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arch: riscv: Add function to clear all unlocked PMP entries #96185

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arch: riscv: Add function to clear all unlocked PMP entries #96185

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48 changes: 48 additions & 0 deletions arch/riscv/core/pmp.c
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Original file line number Diff line number Diff line change
Expand Up @@ -345,6 +345,54 @@ static unsigned long global_pmp_last_addr;
/* End of global PMP entry range */
static unsigned int global_pmp_end_index;

void riscv_pmp_clear_all(void)
{
/*
* Ensure we are in M-mode and that memory accesses use M-mode privileges
* (MPRV=0). We also set MPP to M-mode to establish a predictable prior privilege level.
*/
csr_clear(mstatus, MSTATUS_MPRV);
csr_set(mstatus, MSTATUS_MPP);

unsigned long pmp_cfg[CONFIG_PMP_SLOTS / PMPCFG_STRIDE];

#ifdef CONFIG_64BIT
pmp_cfg[0] = csr_read(pmpcfg0);
#if CONFIG_PMP_SLOTS > 8
pmp_cfg[1] = csr_read(pmpcfg2);
#endif
#else
pmp_cfg[0] = csr_read(pmpcfg0);
pmp_cfg[1] = csr_read(pmpcfg1);
#if CONFIG_PMP_SLOTS > 8
pmp_cfg[2] = csr_read(pmpcfg2);
pmp_cfg[3] = csr_read(pmpcfg3);
#endif
#endif

uint8_t *pmp_n_cfg = (uint8_t *)pmp_cfg;

for (int index = 0; index < CONFIG_PMP_SLOTS; ++index) {
if ((pmp_n_cfg[index] & PMP_L) == 0) {
pmp_n_cfg[index] &= ~PMP_A;
}
}

#ifdef CONFIG_64BIT
csr_write(pmpcfg0, pmp_cfg[0]);
#if CONFIG_PMP_SLOTS > 8
csr_write(pmpcfg2, pmp_cfg[1]);
#endif
#else
csr_write(pmpcfg0, pmp_cfg[0]);
csr_write(pmpcfg1, pmp_cfg[1]);
#if CONFIG_PMP_SLOTS > 8
csr_write(pmpcfg2, pmp_cfg[2]);
csr_write(pmpcfg3, pmp_cfg[3]);
#endif
#endif
}

/**
* @Brief Initialize the PMP with global entries on each CPU
*/
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11 changes: 11 additions & 0 deletions arch/riscv/include/pmp.h
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Original file line number Diff line number Diff line change
Expand Up @@ -15,4 +15,15 @@ void z_riscv_pmp_usermode_init(struct k_thread *thread);
void z_riscv_pmp_usermode_prepare(struct k_thread *thread);
void z_riscv_pmp_usermode_enable(struct k_thread *thread);

/**
* @brief Resets all unlocked PMP entries to OFF mode (Null Region).
*
* This function is used to securely clear the PMP configuration. It first
* ensures the execution context is M-mode by setting MSTATUS_MPRV=0 and
* MSTATUS_MPP=M-mode. It then reads all pmpcfgX CSRs, iterates through
* the configuration bytes, and clears the Address Matching Mode bits (PMP_A)
* for any entry that is not locked (PMP_L is clear), effectively disabling the region.
*/
void riscv_pmp_clear_all(void);

#endif /* PMP_H_ */