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/***************************************************************************
* Copyright (c) 2024 Microsoft Corporation
* Copyright (c) 2026-present Eclipse ThreadX contributors
*
* This program and the accompanying materials are made available under the
* terms of the MIT License which is available at
* https://opensource.org/licenses/MIT.
*
* SPDX-License-Identifier: MIT
**************************************************************************/
/**************************************************************************/
/**************************************************************************/
/** */
/** ThreadX Component */
/** */
/** Thread */
/** */
/**************************************************************************/
/**************************************************************************/
#ifdef TX_INCLUDE_USER_DEFINE_FILE
#include "tx_user.h"
#endif
.syntax unified
#if defined(THUMB_MODE)
.thumb
#else
.arm
#endif
.global _tx_thread_system_state
.global _tx_thread_current_ptr
.global __tx_irq_processing_return
/* No 16-bit Thumb mode veneer code is needed for _tx_thread_context_save
since it will never be called 16-bit mode. */
.text
.align 2
/**************************************************************************/
/* */
/* FUNCTION RELEASE */
/* */
/* _tx_thread_context_save ARMv7-A */
/* 6.4.0 */
/* AUTHOR */
/* */
/* William E. Lamie, Microsoft Corporation */
/* */
/* DESCRIPTION */
/* */
/* This function saves the context of an executing thread in the */
/* beginning of interrupt processing. The function also ensures that */
/* the system stack is used upon return to the calling ISR. */
/* */
/* INPUT */
/* */
/* None */
/* */
/* OUTPUT */
/* */
/* None */
/* */
/* CALLS */
/* */
/* None */
/* */
/* CALLED BY */
/* */
/* ISRs */
/* */
/**************************************************************************/
.global _tx_thread_context_save
.type _tx_thread_context_save,function
_tx_thread_context_save:
/* Upon entry to this routine, it is assumed that IRQ interrupts are locked
out, we are in IRQ mode, and all registers are intact. */
/* Check for a nested interrupt condition. */
PUSH {r0-r3} // Save some working registers
#ifdef TX_ENABLE_FIQ_SUPPORT
CPSID if // Disable FIQ interrupts
#endif
LDR r3, =_tx_thread_system_state // Pickup address of system state variable
LDR r2, [r3] // Pickup system state
CMP r2, #0 // Is this the first interrupt?
BEQ __tx_thread_not_nested_save // Yes, not a nested context save
/* Nested interrupt condition. */
ADD r2, #1 // Increment the interrupt counter
STR r2, [r3] // Store it back in the variable
/* Save the rest of the scratch registers on the stack and return to the
calling ISR. */
MRS r0, SPSR // Pickup saved SPSR
SUB lr, #4 // Adjust point of interrupt
PUSH {r0, r10, r12, lr} // Store other registers
/* Return to the ISR. */
MOV r10, #0 // Clear stack limit
#if (defined(TX_ENABLE_EXECUTION_CHANGE_NOTIFY) || defined(TX_EXECUTION_PROFILE_ENABLE))
/* Call the ISR enter function to indicate an ISR is executing. */
PUSH {lr} // Save ISR lr
BL _tx_execution_isr_enter // Call the ISR enter function
POP {lr} // Recover ISR lr
#endif
B __tx_irq_processing_return // Continue IRQ processing
__tx_thread_not_nested_save:
/* Otherwise, not nested, check to see if a thread was running. */
ADD r2, #1 // Increment the interrupt counter
STR r2, [r3] // Store it back in the variable
LDR r1, =_tx_thread_current_ptr // Pickup address of current thread ptr
LDR r0, [r1] // Pickup current thread pointer
CMP r0, #0 // Is it NULL?
BEQ __tx_thread_idle_system_save // If so, interrupt occurred in
// scheduling loop - nothing needs saving!
/* Save minimal context of interrupted thread. */
MRS r2, SPSR // Pickup saved SPSR
SUB lr, #4 // Adjust point of interrupt
PUSH {r2, r10, r12, lr} // Store other registers
MOV r10, #0 // Clear stack limit
#if (defined(TX_ENABLE_EXECUTION_CHANGE_NOTIFY) || defined(TX_EXECUTION_PROFILE_ENABLE))
/* Call the ISR enter function to indicate an ISR is executing. */
PUSH {lr} // Save ISR lr
BL _tx_execution_isr_enter // Call the ISR enter function
POP {lr} // Recover ISR lr
#endif
B __tx_irq_processing_return // Continue IRQ processing
__tx_thread_idle_system_save:
/* Interrupt occurred in the scheduling loop. */
/* Not much to do here, just adjust the stack pointer, and return to IRQ
processing. */
MOV r10, #0 // Clear stack limit
#if (defined(TX_ENABLE_EXECUTION_CHANGE_NOTIFY) || defined(TX_EXECUTION_PROFILE_ENABLE))
/* Call the ISR enter function to indicate an ISR is executing. */
PUSH {lr} // Save ISR lr
BL _tx_execution_isr_enter // Call the ISR enter function
POP {lr} // Recover ISR lr
#endif
ADD sp, #16 // Recover saved registers
B __tx_irq_processing_return // Continue IRQ processing
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