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| author | Sascha Silbe <silbe@linux.vnet.ibm.com> | 2016-07-04 17:16:47 +0200 |
|---|---|---|
| committer | Martin Schwidefsky <schwidefsky@de.ibm.com> | 2016-08-08 15:41:31 +0200 |
| commit | bf47dc572aaf53c3f2311c71e03ec01be3131fd6 (patch) | |
| tree | 199076746e7013463f782b78dcfa1b86fb463986 | |
| parent | 29b4817d4018df78086157ea3a55c1d9424a7cfc (diff) | |
| download | linux-bf47dc572aaf53c3f2311c71e03ec01be3131fd6.tar.gz linux-bf47dc572aaf53c3f2311c71e03ec01be3131fd6.tar.bz2 linux-bf47dc572aaf53c3f2311c71e03ec01be3131fd6.zip | |
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: Sascha Silbe <silbe@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
| -rw-r--r-- | arch/s390/boot/compressed/head.S | 11 | ||||
| -rw-r--r-- | arch/s390/kernel/head.S | 4 |
2 files changed, 11 insertions, 4 deletions
diff --git a/arch/s390/boot/compressed/head.S b/arch/s390/boot/compressed/head.S index f86a4eef28a9..28c4f96a2d9c 100644 --- a/arch/s390/boot/compressed/head.S +++ b/arch/s390/boot/compressed/head.S @@ -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: diff --git a/arch/s390/kernel/head.S b/arch/s390/kernel/head.S index 56e4d8234ef2..4431905f8cfa 100644 --- a/arch/s390/kernel/head.S +++ b/arch/s390/kernel/head.S @@ -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: |