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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-07 18:49:45 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-07 18:49:45 +0000
commit2c3c1048746a4622d8c89a29670120dc8fab93c4 (patch)
tree848558de17fb3008cdf4d861b01ac7781903ce39 /arch/x86/boot/compressed/head_32.S
parentInitial commit. (diff)
downloadlinux-2c3c1048746a4622d8c89a29670120dc8fab93c4.tar.xz
linux-2c3c1048746a4622d8c89a29670120dc8fab93c4.zip
Adding upstream version 6.1.76.upstream/6.1.76
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'arch/x86/boot/compressed/head_32.S')
-rw-r--r--arch/x86/boot/compressed/head_32.S224
1 files changed, 224 insertions, 0 deletions
diff --git a/arch/x86/boot/compressed/head_32.S b/arch/x86/boot/compressed/head_32.S
new file mode 100644
index 000000000..3b354eb95
--- /dev/null
+++ b/arch/x86/boot/compressed/head_32.S
@@ -0,0 +1,224 @@
+/* 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>
+
+/*
+ * 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
+
+#ifdef CONFIG_EFI_STUB
+/*
+ * If we were loaded via the EFI LoadImage service, startup_32() will be at an
+ * offset to the start of the space allocated for the image. efi_pe_entry() will
+ * set up image_offset to tell us where the image actually starts, so that we
+ * can use the full available buffer.
+ * image_offset = startup_32 - image_base
+ * Otherwise image_offset will be zero and has no effect on the calculations.
+ */
+ subl image_offset@GOTOFF(%edx), %ebx
+#endif
+
+ 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)
+
+#ifdef CONFIG_EFI_STUB
+SYM_FUNC_START(efi32_stub_entry)
+ add $0x4, %esp
+ movl 8(%esp), %esi /* save boot_params pointer */
+ call efi_main
+ /* efi_main returns the possibly relocated address of startup_32 */
+ jmp *%eax
+SYM_FUNC_END(efi32_stub_entry)
+SYM_FUNC_ALIAS(efi_stub_entry, efi32_stub_entry)
+#endif
+
+ .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 output_len@GOTOFF(%ebx) /* decompressed length, end of relocs */
+ pushl %ebp /* output address */
+ pushl input_len@GOTOFF(%ebx) /* input_len */
+ leal input_data@GOTOFF(%ebx), %eax
+ pushl %eax /* input_data */
+ leal boot_heap@GOTOFF(%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
+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)
+
+#ifdef CONFIG_EFI_STUB
+SYM_DATA(image_offset, .long 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: