Merge pull request #54 from NotAShelf/notashelf/push-ypvyyznuosqk

various: replace libc invocations with `std::env` and handwritten syscall wrappers

Cargo.lock

@@ -571,7 +571,6 @@ version = "0.4.13"
 dependencies = [
  "criterion",
  "hotpath",
- "libc",
 ]
 
 [[package]]

Cargo.toml

@@ -19,7 +19,6 @@ path = "src/main.rs"
 
 [dependencies]
 hotpath = { optional = true, version = "0.13.0" }
-libc    = "0.2.183"
 
 [dev-dependencies]
 criterion = "0.8.1"

src/colors.rs

@@ -37,8 +37,8 @@ impl Colors {
 }
 
 pub static COLORS: LazyLock<Colors> = LazyLock::new(|| {
-  const NO_COLOR: *const libc::c_char = c"NO_COLOR".as_ptr();
-  let is_no_color = unsafe { !libc::getenv(NO_COLOR).is_null() };
+  // Only presence matters; value is irrelevant per the NO_COLOR spec
+  let is_no_color = std::env::var_os("NO_COLOR").is_some();
   Colors::new(is_no_color)
 });
 

src/desktop.rs

@@ -1,27 +1,22 @@
-use std::{ffi::CStr, fmt::Write};
+use std::{ffi::OsStr, fmt::Write};
 
 #[must_use]
 #[cfg_attr(feature = "hotpath", hotpath::measure)]
 pub fn get_desktop_info() -> String {
-  // Retrieve the environment variables and handle Result types
-  let desktop_str = unsafe {
-    let ptr = libc::getenv(c"XDG_CURRENT_DESKTOP".as_ptr());
-    if ptr.is_null() {
-      "Unknown"
-    } else {
-      let s = CStr::from_ptr(ptr).to_str().unwrap_or("Unknown");
-      s.strip_prefix("none+").unwrap_or(s)
-    }
-  };
+  let desktop_os = std::env::var_os("XDG_CURRENT_DESKTOP");
+  let session_os = std::env::var_os("XDG_SESSION_TYPE");
 
-  let backend_str = unsafe {
-    let ptr = libc::getenv(c"XDG_SESSION_TYPE".as_ptr());
-    if ptr.is_null() {
-      "Unknown"
-    } else {
-      let s = CStr::from_ptr(ptr).to_str().unwrap_or("Unknown");
-      if s.is_empty() { "Unknown" } else { s }
-    }
+  let desktop_raw = desktop_os
+    .as_deref()
+    .and_then(OsStr::to_str)
+    .unwrap_or("Unknown");
+  let desktop_str = desktop_raw.strip_prefix("none+").unwrap_or(desktop_raw);
+
+  let session_raw = session_os.as_deref().and_then(OsStr::to_str).unwrap_or("");
+  let backend_str = if session_raw.is_empty() {
+    "Unknown"
+  } else {
+    session_raw
   };
 
   // Pre-calculate capacity: desktop_len + " (" + backend_len + ")"

src/lib.rs

@@ -5,42 +5,44 @@ pub mod syscall;
 pub mod system;
 pub mod uptime;
 
-use std::mem::MaybeUninit;
+use std::{ffi::CStr, mem::MaybeUninit};
 
-/// Wrapper for `libc::utsname` with safe accessor methods
-pub struct UtsName(libc::utsname);
+use crate::syscall::{UtsNameBuf, sys_uname};
+
+/// Wrapper for `utsname` with safe accessor methods
+pub struct UtsName(UtsNameBuf);
 
 impl UtsName {
-  /// Calls `uname` syscall and returns a `UtsName` wrapper
+  /// Calls `uname(2)` syscall and returns a `UtsName` wrapper
   ///
   /// # Errors
   ///
   /// Returns an error if the `uname` syscall fails
   pub fn uname() -> Result<Self, std::io::Error> {
     let mut uts = MaybeUninit::uninit();
-    if unsafe { libc::uname(uts.as_mut_ptr()) } != 0 {
+    if unsafe { sys_uname(uts.as_mut_ptr()) } != 0 {
       return Err(std::io::Error::last_os_error());
     }
     Ok(Self(unsafe { uts.assume_init() }))
   }
 
   #[must_use]
-  pub const fn nodename(&self) -> &std::ffi::CStr {
-    unsafe { std::ffi::CStr::from_ptr(self.0.nodename.as_ptr()) }
+  pub const fn nodename(&self) -> &CStr {
+    unsafe { CStr::from_ptr(self.0.nodename.as_ptr().cast()) }
   }
 
   #[must_use]
-  pub const fn sysname(&self) -> &std::ffi::CStr {
-    unsafe { std::ffi::CStr::from_ptr(self.0.sysname.as_ptr()) }
+  pub const fn sysname(&self) -> &CStr {
+    unsafe { CStr::from_ptr(self.0.sysname.as_ptr().cast()) }
   }
 
   #[must_use]
-  pub const fn release(&self) -> &std::ffi::CStr {
-    unsafe { std::ffi::CStr::from_ptr(self.0.release.as_ptr()) }
+  pub const fn release(&self) -> &CStr {
+    unsafe { CStr::from_ptr(self.0.release.as_ptr().cast()) }
   }
 
   #[must_use]
-  pub const fn machine(&self) -> &std::ffi::CStr {
-    unsafe { std::ffi::CStr::from_ptr(self.0.machine.as_ptr()) }
+  pub const fn machine(&self) -> &CStr {
+    unsafe { CStr::from_ptr(self.0.machine.as_ptr().cast()) }
   }
 }

src/main.rs

@@ -99,14 +99,19 @@ fn print_system_info(
     {blue}     ▟█▘ ▜█▖    {cyan}▝█▛         {cyan}  {blue}Colors{reset}        {colors}\n\n"
   )?;
 
-  let len = cursor.position() as usize;
+  let len =
+    usize::try_from(cursor.position()).expect("cursor position fits usize");
   // Direct syscall to avoid stdout buffering allocation
-  let written = unsafe { libc::write(libc::STDOUT_FILENO, buf.as_ptr().cast(), len) };
+  let written = unsafe { syscall::sys_write(1, buf.as_ptr(), len) };
   if written < 0 {
     return Err(io::Error::last_os_error().into());
   }
+  #[allow(clippy::cast_sign_loss)] // non-negative verified by the guard above
   if written as usize != len {
-    return Err(io::Error::new(io::ErrorKind::WriteZero, "partial write to stdout").into());
+    return Err(
+      io::Error::new(io::ErrorKind::WriteZero, "partial write to stdout")
+        .into(),
+    );
   }
   Ok(())
 }

src/syscall.rs

@@ -123,6 +123,63 @@ pub unsafe fn sys_read(fd: i32, buf: *mut u8, count: usize) -> isize {
   }
 }
 
+/// Direct syscall to write to a file descriptor
+///
+/// # Returns
+///
+/// Number of bytes written or -1 on error
+///
+/// # Safety
+///
+/// The caller must ensure that:
+///
+/// - `buf` points to a valid readable buffer of at least `count` bytes
+/// - `fd` is a valid open file descriptor
+#[inline]
+#[must_use]
+pub unsafe fn sys_write(fd: i32, buf: *const u8, count: usize) -> isize {
+  #[cfg(target_arch = "x86_64")]
+  unsafe {
+    let ret: i64;
+    std::arch::asm!(
+      "syscall",
+      in("rax") 1i64,  // SYS_write
+      in("rdi") fd,
+      in("rsi") buf,
+      in("rdx") count,
+      lateout("rax") ret,
+      lateout("rcx") _,
+      lateout("r11") _,
+      options(nostack)
+    );
+    #[allow(clippy::cast_possible_truncation)]
+    {
+      ret as isize
+    }
+  }
+  #[cfg(target_arch = "aarch64")]
+  unsafe {
+    let ret: i64;
+    std::arch::asm!(
+      "svc #0",
+      in("x8") 64i64,  // SYS_write
+      in("x0") fd,
+      in("x1") buf,
+      in("x2") count,
+      lateout("x0") ret,
+      options(nostack)
+    );
+    #[allow(clippy::cast_possible_truncation)]
+    {
+      ret as isize
+    }
+  }
+  #[cfg(not(any(target_arch = "x86_64", target_arch = "aarch64")))]
+  {
+    compile_error!("Unsupported architecture for inline assembly syscalls");
+  }
+}
+
 /// Direct syscall to close a file descriptor
 ///
 /// # Safety
@@ -169,6 +226,149 @@ pub unsafe fn sys_close(fd: i32) -> i32 {
   }
 }
 
+/// Raw buffer for the `uname(2)` syscall.
+///
+/// Linux ABI hasfive fields of `[i8; 65]`: sysname, nodename, release, version,
+/// machine. The `domainname` field (GNU extension, `[i8; 65]`) follows but is
+/// not used, nor any useful to us here.
+#[repr(C)]
+#[allow(dead_code)]
+pub struct UtsNameBuf {
+  pub sysname:    [i8; 65],
+  pub nodename:   [i8; 65],
+  pub release:    [i8; 65],
+  pub version:    [i8; 65],
+  pub machine:    [i8; 65],
+  pub domainname: [i8; 65], // GNU extension, included for correct struct size
+}
+
+/// Direct `uname(2)` syscall
+///
+/// # Returns
+///
+/// 0 on success, negative on error
+///
+/// # Safety
+///
+/// The caller must ensure `buf` points to a valid `UtsNameBuf`.
+#[inline]
+#[allow(dead_code)]
+pub unsafe fn sys_uname(buf: *mut UtsNameBuf) -> i32 {
+  #[cfg(target_arch = "x86_64")]
+  unsafe {
+    let ret: i64;
+    std::arch::asm!(
+      "syscall",
+      in("rax") 63i64,  // SYS_uname
+      in("rdi") buf,
+      lateout("rax") ret,
+      lateout("rcx") _,
+      lateout("r11") _,
+      options(nostack)
+    );
+    #[allow(clippy::cast_possible_truncation)]
+    {
+      ret as i32
+    }
+  }
+  #[cfg(target_arch = "aarch64")]
+  unsafe {
+    let ret: i64;
+    std::arch::asm!(
+      "svc #0",
+      in("x8") 160i64,  // SYS_uname
+      in("x0") buf,
+      lateout("x0") ret,
+      options(nostack)
+    );
+    #[allow(clippy::cast_possible_truncation)]
+    {
+      ret as i32
+    }
+  }
+  #[cfg(not(any(target_arch = "x86_64", target_arch = "aarch64")))]
+  {
+    compile_error!("Unsupported architecture for inline assembly syscalls");
+  }
+}
+
+/// Raw buffer for the `statfs(2)` syscall.
+///
+/// Linux ABI (`x86_64` and `aarch64`): the fields we use are at the same
+/// offsets on both architectures. Only the fields needed for disk usage are
+/// declared; the remainder of the 120-byte struct is covered by `_pad`.
+#[repr(C)]
+pub struct StatfsBuf {
+  pub f_type:    i64,
+  pub f_bsize:   i64,
+  pub f_blocks:  u64,
+  pub f_bfree:   u64,
+  pub f_bavail:  u64,
+  pub f_files:   u64,
+  pub f_ffree:   u64,
+  pub f_fsid:    [i32; 2],
+  pub f_namelen: i64,
+  pub f_frsize:  i64,
+  pub f_flags:   i64,
+
+  #[allow(clippy::pub_underscore_fields, reason = "This is not a public API")]
+  pub _pad: [i64; 4],
+}
+
+/// Direct `statfs(2)` syscall
+///
+/// # Returns
+///
+/// 0 on success, negative errno on error
+///
+/// # Safety
+///
+/// The caller must ensure that:
+///
+/// - `path` points to a valid null-terminated string
+/// - `buf` points to a valid `StatfsBuf`
+#[inline]
+pub unsafe fn sys_statfs(path: *const u8, buf: *mut StatfsBuf) -> i32 {
+  #[cfg(target_arch = "x86_64")]
+  unsafe {
+    let ret: i64;
+    std::arch::asm!(
+      "syscall",
+      in("rax") 137i64,  // SYS_statfs
+      in("rdi") path,
+      in("rsi") buf,
+      lateout("rax") ret,
+      lateout("rcx") _,
+      lateout("r11") _,
+      options(nostack)
+    );
+    #[allow(clippy::cast_possible_truncation)]
+    {
+      ret as i32
+    }
+  }
+  #[cfg(target_arch = "aarch64")]
+  unsafe {
+    let ret: i64;
+    std::arch::asm!(
+      "svc #0",
+      in("x8") 43i64,  // SYS_statfs
+      in("x0") path,
+      in("x1") buf,
+      lateout("x0") ret,
+      options(nostack)
+    );
+    #[allow(clippy::cast_possible_truncation)]
+    {
+      ret as i32
+    }
+  }
+  #[cfg(not(any(target_arch = "x86_64", target_arch = "aarch64")))]
+  {
+    compile_error!("Unsupported architecture for inline assembly syscalls");
+  }
+}
+
 /// Read entire file using direct syscalls. This avoids libc overhead and can be
 /// significantly faster for small files.
 ///

src/system.rs

@@ -1,18 +1,19 @@
-use std::{ffi::CStr, fmt::Write as _, io, mem::MaybeUninit};
+use std::{ffi::OsStr, fmt::Write as _, io, mem::MaybeUninit};
 
-use crate::{UtsName, colors::COLORS, syscall::read_file_fast};
+use crate::{
+  UtsName,
+  colors::COLORS,
+  syscall::{StatfsBuf, read_file_fast, sys_statfs},
+};
 
 #[must_use]
 #[cfg_attr(feature = "hotpath", hotpath::measure)]
 pub fn get_username_and_hostname(utsname: &UtsName) -> String {
-  let username = unsafe {
-    let ptr = libc::getenv(c"USER".as_ptr());
-    if ptr.is_null() {
-      "unknown_user"
-    } else {
-      CStr::from_ptr(ptr).to_str().unwrap_or("unknown_user")
-    }
-  };
+  let username_os = std::env::var_os("USER");
+  let username = username_os
+    .as_deref()
+    .and_then(OsStr::to_str)
+    .unwrap_or("unknown_user");
   let hostname = utsname.nodename().to_str().unwrap_or("unknown_host");
 
   let capacity = COLORS.yellow.len()
@@ -38,16 +39,13 @@ pub fn get_username_and_hostname(utsname: &UtsName) -> String {
 #[must_use]
 #[cfg_attr(feature = "hotpath", hotpath::measure)]
 pub fn get_shell() -> String {
-  unsafe {
-    let ptr = libc::getenv(c"SHELL".as_ptr());
-    if ptr.is_null() {
-      return "unknown_shell".into();
-    }
-
-    let bytes = CStr::from_ptr(ptr).to_bytes();
-    let start = bytes.iter().rposition(|&b| b == b'/').map_or(0, |i| i + 1);
-    let name = std::str::from_utf8_unchecked(&bytes[start..]);
-    name.into()
+  let shell_os = std::env::var_os("SHELL");
+  let shell = shell_os.as_deref().and_then(OsStr::to_str).unwrap_or("");
+  let start = shell.rfind('/').map_or(0, |i| i + 1);
+  if shell.is_empty() {
+    "unknown_shell".into()
+  } else {
+    shell[start..].into()
   }
 }
 
@@ -59,15 +57,16 @@ pub fn get_shell() -> String {
 #[cfg_attr(feature = "hotpath", hotpath::measure)]
 #[allow(clippy::cast_precision_loss)]
 pub fn get_root_disk_usage() -> Result<String, io::Error> {
-  let mut vfs = MaybeUninit::uninit();
+  let mut vfs = MaybeUninit::<StatfsBuf>::uninit();
   let path = b"/\0";
 
-  if unsafe { libc::statvfs(path.as_ptr().cast(), vfs.as_mut_ptr()) } != 0 {
+  if unsafe { sys_statfs(path.as_ptr(), vfs.as_mut_ptr()) } != 0 {
     return Err(io::Error::last_os_error());
   }
 
   let vfs = unsafe { vfs.assume_init() };
-  let block_size = vfs.f_bsize;
+  #[allow(clippy::cast_sign_loss)]
+  let block_size = vfs.f_bsize as u64;
   let total_blocks = vfs.f_blocks;
   let available_blocks = vfs.f_bavail;
 
@@ -158,12 +157,12 @@ pub fn get_memory_usage() -> Result<String, io::Error> {
     }
 
     #[allow(clippy::cast_precision_loss)]
-    let total_memory_gb = total_memory_kb as f64 / 1024.0 / 1024.0;
+    let total_gb = total_memory_kb as f64 / 1024.0 / 1024.0;
     #[allow(clippy::cast_precision_loss)]
-    let available_memory_gb = available_memory_kb as f64 / 1024.0 / 1024.0;
-    let used_memory_gb = total_memory_gb - available_memory_gb;
+    let available_gb = available_memory_kb as f64 / 1024.0 / 1024.0;
+    let used_memory_gb = total_gb - available_gb;
 
-    Ok((used_memory_gb, total_memory_gb))
+    Ok((used_memory_gb, total_gb))
   }
 
   let (used_memory, total_memory) = parse_memory_info()?;

src/uptime.rs

@@ -17,14 +17,41 @@ fn itoa(mut n: u64, buf: &mut [u8]) -> &str {
   unsafe { std::str::from_utf8_unchecked(&buf[i..]) }
 }
 
-/// Direct `sysinfo` syscall using inline assembly
+/// Raw buffer for the `sysinfo(2)` syscall.
+///
+/// In the Linux ABI `uptime` is a `long` at offset 0. The remaining fields are
+/// not needed, but are declared to give the struct its correct size (112 bytes
+/// on 64-bit Linux).
+///
+/// The layout matches the kernel's `struct sysinfo` *exactly*:
+/// `mem_unit` ends at offset 108, then 4 bytes of implicit padding to 112.
+#[repr(C)]
+struct SysInfo {
+  uptime:    i64,
+  loads:     [u64; 3],
+  totalram:  u64,
+  freeram:   u64,
+  sharedram: u64,
+  bufferram: u64,
+  totalswap: u64,
+  freeswap:  u64,
+  procs:     u16,
+  _pad:      u16,
+  _pad2:     u32, // alignment padding to reach 8-byte boundary for totalhigh
+  totalhigh: u64,
+  freehigh:  u64,
+  mem_unit:  u32,
+  // 4 bytes implicit trailing padding to reach 112 bytes total; no field
+  // needed
+}
+
+/// Direct `sysinfo(2)` syscall using inline assembly
 ///
 /// # Safety
 ///
-/// This function uses inline assembly to make a direct syscall.
 /// The caller must ensure the sysinfo pointer is valid.
 #[inline]
-unsafe fn sys_sysinfo(info: *mut libc::sysinfo) -> i64 {
+unsafe fn sys_sysinfo(info: *mut SysInfo) -> i64 {
   #[cfg(target_arch = "x86_64")]
   {
     let ret: i64;
@@ -59,7 +86,7 @@ unsafe fn sys_sysinfo(info: *mut libc::sysinfo) -> i64 {
 
   #[cfg(not(any(target_arch = "x86_64", target_arch = "aarch64")))]
   {
-    unsafe { libc::sysinfo(info) as i64 }
+    compile_error!("Unsupported architecture for inline assembly syscalls");
   }
 }