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Implement g_nvic_prio_bits for UVISOR_DISABLED #195

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Merged
merged 1 commit into from
Mar 18, 2016
Merged

Implement g_nvic_prio_bits for UVISOR_DISABLED #195

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17 changes: 16 additions & 1 deletion api/src/disabled.c
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Original file line number Diff line number Diff line change
Expand Up @@ -21,6 +21,9 @@
#include <stdint.h>
#include <string.h>

/* Number of implemented priority bits */
uint8_t g_nvic_prio_bits;

/* Symbols exported by the mbed linker script */
UVISOR_EXTERN uint32_t __uvisor_cfgtbl_ptr_start;
UVISOR_EXTERN uint32_t __uvisor_cfgtbl_ptr_end;
Expand Down Expand Up @@ -186,7 +189,8 @@ static void uvisor_disabled_default_vector(void)

void uvisor_disabled_set_vector(uint32_t irqn, uint32_t vector)
{
uint8_t box_id;
uint8_t prio_bits, box_id;
uint8_t volatile *prio;

/* Check IRQn.
* We only allow user IRQs to be registered (NVIC). This is consistent with
Expand All @@ -204,6 +208,17 @@ void uvisor_disabled_set_vector(uint32_t irqn, uint32_t vector)
* user vectors explicitly set using this API are registered in the table. */
if (SCB->VTOR != (uint32_t) g_irq_table) {
SCB->VTOR = (uint32_t) g_irq_table;

/* Detect the number of implemented priority bits.
* The architecture specifies that unused/not implemented bits in the
* NVIC IP registers read back as 0. */
__disable_irq();
prio = (uint8_t volatile *) &(NVIC->IP[0]);
prio_bits = *prio;
*prio = 0xFFU;
g_nvic_prio_bits = (uint8_t) __builtin_popcount(*prio);
*prio = prio_bits;
__enable_irq();
}

/* Register IRQ.
Expand Down