linux-kernel - Re: [PATCH v2] qla2xxx: silence two GCC warnings

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Date:	Thu, 4 Oct 2012 12:42:42 -0500
From:	Saurav Kashyap <saurav.kashyap@...gic.com>
To:	Paul Bolle <pebolle@...cali.nl>,
	Andrew Vasquez <andrew.vasquez@...gic.com>,
	Dept-Eng Linux Driver <Linux-Driver@...gic.com>,
	"James E.J. Bottomley" <JBottomley@...allels.com>,
	Rolf Eike Beer <eike-kernel@...tec.de>
CC:	"linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] qla2xxx: silence two GCC warnings





>Compiling qla_gs.o (part of the qla2xxx module) triggers two GCC
>warnings:
>    drivers/scsi/qla2xxx/qla_gs.c: In function Œqla2x00_fdmi_rhba¹:
>    drivers/scsi/qla2xxx/qla_gs.c:1339:7: warning: array subscript is
>above array bounds [-Warray-bounds]
>    drivers/scsi/qla2xxx/qla_gs.c: In function Œqla2x00_fdmi_register¹:
>    drivers/scsi/qla2xxx/qla_gs.c:1663:15: warning: array subscript is
>above array bounds [-Warray-bounds]
>
>It seems that the sequence of a strcpy followed by a strlen confuses GCC
>when it is keeping track of array bounds here. (It is not clear to me
>which array triggers this warning and by how much GCC thinks the
>subscript is above its bounds. Neither is it clear to me why comparable
>code in these two functions doesn't trigger this warning.)
>
>An easy way to silence these warnings is to use preprocessor macros
>here, as that apparently gives GCC enough information to keep track of
>array bounds.
>
>Signed-off-by: Paul Bolle <pebolle@...cali.nl>
>---
>0) Rolf suggested to not use magic constants, to make sure things keep
>working when these strings change in the future. A trivial solution is
>to use preprocessor macros. I needed to add one for the manufacturer
>string.
>
>1) Still only compile tested.
>
> drivers/scsi/qla2xxx/qla_def.h | 1 +
> drivers/scsi/qla2xxx/qla_gs.c  | 6 +++---
> 2 files changed, 4 insertions(+), 3 deletions(-)
>
>diff --git a/drivers/scsi/qla2xxx/qla_def.h
>b/drivers/scsi/qla2xxx/qla_def.h
>index 39007f5..8895038 100644
>--- a/drivers/scsi/qla2xxx/qla_def.h
>+++ b/drivers/scsi/qla2xxx/qla_def.h
>@@ -37,6 +37,7 @@
> #include "qla_nx.h"
> #define QLA2XXX_DRIVER_NAME   "qla2xxx"
> #define QLA2XXX_APIDEV                "ql2xapidev"
>+#define QLA2XXX_MANUFACTURER  "QLogic Corporation"
>
> /*
>  * We have MAILBOX_REGISTER_COUNT sized arrays in a few places,
>diff --git a/drivers/scsi/qla2xxx/qla_gs.c b/drivers/scsi/qla2xxx/qla_gs.c
>index 05260d2..1714035 100644
>--- a/drivers/scsi/qla2xxx/qla_gs.c
>+++ b/drivers/scsi/qla2xxx/qla_gs.c
>@@ -1325,8 +1325,8 @@ qla2x00_fdmi_rhba(scsi_qla_host_t *vha)
>       /* Manufacturer. */
>       eiter = (struct ct_fdmi_hba_attr *) (entries + size);
>       eiter->type = __constant_cpu_to_be16(FDMI_HBA_MANUFACTURER);
>-      strcpy(eiter->a.manufacturer, "QLogic Corporation");
>-      alen = strlen(eiter->a.manufacturer);
>+      strcpy(eiter->a.manufacturer, QLA2XXX_MANUFACTURER);
>+      alen = strlen(QLA2XXX_MANUFACTURER);

Hi Paul,
It looks fine except one small thing. Instead of strcpy, strncpy will be
better option something like this

+       alen = strlen(QLA2XXX_MANUFACTURER);
+       strncpy(eiter->a.manufacturer, QLA2XXX_MANUFACTURER, alen);

Thanks,
~Saurav


>       alen += (alen & 3) ? (4 - (alen & 3)) : 4;
>       eiter->len = cpu_to_be16(4 + alen);
>       size += 4 + alen;
>@@ -1647,7 +1647,7 @@ qla2x00_fdmi_rpa(scsi_qla_host_t *vha)
>       eiter = (struct ct_fdmi_port_attr *) (entries + size);
>       eiter->type = __constant_cpu_to_be16(FDMI_PORT_OS_DEVICE_NAME);
>       strcpy(eiter->a.os_dev_name, QLA2XXX_DRIVER_NAME);
>-      alen = strlen(eiter->a.os_dev_name);
>+      alen = strlen(QLA2XXX_DRIVER_NAME);
>       alen += (alen & 3) ? (4 - (alen & 3)) : 4;
>       eiter->len = cpu_to_be16(4 + alen);
>       size += 4 + alen;
>--
>1.7.11.4
>
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