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x86, boot: set up the decompression stack as early as possible

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Set up the decompression stack as soon as we know where it needs to
go.  That way we have a full-service stack as soon as possible, rather
than relying on the BP_scratch field.

Note that the stack does need to be empty during bss zeroing (or
else the stack needs to be moved out of the bss segment, which is also
an option.)

[ Impact: cleanup, minor paranoia ]

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
This commit is contained in:
H. Peter Anvin 2009-05-08 16:27:41 -07:00
parent 5b11f1cee5
commit 0a13773670
2 changed files with 12 additions and 14 deletions
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10
arch/x86/boot/compressed/head_32.S
View file

@ -88,6 +88,9 @@ ENTRY(startup_32)
addl $4095, %ebx
andl $~4095, %ebx
/* Set up the stack */
leal boot_stack_end(%ebx), %esp
/*
* Copy the compressed kernel to the end of our buffer
* where decompression in place becomes safe.
@ -122,7 +125,7 @@ ENDPROC(startup_32)
relocated:
/*
* Clear BSS
* Clear BSS (stack is currently empty)
*/
xorl %eax, %eax
leal _bss(%ebx), %edi
@ -131,11 +134,6 @@ relocated:
cld
rep stosb
/*
* Setup the stack for the decompressor
*/
leal boot_stack_end(%ebx), %esp
/*
* Do the decompression, and jump to the new kernel..
*/

16
arch/x86/boot/compressed/head_64.S
View file

@ -249,6 +249,13 @@ ENTRY(startup_64)
addq $(32768 + 18 + 4095), %rbx
andq $~4095, %rbx
/* Set up the stack */
leaq boot_stack_end(%rbx), %rsp
/* Zero EFLAGS */
pushq $0
popfq
/*
* Copy the compressed kernel to the end of our buffer
* where decompression in place becomes safe.
@ -273,7 +280,7 @@ ENTRY(startup_64)
relocated:
/*
* Clear BSS
* Clear BSS (stack is currently empty)
*/
xorq %rax, %rax
leaq _bss(%rbx), %rdi
@ -282,13 +289,6 @@ relocated:
cld
rep stosb
/* Setup the stack */
leaq boot_stack_end(%rip), %rsp
/* zero EFLAGS after setting rsp */
pushq $0
popfq
/*
* Do the decompression, and jump to the new kernel..
*/