aboutsummaryrefslogtreecommitdiff
path: root/arch/i386/boot/compressed/head_32.S
diff options
context:
space:
mode:
Diffstat (limited to 'arch/i386/boot/compressed/head_32.S')
-rw-r--r--arch/i386/boot/compressed/head_32.S180
1 files changed, 180 insertions, 0 deletions
diff --git a/arch/i386/boot/compressed/head_32.S b/arch/i386/boot/compressed/head_32.S
new file mode 100644
index 00000000000..f35ea223752
--- /dev/null
+++ b/arch/i386/boot/compressed/head_32.S
@@ -0,0 +1,180 @@
+/*
+ * 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/linkage.h>
+#include <asm/segment.h>
+#include <asm/page.h>
+#include <asm/boot.h>
+
+.section ".text.head","ax",@progbits
+ .globl startup_32
+
+startup_32:
+ cld
+ cli
+ movl $(__BOOT_DS),%eax
+ movl %eax,%ds
+ movl %eax,%es
+ movl %eax,%fs
+ movl %eax,%gs
+ movl %eax,%ss
+
+/* 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 (0x1e4+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
+ addl $(CONFIG_PHYSICAL_ALIGN - 1), %ebx
+ andl $(~(CONFIG_PHYSICAL_ALIGN - 1)), %ebx
+#else
+ movl $LOAD_PHYSICAL_ADDR, %ebx
+#endif
+
+ /* Replace the compressed data size with the uncompressed size */
+ subl input_len(%ebp), %ebx
+ movl output_len(%ebp), %eax
+ addl %eax, %ebx
+ /* Add 8 bytes for every 32K input block */
+ shrl $12, %eax
+ addl %eax, %ebx
+ /* Add 32K + 18 bytes of extra slack */
+ addl $(32768 + 18), %ebx
+ /* Align on a 4K boundary */
+ addl $4095, %ebx
+ andl $~4095, %ebx
+
+/* Copy the compressed kernel to the end of our buffer
+ * where decompression in place becomes safe.
+ */
+ pushl %esi
+ leal _end(%ebp), %esi
+ leal _end(%ebx), %edi
+ movl $(_end - startup_32), %ecx
+ std
+ rep
+ movsb
+ cld
+ popl %esi
+
+/* Compute the kernel start address.
+ */
+#ifdef CONFIG_RELOCATABLE
+ addl $(CONFIG_PHYSICAL_ALIGN - 1), %ebp
+ andl $(~(CONFIG_PHYSICAL_ALIGN - 1)), %ebp
+#else
+ movl $LOAD_PHYSICAL_ADDR, %ebp
+#endif
+
+/*
+ * Jump to the relocated address.
+ */
+ leal relocated(%ebx), %eax
+ jmp *%eax
+.section ".text"
+relocated:
+
+/*
+ * Clear BSS
+ */
+ xorl %eax,%eax
+ leal _edata(%ebx),%edi
+ leal _end(%ebx), %ecx
+ subl %edi,%ecx
+ cld
+ rep
+ stosb
+
+/*
+ * Setup the stack for the decompressor
+ */
+ leal stack_end(%ebx), %esp
+
+/*
+ * Do the decompression, and jump to the new kernel..
+ */
+ movl output_len(%ebx), %eax
+ pushl %eax
+ pushl %ebp # output address
+ movl input_len(%ebx), %eax
+ pushl %eax # input_len
+ leal input_data(%ebx), %eax
+ pushl %eax # input_data
+ leal _end(%ebx), %eax
+ pushl %eax # end of the image as third argument
+ pushl %esi # real mode pointer as second arg
+ call decompress_kernel
+ addl $20, %esp
+ popl %ecx
+
+#if CONFIG_RELOCATABLE
+/* Find the address of the relocations.
+ */
+ movl %ebp, %edi
+ addl %ecx, %edi
+
+/* Calculate the delta between where vmlinux was compiled to run
+ * and where it was actually loaded.
+ */
+ movl %ebp, %ebx
+ subl $LOAD_PHYSICAL_ADDR, %ebx
+ jz 2f /* Nothing to be done if loaded at compiled addr. */
+/*
+ * Process relocations.
+ */
+
+1: subl $4, %edi
+ movl 0(%edi), %ecx
+ testl %ecx, %ecx
+ jz 2f
+ addl %ebx, -__PAGE_OFFSET(%ebx, %ecx)
+ jmp 1b
+2:
+#endif
+
+/*
+ * Jump to the decompressed kernel.
+ */
+ xorl %ebx,%ebx
+ jmp *%ebp
+
+.bss
+.balign 4
+stack:
+ .fill 4096, 1, 0
+stack_end: