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[net-next,v2,2/5] bitops: add non-atomic bitops for pointers

Message ID 20210622195527.1110497-3-memxor@gmail.com (mailing list archive)
State Superseded
Delegated to: BPF
Headers show
Series Generic XDP improvements | expand

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netdev/cc_maintainers warning 9 maintainers not CCed: yhs@fb.com akpm@linux-foundation.org kpsingh@kernel.org andriy.shevchenko@linux.intel.com geert+renesas@glider.be linux@rasmusvillemoes.dk songliubraving@fb.com richard.weiyang@linux.alibaba.com yury.norov@gmail.com
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netdev/build_32bit success Errors and warnings before: 19248 this patch: 19248
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Commit Message

Kumar Kartikeya Dwivedi June 22, 2021, 7:55 p.m. UTC
cpumap needs to set, clear, and test the lowest bit in skb pointer in
various places. To make these checks less noisy, add pointer friendly
bitop macros that also do some typechecking to sanitize the argument.

These wrap the non-atomic bitops __set_bit, __clear_bit, and test_bit
but for pointer arguments. Pointer's address has to be passed in and it
is treated as an unsigned long *, since width and representation of
pointer and unsigned long match on targets Linux supports. They are
prefixed with double underscore to indicate lack of atomicity.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 include/linux/bitops.h    | 19 +++++++++++++++++++
 include/linux/typecheck.h | 10 ++++++++++
 2 files changed, 29 insertions(+)
diff mbox series

Patch

diff --git a/include/linux/bitops.h b/include/linux/bitops.h
index 26bf15e6cd35..a9e336b9fa4d 100644
--- a/include/linux/bitops.h
+++ b/include/linux/bitops.h
@@ -4,6 +4,7 @@ 
 
 #include <asm/types.h>
 #include <linux/bits.h>
+#include <linux/typecheck.h>
 
 #include <uapi/linux/kernel.h>
 
@@ -253,6 +254,24 @@  static __always_inline void __assign_bit(long nr, volatile unsigned long *addr,
 		__clear_bit(nr, addr);
 }
 
+#define __ptr_set_bit(nr, addr)                         \
+	({                                              \
+		typecheck_pointer(*(addr));             \
+		__set_bit(nr, (unsigned long *)(addr)); \
+	})
+
+#define __ptr_clear_bit(nr, addr)                         \
+	({                                                \
+		typecheck_pointer(*(addr));               \
+		__clear_bit(nr, (unsigned long *)(addr)); \
+	})
+
+#define __ptr_test_bit(nr, addr)                       \
+	({                                             \
+		typecheck_pointer(*(addr));            \
+		test_bit(nr, (unsigned long *)(addr)); \
+	})
+
 #ifdef __KERNEL__
 
 #ifndef set_mask_bits
diff --git a/include/linux/typecheck.h b/include/linux/typecheck.h
index 20d310331eb5..33c78f27147a 100644
--- a/include/linux/typecheck.h
+++ b/include/linux/typecheck.h
@@ -22,4 +22,14 @@ 
 	(void)__tmp; \
 })
 
+/*
+ * Check at compile that something is a pointer type.
+ * Always evaluates to 1 so you may use it easily in comparisons.
+ */
+#define typecheck_pointer(x) \
+({	typeof(x) __dummy; \
+	(void)sizeof(*__dummy); \
+	1; \
+})
+
 #endif		/* TYPECHECK_H_INCLUDED */