diff --git a/arch/arm/core/cortex_m/__aeabi_read_tp.S b/arch/arm/core/cortex_m/__aeabi_read_tp.S
index 8aeba3e5d12..745fda73b9b 100644
--- a/arch/arm/core/cortex_m/__aeabi_read_tp.S
+++ b/arch/arm/core/cortex_m/__aeabi_read_tp.S
@@ -12,8 +12,14 @@ GTEXT(__aeabi_read_tp)
 
 GDATA(z_arm_tls_ptr)
 
+/* Grab the TLS pointer and store in R0.
+ * According to the Run-Time ABI for the Arm® Architecture section 5.3.5, this
+ * function may only clobber r0, ip, lr & CPSR.
+ *
+ * This can only be guaranteed by either implementing a naked C function with
+ * inline assembly, or plain assembly.
+ */
 SECTION_FUNC(TEXT, __aeabi_read_tp)
-	/* Grab the TLS pointer and store in R0 */
 	ldr r0, =z_arm_tls_ptr
 	ldr r0, [r0]
 	bx lr