linux-kernel - [PATCH 4.9 04/97] ethtool: reduce stack usage with clang

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Message-Id: <20200122092756.417996785@linuxfoundation.org>
Date:   Wed, 22 Jan 2020 10:28:08 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Arnd Bergmann <arnd@...db.de>,
        Michal Kubecek <mkubecek@...e.cz>,
        "David S. Miller" <davem@...emloft.net>,
        Miles Chen <miles.chen@...iatek.com>
Subject: [PATCH 4.9 04/97] ethtool: reduce stack usage with clang

From: Arnd Bergmann <arnd@...db.de>

commit 3499e87ea0413ee5b2cc028f4c8ed4d424bc7f98 upstream.

clang inlines the dev_ethtool() more aggressively than gcc does, leading
to a larger amount of used stack space:

net/core/ethtool.c:2536:24: error: stack frame size of 1216 bytes in function 'dev_ethtool' [-Werror,-Wframe-larger-than=]

Marking the sub-functions that require the most stack space as
noinline_for_stack gives us reasonable behavior on all compilers.

Signed-off-by: Arnd Bergmann <arnd@...db.de>
Reviewed-by: Michal Kubecek <mkubecek@...e.cz>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Miles Chen <miles.chen@...iatek.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 net/core/ethtool.c |   16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

--- a/net/core/ethtool.c
+++ b/net/core/ethtool.c
@@ -2332,9 +2332,10 @@ out:
 	return ret;
 }
 
-static int ethtool_get_per_queue_coalesce(struct net_device *dev,
-					  void __user *useraddr,
-					  struct ethtool_per_queue_op *per_queue_opt)
+static noinline_for_stack int
+ethtool_get_per_queue_coalesce(struct net_device *dev,
+			       void __user *useraddr,
+			       struct ethtool_per_queue_op *per_queue_opt)
 {
 	u32 bit;
 	int ret;
@@ -2364,9 +2365,10 @@ static int ethtool_get_per_queue_coalesc
 	return 0;
 }
 
-static int ethtool_set_per_queue_coalesce(struct net_device *dev,
-					  void __user *useraddr,
-					  struct ethtool_per_queue_op *per_queue_opt)
+static noinline_for_stack int
+ethtool_set_per_queue_coalesce(struct net_device *dev,
+			       void __user *useraddr,
+			       struct ethtool_per_queue_op *per_queue_opt)
 {
 	u32 bit;
 	int i, ret = 0;
@@ -2423,7 +2425,7 @@ roll_back:
 	return ret;
 }
 
-static int ethtool_set_per_queue(struct net_device *dev,
+static int noinline_for_stack ethtool_set_per_queue(struct net_device *dev,
 				 void __user *useraddr, u32 sub_cmd)
 {
 	struct ethtool_per_queue_op per_queue_opt;