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x86/debug: Handle early WARN_ONs proper 

Hans managed to trigger a WARN very early in the boot which killed his
(Virtual) box.

The reason is that the recent rework of WARN() to use UD0 forgot to add the
fixup_bug() call to early_fixup_exception(). As a result the kernel does
not handle the WARN_ON injected UD0 exception and panics.

Add the missing fixup call, so early UD's injected by WARN() get handled.

Fixes: 9a93848fe7 ("x86/debug: Implement __WARN() using UD0")
Reported-and-tested-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Frank Mehnert <frank.mehnert@oracle.com>
Cc: Hans de Goede <hdegoede@redhat.com>
Cc: Michael Thayer <michael.thayer@oracle.com>
Link: http://lkml.kernel.org/r/20170612180108.w4vgu2ckucmllf3a@hirez.programming.kicks-ass.net
hifive-unleashed-5.1
Peter Zijlstra 2017-06-12 13:52:46 +02:00 committed by Thomas Gleixner
parent 32c1431eea
commit 8a524f803a
3 changed files with 5 additions and 1 deletions
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1
arch/x86/include/asm/extable.h
View File

@ -29,6 +29,7 @@ struct pt_regs;
} while (0)
extern int fixup_exception(struct pt_regs *regs, int trapnr);
extern int fixup_bug(struct pt_regs *regs, int trapnr);
extern bool ex_has_fault_handler(unsigned long ip);
extern void early_fixup_exception(struct pt_regs *regs, int trapnr);

2
arch/x86/kernel/traps.c
View File

@ -182,7 +182,7 @@ int is_valid_bugaddr(unsigned long addr)
return ud == INSN_UD0 || ud == INSN_UD2;
}
static int fixup_bug(struct pt_regs *regs, int trapnr)
int fixup_bug(struct pt_regs *regs, int trapnr)
{
if (trapnr != X86_TRAP_UD)
return 0;

3
arch/x86/mm/extable.c
View File

@ -162,6 +162,9 @@ void __init early_fixup_exception(struct pt_regs *regs, int trapnr)
if (fixup_exception(regs, trapnr))
return;
if (fixup_bug(regs, trapnr))
return;
fail:
early_printk("PANIC: early exception 0x%02x IP %lx:%lx error %lx cr2 0x%lx\n",
(unsigned)trapnr, (unsigned long)regs->cs, regs->ip,