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authorLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 15:20:36 -0700
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 15:20:36 -0700
commit1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch)
tree0bba044c4ce775e45a88a51686b5d9f90697ea9d /arch/i386/boot/compressed/head.S
downloadconfigs-1da177e4c3f41524e886b7f1b8a0c1fc7321cac2.tar.gz
Linux-2.6.12-rc2v2.6.12-rc2
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
Diffstat (limited to 'arch/i386/boot/compressed/head.S')
-rw-r--r--arch/i386/boot/compressed/head.S128
1 files changed, 128 insertions, 0 deletions
diff --git a/arch/i386/boot/compressed/head.S b/arch/i386/boot/compressed/head.S
new file mode 100644
index 00000000000..c5e80b69e7d
--- /dev/null
+++ b/arch/i386/boot/compressed/head.S
@@ -0,0 +1,128 @@
+/*
+ * 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>
+
+ .globl startup_32
+
+startup_32:
+ cld
+ cli
+ movl $(__BOOT_DS),%eax
+ movl %eax,%ds
+ movl %eax,%es
+ movl %eax,%fs
+ movl %eax,%gs
+
+ lss stack_start,%esp
+ xorl %eax,%eax
+1: incl %eax # check that A20 really IS enabled
+ movl %eax,0x000000 # loop forever if it isn't
+ cmpl %eax,0x100000
+ je 1b
+
+/*
+ * Initialize eflags. Some BIOS's leave bits like NT set. This would
+ * confuse the debugger if this code is traced.
+ * XXX - best to initialize before switching to protected mode.
+ */
+ pushl $0
+ popfl
+/*
+ * Clear BSS
+ */
+ xorl %eax,%eax
+ movl $_edata,%edi
+ movl $_end,%ecx
+ subl %edi,%ecx
+ cld
+ rep
+ stosb
+/*
+ * Do the decompression, and jump to the new kernel..
+ */
+ subl $16,%esp # place for structure on the stack
+ movl %esp,%eax
+ pushl %esi # real mode pointer as second arg
+ pushl %eax # address of structure as first arg
+ call decompress_kernel
+ orl %eax,%eax
+ jnz 3f
+ popl %esi # discard address
+ popl %esi # real mode pointer
+ xorl %ebx,%ebx
+ ljmp $(__BOOT_CS), $0x100000
+
+/*
+ * We come here, if we were loaded high.
+ * We need to move the move-in-place routine down to 0x1000
+ * and then start it with the buffer addresses in registers,
+ * which we got from the stack.
+ */
+3:
+ movl $move_routine_start,%esi
+ movl $0x1000,%edi
+ movl $move_routine_end,%ecx
+ subl %esi,%ecx
+ addl $3,%ecx
+ shrl $2,%ecx
+ cld
+ rep
+ movsl
+
+ popl %esi # discard the address
+ popl %ebx # real mode pointer
+ popl %esi # low_buffer_start
+ popl %ecx # lcount
+ popl %edx # high_buffer_start
+ popl %eax # hcount
+ movl $0x100000,%edi
+ cli # make sure we don't get interrupted
+ ljmp $(__BOOT_CS), $0x1000 # and jump to the move routine
+
+/*
+ * Routine (template) for moving the decompressed kernel in place,
+ * if we were high loaded. This _must_ PIC-code !
+ */
+move_routine_start:
+ movl %ecx,%ebp
+ shrl $2,%ecx
+ rep
+ movsl
+ movl %ebp,%ecx
+ andl $3,%ecx
+ rep
+ movsb
+ movl %edx,%esi
+ movl %eax,%ecx # NOTE: rep movsb won't move if %ecx == 0
+ addl $3,%ecx
+ shrl $2,%ecx
+ rep
+ movsl
+ movl %ebx,%esi # Restore setup pointer
+ xorl %ebx,%ebx
+ ljmp $(__BOOT_CS), $0x100000
+move_routine_end: