From: Helge Deller <deller@gmx.de>
Date: Thu, 8 Jun 2017 20:06:54 +0000 (+0200)
Subject: parisc: Avoid zeroing gr[0] in fixup_exception()
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=b752c7b20709e0ecee0f7d4ef6ef82fcc27408b6;p=GitHub%2Fmoto-9609%2Fandroid_kernel_motorola_exynos9610.git

parisc: Avoid zeroing gr[0] in fixup_exception()

Register gr[0] holds the PSW in interrupt context. It's absolutely
unlikely that the compiler will use register zero in a get_user() call,
but better BUG on such a case in fixup_exception() anyway.

Signed-off-by: Helge Deller <deller@gmx.de>
---

diff --git a/arch/parisc/mm/fault.c b/arch/parisc/mm/fault.c
index fdc34cf4eb0e..41448f7b2b2a 100644
--- a/arch/parisc/mm/fault.c
+++ b/arch/parisc/mm/fault.c
@@ -154,6 +154,7 @@ int fixup_exception(struct pt_regs *regs)
 			/* zero target register for get_user() */
 			if (parisc_acctyp(0, regs->iir) == VM_READ) {
 				int treg = regs->iir & 0x1f;
+				BUG_ON(treg == 0);
 				regs->gr[treg] = 0;
 			}
 		}