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kernel: overhaul stack specification

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The core kernel computes the initial stack pointer
for a thread, properly aligning it and subtracting out
any random offsets or thread-local storage areas.
arch_new_thread() no longer needs to make any calculations,
an initial stack frame may be placed at the bounds of
the new 'stack_ptr' parameter passed in. This parameter
replaces 'stack_size'.

thread->stack_info is now set before arch_new_thread()
is invoked, z_new_thread_init() has been removed.
The values populated may need to be adjusted on arches
which carve-out MPU guard space from the actual stack
buffer.

thread->stack_info now has a new member 'delta' which
indicates any offset applied for TLS or random offset.
It's used so the calculations don't need to be repeated
if the thread later drops to user mode.

CONFIG_INIT_STACKS logic is now performed inside
z_setup_new_thread(), before arch_new_thread() is called.

thread->stack_info is now defined as the canonical
user-accessible area within the stack object, including
random offsets and TLS. It will never include any
carved-out memory for MPU guards and must be updated at
runtime if guards are removed.

Available stack space is now optimized. Some arches may
need to significantly round up the buffer size to account
for page-level granularity or MPU power-of-two requirements.
This space is now accounted for and used by virtue of
the Z_THREAD_STACK_SIZE_ADJUST() call in z_setup_new_thread.

Signed-off-by: Andrew Boie <andrew.p.boie@intel.com>
This commit is contained in:
Andrew Boie 2020-04-23 13:55:56 -07:00 • committed by Anas Nashif
commit b0c155f3ca
27 changed files with 570 additions and 764 deletions
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15
include/kernel.h
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@ -527,11 +527,20 @@ struct _thread_stack_info {
*/
uintptr_t start;
/* Stack Size - Thread writable stack buffer size. Represents
* the size of the actual area, starting from the start member,
* that should be writable by the thread
/* Thread writable stack buffer size. Represents the size of the actual
* buffer, starting from the 'start' member, that should be writable by
* the thread. This comprises of the thread stack area, any area reserved
* for local thread data storage, as well as any area left-out due to
* random adjustments applied to the initial thread stack pointer during
* thread initialization.
*/
size_t size;
/* Adjustment value to the size member, removing any storage
* used for TLS or random stack base offsets. (start + size - delta)
* is the initial stack pointer for a thread. May be 0.
*/
size_t delta;
};
typedef struct _thread_stack_info _thread_stack_info_t;