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SubjectRe: [PATCH] s390: enable detection of kernel version from bzImage
Date
On Tue, 16 Jul 2019 00:12:19 +0200
Vasily Gorbik <gor@linux.ibm.com> wrote:

> Extend "parmarea" to include an offset of the version string, which is
> stored as 8-byte big endian value.
>
> To retrieve version string from bzImage reliably, one should check the
> presence of "S390EP" ascii string at 0x10008 (available since v3.2),
> then read the version string offset from 0x10428 (which has been 0
> since v3.2 up to now). The string is null terminated.
>
> Could be retrieved with the following "file" command magic (requires
> file v5.34):
> 8 string \x02\x00\x00\x18\x60\x00\x00\x50\x02\x00\x00\x68\x60\x00\x00\x50\x40\x40\x40\x40\x40\x40\x40\x40 Linux S390
> >0x10008 string S390EP
> >>0x10428 bequad >0
> >>>(0x10428.Q) string >\0 \b, version %s
>
> Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

This looks great! Much cleaner than the original approach.

Thank you,
Petr T

> ---
> arch/s390/boot/Makefile | 2 +-
> arch/s390/boot/head.S | 1 +
> arch/s390/boot/version.c | 6 ++++++
> arch/s390/include/asm/setup.h | 4 +++-
> 4 files changed, 11 insertions(+), 2 deletions(-)
> create mode 100644 arch/s390/boot/version.c
>
> diff --git a/arch/s390/boot/Makefile b/arch/s390/boot/Makefile
> index 7cba96e7587b..4cf0bddb7d92 100644
> --- a/arch/s390/boot/Makefile
> +++ b/arch/s390/boot/Makefile
> @@ -36,7 +36,7 @@ CFLAGS_sclp_early_core.o += -I$(srctree)/drivers/s390/char
>
> obj-y := head.o als.o startup.o mem_detect.o ipl_parm.o ipl_report.o
> obj-y += string.o ebcdic.o sclp_early_core.o mem.o ipl_vmparm.o cmdline.o
> -obj-y += ctype.o text_dma.o
> +obj-y += version.o ctype.o text_dma.o
> obj-$(CONFIG_PROTECTED_VIRTUALIZATION_GUEST) += uv.o
> obj-$(CONFIG_RELOCATABLE) += machine_kexec_reloc.o
> obj-$(CONFIG_RANDOMIZE_BASE) += kaslr.o
> diff --git a/arch/s390/boot/head.S b/arch/s390/boot/head.S
> index 028aab03a9e7..2087bed6e60f 100644
> --- a/arch/s390/boot/head.S
> +++ b/arch/s390/boot/head.S
> @@ -361,6 +361,7 @@ ENTRY(startup_kdump)
> .quad 0 # INITRD_SIZE
> .quad 0 # OLDMEM_BASE
> .quad 0 # OLDMEM_SIZE
> + .quad kernel_version # points to kernel version string
>
> .org COMMAND_LINE
> .byte "root=/dev/ram0 ro"
> diff --git a/arch/s390/boot/version.c b/arch/s390/boot/version.c
> new file mode 100644
> index 000000000000..ea5e49651931
> --- /dev/null
> +++ b/arch/s390/boot/version.c
> @@ -0,0 +1,6 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#include <generated/utsrelease.h>
> +#include <generated/compile.h>
> +
> +const char kernel_version[] = UTS_RELEASE
> + " (" LINUX_COMPILE_BY "@" LINUX_COMPILE_HOST ") " UTS_VERSION;
> diff --git a/arch/s390/include/asm/setup.h b/arch/s390/include/asm/setup.h
> index 925889d360c1..e5d28a475f76 100644
> --- a/arch/s390/include/asm/setup.h
> +++ b/arch/s390/include/asm/setup.h
> @@ -54,6 +54,7 @@
> #define INITRD_SIZE_OFFSET 0x10410
> #define OLDMEM_BASE_OFFSET 0x10418
> #define OLDMEM_SIZE_OFFSET 0x10420
> +#define KERNEL_VERSION_OFFSET 0x10428
> #define COMMAND_LINE_OFFSET 0x10480
>
> #ifndef __ASSEMBLY__
> @@ -74,7 +75,8 @@ struct parmarea {
> unsigned long initrd_size; /* 0x10410 */
> unsigned long oldmem_base; /* 0x10418 */
> unsigned long oldmem_size; /* 0x10420 */
> - char pad1[0x10480 - 0x10428]; /* 0x10428 - 0x10480 */
> + unsigned long kernel_version; /* 0x10428 */
> + char pad1[0x10480 - 0x10430]; /* 0x10430 - 0x10480 */
> char command_line[ARCH_COMMAND_LINE_SIZE]; /* 0x10480 */
> };
>

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