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libbpf: xsk: Remove linux/compiler.h header

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In commit 291471dd1559 ("libbpf, xsk: Add libbpf_smp_store_release
libbpf_smp_load_acquire") linux/compiler.h was added as a dependency
to xsk.h, which is the user-facing API. This makes it harder for
userspace application to consume the library. Here the header
inclusion is removed, and instead {READ,WRITE}_ONCE() is added
explicitly.

Signed-off-by: Björn Töpel <bjorn.topel@intel.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210310080929.641212-2-bjorn.topel@gmail.com
This commit is contained in:
Björn Töpel 2021-03-10 09:09:28 +01:00 committed by Andrii Nakryiko
parent a9c80b03e5
commit 2882c48bf8
1 changed files with 17 additions and 10 deletions
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27
tools/lib/bpf/libbpf_util.h
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@ -5,25 +5,30 @@
#define __LIBBPF_LIBBPF_UTIL_H
#include <stdbool.h>
#include <linux/compiler.h>
#ifdef __cplusplus
extern "C" {
#endif
/* Use these barrier functions instead of smp_[rw]mb() when they are
* used in a libbpf header file. That way they can be built into the
* application that uses libbpf.
/* Load-Acquire Store-Release barriers used by the XDP socket
* library. The following macros should *NOT* be considered part of
* the xsk.h API, and is subject to change anytime.
*
* LIBRARY INTERNAL
*/
#define __XSK_READ_ONCE(x) (*(volatile typeof(x) *)&x)
#define __XSK_WRITE_ONCE(x, v) (*(volatile typeof(x) *)&x) = (v)
#if defined(__i386__) || defined(__x86_64__)
# define libbpf_smp_store_release(p, v) \
do { \
asm volatile("" : : : "memory"); \
WRITE_ONCE(*p, v); \
__XSK_WRITE_ONCE(*p, v); \
} while (0)
# define libbpf_smp_load_acquire(p) \
({ \
typeof(*p) ___p1 = READ_ONCE(*p); \
typeof(*p) ___p1 = __XSK_READ_ONCE(*p); \
asm volatile("" : : : "memory"); \
___p1; \
})
@ -41,11 +46,11 @@ extern "C" {
# define libbpf_smp_store_release(p, v) \
do { \
asm volatile ("fence rw,w" : : : "memory"); \
WRITE_ONCE(*p, v); \
__XSK_WRITE_ONCE(*p, v); \
} while (0)
# define libbpf_smp_load_acquire(p) \
({ \
typeof(*p) ___p1 = READ_ONCE(*p); \
typeof(*p) ___p1 = __XSK_READ_ONCE(*p); \
asm volatile ("fence r,rw" : : : "memory"); \
___p1; \
})
@ -55,19 +60,21 @@ extern "C" {
#define libbpf_smp_store_release(p, v) \
do { \
__sync_synchronize(); \
WRITE_ONCE(*p, v); \
__XSK_WRITE_ONCE(*p, v); \
} while (0)
#endif
#ifndef libbpf_smp_load_acquire
#define libbpf_smp_load_acquire(p) \
({ \
typeof(*p) ___p1 = READ_ONCE(*p); \
typeof(*p) ___p1 = __XSK_READ_ONCE(*p); \
__sync_synchronize(); \
___p1; \
})
#endif
/* LIBRARY INTERNAL -- END */
#ifdef __cplusplus
} /* extern "C" */
#endif