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kernel: add stack object alignment macro interface

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A new macro Z_THREAD_STACK_OBJ_ALIGN() defines the alignment
of the lowest memory address of a stack object.

Related is a new arch interface ARCH_THREAD_STACK_OBJ_ALIGN()
which lets arches specifiy this. ARCH_STACK_PTR_ALIGN or a
power-of-two ceiling is used if not defined.

The default stack macros now use this instead of hard-coding
ARCH_STACK_PTR_ALIGN.

Signed-off-by: Andrew Boie <andrew.p.boie@intel.com>
This commit is contained in:
Andrew Boie 2020-04-20 15:15:15 -07:00 • committed by Anas Nashif
commit db0d6aedfb
2 changed files with 49 additions and 5 deletions
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10
include/sys/arch_interface.h
View file

@ -116,6 +116,16 @@ static inline uint32_t arch_k_cycle_get_32(void);
*
* @see Z_STACK_PTR_ALIGN
*/
/**
* @def ARCH_THREAD_STACK_OBJ_ALIGN(size)
*
* Required alignment of the lowest address of a stack object.
*
* Optional definition.
*
* @see Z_THREAD_STACK_OBJ_ALIGN
*/
/** @} */
/**

44
include/sys/thread_stack.h
View file

@ -53,6 +53,37 @@ struct __packed z_thread_stack_element {
*/
#define Z_STACK_PTR_ALIGN(ptr) ROUND_DOWN((ptr), ARCH_STACK_PTR_ALIGN)
/**
* @brief Properly align the lowest address of a stack object
*
* Return an alignment value for the lowest address of a stack object, taking
* into consideration all alignment constraints imposed by the CPU, ABI, and
* any memory management policies, including any alignment required by
* reserved platform data within the stack object. This will always be at least
* ARCH_STACK_PTR_ALIGN or an even multiple thereof.
*
* Depending on hardware, this is either a fixed value or a function of the
* provided size. The requested size is significant only if
* CONFIG_MPU_REQUIRES_POWER_OF_TWO_ALIGNMENT is enabled.
*
* If CONFIG_USERSPACE is enabled, this determines the alignment of stacks
* which may be used by user mode threads, or threads running in supervisor
* mode which may later drop privileges to user mode.
*
* Arches define this with ARCH_THREAD_STACK_OBJ_ALIGN().
*
* If ARCH_THREAD_STACK_OBJ_ALIGN is not defined assume ARCH_STACK_PTR_ALIGN
* is appropriate.
*
* @param size Requested size of the stack buffer (which could be ignored)
* @return Alignment of the stack object
*/
#if defined(ARCH_THREAD_STACK_OBJ_ALIGN)
#define Z_THREAD_STACK_OBJ_ALIGN(size) ARCH_THREAD_STACK_OBJ_ALIGN(size)
#else
#define Z_THREAD_STACK_OBJ_ALIGN(size) ARCH_STACK_PTR_ALIGN
#endif /* ARCH_THREAD_STACK_OBJ_ALIGN */
/**
* @brief Obtain an extern reference to a stack
*
@ -85,7 +116,7 @@ static inline char *Z_THREAD_STACK_BUFFER(k_thread_stack_t *sym)
*
* This declares a region of memory suitable for use as a thread's stack.
*
* This is the generic, historical definition. Align to ARCH_STACK_PTR_ALIGN
* This is the generic, historical definition. Align to Z_THREAD_STACK_OBJ_ALIGN
* and put in 'noinit' section so that it isn't zeroed at boot
*
* The declared symbol will always be a k_thread_stack_t which can be passed to
@ -108,7 +139,8 @@ static inline char *Z_THREAD_STACK_BUFFER(k_thread_stack_t *sym)
*/
#define K_THREAD_STACK_DEFINE(sym, size) \
struct z_thread_stack_element __noinit \
__aligned(ARCH_STACK_PTR_ALIGN) sym[size]
__aligned(Z_THREAD_STACK_OBJ_ALIGN(size)) \
sym[size]
/**
* @brief Calculate size of stacks to be allocated in a stack array
@ -128,7 +160,7 @@ static inline char *Z_THREAD_STACK_BUFFER(k_thread_stack_t *sym)
* Create an array of equally sized stacks. See K_THREAD_STACK_DEFINE
* definition for additional details and constraints.
*
* This is the generic, historical definition. Align to ARCH_STACK_PTR_ALIGN
* This is the generic, historical definition. Align to Z_THREAD_STACK_OBJ_ALIGN
* and put in 'noinit' section so that it isn't zeroed at boot
*
* @param sym Thread stack symbol name
@ -137,7 +169,7 @@ static inline char *Z_THREAD_STACK_BUFFER(k_thread_stack_t *sym)
*/
#define K_THREAD_STACK_ARRAY_DEFINE(sym, nmemb, size) \
struct z_thread_stack_element __noinit \
__aligned(ARCH_STACK_PTR_ALIGN) \
__aligned(Z_THREAD_STACK_OBJ_ALIGN(size)) \
sym[nmemb][K_THREAD_STACK_LEN(size)]
/**
@ -153,7 +185,9 @@ static inline char *Z_THREAD_STACK_BUFFER(k_thread_stack_t *sym)
* @param size Size of the stack memory region
*/
#define K_THREAD_STACK_MEMBER(sym, size) \
struct z_thread_stack_element __aligned(ARCH_STACK_PTR_ALIGN) sym[size]
struct z_thread_stack_element \
__aligned(Z_THREAD_STACK_OBJ_ALIGN(size)) \
sym[size]
/**
* @brief Return the size in bytes of a stack memory region