diff --git a/src/target/efm32.c b/src/target/efm32.c
index f821878..6ad4f32 100644
--- a/src/target/efm32.c
+++ b/src/target/efm32.c
@@ -584,7 +584,10 @@ static efm32_device_t const * efm32_get_device(size_t index)
 /**
  * Probe
  */
-static char efm32_variant_string[60];
+struct efm32_priv_s {
+	char efm32_variant_string[60];
+};
+
 bool efm32_probe(target *t)
 {
 	uint8_t di_version = 1;
@@ -636,13 +639,17 @@ bool efm32_probe(target *t)
 	uint32_t ram_size   = ram_kib   * 0x400;
 	uint32_t flash_page_size = device->flash_page_size;
 
-	snprintf(efm32_variant_string, sizeof(efm32_variant_string), "%c\b%c\b%s %d F%d %s",
+	struct efm32_priv_s *priv_storage = calloc(1, sizeof(*priv_storage));
+	t->target_storage = (void*)priv_storage;
+
+	snprintf(priv_storage->efm32_variant_string,
+			 sizeof(priv_storage->efm32_variant_string), "%c\b%c\b%s %d F%d %s",
 			di_version + 48, (uint8_t)device_index + 32,
 			device->name, part_number, flash_kib, device->description);
 
 	/* Setup Target */
 	t->target_options |= CORTEXM_TOPT_INHIBIT_SRST;
-	t->driver = efm32_variant_string;
+	t->driver = priv_storage->efm32_variant_string;
 	tc_printf(t, "flash size %d page size %d\n", flash_size, flash_page_size);
 	target_add_ram (t, SRAM_BASE, ram_size);
 	efm32_add_flash(t, 0x00000000, flash_size, flash_page_size);
@@ -980,7 +987,10 @@ static bool nop_function(void)
 /**
  * AAP Probe
  */
-char aap_driver_string[42];
+struct efm32_aap_priv_s {
+       char aap_driver_string[42];
+};
+
 void efm32_aap_probe(ADIv5_AP_t *ap)
 {
 	if ((ap->idr & EFM32_APP_IDR_MASK) == EFM32_AAP_IDR) {
@@ -1004,10 +1014,11 @@ void efm32_aap_probe(ADIv5_AP_t *ap)
 	/* Read status */
 	DEBUG_INFO("EFM32: AAP STATUS=%08"PRIx32"\n", adiv5_ap_read(ap, AAP_STATUS));
 
-	sprintf(aap_driver_string,
+	struct efm32_aap_priv_s *priv_storage = calloc(1, sizeof(*priv_storage));
+	sprintf(priv_storage->aap_driver_string,
 			"EFM32 Authentication Access Port rev.%d",
 			aap_revision);
-	t->driver = aap_driver_string;
+	t->driver = priv_storage->aap_driver_string;
 	t->attach = (void*)nop_function;
 	t->detach = (void*)nop_function;
 	t->check_error = (void*)nop_function;
diff --git a/src/target/samd.c b/src/target/samd.c
index 525a43b..02879fb 100644
--- a/src/target/samd.c
+++ b/src/target/samd.c
@@ -441,7 +441,10 @@ static void samd_add_flash(target *t, uint32_t addr, size_t length)
 	target_add_flash(t, f);
 }
 
-static char samd_variant_string[60];
+struct samd_priv_s {
+	char samd_variant_string[60];
+};
+
 bool samd_probe(target *t)
 {
 	ADIv5_AP_t *ap = cortexm_ap(t);
@@ -460,6 +463,9 @@ bool samd_probe(target *t)
 	if ((did & SAMD_DID_MASK) != SAMD_DID_CONST_VALUE)
 		return false;
 
+	struct samd_priv_s *priv_storage = calloc(1, sizeof(*priv_storage));
+	t->target_storage = (void*)priv_storage;
+
 	uint32_t ctrlstat = target_mem_read32(t, SAMD_DSU_CTRLSTAT);
 	struct samd_descr samd = samd_parse_device_id(did);
 
@@ -468,14 +474,14 @@ bool samd_probe(target *t)
 
 	/* Part String */
 	if (protected) {
-		sprintf(samd_variant_string,
+		sprintf(priv_storage->samd_variant_string,
 		        "Atmel SAM%c%d%c%d%c%s (rev %c) (PROT=1)",
 		        samd.family,
 		        samd.series, samd.pin, samd.mem,
 		        samd.variant,
 		        samd.package, samd.revision);
 	} else {
-		sprintf(samd_variant_string,
+		sprintf(priv_storage->samd_variant_string,
 		        "Atmel SAM%c%d%c%d%c%s (rev %c)",
 		        samd.family,
 		        samd.series, samd.pin, samd.mem,
@@ -484,7 +490,7 @@ bool samd_probe(target *t)
 	}
 
 	/* Setup Target */
-	t->driver = samd_variant_string;
+	t->driver = priv_storage->samd_variant_string;
 	t->reset = samd_reset;
 
 	if (samd.series == 20 && samd.revision == 'B') {
diff --git a/src/target/samx5x.c b/src/target/samx5x.c
index 4569ae4..d0abff6 100644
--- a/src/target/samx5x.c
+++ b/src/target/samx5x.c
@@ -344,7 +344,10 @@ static void samx5x_add_flash(target *t, uint32_t addr, size_t length,
 	target_add_flash(t, f);
 }
 
-static char samx5x_variant_string[60];
+struct samx5x_priv_s {
+	char samx5x_variant_string[60];
+};
+
 bool samx5x_probe(target *t)
 {
 	ADIv5_AP_t *ap = cortexm_ap(t);
@@ -370,20 +373,25 @@ bool samx5x_probe(target *t)
 	bool protected = (ctrlstat & SAMX5X_STATUSB_PROT);
 
 	/* Part String */
+	struct samx5x_priv_s *priv_storage = calloc(1, sizeof(*priv_storage));
+	t->target_storage = (void*)priv_storage;
+
 	if (protected) {
-		snprintf(samx5x_variant_string, sizeof(samx5x_variant_string),
+		snprintf(priv_storage->samx5x_variant_string,
+				 sizeof(priv_storage->samx5x_variant_string),
 			 "Microchip SAM%c%d%c%dA (rev %c) (PROT=1)",
 			 samx5x.series_letter, samx5x.series_number,
 			 samx5x.pin, samx5x.mem, samx5x.revision);
 	} else {
-		snprintf(samx5x_variant_string, sizeof(samx5x_variant_string),
+		snprintf(priv_storage->samx5x_variant_string,
+				 sizeof(priv_storage->samx5x_variant_string),
 			 "Microchip SAM%c%d%c%dA (rev %c)",
 			 samx5x.series_letter, samx5x.series_number,
 			 samx5x.pin, samx5x.mem, samx5x.revision);
 	}
 
 	/* Setup Target */
-	t->driver = samx5x_variant_string;
+	t->driver = priv_storage->samx5x_variant_string;
 	t->reset = samx5x_reset;
 
 	if (protected) {