From 1d7cf255eefbb479d0eea9aa3b6372a1e52f8c62 Mon Sep 17 00:00:00 2001 From: Ian Rogers Date: Thu, 16 Oct 2025 13:51:25 -0700 Subject: [PATCH] tools headers: Update the linux/unaligned.h copy with the kernel sources To pick up the changes in: vdso: Switch get/put_unaligned() from packed struct to memcpy As the code is dependent on __unqual_scalar_typeof, update also the tools version of compiler_types.h to include this. Signed-off-by: Ian Rogers Signed-off-by: Thomas Gleixner Link: https://patch.msgid.link/20251016205126.2882625-4-irogers@google.com --- tools/include/linux/compiler_types.h | 22 +++++++++++++++ tools/include/vdso/unaligned.h | 41 ++++++++++++++++++++++++---- 2 files changed, 57 insertions(+), 6 deletions(-) diff --git a/tools/include/linux/compiler_types.h b/tools/include/linux/compiler_types.h index d09f9dc172a48..890982283a5ee 100644 --- a/tools/include/linux/compiler_types.h +++ b/tools/include/linux/compiler_types.h @@ -40,4 +40,26 @@ #define asm_goto_output(x...) asm goto(x) #endif +/* + * __unqual_scalar_typeof(x) - Declare an unqualified scalar type, leaving + * non-scalar types unchanged. + */ +/* + * Prefer C11 _Generic for better compile-times and simpler code. Note: 'char' + * is not type-compatible with 'signed char', and we define a separate case. + */ +#define __scalar_type_to_expr_cases(type) \ + unsigned type: (unsigned type)0, \ + signed type: (signed type)0 + +#define __unqual_scalar_typeof(x) typeof( \ + _Generic((x), \ + char: (char)0, \ + __scalar_type_to_expr_cases(char), \ + __scalar_type_to_expr_cases(short), \ + __scalar_type_to_expr_cases(int), \ + __scalar_type_to_expr_cases(long), \ + __scalar_type_to_expr_cases(long long), \ + default: (x))) + #endif /* __LINUX_COMPILER_TYPES_H */ diff --git a/tools/include/vdso/unaligned.h b/tools/include/vdso/unaligned.h index ff0c06b6513ef..9076483c9fbbd 100644 --- a/tools/include/vdso/unaligned.h +++ b/tools/include/vdso/unaligned.h @@ -2,14 +2,43 @@ #ifndef __VDSO_UNALIGNED_H #define __VDSO_UNALIGNED_H -#define __get_unaligned_t(type, ptr) ({ \ - const struct { type x; } __packed * __get_pptr = (typeof(__get_pptr))(ptr); \ - __get_pptr->x; \ +#include + +/** + * __get_unaligned_t - read an unaligned value from memory. + * @type: the type to load from the pointer. + * @ptr: the pointer to load from. + * + * Use memcpy to affect an unaligned type sized load avoiding undefined behavior + * from approaches like type punning that require -fno-strict-aliasing in order + * to be correct. As type may be const, use __unqual_scalar_typeof to map to a + * non-const type - you can't memcpy into a const type. The + * __get_unaligned_ctrl_type gives __unqual_scalar_typeof its required + * expression rather than type, a pointer is used to avoid warnings about mixing + * the use of 0 and NULL. The void* cast silences ubsan warnings. + */ +#define __get_unaligned_t(type, ptr) ({ \ + type *__get_unaligned_ctrl_type __always_unused = NULL; \ + __unqual_scalar_typeof(*__get_unaligned_ctrl_type) __get_unaligned_val; \ + __builtin_memcpy(&__get_unaligned_val, (void *)(ptr), \ + sizeof(__get_unaligned_val)); \ + __get_unaligned_val; \ }) -#define __put_unaligned_t(type, val, ptr) do { \ - struct { type x; } __packed * __put_pptr = (typeof(__put_pptr))(ptr); \ - __put_pptr->x = (val); \ +/** + * __put_unaligned_t - write an unaligned value to memory. + * @type: the type of the value to store. + * @val: the value to store. + * @ptr: the pointer to store to. + * + * Use memcpy to affect an unaligned type sized store avoiding undefined + * behavior from approaches like type punning that require -fno-strict-aliasing + * in order to be correct. The void* cast silences ubsan warnings. + */ +#define __put_unaligned_t(type, val, ptr) do { \ + type __put_unaligned_val = (val); \ + __builtin_memcpy((void *)(ptr), &__put_unaligned_val, \ + sizeof(__put_unaligned_val)); \ } while (0) #endif /* __VDSO_UNALIGNED_H */ -- 2.47.3