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fix(riscv64): boot StarryOS with RustSBI on riscv64 without IllegalInstruction trap #131

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fix(riscv64): boot StarryOS with RustSBI on riscv64 without IllegalInstruction trap #131

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1a4dfd7
fix(riscv64): initialize FP state before user init under RustSBI
LetsWalkInLine Mar 20, 2026
abc87fc
chore(make): make QEMU BIOS configurable for RustSBI validation
LetsWalkInLine Mar 20, 2026
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10 changes: 10 additions & 0 deletions kernel/src/entry.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -16,8 +16,18 @@ use crate::{
task::{ProcessData, Thread, add_task_to_table, new_user_task, spawn_alarm_task},
};

#[cfg(target_arch = "riscv64")]
#[inline]
fn init_riscv_fp_state() {
use riscv::register::sstatus::{self, FS};
unsafe { sstatus::set_fs(FS::Dirty) };
}

/// Initialize and run initproc.
pub fn init(args: &[String], envs: &[String]) {
#[cfg(target_arch = "riscv64")]
init_riscv_fp_state();

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Copilot AI Mar 20, 2026

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sstatus.FS is a per-hart CSR on RISC-V. Initializing it only in entry::init() (which appears to run once during initproc setup) may leave secondary harts with FS=Off, so any FP/SIMD instruction executed on those harts could still trap. Consider moving this to an earlier per-CPU/hart init hook (e.g., in the platform/axruntime CPU bring-up path) or otherwise ensuring it runs on every hart before scheduling begins there.

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pseudofs::mount_all().expect("Failed to mount pseudofs");
spawn_alarm_task();

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2 changes: 2 additions & 0 deletions make/Makefile
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Expand Up @@ -27,6 +27,7 @@
# - `MEM`: Memory size (default is 128M)
# - `DISK_IMG`: Path to the virtual disk image
# - `ACCEL`: Enable hardware acceleration (KVM on linux)
# - `QEMU_BIOS`: QEMU BIOS firmware path (default is `default`)
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Copilot AI Mar 20, 2026

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The QEMU_BIOS help text says it's a “firmware path”, but the default value is the special QEMU selector default (not a filesystem path). Consider rewording to clarify it can be either default or a BIOS/firmware image path so users don’t assume it must be a path.

Suggested change
# - `QEMU_BIOS`: QEMU BIOS firmware path (default is `default`)
# - `QEMU_BIOS`: QEMU BIOS selector (`default`) or firmware image path (default is `default`)

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# - `QEMU_LOG`: Enable QEMU logging (log file is "qemu.log")
# - `NET_DUMP`: Enable network packet dump (log file is "netdump.pcap")
# - `NET_DEV`: QEMU netdev backend types: user, tap, bridge
Expand Down Expand Up @@ -69,6 +70,7 @@ MEM ?=
ACCEL ?=
ICOUNT ?= n
QEMU_ARGS ?=
QEMU_BIOS ?= default

DISK_IMG ?= disk.img
QEMU_LOG ?= n
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3 changes: 2 additions & 1 deletion make/qemu.mk
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Expand Up @@ -2,6 +2,7 @@

QEMU := qemu-system-$(ARCH)


ifeq ($(BUS), mmio)
vdev-suffix := device
else ifeq ($(BUS), pci)
Expand Down Expand Up @@ -30,7 +31,7 @@ qemu_args-x86_64 := \

qemu_args-riscv64 := \
-machine $(machine) \
-bios default \
-bios $(QEMU_BIOS) \
-kernel $(FINAL_IMG)

qemu_args-aarch64 := \
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