Merge branch 'ipv6-overflow-arith' (ec3661b4) · Commits · 戴 / test

Hannes Frederic Sowa says: ==================== overflow-arith: begin to add support for overflow builtins functions I add a new header, linux/overflow-arith.h, as the central place to add overflow and wrap-around checking functions. The reason I am doing so is that it can make use of compiler supported builtin functions which can leverage hardware. As I need this for a fix in the ipv6 stack, which is also included in this series, I propose to add it sooner than later over Davem's net tree. This is also the reason why I start slowly with only the one function I need at this time. ==================== Signed-off-by:

David S. Miller <davem@davemloft.net>

include/linux/compiler-gcc.h

+4 −0

Original line number	Diff line number	Diff line
		@@ -237,6 +237,10 @@
		#define KASAN_ABI_VERSION 3
		#endif

		#if GCC_VERSION >= 50000
		#define CC_HAVE_BUILTIN_OVERFLOW
		#endif

		#endif /* gcc version >= 40000 specific checks */

		#if !defined(__noclone)

include/linux/overflow-arith.h

0 → 100644

+18 −0

Original line number	Diff line number	Diff line
		#pragma once

		#include <linux/kernel.h>

		#ifdef CC_HAVE_BUILTIN_OVERFLOW

		#define overflow_usub __builtin_usub_overflow

		#else

		static inline bool overflow_usub(unsigned int a, unsigned int b,
		unsigned int *res)
		{
		*res = a - b;
		return *res > a ? true : false;
		}

		#endif

net/ipv6/ip6_output.c

+5 −1

Original line number	Diff line number	Diff line
		@@ -28,6 +28,7 @@

		#include <linux/errno.h>
		#include <linux/kernel.h>
		#include <linux/overflow-arith.h>
		#include <linux/string.h>
		#include <linux/socket.h>
		#include <linux/net.h>
		@@ -584,7 +585,10 @@ int ip6_fragment(struct sock sk, struct sk_buff skb,
		if (np->frag_size)
		mtu = np->frag_size;
		}
		mtu -= hlen + sizeof(struct frag_hdr);

		if (overflow_usub(mtu, hlen + sizeof(struct frag_hdr), &mtu) \|\|
		mtu <= 7)
		goto fail_toobig;

		frag_id = ipv6_select_ident(net, &ipv6_hdr(skb)->daddr,
		&ipv6_hdr(skb)->saddr);

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