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Fix hardfault in MPU configuration #1193

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Mar 8, 2023
Merged

Fix hardfault in MPU configuration #1193

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33 changes: 17 additions & 16 deletions sys/kern/src/arch/arm_m.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -339,9 +339,6 @@ pub fn apply_memory_protection(task: &task::Task) {
};

for (i, region) in task.region_table().iter().enumerate() {
let rbar = (i as u32) // region number
| (1 << 4) // honor the region number
| region.base;
let ratts = region.attributes;
let xn = !ratts.contains(RegionAttributes::EXECUTE);
// These AP encodings are chosen such that we never deny *privileged*
Expand Down Expand Up @@ -406,15 +403,17 @@ pub fn apply_memory_protection(task: &task::Task) {
// with it.
let l2size = 30 - region.size.leading_zeros();

let rasr = (xn as u32) << 28
| ap << 24
| tex << 19
| scb << 16
| l2size << 1
| (1 << 0); // enable
// Region attribute and size register; note that enable (bit 0) is not
// set here, because it's possible to hard-fault midway through region
// configuration if address and size are incompatible while the region
// is enabled.
let rasr =
(xn as u32) << 28 | ap << 24 | tex << 19 | scb << 16 | l2size << 1;
unsafe {
mpu.rbar.write(rbar);
mpu.rasr.write(rasr);
mpu.rnr.write(i as u32); // Select the region
mpu.rasr.write(rasr); // configure, but leave disabled
mpu.rbar.write(region.base); // set region address
mpu.rasr.write(rasr | 1); // enable the region
}
}
}
Expand Down Expand Up @@ -464,10 +463,11 @@ pub fn apply_memory_protection(task: &task::Task) {
(0b0100_0100 | rw | rw << 4, 0b00)
};

// RLAR = our upper bound
let rlar = (region.base + region.size - 32)
| (i as u32) << 1 // AttrIndx
| (1 << 0); // enable
// RLAR = our upper bound; note that enable (bit 0) is not set, because
// it's possible to hard-fault midway through region configuration if
// address and size are incompatible while the region is enabled.
let rlar = (region.base + region.size - 32) // upper bound
| (i as u32) << 1; // AttrIndx

// RBAR = the base
let rbar = (xn as u32)
Expand All @@ -477,6 +477,7 @@ pub fn apply_memory_protection(task: &task::Task) {

unsafe {
mpu.rnr.write(rnr);
mpu.rlar.write(rlar); // configure but leave disabled
if rnr < 4 {
let mut mair0 = mpu.mair[0].read();
mair0 |= (mair as u32) << (rnr * 8);
Expand All @@ -487,7 +488,7 @@ pub fn apply_memory_protection(task: &task::Task) {
mpu.mair[1].write(mair1);
}
mpu.rbar.write(rbar);
mpu.rlar.write(rlar);
mpu.rlar.write(rlar | 1); // enable the region
}
}

Expand Down