runtime: bump libfringe, impl ecall abi

See libfringe PR: M-Labs/libfringe#1

artiq/firmware/Cargo.lock

@@ -163,9 +163,9 @@ dependencies = [
 [[package]]
 name = "fringe"
 version = "1.2.1"
-source = "git+https://git.m-labs.hk/M-Labs/libfringe.git?rev=9748bb#9748bb8af86c131d45be1238ea4d5f965a974630"
+source = "git+https://git.m-labs.hk/M-Labs/libfringe.git?rev=3ecbe5#3ecbe53f7644b18ee46ebd5b2ca12c9cbceec43a"
 dependencies = [
- "libc 0.2.101",
+ "libc 0.2.103",
 ]
 
 [[package]]

artiq/firmware/runtime/Cargo.toml

@@ -32,6 +32,6 @@ riscv = { version = "0.6.0", features = ["inline-asm"] }
 
 [dependencies.fringe]
 git = "https://git.m-labs.hk/M-Labs/libfringe.git"
-rev = "9748bb"
+rev = "3ecbe5"
 default-features = false
 features = ["alloc"]

artiq/firmware/runtime/main.rs

@@ -290,6 +290,18 @@ pub extern fn exception(regs: *const TrapFrame) {
         mcause::Trap::Interrupt(source) => {
             info!("Called interrupt with {:?}", source);
         },
+
+        mcause::Trap::Exception(mcause::Exception::UserEnvCall) => {
+            unsafe {
+                if (*regs).a7 == 0 {
+                    pmp::pop_pmp_region()
+                } else {
+                    pmp::push_pmp_region((*regs).a7)
+                }
+            }
+            mepc::write(pc + 4);
+        },
+
         mcause::Trap::Exception(e) => {
             println!("Trap frame: {:x?}", unsafe { *regs });
 

artiq/firmware/runtime/sched.rs

@@ -61,7 +61,8 @@ impl Thread {
         let spawned = io.spawned.clone();
         let sockets = io.sockets.clone();
 
-        let stack = OwnedStack::new(stack_size);
+        // Add a 4k stack guard to the stack of any new threads
+        let stack = OwnedStack::new(stack_size + 4096);
         ThreadHandle::new(Thread {
             generator: Generator::unsafe_new(stack, |yielder, _| {
                 f(Io {