arch: riscv: Add function to clear all unlocked PMP entries #97310
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tested on my side: ---> Call the |
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Introduce the new function `riscv_pmp_clear_all()` to reset the Physical Memory Protection (PMP) configuration. This function iterates through all configured PMP slots. For each entry, it writes 0x0 to the entry's 8-bit configuration register. This action attempts to clear all fields, including the Address Matching Mode (A) bits (setting the region type to OFF), the permission bits (R, W, X), and the Lock (L) bit. According to the RISC-V specification, any writes to the configuration or address registers of a locked PMP entry are ignored. Thus, locked entries will remain unchanged, while all non-locked entries will be effectively disabled and their permissions cleared. The function ensures it operates in Machine mode with MSTATUS.MPRV = 0 and MSTATUS.MPP = M-mode before modifying any PMP Control and Status Registers (CSRs). This provides a mechanism to clear all non-locked PMP regions, returning them to a default disabled state. The function declaration is exposed in the `include/zephyr/arch/riscv/pmp.h` header file, making it available for inclusion and use by external modules. It is recommended for firmware to call this function before transitioning from a Read-Only (RO) stage to a Read-Write (RW) stage. This ensures that any PMP settings established during the RO phase, which might no longer be appropriate, are cleared, providing a clean and secure base PMP configuration for the RW firmware. Signed-off-by: Firas Sammoura <[email protected]>
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Introduce the new function
riscv_pmp_clear_all()to securely reset the Physical Memory Protection (PMP) configuration.This function iterates through all configured PMP slots. For each entry, it checks if the Lock (L) bit is set. If the entry is not locked, it clears the Address Matching Mode (A) bits, effectively setting the region type to OFF (Null Region), disabling the entry.
The function ensures it operates in Machine mode with MSTATUS.MPRV = 0 before modifying any PMP Control and Status Registers (CSRs).
This provides a mechanism to clear all non-locked PMP regions, returning them to a default disabled state. The function is exposed in the pmp.h header file.