linux-kernel - [PATCH] mtd: rawnand: mxc: remove __init qualifier from mxcnd_probe

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Date:   Fri, 22 Jun 2018 16:50:25 +0200
From:   Martin Kaiser <martin@...ser.cx>
To:     Boris Brezillon <boris.brezillon@...tlin.com>,
        David Woodhouse <dwmw2@...radead.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Fabio Estevam <fabio.estevam@....com>,
        Miquel Raynal <miquel.raynal@...tlin.com>
Cc:     linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Martin Kaiser <martin@...ser.cx>
Subject: [PATCH] mtd: rawnand: mxc: remove __init qualifier from mxcnd_probe_dt

mxcnd_probe_dt is called from mxcnd_probe, which is not marked as __init.

Using the sysfs unbind, bind nodes, mxcnd_probe and mxcnd_probe_dt can
potentially be called at any time. After the __init functions are cleaned,
mxcnd_probe_dt is no longer available. Calling it anyway causes a crash.

Signed-off-by: Martin Kaiser <martin@...ser.cx>
---
I hope that my understanding is correct.

In practice, I could not get the kernel to crash, my compiler would
inline mxcnd_probe_dt into mxcnd_probe and ignore the __init.

If I marked mxcnd_probe_dt as noinline, I could trigger a crash as
follows

[root@...t ]# echo bb000000.nand > /sys/bus/platform/drivers/mxc_nand/unbind
[root@...t ]# echo bb000000.nand > /sys/bus/platform/drivers/mxc_nand/bind
Internal error: Oops - undefined instruction: 0 [#1] ARM
...

 drivers/mtd/nand/raw/mxc_nand.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/mtd/nand/raw/mxc_nand.c b/drivers/mtd/nand/raw/mxc_nand.c
index 26cef21..90cfb5e 100644
--- a/drivers/mtd/nand/raw/mxc_nand.c
+++ b/drivers/mtd/nand/raw/mxc_nand.c
@@ -1686,7 +1686,7 @@ static const struct of_device_id mxcnd_dt_ids[] = {
 };
 MODULE_DEVICE_TABLE(of, mxcnd_dt_ids);
 
-static int __init mxcnd_probe_dt(struct mxc_nand_host *host)
+static int mxcnd_probe_dt(struct mxc_nand_host *host)
 {
 	struct device_node *np = host->dev->of_node;
 	const struct of_device_id *of_id =
@@ -1700,7 +1700,7 @@ static int __init mxcnd_probe_dt(struct mxc_nand_host *host)
 	return 0;
 }
 #else
-static int __init mxcnd_probe_dt(struct mxc_nand_host *host)
+static int mxcnd_probe_dt(struct mxc_nand_host *host)
 {
 	return 1;
 }
-- 
2.1.4