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a339671db6
Type punning is necessary for get/put_unaligned() but the use of a packed struct violates strict aliasing rules, requiring -fno-strict-aliasing to be passed to the C compiler. Switch to using memcpy() so that -fno-strict-aliasing isn't necessary. Signed-off-by: Ian Rogers <irogers@google.com> Signed-off-by: Thomas Gleixner <tglx@kernel.org> Link: https://patch.msgid.link/20251016205126.2882625-3-irogers@google.com
45 lines
1.7 KiB
C
45 lines
1.7 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef __VDSO_UNALIGNED_H
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#define __VDSO_UNALIGNED_H
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#include <linux/compiler_types.h>
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/**
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* __get_unaligned_t - read an unaligned value from memory.
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* @type: the type to load from the pointer.
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* @ptr: the pointer to load from.
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*
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* Use memcpy to affect an unaligned type sized load avoiding undefined behavior
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* from approaches like type punning that require -fno-strict-aliasing in order
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* to be correct. As type may be const, use __unqual_scalar_typeof to map to a
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* non-const type - you can't memcpy into a const type. The
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* __get_unaligned_ctrl_type gives __unqual_scalar_typeof its required
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* expression rather than type, a pointer is used to avoid warnings about mixing
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* the use of 0 and NULL. The void* cast silences ubsan warnings.
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*/
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#define __get_unaligned_t(type, ptr) ({ \
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type *__get_unaligned_ctrl_type __always_unused = NULL; \
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__unqual_scalar_typeof(*__get_unaligned_ctrl_type) __get_unaligned_val; \
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__builtin_memcpy(&__get_unaligned_val, (void *)(ptr), \
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sizeof(__get_unaligned_val)); \
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__get_unaligned_val; \
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})
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/**
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* __put_unaligned_t - write an unaligned value to memory.
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* @type: the type of the value to store.
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* @val: the value to store.
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* @ptr: the pointer to store to.
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*
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* Use memcpy to affect an unaligned type sized store avoiding undefined
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* behavior from approaches like type punning that require -fno-strict-aliasing
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* in order to be correct. The void* cast silences ubsan warnings.
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*/
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#define __put_unaligned_t(type, val, ptr) do { \
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type __put_unaligned_val = (val); \
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__builtin_memcpy((void *)(ptr), &__put_unaligned_val, \
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sizeof(__put_unaligned_val)); \
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} while (0)
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#endif /* __VDSO_UNALIGNED_H */
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