Re: [PATCH] s390/boot: block uncompressed vmlinux booting attempts

From: Guenter Roeck
Date: Mon Jun 25 2018 - 15:40:14 EST


On Mon, Jun 25, 2018 at 05:09:19PM +0200, Vasily Gorbik wrote:
> Since uncompressed kernel image "vmlinux" elf file is not bootable under
> qemu anymore, add a check which would report that.
>
> Qemu users are encouraged to use bzImage or
> arch/s390/boot/compressed/vmlinux instead.
>
> The check relies on s390 linux entry point ABI definition, which is only
> present in bzImage and arch/s390/boot/compressed/vmlinux.
>
> Signed-off-by: Vasily Gorbik <gor@xxxxxxxxxxxxx>

With qemu:

Tested-by: Guenter Roeck <linux@xxxxxxxxxxxx>

> ---
> arch/s390/boot/head.S | 4 ++--
> arch/s390/include/asm/setup.h | 3 ++-
> arch/s390/kernel/early.c | 12 ++++++++++++
> 3 files changed, 16 insertions(+), 3 deletions(-)
>
> diff --git a/arch/s390/boot/head.S b/arch/s390/boot/head.S
> index f09e792df495..f721913b73f1 100644
> --- a/arch/s390/boot/head.S
> +++ b/arch/s390/boot/head.S
> @@ -272,14 +272,14 @@ iplstart:
> .org 0x10000
> ENTRY(startup)
> j .Lep_startup_normal
> - .org 0x10008
> + .org EP_OFFSET
> #
> # This is a list of s390 kernel entry points. At address 0x1000f the number of
> # valid entry points is stored.
> #
> # IMPORTANT: Do not change this table, it is s390 kernel ABI!
> #
> - .ascii "S390EP"
> + .ascii EP_STRING
> .byte 0x00,0x01
> #
> # kdump startup-code at 0x10010, running in 64 bit absolute addressing mode
> diff --git a/arch/s390/include/asm/setup.h b/arch/s390/include/asm/setup.h
> index be02f0558048..1d66016f4170 100644
> --- a/arch/s390/include/asm/setup.h
> +++ b/arch/s390/include/asm/setup.h
> @@ -9,7 +9,8 @@
> #include <linux/const.h>
> #include <uapi/asm/setup.h>
>
> -
> +#define EP_OFFSET 0x10008
> +#define EP_STRING "S390EP"
> #define PARMAREA 0x10400
> #define PARMAREA_END 0x11000
>
> diff --git a/arch/s390/kernel/early.c b/arch/s390/kernel/early.c
> index 827699eb48fa..45c5be3d8777 100644
> --- a/arch/s390/kernel/early.c
> +++ b/arch/s390/kernel/early.c
> @@ -331,8 +331,20 @@ static void __init setup_boot_command_line(void)
> append_to_cmdline(append_ipl_scpdata);
> }
>
> +static void __init check_image_bootable(void)
> +{
> + if (!memcmp(EP_STRING, (void *)EP_OFFSET, strlen(EP_STRING)))
> + return;
> +
> + sclp_early_printk("The linux kernel boot failure: the image is corrupted or not bootable.\n");
> + sclp_early_printk("Please check that you are using bootable kernel image \"bzImage\".\n");
> + sclp_early_printk("(or alternatively \"arch/s390/boot/compressed/vmlinux\" image for qemu)\n");
> + disabled_wait(0xbadb007);
> +}
> +
> void __init startup_init(void)
> {
> + check_image_bootable();
> time_early_init();
> init_kernel_storage_key();
> lockdep_off();
> --
> ââââ 2.18.0.rc2.13.g4da9a5d
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>