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xtensa: set pointer to privileged stack only if user mode

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When initializing the stack at thread creation, we should not
set the pointer to privileged stack pointer yet as the thread
can be a kernel thread. Only when a thread is transitioning to
user mode, then we need to set the pointer to point to
the privileged stack. This is a purely semantic change and
should not affect any functionality.

Signed-off-by: Daniel Leung <daniel.leung@intel.com>
This commit is contained in:
Daniel Leung 2025-03-11 12:00:54 -07:00 • committed by Benjamin Cabé
commit dcf75319e2
1 changed files with 25 additions and 17 deletions
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42
arch/xtensa/core/thread.c
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@ -42,11 +42,7 @@ static void *init_stack(struct k_thread *thread, int *stack_top,
void *ret;
_xtensa_irq_stack_frame_a11_t *frame;
#ifdef CONFIG_USERSPACE
struct xtensa_thread_stack_header *header =
(struct xtensa_thread_stack_header *)thread->stack_obj;
thread->arch.psp = header->privilege_stack +
sizeof(header->privilege_stack);
thread->arch.psp = NULL;
#endif
/* Not-a-cpu ID Ensures that the first time this is run, the
@ -73,18 +69,6 @@ static void *init_stack(struct k_thread *thread, int *stack_top,
frame->bsa.ps = PS_WOE | PS_UM | PS_CALLINC(1);
#ifdef CONFIG_USERSPACE
if ((thread->base.user_options & K_USER) == K_USER) {
#ifdef CONFIG_INIT_STACKS
/* setup_thread_stack() does not initialize the architecture specific
* privileged stack. So we need to do it manually here as this function
* is called by arch_new_thread() via z_setup_new_thread() after
* setup_thread_stack() but before thread starts running.
*
* Note that only user threads have privileged stacks and kernel
* only threads do not.
*/
(void)memset(&header->privilege_stack[0], 0xaa, sizeof(header->privilege_stack));
#endif
frame->bsa.pc = (uintptr_t)arch_user_mode_enter;
} else {
frame->bsa.pc = (uintptr_t)z_thread_entry;
@ -159,6 +143,30 @@ FUNC_NORETURN void arch_user_mode_enter(k_thread_entry_t user_entry,
struct k_thread *current = _current;
size_t stack_end;
struct xtensa_thread_stack_header *header =
(struct xtensa_thread_stack_header *)current->stack_obj;
current->arch.psp = header->privilege_stack +
sizeof(header->privilege_stack);
#ifdef CONFIG_INIT_STACKS
/* setup_thread_stack() does not initialize the architecture specific
* privileged stack. So we need to do it manually here as this function
* is called by arch_new_thread() via z_setup_new_thread() after
* setup_thread_stack() but before thread starts running.
*
* Note that only user threads have privileged stacks and kernel
* only threads do not.
*/
(void)memset(&header->privilege_stack[0], 0xaa, sizeof(header->privilege_stack));
#endif
#ifdef CONFIG_KERNEL_COHERENCE
sys_cache_data_flush_and_invd_range(&header->privilege_stack[0],
sizeof(header->privilege_stack));
#endif
/* Transition will reset stack pointer to initial, discarding
* any old context since this is a one-way operation
*/