arch/arm: Correct exception location "LR - 4" when PC invalid fault case

If PC becomes invalid causing a fault, we replace the system_exception_location with the address at LR. However, since the value of LR is the address to execute after returning, the actual address that caused the fault is the address -4. Therefore, when replacing LR with exception location, it is corrected to address - 4. This will help avoid confusion for developers working on debugging applications such as TRAP. Signed-off-by: eunwoo.nam <[email protected]>
Samsung · Feb 3, 2025 · 3c569ec · 3c569ec
1 parent 2781f32
commit 3c569ec
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Showing 4 changed files with 4 additions and 4 deletions.
diff --git a/os/arch/arm/src/armv7-m/up_memfault.c b/os/arch/arm/src/armv7-m/up_memfault.c
@@ -156,7 +156,7 @@ int up_memfault(int irq, FAR void *context, FAR void *arg)
 	uint32_t mmfar = getreg32(NVIC_MEMMANAGE_ADDR);
 	system_exception_location = regs[REG_R15];
 	if (cfsr & IACCVIOL) {
-		system_exception_location = regs[REG_R14];	/* The PC value might be invalid, so use LR */
+		system_exception_location = regs[REG_R14] - 4;	/* The PC value might be invalid, so use LR */
 	}
 
 	if (!IS_SECURE_STATE()) {

diff --git a/os/arch/arm/src/armv7-m/up_usagefault.c b/os/arch/arm/src/armv7-m/up_usagefault.c
@@ -117,7 +117,7 @@ int up_usagefault(int irq, FAR void *context, FAR void *arg)
 	if (cfsr & INVPC) {
 		/* As PC value might be invalid use LR value to determine if
 		 * the crash occurred in the kernel space or in the user space */
-		system_exception_location = regs[REG_R14];
+		system_exception_location = regs[REG_R14] - 4;
 	}
 
 	/* Add new line to distinguish between normal log and assert log.*/

diff --git a/os/arch/arm/src/armv8-m/up_memfault.c b/os/arch/arm/src/armv8-m/up_memfault.c
@@ -156,7 +156,7 @@ int up_memfault(int irq, FAR void *context, FAR void *arg)
 	uint32_t mmfar = getreg32(NVIC_MEMMANAGE_ADDR);
 	system_exception_location = regs[REG_R15];
 	if (cfsr & IACCVIOL) {
-		system_exception_location = regs[REG_R14];	/* The PC value might be invalid, so use LR */
+		system_exception_location = regs[REG_R14] - 4;	/* The PC value might be invalid, so use LR */
 	}
 
 	/* Add new line to distinguish between normal log and assert log.*/

diff --git a/os/arch/arm/src/armv8-m/up_usagefault.c b/os/arch/arm/src/armv8-m/up_usagefault.c
@@ -120,7 +120,7 @@ int up_usagefault(int irq, FAR void *context, FAR void *arg)
 	if (cfsr & INVPC) {
 		/* As PC value might be invalid use LR value to determine if
 		 * the crash occurred in the kernel space or in the user space */
-		system_exception_location = regs[REG_R14];
+		system_exception_location = regs[REG_R14] - 4;
 	}
 
 	/* Add new line to distinguish between normal log and assert log.*/