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atomics/cpuid_flags fixes from peer review:

Browse Source 
wolfcrypt/src/cpuid.c: cpuid_set_flag() and cpuid_clear_flag() thread safety;

wolfcrypt/src/wc_port.c: comments re __ATOMIC_SEQ_CST and __ATOMIC_ACQUIRE;

wolfssl/wolfcrypt/wc_port.h: single overrideable definitions for WOLFSSL_ATOMIC_COERCE_[U]INT(), and comment cleanup.

also added WOLFSSL_USER_DEFINED_ATOMICS.
This commit is contained in:
Daniel Pouzzner
2025-08-14 09:33:14 -05:00
parent bd4e723f9d
commit cefeb4cd7e
5 changed files with 62 additions and 19 deletions
Download Patch File Download Diff File Expand all files Collapse all files

1
.wolfssl_known_macro_extras
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@@ -877,6 +877,7 @@ WOLFSSL_TLSX_PQC_MLKEM_STORE_PRIV_KEY
WOLFSSL_TRACK_MEMORY_FULL
WOLFSSL_TRAP_MALLOC_SZ
WOLFSSL_UNALIGNED_64BIT_ACCESS
WOLFSSL_USER_DEFINED_ATOMICS
WOLFSSL_USER_FILESYSTEM
WOLFSSL_USER_LOG
WOLFSSL_USER_MUTEX

12
wolfcrypt/src/cpuid.c
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@@ -355,14 +355,18 @@
void cpuid_set_flag(word32 flag)
{
WOLFSSL_ATOMIC_STORE
(cpuid_flags, WOLFSSL_ATOMIC_LOAD(cpuid_flags) | flag);
word32 current_flags = WOLFSSL_ATOMIC_LOAD(cpuid_flags);
while (! wolfSSL_Atomic_Uint_CompareExchange
(&cpuid_flags, &current_flags, current_flags | flag))
WC_RELAX_LONG_LOOP();
}
void cpuid_clear_flag(word32 flag)
{
WOLFSSL_ATOMIC_STORE
(cpuid_flags, WOLFSSL_ATOMIC_LOAD(cpuid_flags) & ~flag);
word32 current_flags = WOLFSSL_ATOMIC_LOAD(cpuid_flags);
while (! wolfSSL_Atomic_Uint_CompareExchange
(&cpuid_flags, &current_flags, current_flags & ~flag))
WC_RELAX_LONG_LOOP();
}
#endif /* HAVE_CPUID */

24
wolfcrypt/src/wc_port.c
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@@ -1310,6 +1310,12 @@ int wolfSSL_Atomic_Int_SubFetch(wolfSSL_Atomic_Int* c, int i)
int wolfSSL_Atomic_Int_CompareExchange(wolfSSL_Atomic_Int* c, int *expected_i,
int new_i)
{
/* For the success path, use full synchronization with barriers --
* "Sequentially-consistent ordering" -- so that all threads see the same
* "single total modification order of all atomic operations" -- but on
* failure we just need to be sure we acquire the value that changed out
* from under us.
*/
return __atomic_compare_exchange_n(c, expected_i, new_i, 0 /* weak */,
__ATOMIC_SEQ_CST, __ATOMIC_ACQUIRE);
}
@@ -1341,6 +1347,12 @@ unsigned int wolfSSL_Atomic_Uint_SubFetch(wolfSSL_Atomic_Uint* c,
int wolfSSL_Atomic_Uint_CompareExchange(
wolfSSL_Atomic_Uint* c, unsigned int *expected_i, unsigned int new_i)
{
/* For the success path, use full synchronization with barriers --
* "Sequentially-consistent ordering" -- so that all threads see the same
* "single total modification order of all atomic operations" -- but on
* failure we just need to be sure we acquire the value that changed out
* from under us.
*/
return __atomic_compare_exchange_n(
c, expected_i, new_i, 0 /* weak */, __ATOMIC_SEQ_CST, __ATOMIC_ACQUIRE);
}
@@ -1383,6 +1395,12 @@ int wolfSSL_Atomic_Int_SubFetch(wolfSSL_Atomic_Int* c, int i)
int wolfSSL_Atomic_Int_CompareExchange(
wolfSSL_Atomic_Int* c, int *expected_i, int new_i)
{
/* For the success path, use full synchronization with barriers --
* "Sequentially-consistent ordering" -- so that all threads see the same
* "single total modification order of all atomic operations" -- but on
* failure we just need to be sure we acquire the value that changed out
* from under us.
*/
return atomic_compare_exchange_strong_explicit(
c, expected_i, new_i, memory_order_seq_cst, memory_order_acquire);
}
@@ -1416,6 +1434,12 @@ unsigned int wolfSSL_Atomic_Uint_SubFetch(wolfSSL_Atomic_Uint* c,
int wolfSSL_Atomic_Uint_CompareExchange(
wolfSSL_Atomic_Uint* c, unsigned int *expected_i, unsigned int new_i)
{
/* For the success path, use full synchronization with barriers --
* "Sequentially-consistent ordering" -- so that all threads see the same
* "single total modification order of all atomic operations" -- but on
* failure we just need to be sure we acquire the value that changed out
* from under us.
*/
return atomic_compare_exchange_strong_explicit(
c, expected_i, new_i, memory_order_seq_cst, memory_order_acquire);
}

2
wolfssl/wolfcrypt/cpuid.h
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@@ -115,7 +115,7 @@
return 0;
}
/* Public APIs to modify flags -- note that these are not threadsafe. */
/* Public APIs to modify flags. */
WOLFSSL_API void cpuid_select_flags(word32 flags);
WOLFSSL_API void cpuid_set_flag(word32 flag);
WOLFSSL_API void cpuid_clear_flag(word32 flag);

42
wolfssl/wolfcrypt/wc_port.h
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@@ -466,13 +466,20 @@
#endif
#ifndef WOLFSSL_NO_ATOMICS
#ifdef SINGLE_THREADED
#if defined(WOLFSSL_USER_DEFINED_ATOMICS)
/* user-supplied bindings for wolfSSL_Atomic_Int etc. */
#if !defined(WOLFSSL_ATOMIC_INITIALIZER) || \
!defined(WOLFSSL_ATOMIC_LOAD) || \
!defined(WOLFSSL_ATOMIC_STORE)
#error WOLFSSL_USER_DEFINED_ATOMICS is set but macro(s) are missing.
#else
#define WOLFSSL_ATOMIC_OPS
#endif
#elif defined(SINGLE_THREADED)
typedef int wolfSSL_Atomic_Int;
typedef unsigned int wolfSSL_Atomic_Uint;
#define WOLFSSL_ATOMIC_INITIALIZER(x) (x)
#define WOLFSSL_ATOMIC_LOAD(x) (x)
#define WOLFSSL_ATOMIC_COERCE_INT(x) ((int)(x))
#define WOLFSSL_ATOMIC_COERCE_UINT(x) ((unsigned int)(x))
#define WOLFSSL_ATOMIC_STORE(x, val) (x) = (val)
#define WOLFSSL_ATOMIC_OPS
#elif defined(HAVE_C___ATOMIC)
@@ -484,8 +491,6 @@
#define WOLFSSL_ATOMIC_INITIALIZER(x) (x)
#define WOLFSSL_ATOMIC_LOAD(x) __atomic_load_n(&(x), \
__ATOMIC_CONSUME)
#define WOLFSSL_ATOMIC_COERCE_INT(x) ((int)(x))
#define WOLFSSL_ATOMIC_COERCE_UINT(x) ((unsigned int)(x))
#define WOLFSSL_ATOMIC_STORE(x, val) __atomic_store_n(&(x), \
val, __ATOMIC_RELEASE)
#define WOLFSSL_ATOMIC_OPS
@@ -498,8 +503,6 @@
typedef atomic_uint wolfSSL_Atomic_Uint;
#define WOLFSSL_ATOMIC_INITIALIZER(x) (x)
#define WOLFSSL_ATOMIC_LOAD(x) atomic_load(&(x))
#define WOLFSSL_ATOMIC_COERCE_INT(x) ((int)(x))
#define WOLFSSL_ATOMIC_COERCE_UINT(x) ((unsigned int)(x))
#define WOLFSSL_ATOMIC_STORE(x, val) atomic_store(&(x), val)
#define WOLFSSL_ATOMIC_OPS
#endif /* WOLFSSL_HAVE_ATOMIC_H */
@@ -515,8 +518,6 @@
typedef volatile unsigned long wolfSSL_Atomic_Uint;
#define WOLFSSL_ATOMIC_INITIALIZER(x) (x)
#define WOLFSSL_ATOMIC_LOAD(x) (x)
#define WOLFSSL_ATOMIC_COERCE_INT(x) ((int)(x))
#define WOLFSSL_ATOMIC_COERCE_UINT(x) ((unsigned int)(x))
#define WOLFSSL_ATOMIC_STORE(x, val) (x) = (val)
#define WOLFSSL_ATOMIC_OPS
#endif
@@ -530,18 +531,31 @@
#ifdef WOLFSSL_NO_ATOMICS
#define WOLFSSL_ATOMIC_INITIALIZER(x) (x)
#define WOLFSSL_ATOMIC_LOAD(x) (x)
#define WOLFSSL_ATOMIC_COERCE_INT(x) ((int)(x))
#define WOLFSSL_ATOMIC_COERCE_UINT(x) ((unsigned int)(x))
#define WOLFSSL_ATOMIC_STORE(x, val) (x) = (val)
#endif /* WOLFSSL_NO_ATOMICS */
#if defined(WOLFSSL_ATOMIC_OPS) && !defined(SINGLE_THREADED)
/* WOLFSSL_ATOMIC_COERCE_INT() needs to accept either a regular int or an
* wolfSSL_Atomic_Int as its argument, and evaluate to a regular int.
* Allows a user-supplied override definition with type introspection.
*/
#ifndef WOLFSSL_ATOMIC_COERCE_INT
#define WOLFSSL_ATOMIC_COERCE_INT(x) ((int)(x))
#endif
#ifndef WOLFSSL_ATOMIC_COERCE_UINT
#define WOLFSSL_ATOMIC_COERCE_UINT(x) ((unsigned int)(x))
#endif
#ifdef WOLFSSL_USER_DEFINED_ATOMICS
/* user-supplied bindings for wolfSSL_Atomic_Int_Init(),
* wolfSSL_Atomic_Int_FetchAdd(), etc.
*/
#elif defined(WOLFSSL_ATOMIC_OPS) && !defined(SINGLE_THREADED)
WOLFSSL_API void wolfSSL_Atomic_Int_Init(wolfSSL_Atomic_Int* c, int i);
WOLFSSL_API void wolfSSL_Atomic_Uint_Init(
wolfSSL_Atomic_Uint* c, unsigned int i);
/* Fetch* functions return the value of the counter immediately preceding
/* FetchOp functions return the value of the counter immediately preceding
* the effects of the operation.
* *Fetch functions return the value of the counter immediately after
* OpFetch functions return the value of the counter immediately after
* the effects of the operation.
*/
WOLFSSL_API int wolfSSL_Atomic_Int_FetchAdd(wolfSSL_Atomic_Int* c, int i);