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riscv: impl pmp

This commit is contained in:
occheung 2021-10-08 14:33:55 +08:00 committed by Sébastien Bourdeauducq
parent 790a20edf6
commit a0bf11b465
3 changed files with 69 additions and 1 deletions

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@ -1,4 +1,5 @@
use super::cache;
use super::{cache, pmp};
use riscv::register::*;
pub unsafe fn reset() -> ! {
llvm_asm!(r#"
@ -16,3 +17,14 @@ pub unsafe fn jump(addr: usize) -> ! {
"# : : "r"(addr) : : "volatile");
loop {}
}
pub unsafe fn start_user(addr: usize) -> ! {
pmp::enable_user_memory();
mstatus::set_mpp(mstatus::MPP::User);
mepc::write(addr);
llvm_asm!(
"mret"
: : : : "volatile"
);
unreachable!()
}

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@ -1,2 +1,3 @@
pub mod cache;
pub mod boot;
pub mod pmp;

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@ -0,0 +1,55 @@
use riscv::register::{pmpaddr0, pmpaddr1, pmpaddr2, pmpaddr3, pmpcfg0};
static mut THREAD_DEPTH: u8 = 0;
const PMP_L : usize = 0b10000000;
const PMP_NAPOT: usize = 0b00011000;
const PMP_X : usize = 0b00000100;
const PMP_W : usize = 0b00000010;
const PMP_R : usize = 0b00000001;
const PMP_OFF : usize = 0b00000000;
#[inline(always)]
pub unsafe fn init_stack_guard(guard_base: usize) {
pmpaddr2::write((guard_base >> 2) | ((0x1000 - 1) >> 3));
pmpcfg0::write((PMP_L | PMP_NAPOT) << 16);
}
#[inline(always)]
pub fn enable_user_memory() {
pmpaddr3::write((0x80000000 - 1) >> 3);
pmpcfg0::write((PMP_L | PMP_NAPOT | PMP_X | PMP_W | PMP_R) << 24);
}
#[inline(always)]
pub unsafe fn push_pmp_region(addr: usize) {
let pmp_addr = (addr >> 2) | ((0x1000 - 1) >> 3);
match THREAD_DEPTH {
// Activate PMP0 when switching from main stack to thread
0 => {
pmpaddr0::write(pmp_addr);
pmpcfg0::write(PMP_NAPOT);
}
// Temporarily activate PMP1 when spawning a thread from a thread
// The thread should swap back to the main stack very soon after init
1 => {
pmpaddr1::write(pmp_addr);
pmpcfg0::write(PMP_NAPOT << 8 | PMP_NAPOT);
}
// Thread *running* another thread should not be possible
_ => unreachable!()
}
THREAD_DEPTH += 1;
}
#[inline(always)]
pub unsafe fn pop_pmp_region() {
THREAD_DEPTH -= 1;
match THREAD_DEPTH {
0 => pmpcfg0::write(PMP_OFF),
1 => pmpcfg0::write(PMP_NAPOT),
_ => unreachable!()
}
}