s390/decompressor: support uncompressed kernel

Implement uncompressed kernel support (when "None" is picked in kernel
compression mode list). In that case an actual decompression code is
skipped and control is passed from boot/head.S to startup_continue in
kernel/head64.S. To achieve that uncompressed kernel payload is
conditionally put at 0x100000 in bzImage.

In reality this is very close to classic uncompressed kernel "image",
but the decompressor has its own build and link process,
kernel/head64.S lives at 0x100000 rather than at 0x11000, and .bss
section is reused for both stages.

Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index baed397..3023fa0 100644 (file)
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -146,6 +146,7 @@ config S390
        select HAVE_KERNEL_LZ4
        select HAVE_KERNEL_LZMA
        select HAVE_KERNEL_LZO
+       select HAVE_KERNEL_UNCOMPRESSED
        select HAVE_KERNEL_XZ
        select HAVE_KPROBES
        select HAVE_KRETPROBES

diff --git a/arch/s390/boot/compressed/Makefile b/arch/s390/boot/compressed/Makefile
index 438e1a5..9d3bd7d 100644 (file)
--- a/arch/s390/boot/compressed/Makefile
+++ b/arch/s390/boot/compressed/Makefile
@@ -9,10 +9,10 @@ KCOV_INSTRUMENT := n
 GCOV_PROFILE := n
 UBSAN_SANITIZE := n
 
-obj-y  := head.o misc.o piggy.o
+obj-y  := $(if $(CONFIG_KERNEL_UNCOMPRESSED),,head.o misc.o) piggy.o
 targets        := vmlinux.lds vmlinux vmlinux.bin vmlinux.bin.gz vmlinux.bin.bz2
 targets += vmlinux.bin.xz vmlinux.bin.lzma vmlinux.bin.lzo vmlinux.bin.lz4
-targets += vmlinux.scr.lds sizes.h $(obj-y)
+targets += vmlinux.scr.lds $(obj-y) $(if $(CONFIG_KERNEL_UNCOMPRESSED),,sizes.h)
 
 KBUILD_AFLAGS := $(KBUILD_AFLAGS_DECOMPRESSOR)
 KBUILD_CFLAGS := $(KBUILD_CFLAGS_DECOMPRESSOR)

diff --git a/arch/s390/boot/compressed/vmlinux.lds.S b/arch/s390/boot/compressed/vmlinux.lds.S
index d43c2db..b8572a8 100644 (file)
--- a/arch/s390/boot/compressed/vmlinux.lds.S
+++ b/arch/s390/boot/compressed/vmlinux.lds.S
@@ -23,13 +23,10 @@ SECTIONS
                *(.text.*)
                _etext = . ;
        }
-       .rodata.compressed : {
-               *(.rodata.compressed)
-       }
        .rodata : {
                _rodata = . ;
                *(.rodata)       /* read-only data */
-               *(.rodata.*)
+               EXCLUDE_FILE (*piggy.o) *(.rodata.*)
                _erodata = . ;
        }
        .data : {
@@ -38,6 +35,13 @@ SECTIONS
                *(.data.*)
                _edata = . ;
        }
+       startup_continue = 0x100000;
+#ifdef CONFIG_KERNEL_UNCOMPRESSED
+       . = 0x100000;
+#endif
+       .rodata.compressed : {
+               *(.rodata.compressed)
+       }
        . = ALIGN(256);
        .bss : {
                _bss = . ;

diff --git a/arch/s390/boot/compressed/vmlinux.scr.lds.S b/arch/s390/boot/compressed/vmlinux.scr.lds.S
index 42a2425..ff01d18 100644 (file)
--- a/arch/s390/boot/compressed/vmlinux.scr.lds.S
+++ b/arch/s390/boot/compressed/vmlinux.scr.lds.S
@@ -2,10 +2,14 @@
 SECTIONS
 {
   .rodata.compressed : {
+#ifndef CONFIG_KERNEL_UNCOMPRESSED
        input_len = .;
        LONG(input_data_end - input_data) input_data = .;
+#endif
        *(.data)
+#ifndef CONFIG_KERNEL_UNCOMPRESSED
        output_len = . - 4;
        input_data_end = .;
+#endif
        }
 }

diff --git a/arch/s390/boot/head.S b/arch/s390/boot/head.S
index 8d98463..f09e792 100644 (file)
--- a/arch/s390/boot/head.S
+++ b/arch/s390/boot/head.S
@@ -310,7 +310,11 @@ ENTRY(startup_kdump)
        l       %r15,.Lstack-.LPG0(%r13)
        ahi     %r15,-STACK_FRAME_OVERHEAD
        brasl   %r14,verify_facilities
+#ifdef CONFIG_KERNEL_UNCOMPRESSED
+       jg      startup_continue
+#else
        jg      startup_decompressor
+#endif
 
 .Lstack:
        .long   0x8000 + (1<<(PAGE_SHIFT+THREAD_SIZE_ORDER))