2019-09-19 14:32:56

by Arnd Bergmann

Subject: [PATCH] [v2] net: stmmac: selftest: avoid large stack usage

Putting a struct stmmac_rss object on the stack is a bad idea,
as it exceeds the warning limit for a stack frame on 32-bit architectures:

drivers/net/ethernet/stmicro/stmmac/stmmac_selftests.c:1221:12: error: stack frame size of 1208 bytes in function '__stmmac_test_l3filt' [-Werror,-Wframe-larger-than=]
drivers/net/ethernet/stmicro/stmmac/stmmac_selftests.c:1338:12: error: stack frame size of 1208 bytes in function '__stmmac_test_l4filt' [-Werror,-Wframe-larger-than=]

As the object is the trivial empty case, change the called function
to accept a NULL pointer to mean the same thing and remove the
large variable in the two callers.

Fixes: 4647e021193d ("net: stmmac: selftests: Add selftest for L3/L4 Filters")
Signed-off-by: Arnd Bergmann <[email protected]>
---
v2: simply configure function, based on feedback from Jose
---
.../net/ethernet/stmicro/stmmac/dwxgmac2_core.c | 5 ++---
.../net/ethernet/stmicro/stmmac/stmmac_selftests.c | 14 ++++----------
2 files changed, 6 insertions(+), 13 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/dwxgmac2_core.c b/drivers/net/ethernet/stmicro/stmmac/dwxgmac2_core.c
index d5173dd02a71..2b277b2c586b 100644
--- a/drivers/net/ethernet/stmicro/stmmac/dwxgmac2_core.c
+++ b/drivers/net/ethernet/stmicro/stmmac/dwxgmac2_core.c
@@ -523,19 +523,18 @@ static int dwxgmac2_rss_configure(struct mac_device_info *hw,
struct stmmac_rss *cfg, u32 num_rxq)
{
void __iomem *ioaddr = hw->pcsr;
- u32 *key = (u32 *)cfg->key;
int i, ret;
u32 value;

value = readl(ioaddr + XGMAC_RSS_CTRL);
- if (!cfg->enable) {
+ if (!cfg || !cfg->enable) {
value &= ~XGMAC_RSSE;
writel(value, ioaddr + XGMAC_RSS_CTRL);
return 0;
}

for (i = 0; i < (sizeof(cfg->key) / sizeof(u32)); i++) {
- ret = dwxgmac2_rss_write_reg(ioaddr, true, i, *key++);
+ ret = dwxgmac2_rss_write_reg(ioaddr, true, i, cfg->key[i]);
if (ret)
return ret;
}
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_selftests.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_selftests.c
index c56e89e1ae56..9c8d210b2d6a 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_selftests.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_selftests.c
@@ -1233,12 +1233,9 @@ static int __stmmac_test_l3filt(struct stmmac_priv *priv, u32 dst, u32 src,
return -EOPNOTSUPP;
if (!priv->dma_cap.l3l4fnum)
return -EOPNOTSUPP;
- if (priv->rss.enable) {
- struct stmmac_rss rss = { .enable = false, };
-
- stmmac_rss_configure(priv, priv->hw, &rss,
+ if (priv->rss.enable)
+ stmmac_rss_configure(priv, priv->hw, NULL,
priv->plat->rx_queues_to_use);
- }

dissector = kzalloc(sizeof(*dissector), GFP_KERNEL);
if (!dissector) {
@@ -1357,12 +1354,9 @@ static int __stmmac_test_l4filt(struct stmmac_priv *priv, u32 dst, u32 src,
return -EOPNOTSUPP;
if (!priv->dma_cap.l3l4fnum)
return -EOPNOTSUPP;
- if (priv->rss.enable) {
- struct stmmac_rss rss = { .enable = false, };
-
- stmmac_rss_configure(priv, priv->hw, &rss,
+ if (priv->rss.enable)
+ stmmac_rss_configure(priv, priv->hw, NULL,
priv->plat->rx_queues_to_use);
- }

dissector = kzalloc(sizeof(*dissector), GFP_KERNEL);
if (!dissector) {
--
2.20.0

2019-09-23 15:18:04

by Jakub Kicinski

Subject: Re: [PATCH] [v2] net: stmmac: selftest: avoid large stack usage

On Thu, 19 Sep 2019 14:33:43 +0200, Arnd Bergmann wrote:
> Putting a struct stmmac_rss object on the stack is a bad idea,
> as it exceeds the warning limit for a stack frame on 32-bit architectures:
>
> drivers/net/ethernet/stmicro/stmmac/stmmac_selftests.c:1221:12: error: stack frame size of 1208 bytes in function '__stmmac_test_l3filt' [-Werror,-Wframe-larger-than=]
> drivers/net/ethernet/stmicro/stmmac/stmmac_selftests.c:1338:12: error: stack frame size of 1208 bytes in function '__stmmac_test_l4filt' [-Werror,-Wframe-larger-than=]
>
> As the object is the trivial empty case, change the called function
> to accept a NULL pointer to mean the same thing and remove the
> large variable in the two callers.
>
> Fixes: 4647e021193d ("net: stmmac: selftests: Add selftest for L3/L4 Filters")
> Signed-off-by: Arnd Bergmann <[email protected]>

Applied, thank you!