Commit 575400d1 authored by H. Peter Anvin's avatar H. Peter Anvin Committed by Andi Kleen
Browse files

[PATCH] i386: Fix the EDD code misparsing the command line 



The EDD code would scan the command line as a fixed array, without
taking account of either whitespace, null-termination, the old
command-line protocol, late overrides early, or the fact that the
command line may not be reachable from INITSEG.

This should fix those problems, and enable us to use a longer command
line.

Signed-off-by: default avatarH. Peter Anvin <hpa@zytor.com>
Signed-off-by: default avatarAndi Kleen <ak@suse.de>
parent 53ee11ae

arch/i386/boot/edd.S

+75 −22
Original line number Diff line number Diff line
@@ -15,42 +15,95 @@ 
#include <asm/setup.h>



#if defined(CONFIG_EDD) || defined(CONFIG_EDD_MODULE)



# It is assumed that %ds == INITSEG here



	movb	$0, (EDD_MBR_SIG_NR_BUF)

	movb	$0, (EDDNR)



# Check the command line for two options:

# Check the command line for options:

# edd=of  disables EDD completely  (edd=off)

# edd=sk  skips the MBR test    (edd=skipmbr)

# edd=on  re-enables EDD (edd=on)



	pushl	%esi

    	cmpl	$0, %cs:cmd_line_ptr

	jz	done_cl

	movw	$edd_mbr_sig_start, %di	# Default to edd=on



	movl	%cs:(cmd_line_ptr), %esi

# ds:esi has the pointer to the command line now

	movl	$(COMMAND_LINE_SIZE-7), %ecx

# loop through kernel command line one byte at a time

cl_loop:

	cmpl	$EDD_CL_EQUALS, (%si)

	andl	%esi, %esi

	jz	old_cl			# Old boot protocol?



# Convert to a real-mode pointer in fs:si

	movl	%esi, %eax

	shrl	$4, %eax

	movw	%ax, %fs

	andw	$0xf, %si

	jmp	have_cl_pointer



# Old-style boot protocol?

old_cl:

	push	%ds			# aka INITSEG

	pop	%fs



	cmpw	$0xa33f, (0x20)

	jne	done_cl			# No command line at all?

	movw	(0x22), %si		# Pointer relative to INITSEG



# fs:si has the pointer to the command line now

have_cl_pointer:



# Loop through kernel command line one byte at a time.  Just in

# case the loader is buggy and failed to null-terminate the command line

# terminate if we get close enough to the end of the segment that we

# cannot fit "edd=XX"...

cl_atspace:

	cmpw	$-5, %si		# Watch for segment wraparound

	jae	done_cl

	movl	%fs:(%si), %eax

	andb	%al, %al		# End of line?

	jz	done_cl

	cmpl	$EDD_CL_EQUALS, %eax

	jz	found_edd_equals

	incl	%esi

	loop	cl_loop

	jmp	done_cl

	cmpb	$0x20, %al		# <= space consider whitespace

	ja	cl_skipword

	incw	%si

	jmp	cl_atspace



cl_skipword:

	cmpw	$-5, %si		# Watch for segment wraparound

	jae	done_cl

	movb	%fs:(%si), %al		# End of string?

	andb	%al, %al

	jz	done_cl

	cmpb	$0x20, %al

	jbe	cl_atspace

	incw	%si

	jmp	cl_skipword



found_edd_equals:

# only looking at first two characters after equals

    	addl	$4, %esi

	cmpw	$EDD_CL_OFF, (%si)	# edd=of

	jz	do_edd_off

	cmpw	$EDD_CL_SKIP, (%si)	# edd=sk

	jz	do_edd_skipmbr

	jmp	done_cl

# late overrides early on the command line, so keep going after finding something

	movw	%fs:4(%si), %ax

	cmpw	$EDD_CL_OFF, %ax	# edd=of

	je	do_edd_off

	cmpw	$EDD_CL_SKIP, %ax	# edd=sk

	je	do_edd_skipmbr

	cmpw	$EDD_CL_ON, %ax		# edd=on

	je	do_edd_on

	jmp	cl_skipword

do_edd_skipmbr:

    	popl	%esi

	jmp	edd_start

	movw	$edd_start, %di

	jmp	cl_skipword

do_edd_off:

	popl	%esi

	jmp	edd_done

	movw	$edd_done, %di

	jmp	cl_skipword

do_edd_on:

	movw	$edd_mbr_sig_start, %di

	jmp	cl_skipword



done_cl:

	popl	%esi



	jmpw	*%di



# Read the first sector of each BIOS disk device and store the 4-byte signature

edd_mbr_sig_start:

include/linux/edd.h

+1 −0
Original line number Diff line number Diff line
@@ -52,6 +52,7 @@ 
#define EDD_CL_EQUALS   0x3d646465     /* "edd=" */

#define EDD_CL_OFF      0x666f         /* "of" for off  */

#define EDD_CL_SKIP     0x6b73         /* "sk" for skipmbr */

#define EDD_CL_ON       0x6e6f	       /* "on" for on */



#ifndef __ASSEMBLY__

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