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Memory Protection Unit (MPU) Enhancements (#705)

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Memory Protection Unit (MPU) Enhancements

This commit introduces a new MPU wrapper that places additional
restrictions on unprivileged tasks. The following is the list of changes
introduced with the new MPU wrapper:

1. Opaque and indirectly verifiable integers for kernel object handles:
   All the kernel object handles (for example, queue handles) are now
   opaque integers. Previously object handles were raw pointers.

2. Saving the task context in Task Control Block (TCB): When a task is
   swapped out by the scheduler, the task's context is now saved in its
   TCB. Previously the task's context was saved on its stack.

3. Execute system calls on a separate privileged only stack: FreeRTOS
   system calls, which execute with elevated privilege, now use a
   separate privileged only stack. Previously system calls used the
   calling task's stack. The application writer can control the size of
   the system call stack using new configSYSTEM_CALL_STACK_SIZE config
   macro.

4. Memory bounds checks: FreeRTOS system calls which accept a pointer
   and de-reference it, now verify that the calling task has required
   permissions to access the memory location referenced by the pointer.

5. System call restrictions: The following system calls are no longer
   available to unprivileged tasks:
    - vQueueDelete
    - xQueueCreateMutex
    - xQueueCreateMutexStatic
    - xQueueCreateCountingSemaphore
    - xQueueCreateCountingSemaphoreStatic
    - xQueueGenericCreate
    - xQueueGenericCreateStatic
    - xQueueCreateSet
    - xQueueRemoveFromSet
    - xQueueGenericReset
    - xTaskCreate
    - xTaskCreateStatic
    - vTaskDelete
    - vTaskPrioritySet
    - vTaskSuspendAll
    - xTaskResumeAll
    - xTaskGetHandle
    - xTaskCallApplicationTaskHook
    - vTaskList
    - vTaskGetRunTimeStats
    - xTaskCatchUpTicks
    - xEventGroupCreate
    - xEventGroupCreateStatic
    - vEventGroupDelete
    - xStreamBufferGenericCreate
    - xStreamBufferGenericCreateStatic
    - vStreamBufferDelete
    - xStreamBufferReset
   Also, an unprivileged task can no longer use vTaskSuspend to suspend
   any task other than itself.

We thank the following people for their inputs in these enhancements:
- David Reiss of Meta Platforms, Inc.
- Lan Luo, Xinhui Shao, Yumeng Wei, Zixia Liu, Huaiyu Yan and Zhen Ling
  of School of Computer Science and Engineering, Southeast University,
  China.
- Xinwen Fu of Department of Computer Science, University of
  Massachusetts Lowell, USA.
- Yuequi Chen, Zicheng Wang, Minghao Lin of University of Colorado
  Boulder, USA.
This commit is contained in:
kar-rahul-aws 2023-07-13 16:51:04 +05:30 • committed by GitHub
parent 18e2937239
commit 97050a17aa
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GPG key ID: 4AEE18F83AFDEB23
123 changed files with 94802 additions and 6515 deletions
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359
portable/IAR/ARM_CM35P/non_secure/portasm.s
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@ -32,12 +32,21 @@ the code is included in C files but excluded by the preprocessor in assembly
files (__ICCARM__ is defined by the IAR C compiler but not by the IAR assembler. */
#include "FreeRTOSConfig.h"
#ifndef configUSE_MPU_WRAPPERS_V1
#define configUSE_MPU_WRAPPERS_V1 0
#endif
EXTERN pxCurrentTCB
EXTERN xSecureContext
EXTERN vTaskSwitchContext
EXTERN vPortSVCHandler_C
EXTERN SecureContext_SaveContext
EXTERN SecureContext_LoadContext
#if ( ( configENABLE_MPU == 1 ) && ( configUSE_MPU_WRAPPERS_V1 == 0 ) )
EXTERN vSystemCallEnter
EXTERN vSystemCallEnter_1
EXTERN vSystemCallExit
#endif
PUBLIC xIsPrivileged
PUBLIC vResetPrivilege
@ -89,50 +98,81 @@ vPortAllocateSecureContext:
THUMB
/*-----------------------------------------------------------*/
#if ( configENABLE_MPU == 1 )
vRestoreContextOfFirstTask:
program_mpu_first_task:
ldr r3, =pxCurrentTCB /* Read the location of pxCurrentTCB i.e. &( pxCurrentTCB ). */
ldr r0, [r3] /* r0 = pxCurrentTCB. */
dmb /* Complete outstanding transfers before disabling MPU. */
ldr r1, =0xe000ed94 /* r1 = 0xe000ed94 [Location of MPU_CTRL]. */
ldr r2, [r1] /* Read the value of MPU_CTRL. */
bic r2, #1 /* r2 = r2 & ~1 i.e. Clear the bit 0 in r2. */
str r2, [r1] /* Disable MPU. */
adds r0, #4 /* r0 = r0 + 4. r0 now points to MAIR0 in TCB. */
ldr r1, [r0] /* r1 = *r0 i.e. r1 = MAIR0. */
ldr r2, =0xe000edc0 /* r2 = 0xe000edc0 [Location of MAIR0]. */
str r1, [r2] /* Program MAIR0. */
adds r0, #4 /* r0 = r0 + 4. r0 now points to first RBAR in TCB. */
ldr r1, =0xe000ed98 /* r1 = 0xe000ed98 [Location of RNR]. */
ldr r2, =0xe000ed9c /* r2 = 0xe000ed9c [Location of RBAR]. */
movs r3, #4 /* r3 = 4. */
str r3, [r1] /* Program RNR = 4. */
ldmia r0!, {r4-r11} /* Read 4 set of RBAR/RLAR registers from TCB. */
stmia r2, {r4-r11} /* Write 4 set of RBAR/RLAR registers using alias registers. */
#if ( configTOTAL_MPU_REGIONS == 16 )
movs r3, #8 /* r3 = 8. */
str r3, [r1] /* Program RNR = 8. */
ldmia r0!, {r4-r11} /* Read 4 set of RBAR/RLAR registers from TCB. */
stmia r2, {r4-r11} /* Write 4 set of RBAR/RLAR registers using alias registers. */
movs r3, #12 /* r3 = 12. */
str r3, [r1] /* Program RNR = 12. */
ldmia r0!, {r4-r11} /* Read 4 set of RBAR/RLAR registers from TCB. */
stmia r2, {r4-r11} /* Write 4 set of RBAR/RLAR registers using alias registers. */
#endif /* configTOTAL_MPU_REGIONS == 16 */
ldr r1, =0xe000ed94 /* r1 = 0xe000ed94 [Location of MPU_CTRL]. */
ldr r2, [r1] /* Read the value of MPU_CTRL. */
orr r2, #1 /* r2 = r1 | 1 i.e. Set the bit 0 in r2. */
str r2, [r1] /* Enable MPU. */
dsb /* Force memory writes before continuing. */
restore_context_first_task:
ldr r3, =pxCurrentTCB /* Read the location of pxCurrentTCB i.e. &( pxCurrentTCB ). */
ldr r1, [r3] /* r1 = pxCurrentTCB.*/
ldr r2, [r1] /* r2 = Location of saved context in TCB. */
restore_special_regs_first_task:
ldmdb r2!, {r0, r3-r5, lr} /* r0 = xSecureContext, r3 = original PSP, r4 = PSPLIM, r5 = CONTROL, LR restored. */
msr psp, r3
msr psplim, r4
msr control, r5
ldr r4, =xSecureContext /* Read the location of xSecureContext i.e. &( xSecureContext ). */
str r0, [r4] /* Restore xSecureContext. */
restore_general_regs_first_task:
ldmdb r2!, {r4-r11} /* r4-r11 contain hardware saved context. */
stmia r3!, {r4-r11} /* Copy the hardware saved context on the task stack. */
ldmdb r2!, {r4-r11} /* r4-r11 restored. */
restore_context_done_first_task:
str r2, [r1] /* Save the location where the context should be saved next as the first member of TCB. */
mov r0, #0
msr basepri, r0 /* Ensure that interrupts are enabled when the first task starts. */
bx lr
#else /* configENABLE_MPU */
vRestoreContextOfFirstTask:
ldr r2, =pxCurrentTCB /* Read the location of pxCurrentTCB i.e. &( pxCurrentTCB ). */
ldr r3, [r2] /* Read pxCurrentTCB. */
ldr r0, [r3] /* Read top of stack from TCB - The first item in pxCurrentTCB is the task top of stack. */
#if ( configENABLE_MPU == 1 )
dmb /* Complete outstanding transfers before disabling MPU. */
ldr r2, =0xe000ed94 /* r2 = 0xe000ed94 [Location of MPU_CTRL]. */
ldr r4, [r2] /* Read the value of MPU_CTRL. */
bic r4, r4, #1 /* r4 = r4 & ~1 i.e. Clear the bit 0 in r4. */
str r4, [r2] /* Disable MPU. */
adds r3, #4 /* r3 = r3 + 4. r3 now points to MAIR0 in TCB. */
ldr r4, [r3] /* r4 = *r3 i.e. r4 = MAIR0. */
ldr r2, =0xe000edc0 /* r2 = 0xe000edc0 [Location of MAIR0]. */
str r4, [r2] /* Program MAIR0. */
ldr r2, =0xe000ed98 /* r2 = 0xe000ed98 [Location of RNR]. */
movs r4, #4 /* r4 = 4. */
str r4, [r2] /* Program RNR = 4. */
adds r3, #4 /* r3 = r3 + 4. r3 now points to first RBAR in TCB. */
ldr r2, =0xe000ed9c /* r2 = 0xe000ed9c [Location of RBAR]. */
ldmia r3!, {r4-r11} /* Read 4 set of RBAR/RLAR registers from TCB. */
stmia r2!, {r4-r11} /* Write 4 set of RBAR/RLAR registers using alias registers. */
ldr r2, =0xe000ed94 /* r2 = 0xe000ed94 [Location of MPU_CTRL]. */
ldr r4, [r2] /* Read the value of MPU_CTRL. */
orr r4, r4, #1 /* r4 = r4 | 1 i.e. Set the bit 0 in r4. */
str r4, [r2] /* Enable MPU. */
dsb /* Force memory writes before continuing. */
#endif /* configENABLE_MPU */
#if ( configENABLE_MPU == 1 )
ldm r0!, {r1-r4} /* Read from stack - r1 = xSecureContext, r2 = PSPLIM, r3 = CONTROL and r4 = EXC_RETURN. */
ldr r5, =xSecureContext
str r1, [r5] /* Set xSecureContext to this task's value for the same. */
msr psplim, r2 /* Set this task's PSPLIM value. */
msr control, r3 /* Set this task's CONTROL value. */
adds r0, #32 /* Discard everything up to r0. */
msr psp, r0 /* This is now the new top of stack to use in the task. */
isb
mov r0, #0
msr basepri, r0 /* Ensure that interrupts are enabled when the first task starts. */
bx r4 /* Finally, branch to EXC_RETURN. */
#else /* configENABLE_MPU */
ldm r0!, {r1-r3} /* Read from stack - r1 = xSecureContext, r2 = PSPLIM and r3 = EXC_RETURN. */
ldr r4, =xSecureContext
str r1, [r4] /* Set xSecureContext to this task's value for the same. */
@ -145,6 +185,7 @@ vRestoreContextOfFirstTask:
mov r0, #0
msr basepri, r0 /* Ensure that interrupts are enabled when the first task starts. */
bx r3 /* Finally, branch to EXC_RETURN. */
#endif /* configENABLE_MPU */
/*-----------------------------------------------------------*/
@ -183,6 +224,143 @@ vClearInterruptMask:
bx lr /* Return. */
/*-----------------------------------------------------------*/
#if ( configENABLE_MPU == 1 )
PendSV_Handler:
ldr r3, =xSecureContext /* Read the location of xSecureContext i.e. &( xSecureContext ). */
ldr r0, [r3] /* Read xSecureContext - Value of xSecureContext must be in r0 as it is used as a parameter later. */
ldr r3, =pxCurrentTCB /* Read the location of pxCurrentTCB i.e. &( pxCurrentTCB ). */
ldr r1, [r3] /* Read pxCurrentTCB - Value of pxCurrentTCB must be in r1 as it is used as a parameter later. */
ldr r2, [r1] /* r2 = Location in TCB where the context should be saved. */
cbz r0, save_ns_context /* No secure context to save. */
save_s_context:
push {r0-r2, lr}
bl SecureContext_SaveContext /* Params are in r0 and r1. r0 = xSecureContext and r1 = pxCurrentTCB. */
pop {r0-r2, lr}
save_ns_context:
mov r3, lr /* r3 = LR (EXC_RETURN). */
lsls r3, r3, #25 /* r3 = r3 << 25. Bit[6] of EXC_RETURN is 1 if secure stack was used, 0 if non-secure stack was used to store stack frame. */
bmi save_special_regs /* r3 < 0 ==> Bit[6] in EXC_RETURN is 1 ==> secure stack was used to store the stack frame. */
save_general_regs:
mrs r3, psp
#if ( ( configENABLE_FPU == 1 ) || ( configENABLE_MVE == 1 ) )
add r3, r3, #0x20 /* Move r3 to location where s0 is saved. */
tst lr, #0x10
ittt eq
vstmiaeq r2!, {s16-s31} /* Store s16-s31. */
vldmiaeq r3, {s0-s16} /* Copy hardware saved FP context into s0-s16. */
vstmiaeq r2!, {s0-s16} /* Store hardware saved FP context. */
sub r3, r3, #0x20 /* Set r3 back to the location of hardware saved context. */
#endif /* configENABLE_FPU || configENABLE_MVE */
stmia r2!, {r4-r11} /* Store r4-r11. */
ldmia r3, {r4-r11} /* Copy the hardware saved context into r4-r11. */
stmia r2!, {r4-r11} /* Store the hardware saved context. */
save_special_regs:
mrs r3, psp /* r3 = PSP. */
mrs r4, psplim /* r4 = PSPLIM. */
mrs r5, control /* r5 = CONTROL. */
stmia r2!, {r0, r3-r5, lr} /* Store xSecureContext, original PSP (after hardware has saved context), PSPLIM, CONTROL and LR. */
str r2, [r1] /* Save the location from where the context should be restored as the first member of TCB. */
select_next_task:
mov r0, #configMAX_SYSCALL_INTERRUPT_PRIORITY
msr basepri, r0 /* Disable interrupts upto configMAX_SYSCALL_INTERRUPT_PRIORITY. */
dsb
isb
bl vTaskSwitchContext
mov r0, #0 /* r0 = 0. */
msr basepri, r0 /* Enable interrupts. */
program_mpu:
ldr r3, =pxCurrentTCB /* Read the location of pxCurrentTCB i.e. &( pxCurrentTCB ). */
ldr r0, [r3] /* r0 = pxCurrentTCB.*/
dmb /* Complete outstanding transfers before disabling MPU. */
ldr r1, =0xe000ed94 /* r1 = 0xe000ed94 [Location of MPU_CTRL]. */
ldr r2, [r1] /* Read the value of MPU_CTRL. */
bic r2, #1 /* r2 = r2 & ~1 i.e. Clear the bit 0 in r2. */
str r2, [r1] /* Disable MPU. */
adds r0, #4 /* r0 = r0 + 4. r0 now points to MAIR0 in TCB. */
ldr r1, [r0] /* r1 = *r0 i.e. r1 = MAIR0. */
ldr r2, =0xe000edc0 /* r2 = 0xe000edc0 [Location of MAIR0]. */
str r1, [r2] /* Program MAIR0. */
adds r0, #4 /* r0 = r0 + 4. r0 now points to first RBAR in TCB. */
ldr r1, =0xe000ed98 /* r1 = 0xe000ed98 [Location of RNR]. */
ldr r2, =0xe000ed9c /* r2 = 0xe000ed9c [Location of RBAR]. */
movs r3, #4 /* r3 = 4. */
str r3, [r1] /* Program RNR = 4. */
ldmia r0!, {r4-r11} /* Read 4 sets of RBAR/RLAR registers from TCB. */
stmia r2, {r4-r11} /* Write 4 set of RBAR/RLAR registers using alias registers. */
#if ( configTOTAL_MPU_REGIONS == 16 )
movs r3, #8 /* r3 = 8. */
str r3, [r1] /* Program RNR = 8. */
ldmia r0!, {r4-r11} /* Read 4 sets of RBAR/RLAR registers from TCB. */
stmia r2, {r4-r11} /* Write 4 set of RBAR/RLAR registers using alias registers. */
movs r3, #12 /* r3 = 12. */
str r3, [r1] /* Program RNR = 12. */
ldmia r0!, {r4-r11} /* Read 4 sets of RBAR/RLAR registers from TCB. */
stmia r2, {r4-r11} /* Write 4 set of RBAR/RLAR registers using alias registers. */
#endif /* configTOTAL_MPU_REGIONS == 16 */
ldr r1, =0xe000ed94 /* r1 = 0xe000ed94 [Location of MPU_CTRL]. */
ldr r2, [r1] /* Read the value of MPU_CTRL. */
orr r2, #1 /* r2 = r2 | 1 i.e. Set the bit 0 in r2. */
str r2, [r1] /* Enable MPU. */
dsb /* Force memory writes before continuing. */
restore_context:
ldr r3, =pxCurrentTCB /* Read the location of pxCurrentTCB i.e. &( pxCurrentTCB ). */
ldr r1, [r3] /* r1 = pxCurrentTCB.*/
ldr r2, [r1] /* r2 = Location of saved context in TCB. */
restore_special_regs:
ldmdb r2!, {r0, r3-r5, lr} /* r0 = xSecureContext, r3 = original PSP, r4 = PSPLIM, r5 = CONTROL, LR restored. */
msr psp, r3
msr psplim, r4
msr control, r5
ldr r4, =xSecureContext /* Read the location of xSecureContext i.e. &( xSecureContext ). */
str r0, [r4] /* Restore xSecureContext. */
cbz r0, restore_ns_context /* No secure context to restore. */
restore_s_context:
push {r1-r3, lr}
bl SecureContext_LoadContext /* Params are in r0 and r1. r0 = xSecureContext and r1 = pxCurrentTCB. */
pop {r1-r3, lr}
restore_ns_context:
mov r0, lr /* r0 = LR (EXC_RETURN). */
lsls r0, r0, #25 /* r0 = r0 << 25. Bit[6] of EXC_RETURN is 1 if secure stack was used, 0 if non-secure stack was used to store stack frame. */
bmi restore_context_done /* r0 < 0 ==> Bit[6] in EXC_RETURN is 1 ==> secure stack was used to store the stack frame. */
restore_general_regs:
ldmdb r2!, {r4-r11} /* r4-r11 contain hardware saved context. */
stmia r3!, {r4-r11} /* Copy the hardware saved context on the task stack. */
ldmdb r2!, {r4-r11} /* r4-r11 restored. */
#if ( ( configENABLE_FPU == 1 ) || ( configENABLE_MVE == 1 ) )
tst lr, #0x10
ittt eq
vldmdbeq r2!, {s0-s16} /* s0-s16 contain hardware saved FP context. */
vstmiaeq r3!, {s0-s16} /* Copy hardware saved FP context on the task stack. */
vldmdbeq r2!, {s16-s31} /* Restore s16-s31. */
#endif /* configENABLE_FPU || configENABLE_MVE */
restore_context_done:
str r2, [r1] /* Save the location where the context should be saved next as the first member of TCB. */
bx lr
#else /* configENABLE_MPU */
PendSV_Handler:
ldr r3, =xSecureContext /* Read the location of xSecureContext i.e. &( xSecureContext ). */
ldr r0, [r3] /* Read xSecureContext - Value of xSecureContext must be in r0 as it is used as a parameter later. */
@ -200,20 +378,11 @@ PendSV_Handler:
ldr r3, =pxCurrentTCB /* Read the location of pxCurrentTCB i.e. &( pxCurrentTCB ). */
ldr r1, [r3] /* Read pxCurrentTCB. */
#if ( configENABLE_MPU == 1 )
subs r2, r2, #16 /* Make space for xSecureContext, PSPLIM, CONTROL and LR on the stack. */
str r2, [r1] /* Save the new top of stack in TCB. */
mrs r1, psplim /* r1 = PSPLIM. */
mrs r3, control /* r3 = CONTROL. */
mov r4, lr /* r4 = LR/EXC_RETURN. */
stmia r2!, {r0, r1, r3, r4} /* Store xSecureContext, PSPLIM, CONTROL and LR on the stack. */
#else /* configENABLE_MPU */
subs r2, r2, #12 /* Make space for xSecureContext, PSPLIM and LR on the stack. */
str r2, [r1] /* Save the new top of stack in TCB. */
mrs r1, psplim /* r1 = PSPLIM. */
mov r3, lr /* r3 = LR/EXC_RETURN. */
stmia r2!, {r0, r1, r3} /* Store xSecureContext, PSPLIM and LR on the stack. */
#endif /* configENABLE_MPU */
b select_next_task
save_ns_context:
@ -224,17 +393,6 @@ PendSV_Handler:
it eq
vstmdbeq r2!, {s16-s31} /* Store the additional FP context registers which are not saved automatically. */
#endif /* configENABLE_FPU || configENABLE_MVE */
#if ( configENABLE_MPU == 1 )
subs r2, r2, #48 /* Make space for xSecureContext, PSPLIM, CONTROL, LR and the remaining registers on the stack. */
str r2, [r1] /* Save the new top of stack in TCB. */
adds r2, r2, #16 /* r2 = r2 + 16. */
stm r2, {r4-r11} /* Store the registers that are not saved automatically. */
mrs r1, psplim /* r1 = PSPLIM. */
mrs r3, control /* r3 = CONTROL. */
mov r4, lr /* r4 = LR/EXC_RETURN. */
subs r2, r2, #16 /* r2 = r2 - 16. */
stmia r2!, {r0, r1, r3, r4} /* Store xSecureContext, PSPLIM, CONTROL and LR on the stack. */
#else /* configENABLE_MPU */
subs r2, r2, #44 /* Make space for xSecureContext, PSPLIM, LR and the remaining registers on the stack. */
str r2, [r1] /* Save the new top of stack in TCB. */
adds r2, r2, #12 /* r2 = r2 + 12. */
@ -243,7 +401,6 @@ PendSV_Handler:
mov r3, lr /* r3 = LR/EXC_RETURN. */
subs r2, r2, #12 /* r2 = r2 - 12. */
stmia r2!, {r0, r1, r3} /* Store xSecureContext, PSPLIM and LR on the stack. */
#endif /* configENABLE_MPU */
select_next_task:
mov r0, #configMAX_SYSCALL_INTERRUPT_PRIORITY
@ -258,51 +415,6 @@ PendSV_Handler:
ldr r1, [r3] /* Read pxCurrentTCB. */
ldr r2, [r1] /* The first item in pxCurrentTCB is the task top of stack. r2 now points to the top of stack. */
#if ( configENABLE_MPU == 1 )
dmb /* Complete outstanding transfers before disabling MPU. */
ldr r3, =0xe000ed94 /* r3 = 0xe000ed94 [Location of MPU_CTRL]. */
ldr r4, [r3] /* Read the value of MPU_CTRL. */
bic r4, r4, #1 /* r4 = r4 & ~1 i.e. Clear the bit 0 in r4. */
str r4, [r3] /* Disable MPU. */
adds r1, #4 /* r1 = r1 + 4. r1 now points to MAIR0 in TCB. */
ldr r4, [r1] /* r4 = *r1 i.e. r4 = MAIR0. */
ldr r3, =0xe000edc0 /* r3 = 0xe000edc0 [Location of MAIR0]. */
str r4, [r3] /* Program MAIR0. */
ldr r3, =0xe000ed98 /* r3 = 0xe000ed98 [Location of RNR]. */
movs r4, #4 /* r4 = 4. */
str r4, [r3] /* Program RNR = 4. */
adds r1, #4 /* r1 = r1 + 4. r1 now points to first RBAR in TCB. */
ldr r3, =0xe000ed9c /* r3 = 0xe000ed9c [Location of RBAR]. */
ldmia r1!, {r4-r11} /* Read 4 sets of RBAR/RLAR registers from TCB. */
stmia r3!, {r4-r11} /* Write 4 set of RBAR/RLAR registers using alias registers. */
ldr r3, =0xe000ed94 /* r3 = 0xe000ed94 [Location of MPU_CTRL]. */
ldr r4, [r3] /* Read the value of MPU_CTRL. */
orr r4, r4, #1 /* r4 = r4 | 1 i.e. Set the bit 0 in r4. */
str r4, [r3] /* Enable MPU. */
dsb /* Force memory writes before continuing. */
#endif /* configENABLE_MPU */
#if ( configENABLE_MPU == 1 )
ldmia r2!, {r0, r1, r3, r4} /* Read from stack - r0 = xSecureContext, r1 = PSPLIM, r3 = CONTROL and r4 = LR. */
msr psplim, r1 /* Restore the PSPLIM register value for the task. */
msr control, r3 /* Restore the CONTROL register value for the task. */
mov lr, r4 /* LR = r4. */
ldr r3, =xSecureContext /* Read the location of xSecureContext i.e. &( xSecureContext ). */
str r0, [r3] /* Restore the task's xSecureContext. */
cbz r0, restore_ns_context /* If there is no secure context for the task, restore the non-secure context. */
ldr r3, =pxCurrentTCB /* Read the location of pxCurrentTCB i.e. &( pxCurrentTCB ). */
ldr r1, [r3] /* Read pxCurrentTCB. */
push {r2, r4}
bl SecureContext_LoadContext /* Restore the secure context. Params are in r0 and r1. r0 = xSecureContext and r1 = pxCurrentTCB. */
pop {r2, r4}
mov lr, r4 /* LR = r4. */
lsls r1, r4, #25 /* r1 = r4 << 25. Bit[6] of EXC_RETURN is 1 if secure stack was used, 0 if non-secure stack was used to store stack frame. */
bpl restore_ns_context /* bpl - branch if positive or zero. If r1 >= 0 ==> Bit[6] in EXC_RETURN is 0 i.e. non-secure stack was used. */
msr psp, r2 /* Remember the new top of stack for the task. */
bx lr
#else /* configENABLE_MPU */
ldmia r2!, {r0, r1, r4} /* Read from stack - r0 = xSecureContext, r1 = PSPLIM and r4 = LR. */
msr psplim, r1 /* Restore the PSPLIM register value for the task. */
mov lr, r4 /* LR = r4. */
@ -319,7 +431,6 @@ PendSV_Handler:
bpl restore_ns_context /* bpl - branch if positive or zero. If r1 >= 0 ==> Bit[6] in EXC_RETURN is 0 i.e. non-secure stack was used. */
msr psp, r2 /* Remember the new top of stack for the task. */
bx lr
#endif /* configENABLE_MPU */
restore_ns_context:
ldmia r2!, {r4-r11} /* Restore the registers that are not automatically restored. */
@ -330,14 +441,50 @@ PendSV_Handler:
#endif /* configENABLE_FPU || configENABLE_MVE */
msr psp, r2 /* Remember the new top of stack for the task. */
bx lr
#endif /* configENABLE_MPU */
/*-----------------------------------------------------------*/
#if ( ( configENABLE_MPU == 1 ) && ( configUSE_MPU_WRAPPERS_V1 == 0 ) )
SVC_Handler:
tst lr, #4
ite eq
mrseq r0, msp
mrsne r0, psp
ldr r1, [r0, #24]
ldrb r2, [r1, #-2]
cmp r2, #4 /* portSVC_SYSTEM_CALL_ENTER. */
beq syscall_enter
cmp r2, #5 /* portSVC_SYSTEM_CALL_ENTER_1. */
beq syscall_enter_1
cmp r2, #6 /* portSVC_SYSTEM_CALL_EXIT. */
beq syscall_exit
b vPortSVCHandler_C
syscall_enter:
mov r1, lr
b vSystemCallEnter
syscall_enter_1:
mov r1, lr
b vSystemCallEnter_1
syscall_exit:
mov r1, lr
b vSystemCallExit
#else /* ( configENABLE_MPU == 1 ) && ( configUSE_MPU_WRAPPERS_V1 == 0 ) */
SVC_Handler:
tst lr, #4
ite eq
mrseq r0, msp
mrsne r0, psp
b vPortSVCHandler_C
#endif /* ( configENABLE_MPU == 1 ) && ( configUSE_MPU_WRAPPERS_V1 == 0 ) */
/*-----------------------------------------------------------*/
vPortFreeSecureContext: