Adds CLI argument handling and usage info to kret tool

Signed-off-by: Godones <chenlinfeng25@outlook.com>

Author: Godones

api/src/syscall/fs/fd_ops.rs

@@ -108,8 +108,6 @@ fn add_to_fd(result: OpenResult, flags: u32) -> AxResult<i32> {
     add_file_like(f, flags & O_CLOEXEC != 0)
 }
 
-// WARN: We need to ensure that the fields in TP_STRUCT__entry are not
-// rearranged.
 tracepoint::define_event_trace!(
     sys_enter_openat,
     TP_lock(crate::lock_api::KSpinNoPreempt<()>),

arceos

@@ -200,6 +200,22 @@ ln -s /lib/ld-musl-loongarch64.so.1 /lib64/ld-musl-loongarch-lp64d.so.1
 
 在aarch64架构下, 使用musl工具链不像其它架构一样会默认进行动态链接，而是默认进行静态链接。如果需要动态链接，需要指定 `rustflags = ["-C", "target-feature=-crt-static"]`。
 
+## 其它信息
+
+内核处理用户态的break异常路径:
+```
+int3
+ → #BP
+ → 内核
+     ├─ 如果是 uprobe：
+     │     → 执行 eBPF
+     │     → 模拟原指令
+     │     → 返回用户态（无 SIGTRAP）
+     │
+     └─ 如果不是：
+           → 发送 SIGTRAP
+```
+
 ## 参考与源码入口
 
 - `core/src/probe_aux.rs`：地址权限调整、可执行页分配、retprobe 实例管理。

docs/eBPF for Starry.md

@@ -1,11 +1,8 @@
 [target.riscv64gc-unknown-linux-musl]
-# rustflags = ["-C", "target-feature=+crt-static"]
 linker = "riscv64-linux-musl-cc"
 
 [target.loongarch64-unknown-linux-musl]
-# rustflags = ["-C", "target-feature=+crt-static"]
 linker = "loongarch64-linux-musl-cc"
 
 [target.aarch64-unknown-linux-musl]
-rustflags = ["-C", "target-feature=-crt-static"]
 linker = "aarch64-linux-musl-cc"

user/musl/.cargo/config.toml

@@ -5,6 +5,18 @@ use tokio::signal;
 
 #[tokio::main]
 async fn main() -> anyhow::Result<()> {
+
+    let args_num = std::env::args().len();
+    if args_num != 2 {
+        println!("Usage: kret {{mangled_func_name}}");
+        println!(
+            "You can get the mangled function name by running `cat /proc/kallsyms | grep -m 1 sys_getpid`"
+        );
+        return Ok(());
+    }
+    let args: Vec<String> = std::env::args().collect();
+    let target_syscall_entry = &args[1];
+
     env_logger::builder()
         .filter_level(log::LevelFilter::Info)
         .format_timestamp(None)
@@ -48,7 +60,8 @@ async fn main() -> anyhow::Result<()> {
     }
     let program: &mut KProbe = ebpf.program_mut("kret").unwrap().try_into()?;
     program.load()?;
-    program.attach("starry_api::syscall::task::thread::sys_getpid", 0)?;
+    // TODO: support mangled symbol name
+    program.attach(target_syscall_entry, 0)?;
 
     let ctrl_c = signal::ctrl_c();
     println!("Waiting for Ctrl-C...");