIE. This is no longer necessary, + * but it doesn't hurt to keep them .hidden. + */ + .hidden _bss + .hidden _ebss + .hidden _end + + __HEAD +SYM_FUNC_START(startup_32) + cld + cli + +/* + * 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 %edx + addl $_GLOBAL_OFFSET_TABLE_+(.-1b), %edx + + /* Load new GDT */ + leal gdt@GOTOFF(%edx), %eax + movl %eax, 2(%eax) + lgdt (%eax) + + /* Load segment registers with our descriptors */ + movl $__BOOT_DS, %eax + movl %eax, %ds + movl %eax, %es + movl %eax, %fs + movl %eax, %gs + movl %eax, %ss + +/* + * %edx contains the address we are loaded at by the boot loader (plus the + * offset to the GOT). The below code calculates %ebx to be the address where + * we should move the kernel image temporarily for safe in-place decompression + * (again, plus the offset to the GOT). + * + * %ebp is calculated to be the address that the kernel will be decompressed to. + */ + +#ifdef CONFIG_RELOCATABLE + leal startup_32@GOTOFF(%edx), %ebx + movl BP_kernel_alignment(%esi), %eax + decl %eax + addl %eax, %ebx + notl %eax + andl %eax, %ebx + cmpl $LOAD_PHYSICAL_ADDR, %ebx + jae 1f +#endif + movl $LOAD_PHYSICAL_ADDR, %ebx +1: + + movl %ebx, %ebp // Save the output address for later + /* Target address to relocate to for decompression */ + addl BP_init_size(%esi), %ebx + subl $_end@GOTOFF, %ebx + + /* Set up the stack */ + leal boot_stack_end@GOTOFF(%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@GOTOFF-4)(%edx), %esi + leal (_bss@GOTOFF-4)(%ebx), %edi + movl $(_bss - startup_32), %ecx + shrl $2, %ecx + std + rep movsl + cld + popl %esi + + /* + * The GDT may get overwritten either during the copy we just did or + * during extract_kernel below. To avoid any issues, repoint the GDTR + * to the new copy of the GDT. + */ + leal gdt@GOTOFF(%ebx), %eax + movl %eax, 2(%eax) + lgdt (%eax) + +/* + * Jump to the relocated address. + */ + leal .Lrelocated@GOTOFF(%ebx), %eax + jmp *%eax +SYM_FUNC_END(startup_32) + + .text +SYM_FUNC_START_LOCAL_NOALIGN(.Lrelocated) + +/* + * Clear BSS (stack is currently empty) + */ + xorl %eax, %eax + leal _bss@GOTOFF(%ebx), %edi + leal _ebss@GOTOFF(%ebx), %ecx + subl %edi, %ecx + shrl $2, %ecx + rep stosl + +/* + * Do the extraction, and jump to the new kernel.. + */ + /* push arguments for extract_kernel: */ + + pushl %ebp /* output address */ + pushl %esi /* real mode pointer */ + call extract_kernel /* returns kernel entry point in %eax */ + addl $24, %esp + +/* + * Jump to the extracted kernel. + */ + xorl %ebx, %ebx + jmp *%eax +SYM_FUNC_END(.Lrelocated) + + .data + .balign 8 +SYM_DATA_START_LOCAL(gdt) + .word gdt_end - gdt - 1 + .long 0 + .word 0 + .quad 0x0000000000000000 /* Reserved */ + .quad 0x00cf9a000000ffff /* __KERNEL_CS */ + .quad 0x00cf92000000ffff /* __KERNEL_DS */ +SYM_DATA_END_LABEL(gdt, SYM_L_LOCAL, gdt_end) + +/* + * Stack and heap for uncompression + */ + .bss + .balign 4 +boot_stack: + .fill BOOT_STACK_SIZE, 1, 0 +boot_stack_end: -- cgit v1.2.3