Fix logic for returning from exceptions to user-mode contexts

2 files changed, 65 insertions, 38 deletions

diff --git a/nuttx/arch/arm/src/armv7-a/arm_syscall.c b/nuttx/arch/arm/src/armv7-a/arm_syscall.c
index a312d9636..eeb8c1fdd 100644
--- a/nuttx/arch/arm/src/armv7-a/arm_syscall.c
+++ b/nuttx/arch/arm/src/armv7-a/arm_syscall.c
@@ -414,9 +414,18 @@ uint32_t *arm_syscall(uint32_t *regs)
         break;
     }
 
+#if defined(CONFIG_DEBUG_SYSCALL)
   /* Report what happened */
 
-  svcdbg("SYSCALL Return: %d \n", regs[REG_R0]);
+  svcdbg("SYSCALL Exit: regs: %p: %d\n", regs);
+  svcdbg("  R0: %08x %08x %08x %08x %08x %08x %08x %08x\n",
+         regs[REG_R0],  regs[REG_R1],  regs[REG_R2],  regs[REG_R3],
+         regs[REG_R4],  regs[REG_R5],  regs[REG_R6],  regs[REG_R7]);
+  svcdbg("  R8: %08x %08x %08x %08x %08x %08x %08x %08x\n",
+         regs[REG_R8],  regs[REG_R9],  regs[REG_R10], regs[REG_R11],
+         regs[REG_R12], regs[REG_R13], regs[REG_R14], regs[REG_R15]);
+  svcdbg("CPSR: %08x\n", regs[REG_CPSR]);
+#endif
 
   /* Return the last value of curent_regs.  This supports context switchs
    * on return from the exception.  That capability is not used here,
diff --git a/nuttx/arch/arm/src/armv7-a/arm_vectors.S b/nuttx/arch/arm/src/armv7-a/arm_vectors.S
index a8a9f38ca..f272460d2 100644
--- a/nuttx/arch/arm/src/armv7-a/arm_vectors.S
+++ b/nuttx/arch/arm/src/armv7-a/arm_vectors.S
@@ -201,11 +201,11 @@ arm_vectorirq:
 
 	/* Restore the CPSR, SVC mode registers and return */
 
-	ldr		r1, [r0, #(4*REG_CPSR)]	/* Setup the return SPSR */
-	msr		spsr, r1				/* Establish the return mode SPSR */
+	ldr		r1, [r0, #(4*REG_CPSR)]	/* Fetch the return SPSR */
+	msr		spsr, r1				/* Set the return mode SPSR */
 
 #ifdef CONFIG_BUILD_KERNEL
-	/* Did we enter from user mode?  If so then we need to restore the
+	/* Are we leaving in user mode?  If so then we need to restore the
 	 * values of USER mode r13(sp) and r14(lr).
 	 */
 
@@ -217,9 +217,12 @@ arm_vectorirq:
 	 * is not in the register list).
 	 */
 
-	add		r1, r0, #(4*REG_R13)	/* R1=address of R13/R14 storage */
-	ldmia	r1, {r13, r14}^			/* Restore to user mode USER R13/R14 */
-	ldmia	r0, {r0-R12,r15}^		/* Return */
+	mov		r13, r0					/* (SVC) R13=Register storage area */
+	ldmia	r13, {r0-R12}			/* Restore common R0-R12 */
+	add		r14, r13, #(4*REG_R13)	/* (SVC) R14=address of R13/R14 storage */
+	ldmia	r14, {r13, r14}^		/* Restore user mode R13/R14 */
+	add		r14, r13, #(4*REG_R15)	/* (SVC) R14=address of R15 storage */
+	ldmia	r14, {r15}^				/* Return */
 
 .Lirqleavesvc:
 #endif
@@ -327,11 +330,11 @@ arm_vectorsvc:
 
 	/* Restore the CPSR, SVC mode registers and return */
 
-	ldr		r1, [r0, #(4*REG_CPSR)]	/* Setup the SVC mode SPSR */
-	msr		spsr, r1				/* Establish the return mode SPSR */
+	ldr		r1, [r0, #(4*REG_CPSR)]	/* Fetch the return SPSR */
+	msr		spsr, r1				/* Set the return mode SPSR */
 
 #ifdef CONFIG_BUILD_KERNEL
-	/* Did we enter from user mode?  If so then we need to restore the
+	/* Are we leaving in user mode?  If so then we need to restore the
 	 * values of USER mode r13(sp) and r14(lr).
 	 */
 
@@ -343,9 +346,12 @@ arm_vectorsvc:
 	 * is not in the register list).
 	 */
 
-	add		r1, r0, #(4*REG_R13)	/* R1=address of R13/R14 storage */
-	ldmia	r1, {r13, r14}^			/* Restore to user mode USER R13/R14 */
-	ldmia	r0, {r0-R12,r15}^		/* Return */
+	mov		r13, r0					/* (SVC) R13=Register storage area */
+	ldmia	r13, {r0-R12}			/* Restore common R0-R12 */
+	add		r14, r13, #(4*REG_R13)	/* (SVC) R14=address of R13/R14 storage */
+	ldmia	r14, {r13, r14}^		/* Restore user mode R13/R14 */
+	add		r14, r13, #(4*REG_R15)	/* (SVC) R14=address of R15 storage */
+	ldmia	r14, {r15}^				/* Return */
 
 .Lleavesvcsvc:
 #endif
@@ -468,11 +474,11 @@ arm_vectordata:
 
 	/* Restore the CPSR, SVC mode registers and return */
 
-	ldr		r1, [r0, #(4*REG_CPSR)]	/* Setup the SVC mode SPSR */
-	msr		spsr_cxsf, r1			/* Establish the return mode SPSR */
+	ldr		r1, [r0, #(4*REG_CPSR)]	/* Fetch the return SPSR */
+	msr		spsr_cxsf, r1			/* Set the return mode SPSR */
 
 #ifdef CONFIG_BUILD_KERNEL
-	/* Did we enter from user mode?  If so then we need to restore the
+	/* Are we leaving in user mode?  If so then we need to restore the
 	 * values of USER mode r13(sp) and r14(lr).
 	 */
 
@@ -484,9 +490,12 @@ arm_vectordata:
 	 * is not in the register list).
 	 */
 
-	add		r1, r0, #(4*REG_R13)	/* R1=address of R13/R14 storage */
-	ldmia	r1, {r13, r14}^			/* Restore to user mode USER R13/R14 */
-	ldmia	r0, {r0-R12,r15}^		/* Return */
+	mov		r13, r0					/* (SVC) R13=Register storage area */
+	ldmia	r13, {r0-R12}			/* Restore common R0-R12 */
+	add		r14, r13, #(4*REG_R13)	/* (SVC) R14=address of R13/R14 storage */
+	ldmia	r14, {r13, r14}^		/* Restore user mode R13/R14 */
+	add		r14, r13, #(4*REG_R15)	/* (SVC) R14=address of R15 storage */
+	ldmia	r14, {r15}^				/* Return */
 
 .Ldabtleavesvc:
 #endif
@@ -611,11 +620,11 @@ arm_vectorprefetch:
 
 	/* Restore the CPSR, SVC mode registers and return */
 
-	ldr		r1, [r0, #(4*REG_CPSR)]	/* Setup the SVC mode SPSR */
-	msr		spsr_cxsf, r1			/* Establish the return mode SPSR */
+	ldr		r1, [r0, #(4*REG_CPSR)]	/* Fetch the return SPSR */
+	msr		spsr_cxsf, r1			/* Set the return mode SPSR */
 
 #ifdef CONFIG_BUILD_KERNEL
-	/* Did we enter from user mode?  If so then we need to restore the
+	/* Are we leaving in user mode?  If so then we need to restore the
 	 * values of USER mode r13(sp) and r14(lr).
 	 */
 
@@ -627,9 +636,12 @@ arm_vectorprefetch:
 	 * is not in the register list).
 	 */
 
-	add		r1, r0, #(4*REG_R13)	/* R1=address of R13/R14 storage */
-	ldmia	r1, {r13, r14}^			/* Restore to user mode USER R13/R14 */
-	ldmia	r0, {r0-R12,r15}^		/* Return */
+	mov		r13, r0					/* (SVC) R13=Register storage area */
+	ldmia	r13, {r0-R12}			/* Restore common R0-R12 */
+	add		r14, r13, #(4*REG_R13)	/* (SVC) R14=address of R13/R14 storage */
+	ldmia	r14, {r13, r14}^		/* Restore user mode R13/R14 */
+	add		r14, r13, #(4*REG_R15)	/* (SVC) R14=address of R15 storage */
+	ldmia	r14, {r15}^				/* Return */
 
 .Lpabtleavesvc:
 #endif
@@ -749,11 +761,11 @@ arm_vectorundefinsn:
 
 	/* Restore the CPSR, SVC mode registers and return */
 
-	ldr		r1, [r0, #(4*REG_CPSR)]	/* Setup the SVC mode SPSR */
-	msr		spsr_cxsf, r1			/* Establish the return mode SPSR */
+	ldr		r1, [r0, #(4*REG_CPSR)]	/* Fetch the return SPSR */
+	msr		spsr_cxsf, r1			/* Set the return mode SPSR */
 
 #ifdef CONFIG_BUILD_KERNEL
-	/* Did we enter from user mode?  If so then we need to restore the
+	/* Are we leaving in user mode?  If so then we need to restore the
 	 * values of USER mode r13(sp) and r14(lr).
 	 */
 
@@ -765,9 +777,12 @@ arm_vectorundefinsn:
 	 * is not in the register list).
 	 */
 
-	add		r1, r0, #(4*REG_R13)	/* R1=address of R13/R14 storage */
-	ldmia	r1, {r13, r14}^			/* Restore to user mode USER R13/R14 */
-	ldmia	r0, {r0-R12,r15}^		/* Return */
+	mov		r13, r0					/* (SVC) R13=Register storage area */
+	ldmia	r13, {r0-R12}			/* Restore common R0-R12 */
+	add		r14, r13, #(4*REG_R13)	/* (SVC) R14=address of R13/R14 storage */
+	ldmia	r14, {r13, r14}^		/* Restore user mode R13/R14 */
+	add		r14, r13, #(4*REG_R15)	/* (SVC) R14=address of R15 storage */
+	ldmia	r14, {r15}^				/* Return */
 
 .Lundefleavesvc:
 #endif
@@ -826,7 +841,7 @@ arm_vectorfiq:
 
 #ifdef CONFIG_BUILD_KERNEL
 	/* Did we enter from user mode?  If so then we need get the values of
-	 * USER mode r13(sp) and r14(lr).
+	 * USER mode rr13(sp) and r14(lr).
 	 */
 
 	and		r1, r4, #PSR_MODE_MASK	/* Interrupted mode */
@@ -897,11 +912,11 @@ arm_vectorfiq:
 
 	/* Restore the CPSR, SVC mode registers and return */
 
-	ldr		r1, [r0, #(4*REG_CPSR)]	/* Setup the SVC mode SPSR */
-	msr		spsr, r1				/* Establish the return mode SPSR */
+	ldr		r1, [r0, #(4*REG_CPSR)]	/* Fetch the return SPSR */
+	msr		spsr, r1				/* Set the return mode SPSR */
 
 #ifdef CONFIG_BUILD_KERNEL
-	/* Did we enter from user mode?  If so then we need to restore the
+	/* Are we leaving in user mode?  If so then we need to restore the
 	 * values of USER mode r13(sp) and r14(lr).
 	 */
 
@@ -913,9 +928,12 @@ arm_vectorfiq:
 	 * is not in the register list).
 	 */
 
-	add		r1, r0, #(4*REG_R13)	/* R1=address of R13/R14 storage */
-	ldmia	r1, {r13, r14}^			/* Restore to user mode USER R13/R14 */
-	ldmia	r0, {r0-R12,r15}^		/* Return */
+	mov		r13, r0					/* (SVC) R13=Register storage area */
+	ldmia	r13, {r0-R12}			/* Restore common R0-R12 */
+	add		r14, r13, #(4*REG_R13)	/* (SVC) R14=address of R13/R14 storage */
+	ldmia	r14, {r13, r14}^		/* Restore user mode R13/R14 */
+	add		r14, r13, #(4*REG_R15)	/* (SVC) R14=address of R15 storage */
+	ldmia	r14, {r15}^				/* Return */
 
 .Lfiqleavesvc:
 #endif