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powerpc/64s: Disallow system reset vs system reset reentrancy

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In preparation for using a dedicated stack for system reset interrupts,
prevent a nested system reset from recovering, in order to simplify
code that is called in crash/debug path. This allows a system reset
interrupt to just use the base stack pointer.

Keep an in_nmi nesting counter similarly to the in_mce counter. Consider
the interrrupt non-recoverable if it is taken inside another system
reset.

Interrupt nesting could be allowed similarly to MCE, but system reset
is a special case that's not for normal operation, so simplicity wins
until there is requirement for nested system reset interrupts.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Nicholas Piggin
2016-12-20 04:30:05 +10:00
committed by Michael Ellerman
parent a3d96f70c1
commit c4f3b52ce7
6 changed files with 51 additions and 7 deletions
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8
arch/powerpc/kernel/traps.c
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@@ -282,11 +282,17 @@ void system_reset_exception(struct pt_regs *regs)
/* See if any machine dependent calls */
if (ppc_md.system_reset_exception) {
if (ppc_md.system_reset_exception(regs))
return;
goto out;
}
die("System Reset", regs, SIGABRT);
out:
#ifdef CONFIG_PPC_BOOK3S_64
BUG_ON(get_paca()->in_nmi == 0);
if (get_paca()->in_nmi > 1)
panic("Unrecoverable nested System Reset");
#endif
/* Must die if the interrupt is not recoverable */
if (!(regs->msr & MSR_RI))
panic("Unrecoverable System Reset");