From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Date: Tue, 5 Jul 2016 05:03:59 +0000 (+1000)
Subject: powerpc: Ensure that ppc_md is empty before probing for machine type
X-Git-Tag: v4.8-rc1~85^2~26
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=84b62c72faa197a5c9b75ee93527add31695fb32;p=karo-tx-linux.git

powerpc: Ensure that ppc_md is empty before probing for machine type

Anything in there will be overwritten, so it helps catching nasty
bugs if we check that it's indeed full of NULL's before we do so.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
---

diff --git a/arch/powerpc/kernel/setup-common.c b/arch/powerpc/kernel/setup-common.c
index 2a3564caafd3..b8ee1c867ee3 100644
--- a/arch/powerpc/kernel/setup-common.c
+++ b/arch/powerpc/kernel/setup-common.c
@@ -575,6 +575,7 @@ void probe_machine(void)
 {
 	extern struct machdep_calls __machine_desc_start;
 	extern struct machdep_calls __machine_desc_end;
+	unsigned int i;
 
 	/*
 	 * Iterate all ppc_md structures until we find the proper
@@ -582,6 +583,17 @@ void probe_machine(void)
 	 */
 	DBG("Probing machine type ...\n");
 
+	/*
+	 * Check ppc_md is empty, if not we have a bug, ie, we setup an
+	 * entry before probe_machine() which will be overwritten
+	 */
+	for (i = 0; i < (sizeof(ppc_md) / sizeof(void *)); i++) {
+		if (((void **)&ppc_md)[i]) {
+			printk(KERN_ERR "Entry %d in ppc_md non empty before"
+			       " machine probe !\n", i);
+		}
+	}
+
 	for (machine_id = &__machine_desc_start;
 	     machine_id < &__machine_desc_end;
 	     machine_id++) {