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armv8-m: Modify ARMv8-M registers stacking procedure
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ARMv8-M TrustZone variant registers stacking
procedure is modified to be consistent with the NTZ port
variant where one `stmdb` instruction is used instead of
using 'subs' instruction along with `stmia` instruction, also,
this result in more efficient context switching
handling (lower latency).

Signed-off-by: Ahmed Ismail <Ahmed.Ismail@arm.com>
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AhmedIsmail02 committed Nov 19, 2024
1 parent 744dc52 commit 5934d2d
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Showing 10 changed files with 60 additions and 130 deletions.
19 changes: 6 additions & 13 deletions portable/ARMv8M/non_secure/portable/GCC/ARM_CM33/portasm.c
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Original file line number Diff line number Diff line change
Expand Up @@ -419,31 +419,24 @@ void vClearInterruptMask( __attribute__( ( unused ) ) uint32_t ulMask ) /* __att
" lsls r1, r3, #25 \n" /* r1 = 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. */
" bpl save_ns_context \n" /* bpl - branch if positive or zero. If r1 >= 0 ==> Bit[6] in EXC_RETURN is 0 i.e. non-secure stack was used. */
" \n"
" ldr r3, =pxCurrentTCB \n" /* Read the location of pxCurrentTCB i.e. &( pxCurrentTCB ). */
" ldr r1, [r3] \n" /* Read pxCurrentTCB.*/
" subs r2, r2, #12 \n" /* Make space for xSecureContext, PSPLIM and LR on the stack. */
" str r2, [r1] \n" /* Save the new top of stack in TCB. */
" mrs r1, psplim \n" /* r1 = PSPLIM. */
" mov r3, lr \n" /* r3 = LR/EXC_RETURN. */
" stmia r2!, {r0, r1, r3} \n" /* Store xSecureContext, PSPLIM and LR on the stack. */
" stmdb r2!, {r0, r1, r3} \n" /* Store xSecureContext, PSPLIM and LR on the stack. */
" b select_next_task \n"
" \n"
" save_ns_context: \n"
" ldr r3, =pxCurrentTCB \n" /* Read the location of pxCurrentTCB i.e. &( pxCurrentTCB ). */
" ldr r1, [r3] \n" /* Read pxCurrentTCB. */
#if ( ( configENABLE_FPU == 1 ) || ( configENABLE_MVE == 1 ) )
" tst lr, #0x10 \n" /* Test Bit[4] in LR. Bit[4] of EXC_RETURN is 0 if the Extended Stack Frame is in use. */
" it eq \n"
" vstmdbeq r2!, {s16-s31} \n" /* Store the additional FP context registers which are not saved automatically. */
#endif /* configENABLE_FPU || configENABLE_MVE */
" subs r2, r2, #44 \n" /* Make space for xSecureContext, PSPLIM, LR and the remaining registers on the stack. */
" str r2, [r1] \n" /* Save the new top of stack in TCB. */
" adds r2, r2, #12 \n" /* r2 = r2 + 12. */
" stm r2, {r4-r11} \n" /* Store the registers that are not saved automatically. */
" stmdb r2!, {r4-r11} \n" /* Store the registers that are not saved automatically. */
" mrs r1, psplim \n" /* r1 = PSPLIM. */
" mov r3, lr \n" /* r3 = LR/EXC_RETURN. */
" subs r2, r2, #12 \n" /* r2 = r2 - 12. */
" stmia r2!, {r0, r1, r3} \n" /* Store xSecureContext, PSPLIM and LR on the stack. */
" stmdb r2!, {r0, r1, r3} \n" /* Store xSecureContext, PSPLIM and LR on the stack. */
" ldr r3, =pxCurrentTCB \n" /* Read the location of pxCurrentTCB i.e. &( pxCurrentTCB ). */
" ldr r1, [r3] \n" /* Read pxCurrentTCB. */
" str r2, [r1] \n" /* Save the new top of stack in TCB. */
" \n"
" select_next_task: \n"
" mov r0, %0 \n" /* r0 = configMAX_SYSCALL_INTERRUPT_PRIORITY */
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19 changes: 6 additions & 13 deletions portable/ARMv8M/non_secure/portable/IAR/ARM_CM33/portasm.s
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Original file line number Diff line number Diff line change
Expand Up @@ -381,31 +381,24 @@ PendSV_Handler:
lsls r1, r3, #25 /* r1 = 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. */
bpl save_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. */

ldr r3, =pxCurrentTCB /* Read the location of pxCurrentTCB i.e. &( pxCurrentTCB ). */
ldr r1, [r3] /* Read pxCurrentTCB. */
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. */
stmdb r2!, {r0, r1, r3} /* Store xSecureContext, PSPLIM and LR on the stack. */
b select_next_task

save_ns_context:
ldr r3, =pxCurrentTCB /* Read the location of pxCurrentTCB i.e. &( pxCurrentTCB ). */
ldr r1, [r3] /* Read pxCurrentTCB. */
#if ( ( configENABLE_FPU == 1 ) || ( configENABLE_MVE == 1 ) )
tst lr, #0x10 /* Test Bit[4] in LR. Bit[4] of EXC_RETURN is 0 if the Extended Stack Frame is in use. */
it eq
vstmdbeq r2!, {s16-s31} /* Store the additional FP context registers which are not saved automatically. */
#endif /* configENABLE_FPU || configENABLE_MVE */
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. */
stm r2, {r4-r11} /* Store the registers that are not saved automatically. */
stmdb r2!, {r4-r11} /* Store the registers that are not saved automatically. */
mrs r1, psplim /* r1 = PSPLIM. */
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. */
stmdb r2!, {r0, r1, r3} /* Store xSecureContext, PSPLIM and LR on the stack. */
ldr r3, =pxCurrentTCB /* Read the location of pxCurrentTCB i.e. &( pxCurrentTCB ). */
ldr r1, [r3] /* Read pxCurrentTCB. */
str r2, [r1] /* Save the new top of stack in TCB. */

select_next_task:
mov r0, #configMAX_SYSCALL_INTERRUPT_PRIORITY
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19 changes: 6 additions & 13 deletions portable/GCC/ARM_CM33/non_secure/portasm.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -419,31 +419,24 @@ void vClearInterruptMask( __attribute__( ( unused ) ) uint32_t ulMask ) /* __att
" lsls r1, r3, #25 \n" /* r1 = 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. */
" bpl save_ns_context \n" /* bpl - branch if positive or zero. If r1 >= 0 ==> Bit[6] in EXC_RETURN is 0 i.e. non-secure stack was used. */
" \n"
" ldr r3, =pxCurrentTCB \n" /* Read the location of pxCurrentTCB i.e. &( pxCurrentTCB ). */
" ldr r1, [r3] \n" /* Read pxCurrentTCB.*/
" subs r2, r2, #12 \n" /* Make space for xSecureContext, PSPLIM and LR on the stack. */
" str r2, [r1] \n" /* Save the new top of stack in TCB. */
" mrs r1, psplim \n" /* r1 = PSPLIM. */
" mov r3, lr \n" /* r3 = LR/EXC_RETURN. */
" stmia r2!, {r0, r1, r3} \n" /* Store xSecureContext, PSPLIM and LR on the stack. */
" stmdb r2!, {r0, r1, r3} \n" /* Store xSecureContext, PSPLIM and LR on the stack. */
" b select_next_task \n"
" \n"
" save_ns_context: \n"
" ldr r3, =pxCurrentTCB \n" /* Read the location of pxCurrentTCB i.e. &( pxCurrentTCB ). */
" ldr r1, [r3] \n" /* Read pxCurrentTCB. */
#if ( ( configENABLE_FPU == 1 ) || ( configENABLE_MVE == 1 ) )
" tst lr, #0x10 \n" /* Test Bit[4] in LR. Bit[4] of EXC_RETURN is 0 if the Extended Stack Frame is in use. */
" it eq \n"
" vstmdbeq r2!, {s16-s31} \n" /* Store the additional FP context registers which are not saved automatically. */
#endif /* configENABLE_FPU || configENABLE_MVE */
" subs r2, r2, #44 \n" /* Make space for xSecureContext, PSPLIM, LR and the remaining registers on the stack. */
" str r2, [r1] \n" /* Save the new top of stack in TCB. */
" adds r2, r2, #12 \n" /* r2 = r2 + 12. */
" stm r2, {r4-r11} \n" /* Store the registers that are not saved automatically. */
" stmdb r2!, {r4-r11} \n" /* Store the registers that are not saved automatically. */
" mrs r1, psplim \n" /* r1 = PSPLIM. */
" mov r3, lr \n" /* r3 = LR/EXC_RETURN. */
" subs r2, r2, #12 \n" /* r2 = r2 - 12. */
" stmia r2!, {r0, r1, r3} \n" /* Store xSecureContext, PSPLIM and LR on the stack. */
" stmdb r2!, {r0, r1, r3} \n" /* Store xSecureContext, PSPLIM and LR on the stack. */
" ldr r3, =pxCurrentTCB \n" /* Read the location of pxCurrentTCB i.e. &( pxCurrentTCB ). */
" ldr r1, [r3] \n" /* Read pxCurrentTCB. */
" str r2, [r1] \n" /* Save the new top of stack in TCB. */
" \n"
" select_next_task: \n"
" mov r0, %0 \n" /* r0 = configMAX_SYSCALL_INTERRUPT_PRIORITY */
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19 changes: 6 additions & 13 deletions portable/GCC/ARM_CM35P/non_secure/portasm.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -419,31 +419,24 @@ void vClearInterruptMask( __attribute__( ( unused ) ) uint32_t ulMask ) /* __att
" lsls r1, r3, #25 \n" /* r1 = 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. */
" bpl save_ns_context \n" /* bpl - branch if positive or zero. If r1 >= 0 ==> Bit[6] in EXC_RETURN is 0 i.e. non-secure stack was used. */
" \n"
" ldr r3, =pxCurrentTCB \n" /* Read the location of pxCurrentTCB i.e. &( pxCurrentTCB ). */
" ldr r1, [r3] \n" /* Read pxCurrentTCB.*/
" subs r2, r2, #12 \n" /* Make space for xSecureContext, PSPLIM and LR on the stack. */
" str r2, [r1] \n" /* Save the new top of stack in TCB. */
" mrs r1, psplim \n" /* r1 = PSPLIM. */
" mov r3, lr \n" /* r3 = LR/EXC_RETURN. */
" stmia r2!, {r0, r1, r3} \n" /* Store xSecureContext, PSPLIM and LR on the stack. */
" stmdb r2!, {r0, r1, r3} \n" /* Store xSecureContext, PSPLIM and LR on the stack. */
" b select_next_task \n"
" \n"
" save_ns_context: \n"
" ldr r3, =pxCurrentTCB \n" /* Read the location of pxCurrentTCB i.e. &( pxCurrentTCB ). */
" ldr r1, [r3] \n" /* Read pxCurrentTCB. */
#if ( ( configENABLE_FPU == 1 ) || ( configENABLE_MVE == 1 ) )
" tst lr, #0x10 \n" /* Test Bit[4] in LR. Bit[4] of EXC_RETURN is 0 if the Extended Stack Frame is in use. */
" it eq \n"
" vstmdbeq r2!, {s16-s31} \n" /* Store the additional FP context registers which are not saved automatically. */
#endif /* configENABLE_FPU || configENABLE_MVE */
" subs r2, r2, #44 \n" /* Make space for xSecureContext, PSPLIM, LR and the remaining registers on the stack. */
" str r2, [r1] \n" /* Save the new top of stack in TCB. */
" adds r2, r2, #12 \n" /* r2 = r2 + 12. */
" stm r2, {r4-r11} \n" /* Store the registers that are not saved automatically. */
" stmdb r2!, {r4-r11} \n" /* Store the registers that are not saved automatically. */
" mrs r1, psplim \n" /* r1 = PSPLIM. */
" mov r3, lr \n" /* r3 = LR/EXC_RETURN. */
" subs r2, r2, #12 \n" /* r2 = r2 - 12. */
" stmia r2!, {r0, r1, r3} \n" /* Store xSecureContext, PSPLIM and LR on the stack. */
" stmdb r2!, {r0, r1, r3} \n" /* Store xSecureContext, PSPLIM and LR on the stack. */
" ldr r3, =pxCurrentTCB \n" /* Read the location of pxCurrentTCB i.e. &( pxCurrentTCB ). */
" ldr r1, [r3] \n" /* Read pxCurrentTCB. */
" str r2, [r1] \n" /* Save the new top of stack in TCB. */
" \n"
" select_next_task: \n"
" mov r0, %0 \n" /* r0 = configMAX_SYSCALL_INTERRUPT_PRIORITY */
Expand Down
19 changes: 6 additions & 13 deletions portable/GCC/ARM_CM55/non_secure/portasm.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -419,31 +419,24 @@ void vClearInterruptMask( __attribute__( ( unused ) ) uint32_t ulMask ) /* __att
" lsls r1, r3, #25 \n" /* r1 = 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. */
" bpl save_ns_context \n" /* bpl - branch if positive or zero. If r1 >= 0 ==> Bit[6] in EXC_RETURN is 0 i.e. non-secure stack was used. */
" \n"
" ldr r3, =pxCurrentTCB \n" /* Read the location of pxCurrentTCB i.e. &( pxCurrentTCB ). */
" ldr r1, [r3] \n" /* Read pxCurrentTCB.*/
" subs r2, r2, #12 \n" /* Make space for xSecureContext, PSPLIM and LR on the stack. */
" str r2, [r1] \n" /* Save the new top of stack in TCB. */
" mrs r1, psplim \n" /* r1 = PSPLIM. */
" mov r3, lr \n" /* r3 = LR/EXC_RETURN. */
" stmia r2!, {r0, r1, r3} \n" /* Store xSecureContext, PSPLIM and LR on the stack. */
" stmdb r2!, {r0, r1, r3} \n" /* Store xSecureContext, PSPLIM and LR on the stack. */
" b select_next_task \n"
" \n"
" save_ns_context: \n"
" ldr r3, =pxCurrentTCB \n" /* Read the location of pxCurrentTCB i.e. &( pxCurrentTCB ). */
" ldr r1, [r3] \n" /* Read pxCurrentTCB. */
#if ( ( configENABLE_FPU == 1 ) || ( configENABLE_MVE == 1 ) )
" tst lr, #0x10 \n" /* Test Bit[4] in LR. Bit[4] of EXC_RETURN is 0 if the Extended Stack Frame is in use. */
" it eq \n"
" vstmdbeq r2!, {s16-s31} \n" /* Store the additional FP context registers which are not saved automatically. */
#endif /* configENABLE_FPU || configENABLE_MVE */
" subs r2, r2, #44 \n" /* Make space for xSecureContext, PSPLIM, LR and the remaining registers on the stack. */
" str r2, [r1] \n" /* Save the new top of stack in TCB. */
" adds r2, r2, #12 \n" /* r2 = r2 + 12. */
" stm r2, {r4-r11} \n" /* Store the registers that are not saved automatically. */
" stmdb r2!, {r4-r11} \n" /* Store the registers that are not saved automatically. */
" mrs r1, psplim \n" /* r1 = PSPLIM. */
" mov r3, lr \n" /* r3 = LR/EXC_RETURN. */
" subs r2, r2, #12 \n" /* r2 = r2 - 12. */
" stmia r2!, {r0, r1, r3} \n" /* Store xSecureContext, PSPLIM and LR on the stack. */
" stmdb r2!, {r0, r1, r3} \n" /* Store xSecureContext, PSPLIM and LR on the stack. */
" ldr r3, =pxCurrentTCB \n" /* Read the location of pxCurrentTCB i.e. &( pxCurrentTCB ). */
" ldr r1, [r3] \n" /* Read pxCurrentTCB. */
" str r2, [r1] \n" /* Save the new top of stack in TCB. */
" \n"
" select_next_task: \n"
" mov r0, %0 \n" /* r0 = configMAX_SYSCALL_INTERRUPT_PRIORITY */
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