[PATCH] caif: reduce stack size with KASAN

From: Arnd Bergmann
Date: Tue Jan 16 2018 - 11:34:35 EST

When CONFIG_KASAN is set, we can use relatively large amounts of kernel
stack space:

net/caif/cfctrl.c:555:1: warning: the frame size of 1600 bytes is larger than 1280 bytes [-Wframe-larger-than=]

This adds convenience wrappers around cfpkt_extr_head(), which is responsible
for most of the stack growth. With those wrapper functions, gcc apparently
starts reusing the stack slots for each instance, thus avoiding the
problem.

Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
---
I sent this in December, but apparently got the wrong Cc list.
It also seems that Dmitry Tarnyagin's email address as listed
in the MAINTAINERS file is invalid.

Resending now.
---
include/net/caif/cfpkt.h | 27 ++++++++++++++++++++++++++
net/caif/cfctrl.c | 50 +++++++++++++++++++++---------------------------
2 files changed, 49 insertions(+), 28 deletions(-)

diff --git a/include/net/caif/cfpkt.h b/include/net/caif/cfpkt.h
index fe328c52c46b..801489bb14c3 100644
--- a/include/net/caif/cfpkt.h
+++ b/include/net/caif/cfpkt.h
@@ -32,6 +32,33 @@ void cfpkt_destroy(struct cfpkt *pkt);
*/
int cfpkt_extr_head(struct cfpkt *pkt, void *data, u16 len);

+static inline u8 cfpkt_extr_head_u8(struct cfpkt *pkt)
+{
+ u8 tmp;
+
+ cfpkt_extr_head(pkt, &tmp, 1);
+
+ return tmp;
+}
+
+static inline u16 cfpkt_extr_head_u16(struct cfpkt *pkt)
+{
+ __le16 tmp;
+
+ cfpkt_extr_head(pkt, &tmp, 2);
+
+ return le16_to_cpu(tmp);
+}
+
+static inline u32 cfpkt_extr_head_u32(struct cfpkt *pkt)
+{
+ __le32 tmp;
+
+ cfpkt_extr_head(pkt, &tmp, 4);
+
+ return le32_to_cpu(tmp);
+}
+
/*
* Peek header from packet.
* Reads data from packet without changing packet.
diff --git a/net/caif/cfctrl.c b/net/caif/cfctrl.c
index 655ed7032150..a1e85f032108 100644
--- a/net/caif/cfctrl.c
+++ b/net/caif/cfctrl.c
@@ -352,15 +352,14 @@ static int cfctrl_recv(struct cflayer *layer, struct cfpkt *pkt)
u8 cmdrsp;
u8 cmd;
int ret = -1;
- u16 tmp16;
u8 len;
u8 param[255];
- u8 linkid;
+ u8 linkid = 0;
struct cfctrl *cfctrl = container_obj(layer);
struct cfctrl_request_info rsp, *req;


- cfpkt_extr_head(pkt, &cmdrsp, 1);
+ cmdrsp = cfpkt_extr_head_u8(pkt);
cmd = cmdrsp & CFCTRL_CMD_MASK;
if (cmd != CFCTRL_CMD_LINK_ERR
&& CFCTRL_RSP_BIT != (CFCTRL_RSP_BIT & cmdrsp)
@@ -378,13 +377,12 @@ static int cfctrl_recv(struct cflayer *layer, struct cfpkt *pkt)
u8 physlinkid;
u8 prio;
u8 tmp;
- u32 tmp32;
u8 *cp;
int i;
struct cfctrl_link_param linkparam;
memset(&linkparam, 0, sizeof(linkparam));

- cfpkt_extr_head(pkt, &tmp, 1);
+ tmp = cfpkt_extr_head_u8(pkt);

serv = tmp & CFCTRL_SRV_MASK;
linkparam.linktype = serv;
@@ -392,13 +390,13 @@ static int cfctrl_recv(struct cflayer *layer, struct cfpkt *pkt)
servtype = tmp >> 4;
linkparam.chtype = servtype;

- cfpkt_extr_head(pkt, &tmp, 1);
+ tmp = cfpkt_extr_head_u8(pkt);
physlinkid = tmp & 0x07;
prio = tmp >> 3;

linkparam.priority = prio;
linkparam.phyid = physlinkid;
- cfpkt_extr_head(pkt, &endpoint, 1);
+ endpoint = cfpkt_extr_head_u8(pkt);
linkparam.endpoint = endpoint & 0x03;

switch (serv) {
@@ -407,45 +405,43 @@ static int cfctrl_recv(struct cflayer *layer, struct cfpkt *pkt)
if (CFCTRL_ERR_BIT & cmdrsp)
break;
/* Link ID */
- cfpkt_extr_head(pkt, &linkid, 1);
+ linkid = cfpkt_extr_head_u8(pkt);
break;
case CFCTRL_SRV_VIDEO:
- cfpkt_extr_head(pkt, &tmp, 1);
+ tmp = cfpkt_extr_head_u8(pkt);
linkparam.u.video.connid = tmp;
if (CFCTRL_ERR_BIT & cmdrsp)
break;
/* Link ID */
- cfpkt_extr_head(pkt, &linkid, 1);
+ linkid = cfpkt_extr_head_u8(pkt);
break;

case CFCTRL_SRV_DATAGRAM:
- cfpkt_extr_head(pkt, &tmp32, 4);
linkparam.u.datagram.connid =
- le32_to_cpu(tmp32);
+ cfpkt_extr_head_u32(pkt);
if (CFCTRL_ERR_BIT & cmdrsp)
break;
/* Link ID */
- cfpkt_extr_head(pkt, &linkid, 1);
+ linkid = cfpkt_extr_head_u8(pkt);
break;
case CFCTRL_SRV_RFM:
/* Construct a frame, convert
* DatagramConnectionID
* to network format long and copy it out...
*/
- cfpkt_extr_head(pkt, &tmp32, 4);
linkparam.u.rfm.connid =
- le32_to_cpu(tmp32);
+ cfpkt_extr_head_u32(pkt);
cp = (u8 *) linkparam.u.rfm.volume;
- for (cfpkt_extr_head(pkt, &tmp, 1);
+ for (tmp = cfpkt_extr_head_u8(pkt);
cfpkt_more(pkt) && tmp != '\0';
- cfpkt_extr_head(pkt, &tmp, 1))
+ tmp = cfpkt_extr_head_u8(pkt))
*cp++ = tmp;
*cp = '\0';

if (CFCTRL_ERR_BIT & cmdrsp)
break;
/* Link ID */
- cfpkt_extr_head(pkt, &linkid, 1);
+ linkid = cfpkt_extr_head_u8(pkt);

break;
case CFCTRL_SRV_UTIL:
@@ -454,13 +450,11 @@ static int cfctrl_recv(struct cflayer *layer, struct cfpkt *pkt)
* to network format long and copy it out...
*/
/* Fifosize KB */
- cfpkt_extr_head(pkt, &tmp16, 2);
linkparam.u.utility.fifosize_kb =
- le16_to_cpu(tmp16);
+ cfpkt_extr_head_u16(pkt);
/* Fifosize bufs */
- cfpkt_extr_head(pkt, &tmp16, 2);
linkparam.u.utility.fifosize_bufs =
- le16_to_cpu(tmp16);
+ cfpkt_extr_head_u16(pkt);
/* name */
cp = (u8 *) linkparam.u.utility.name;
caif_assert(sizeof(linkparam.u.utility.name)
@@ -468,24 +462,24 @@ static int cfctrl_recv(struct cflayer *layer, struct cfpkt *pkt)
for (i = 0;
i < UTILITY_NAME_LENGTH
&& cfpkt_more(pkt); i++) {
- cfpkt_extr_head(pkt, &tmp, 1);
+ tmp = cfpkt_extr_head_u8(pkt);
*cp++ = tmp;
}
/* Length */
- cfpkt_extr_head(pkt, &len, 1);
+ len = cfpkt_extr_head_u8(pkt);
linkparam.u.utility.paramlen = len;
/* Param Data */
cp = linkparam.u.utility.params;
while (cfpkt_more(pkt) && len--) {
- cfpkt_extr_head(pkt, &tmp, 1);
+ tmp = cfpkt_extr_head_u8(pkt);
*cp++ = tmp;
}
if (CFCTRL_ERR_BIT & cmdrsp)
break;
/* Link ID */
- cfpkt_extr_head(pkt, &linkid, 1);
+ linkid = cfpkt_extr_head_u8(pkt);
/* Length */
- cfpkt_extr_head(pkt, &len, 1);
+ len = cfpkt_extr_head_u8(pkt);
/* Param Data */
cfpkt_extr_head(pkt, &param, len);
break;
@@ -522,7 +516,7 @@ static int cfctrl_recv(struct cflayer *layer, struct cfpkt *pkt)
}
break;
case CFCTRL_CMD_LINK_DESTROY:
- cfpkt_extr_head(pkt, &linkid, 1);
+ linkid = cfpkt_extr_head_u8(pkt);
cfctrl->res.linkdestroy_rsp(cfctrl->serv.layer.up, linkid);
break;
case CFCTRL_CMD_LINK_ERR:
--
2.9.0