libtock-rs apps don't really fit on the HiFive1

[alistair23]

Currently libtock-rs apps barely fit on the HiFive1 board.

Build the libtock-rs examples

PLATFORM=riscv32 cargo build --target=riscv32imac-unknown-none-elf --examples

Create a tbf file for the hello_world example

/scratch/alistair/software/tock/elf2tab/target/debug/elf2tab -o ./Tock-app.tab ./target/riscv32imac-unknown-none-elf/debug/examples/hello_world --stack 2048 --app-heap 1024 --kernel-heap 1024 -v --protected-region-size=64

Run the TBF file with master Tock (c94059d3e25dc635e682facff4894ef43b9aca0e and no debug) and QEMU:

/scratch/alistair/software/qemu/build/riscv32-softmmu/qemu-system-riscv32 -m 1G -M sifive_e -kernel /scratch/alistair/software/tock/tock/boards/hifive1/target/riscv32imac-unknown-none-elf/release/hifive1 -device loader,file=/scratch/alistair/software/tock/libtock-rs/target/riscv32imac-unknown-none-elf/debug/examples/hello_world.tbf,addr=0x20430000 -nographic
HiFive1 initialization complete. Entering main loop
Hello Tock World

It works and runs correctly :)

Now try to run the timer app

/scratch/alistair/software/tock/elf2tab/target/debug/elf2tab -o ./Tock-app.tab ./target/riscv32imac-unknown-none-elf/debug/examples/timer --stack 2048 --app-heap 1024 --kernel-heap 1024 -v --protected-region-size=64
/scratch/alistair/software/qemu/build/riscv32-softmmu/qemu-system-riscv32 -m 1G -M sifive_e -kernel /scratch/alistair/software/tock/tock/boards/hifive1/target/riscv32imac-unknown-none-elf/release/hifive1 -device loader,file=/scratch/alistair/software/tock/libtock-rs/target/riscv32imac-unknown-none-elf/debug/examples/timer.tbf,addr=0x20430000 -nographic

and you will see this:

HiFive1 initialization complete. Entering main loop
...
---| App Status |---
App:    -   [Running]
 Events Queued: 0   Syscall Count: 5   Dropped Callback Count: 0
 Restart Count: 0
 Last Syscall: None

 ╔═══════════╤══════════════════════════════════════════╗
 ║  Address  │ Region Name    Used | Allocated (bytes)  ║
 ╚0x800036F8═╪══════════════════════════════════════════╝
             │ ▼ Grant         756 |    756          
  0x80003404 ┼───────────────────────────────────────────
             │ Unused
  0x80003004 ┼───────────────────────────────────────────
             │ ▲ Heap         1024 |   2048               S
  0x80002C04 ┼─────────────────────────────────────────── R
             │ Data              4 |      4               A
  0x80002C00 ┼─────────────────────────────────────────── M
             │ ▼ Stack        3136 |   2048 EXCEEDED!
  0x80001FC0 ┼───────────────────────────────────────────
             │ Unused
  0x80002400 ┴───────────────────────────────────────────
             .....
  0x20440000 ┬─────────────────────────────────────────── F
             │ App Flash     65472                        L
  0x20430040 ┼─────────────────────────────────────────── A
             │ Protected        64                        S
  0x20430000 ┴─────────────────────────────────────────── H
...

If you enable debug options for the Tock kernel you will see this:

HiFive1 initialization complete. Entering main loop
Loading processes from flash=0x20430000 into sram=[0x80002400:0x80003800]
Loaded process[0] from flash=[0x20430000:0x20440000] into sram=[0x80002400:0x800036F8] = Some("")
[!] flash=0x20440000 - not a valid TBF header
Loaded process[1] from flash=[0x20440000:0x20440000] into sram=[0x800036F8:0x800036F8] = None


Kernel panic at /scratch/alistair/software/tock/tock/chips/e310x/src/chip.rs:152:
	"load fault 10
"
	Kernel version release-1.4-627-gc94059d3

---| RISC-V Machine State |---
Cause (mcause): Load access fault (interrupt=false, exception code=5)
Value (mtval):  0x00000010
...

If you enable PMP on Tock then you can't even load the app

HiFive1 initialization complete. Entering main loop
Loading processes from flash=0x20430000 into sram=[0x80002400:0x80003800]
[!] flash=[0x20430000:0x20440000] process=Some("") - couldn't allocate memory region of size >= 0x13A0
Loaded process[0] from flash=[0x20430000:0x20440000] into sram=[0x80002400:0x80002400] = None
[!] flash=0x20440000 - not a valid TBF header
Loaded process[1] from flash=[0x20440000:0x20440000] into sram=[0x80002400:0x80002400] = None

Basically it's really hard to fit the libtock-rs apps with Tock for the HiFive1. As it's the only board supported in QEMU this is a pain. It might be worth looking at trying to shrink the app sizes.

[alistair23]

Increasing the RAM size (in QEMU and Tock) and then the application size and Tock stack size fixes all of the memory issues, but that won't work on HW.