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Commit bf47dc57 authored by Sascha Silbe's avatar Sascha Silbe Committed by Martin Schwidefsky
Browse files

s390: clarify compressed image code path 



The way the decompressor is hooked into the start-up code is rather
subtle, with a mix of multiply-defined symbols and hardcoded address
literals. Add some comments at the junction points to clarify how it
works.

Signed-off-by: default avatarSascha Silbe <silbe@linux.vnet.ibm.com>
Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
parent 29b4817d

arch/s390/boot/compressed/head.S

+8 −3
Original line number Diff line number Diff line
@@ -21,16 +21,21 @@ ENTRY(startup_continue) 
	lg	%r15,.Lstack-.LPG1(%r13)

	aghi	%r15,-160

	brasl	%r14,decompress_kernel

	# setup registers for memory mover & branch to target

	# Set up registers for memory mover. We move the decompressed image to

	# 0x11000, starting at offset 0x11000 in the decompressed image so

	# that code living at 0x11000 in the image will end up at 0x11000 in

	# memory.

	lgr	%r4,%r2

	lg	%r2,.Loffset-.LPG1(%r13)

	la	%r4,0(%r2,%r4)

	lg	%r3,.Lmvsize-.LPG1(%r13)

	lgr	%r5,%r3

	# move the memory mover someplace safe

	# Move the memory mover someplace safe so it doesn't overwrite itself.

	la	%r1,0x200

	mvc	0(mover_end-mover,%r1),mover-.LPG1(%r13)

	# decompress image is started at 0x11000

	# When the memory mover is done we pass control to

	# arch/s390/kernel/head64.S:startup_continue which lives at 0x11000 in

	# the decompressed image.

	lgr	%r6,%r2

	br	%r1

mover:

arch/s390/kernel/head.S

+3 −1
Original line number Diff line number Diff line
@@ -309,7 +309,9 @@ ENTRY(startup_kdump) 
	l	%r15,.Lstack-.LPG0(%r13)

	ahi	%r15,-STACK_FRAME_OVERHEAD

	brasl	%r14,verify_facilities

	/* Continue with startup code in head64.S */

# For uncompressed images, continue in

# arch/s390/kernel/head64.S. For compressed images, continue in

# arch/s390/boot/compressed/head.S.

	jg	startup_continue



.Lstack: