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authorThomas Gleixner <tglx@linutronix.de>2017-10-16 12:12:16 +0200
committerThomas Gleixner <tglx@linutronix.de>2017-10-16 20:47:37 +0200
commit9c48c0965b97e14ddcf75490a754e84e05aaa062 (patch)
tree1a24a02d690d967b29fbd65a21211fd4c4d8d6ab /arch
parente6fc454b7794fc45c27364c7896b8f03094635ee (diff)
x86/idt: Initialize early IDT before cr4_init_shadow()
Moving the early IDT setup out of assembly code breaks the boot on first generation 486 systems. The reason is that the call of idt_setup_early_handler, which sets up the early handlers was added after the call to cr4_init_shadow(). cr4_init_shadow() tries to read CR4 which is not available on those systems. The accessor function uses a extable fixup to handle the resulting fault. As the IDT is not set up yet, the cr4 read exception causes an instantaneous reboot for obvious reasons. Call idt_setup_early_handler() before cr4_init_shadow() so IDT is set up before the first exception hits. Fixes: 87e81786b13b ("x86/idt: Move early IDT setup out of 32-bit asm") Reported-and-tested-by: Matthew Whitehead <whiteheadm@acm.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Andy Lutomirski <luto@kernel.org> Link: https://lkml.kernel.org/r/alpine.DEB.2.20.1710161210290.1973@nanos
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/kernel/head32.c5
1 files changed, 3 insertions, 2 deletions
diff --git a/arch/x86/kernel/head32.c b/arch/x86/kernel/head32.c
index cf2ce063f65a..2902ca4d5993 100644
--- a/arch/x86/kernel/head32.c
+++ b/arch/x86/kernel/head32.c
@@ -30,10 +30,11 @@ static void __init i386_default_early_setup(void)
asmlinkage __visible void __init i386_start_kernel(void)
{
- cr4_init_shadow();
-
+ /* Make sure IDT is set up before any exception happens */
idt_setup_early_handler();
+ cr4_init_shadow();
+
sanitize_boot_params(&boot_params);
x86_early_init_platform_quirks();