xiaoxiang781216 commented on code in PR #19123:
URL: https://github.com/apache/nuttx/pull/19123#discussion_r3410754766
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arch/arm/src/armv8-m/Kconfig:
##########
@@ -155,3 +155,15 @@ config ARMV8M_CMSE
bool "ARMv8-M Security Extensions"
---help---
Enable ARMv8-M Security Extensions.
+
+config ARMV8M_SP_CONTEXT_RESTORE
Review Comment:
this behavior isn't specific to cortex-m arch, it's better to move into
nuttx/sched/Kconfig after line 1596 and depend on ENABLE_ALL_SIGNALS
##########
arch/arm/src/armv8-m/arm_exception.S:
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@@ -237,6 +235,78 @@ exception_common:
ldmia r0!, {r1} /* Get psplim/msplim */
#endif
+#ifdef CONFIG_ARMV8M_SP_CONTEXT_RESTORE
+ /* Check if the desired SP (r2) differs from the implied SP.
+ * The implied SP after exception return = r0 + hw_frame_size,
+ * where hw_frame_size depends on whether the frame includes FPU
+ * state (determined by EXC_RETURN bit 4 in r14).
+ * If they differ, we must relocate the HW frame so that the final
+ * SP after hardware pop equals the desired value (r2).
+ */
+
+ push {r1, r3} /* Save psplim
+ basepri on MSP */
Review Comment:
it's more simple to do the context copy in c code(after `case
SYS_signal_handler_return:`.
##########
arch/arm/src/armv8-m/arm_exception.S:
##########
@@ -237,6 +235,78 @@ exception_common:
ldmia r0!, {r1} /* Get psplim/msplim */
#endif
+#ifdef CONFIG_ARMV8M_SP_CONTEXT_RESTORE
+ /* Check if the desired SP (r2) differs from the implied SP.
+ * The implied SP after exception return = r0 + hw_frame_size,
+ * where hw_frame_size depends on whether the frame includes FPU
+ * state (determined by EXC_RETURN bit 4 in r14).
+ * If they differ, we must relocate the HW frame so that the final
+ * SP after hardware pop equals the desired value (r2).
+ */
+
+ push {r1, r3} /* Save psplim
+ basepri on MSP */
+
+#ifdef CONFIG_ARCH_FPU
+ /* Determine actual HW frame size from EXC_RETURN:
+ * bit 4 set (STD_CONTEXT): 8 words = 32 bytes (no FPU)
+ * bit 4 clear: 26 words = 104 bytes (with FPU)
+ */
+
+ tst r14, #EXC_RETURN_STD_CONTEXT
+ ite ne
Review Comment:
use tab in all places to keep the alignment
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