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

From: Vasily Gorbik
Date: Mon Jun 25 2018 - 11:09:35 EST


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>
---
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();
--
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