arch: riscv: Add function to clear all unlocked PMP entries #97310
+220
−1
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
zephyrbot
added
area: RISCV
zephyrbot
requested review from
VynDragon,
dcpleung,
edersondisouza,
fkokosinski,
katsuster,
kgugala,
masz-nordic,
mgielda,
nashif,
npitre,
tgorochowik and
ycsin
fsammoura1980
force-pushed
the
reset_pmp
branch
from
2a291aa to
4507398
Compare
|
tested on my side: ---> Call the |
fsammoura1980
force-pushed
the
reset_pmp
branch
5 times, most recently
from
a13cada to
d17e907
Compare
fkokosinski
requested changes
Oct 10, 2025
There was a problem hiding this comment.
This would need automated testing in https://github.com/zephyrproject-rtos/zephyr/tree/main/tests/arch/riscv/pmp
This is better suited to be tested once the multi-threading units test get merged: I have experimented with the framework and I should be able to add unit tests. Currently, we are only testing single threads (no multithreading config) and all entries are locked. So adding a PMP reset will not yield meaningful results. |
fsammoura1980
force-pushed
the
reset_pmp
branch
2 times, most recently
from
617f99f to
a74f2ae
Compare
Introduce `z_riscv_pmp_write_config` to abstract writing to pmpcfg registers. This function handles the differing register layouts and slot counts between RV32 and RV64 architectures, writing to the appropriate pmpcfg0, pmpcfg1, pmpcfg2, or pmpcfg3 CSRs as needed based on CONFIG_PMP_SLOTS. Signed-off-by: Firas Sammoura <[email protected]>
fsammoura1980
force-pushed
the
reset_pmp
branch
from
a74f2ae to
599bde7
Compare
zephyrbot
added
the
area: Tests
fsammoura1980
force-pushed
the
reset_pmp
branch
2 times, most recently
from
b176616 to
c2e5694
Compare
The PR has been modified and a uint test was included |
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]>
fsammoura1980
force-pushed
the
reset_pmp
branch
3 times, most recently
from
21ad35f to
1dad080
Compare
Adds a new test suite to verify the behavior of `riscv_pmp_clear_all()`. These tests ensure that the function correctly clears all unlocked PMP entries while preserving any entries that are locked. Signed-off-by: Firas Sammoura <[email protected]>
fsammoura1980
force-pushed
the
reset_pmp
branch
from
1dad080 to
4d6025c
Compare
|
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
5 participants
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
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.