sys_stat: initial implementation

* add checking methods in VirtAddr
* impl sys_stat
* add method to read sizeof(T) bytes and get a mutable reference to T in
VirtAddr

Signed-off-by: Andy-Python-Programmer <[email protected]>

Author: Andy-Python-Programmer

patches/mlibc/mlibc.patch

@@ -1,25 +1,100 @@
-From 8917c56f1216c079d9a3560b03d4cc30c96920c5 Mon Sep 17 00:00:00 2001
+From d1583428ad4f44bb2ca458e06e3a0c60f2c45737 Mon Sep 17 00:00:00 2001
 From: Andy-Python-Programmer <[email protected]>
 Date: Thu, 10 Feb 2022 19:12:25 +1100
 Subject: [PATCH] yes
 
 Signed-off-by: Andy-Python-Programmer <[email protected]>
 ---
- sysdeps/aero/generic/filesystem.cpp | 1 -
- 1 file changed, 1 deletion(-)
+ .gitignore                          |  7 +++++++
+ sysdeps/aero/generic/filesystem.cpp | 28 +++++++++++++++++++++-------
+ sysdeps/aero/include/aero/syscall.h |  5 +++++
+ 3 files changed, 33 insertions(+), 7 deletions(-)
 
+diff --git a/.gitignore b/.gitignore
+index dbb35e8b..384b3395 100644
+--- a/.gitignore
++++ b/.gitignore
+@@ -8,3 +8,10 @@ subprojects/cxxshim
+ subprojects/frigg
+ .vscode
+ .clang-format
++
++# clangd files
++# 
++# * The compile commands json is usually generated by the build system
++# if not, it can be constructed manually and should be in the root of
++# of the project directory.
++compile_commands.json
 diff --git a/sysdeps/aero/generic/filesystem.cpp b/sysdeps/aero/generic/filesystem.cpp
-index 0e73b63..54252ba 100644
+index 6a13f19c..ec81503c 100644
 --- a/sysdeps/aero/generic/filesystem.cpp
 +++ b/sysdeps/aero/generic/filesystem.cpp
-@@ -256,7 +256,6 @@ int sys_pselect(int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds,
+@@ -84,9 +84,24 @@ int sys_access(const char *filename, int mode) {
+ 
+ int sys_stat(fsfd_target fsfdt, int fd, const char *path, int flags,
+              struct stat *statbuf) {
+-    mlibc::infoLogger() << "sys_stat() is unimplemented" << frg::endlog;
++    auto result = 0;
++
++    switch (fsfdt) {
++        case fsfd_target::path: {
++            result = syscall(SYS_STAT, path, strlen(path), statbuf);
++            break;
++        }
++
++        default: {
++			mlibc::infoLogger() << "mlibc warning: sys_stat: unsupported fsfd target" << frg::endlog;
++			return EINVAL;
++        }
++    }
++
++    if (result < 0) {
++        return -result;
++    }    
+ 
+-    memset(statbuf, 0, sizeof(struct stat));
+     return 0;
+ }
+ 
+@@ -192,10 +207,10 @@ int sys_read_entries(int handle, void *buffer, size_t max_size,
+     auto entry = (struct aero_dir_entry *)buffer;
+ 
+     struct dirent dirent = {
+-        .d_ino = entry->inode,
+-        .d_off = entry->offset,
+-        .d_reclen = entry->reclen,
+-        .d_type = entry->filetyp,
++        .d_ino = static_cast<ino_t>(entry->inode),
++        .d_off = static_cast<off_t>(entry->offset),
++        .d_reclen = static_cast<unsigned short>(entry->reclen),
++        .d_type = static_cast<unsigned char>(entry->filetyp),
+     };
+ 
+     // The reclen is the size of the dirent struct, plus the size of the name.
+@@ -252,7 +267,6 @@ int sys_pselect(int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds,
                  const struct timespec *timeout, const sigset_t *sigmask,
                  int *num_events) {
      mlibc::infoLogger() << "sys_pselect() is not implemented" << frg::endlog;
 -    *num_events = 10;
      return 0;
  }
 
+diff --git a/sysdeps/aero/include/aero/syscall.h b/sysdeps/aero/include/aero/syscall.h
+index 07b1b51b..1e3178d2 100644
+--- a/sysdeps/aero/include/aero/syscall.h
++++ b/sysdeps/aero/include/aero/syscall.h
+@@ -49,6 +49,11 @@
+ #define SYS_DUP 42
+ #define SYS_FCNTL 43
+ #define SYS_DUP2 44
++#define SYS_IPC_SEND 45
++#define SYS_IPC_RECV 46
++#define SYS_DISCOVER_ROOT 47
++#define SYS_BECOME_ROOT 48
++#define SYS_STAT 49
+ 
+ // Invalid syscall used to trigger a log error in the kernel (as a hint)
+ // so, that we can implement the syscall in the kernel.
 -- 
 2.25.1
 

src/aero_kernel/src/fs/inode.rs

@@ -79,6 +79,9 @@ pub trait INodeInterface: Send + Sync + Downcastable {
         Err(FileSystemError::NotSupported)
     }
 
+    fn stat(&self) -> Result<aero_syscall::Stat> {
+        Err(FileSystemError::NotSupported)
+    }
     /// Creates a new dev inode with the provided `name` and the device `marker` in
     /// the filesystem.
     ///

src/aero_kernel/src/fs/ramfs.rs

@@ -114,6 +114,12 @@ impl LockedRamINode {
 }
 
 impl INodeInterface for LockedRamINode {
+    fn stat(&self) -> Result<aero_syscall::Stat> {
+        // todo(andy): implement `stat` for ramfs files. This is a workaround
+        // to make not programs crash when they try to stat a ramfs file.
+        Ok(aero_syscall::Stat::default())
+    }
+
     fn touch(&self, parent: DirCacheItem, name: &str) -> Result<DirCacheItem> {
         Ok(DirEntry::new(
             parent,

src/aero_kernel/src/mem/paging/addr.rs

@@ -94,6 +94,39 @@ impl VirtAddr {
         self.as_ptr::<T>() as *mut T
     }
 
+    /// If the virtual address is a valid userland address, the [`Some`] varient is returned
+    /// contaning the address, else the [`None`] variant is returned.
+    ///
+    /// ## Example
+    /// ```no_run
+    /// let address: VirtAddr = VirtAddr::new(stat)
+    ///     .validate_user()
+    ///     .ok_or(AeroSyscallError::EFAULT)?;
+    /// ```
+    pub fn validate_user(self) -> Option<Self> {
+        if self <= crate::arch::task::userland_last_address() {
+            Some(self)
+        } else {
+            None
+        }
+    }
+
+    /// Reads `sizeof(T)` bytes from the virtual address and returns a mutable reference
+    /// to the value (`&mut T`).
+    ///
+    /// ## Example
+    /// ```no_run
+    /// let address: SomeStruct = VirtAddr::new(0xcafebabe)
+    ///     .read_mut::<SomeStruct>();
+    /// ```
+    ///
+    /// ## Safety
+    /// * The virtual address must be valid.
+    /// * It must be safe to read `sizeof(T)` bytes from the virtual address.
+    pub unsafe fn read_mut<'struc, T>(&self) -> &'struc mut T {
+        &mut *(self.as_mut_ptr() as *mut T)
+    }
+
     /// Aligns the virtual address downwards to the given alignment.
     ///
     /// See the `align_down` function for more information.

src/aero_kernel/src/syscall/fs.rs

@@ -23,6 +23,7 @@ use aero_syscall::{AeroSyscallError, OpenFlags};
 use crate::fs::inode::DirEntry;
 use crate::fs::pipe::Pipe;
 use crate::fs::{self, lookup_path, LookupMode};
+use crate::mem::paging::VirtAddr;
 use crate::userland::scheduler;
 
 use crate::fs::Path;
@@ -362,3 +363,22 @@ pub fn fcntl(fd: usize, command: usize, arg: usize) -> Result<usize, AeroSyscall
         _ => unimplemented!(),
     }
 }
+
+pub fn stat(path: usize, path_size: usize, stat_struct: usize) -> Result<usize, AeroSyscallError> {
+    let stat_struct = VirtAddr::new(stat_struct as _)
+        .validate_user()
+        .ok_or(AeroSyscallError::EFAULT)?;
+
+    // SAFETY: The user provided address is validated above.
+    let stat_struct = unsafe { stat_struct.read_mut::<aero_syscall::Stat>() };
+
+    let path = validate_str(path as *mut u8, path_size).ok_or(AeroSyscallError::EINVAL)?;
+    log::debug!("sys_stat: {path}");
+
+    let path = Path::new(path);
+
+    let file = fs::lookup_path(path)?;
+    *stat_struct = file.inode().stat()?;
+
+    Ok(0)
+}

src/aero_kernel/src/syscall/mod.rs

@@ -184,6 +184,7 @@ pub fn generic_do_syscall(
         SYS_DUP => fs::dup(b, c),
         SYS_DUP2 => fs::dup2(b, c, d),
         SYS_FCNTL => fs::fcntl(b, c, d),
+        SYS_STAT => fs::stat(b, c, d),
 
         SYS_SOCKET => net::socket(b, c, d),
         SYS_BIND => net::bind(b, c, d),

src/aero_syscall/src/consts.rs

@@ -67,6 +67,7 @@ pub const SYS_IPC_SEND: usize = 45;
 pub const SYS_IPC_RECV: usize = 46;
 pub const SYS_IPC_DISCOVER_ROOT: usize = 47;
 pub const SYS_IPC_BECOME_ROOT: usize = 48;
+pub const SYS_STAT: usize = 49;
 
 // fcntl constants:
 pub const F_GETFD: usize = 3;

src/aero_syscall/src/lib.rs

@@ -284,7 +284,7 @@ impl Default for Utsname {
     }
 }
 
-#[derive(Default, Clone)]
+#[derive(Default, Clone, Debug)]
 #[repr(C)]
 pub struct TimeSpec {
     pub tv_sec: isize,
@@ -874,3 +874,68 @@ pub fn sys_ipc_become_root() -> Result<(), AeroSyscallError> {
     let value = syscall0(prelude::SYS_IPC_BECOME_ROOT);
     isize_as_syscall_result(value as _).map(|_| ())
 }
+
+// sysdeps/aero/include/abi-bits/stat.h
+bitflags::bitflags! {
+    #[derive(Default)]
+    pub struct Mode: u32 {
+        const S_IFMT   = 0x0F000;
+        const S_IFBLK  = 0x06000;
+        const S_IFCHR  = 0x02000;
+        const S_IFIFO  = 0x01000;
+        const S_IFREG  = 0x08000;
+        const S_IFDIR  = 0x04000;
+        const S_IFLNK  = 0x0A000;
+        const S_IFSOCK = 0x0C000;
+
+        const S_IRWXU = 0700;
+        const S_IRUSR = 0400;
+        const S_IWUSR = 0200;
+        const S_IXUSR = 0100;
+        const S_IRWXG = 070;
+        const S_IRGRP = 040;
+        const S_IWGRP = 020;
+        const S_IXGRP = 010;
+        const S_IRWXO = 07;
+        const S_IROTH = 04;
+        const S_IWOTH = 02;
+        const S_IXOTH = 01;
+        const S_ISUID = 04000;
+        const S_ISGID = 02000;
+        const S_ISVTX = 01000;
+
+        const S_IREAD  = Self::S_IRUSR.bits();
+        const S_IWRITE = Self::S_IWUSR.bits();
+        const S_IEXEC  = Self::S_IXUSR.bits();
+    }
+}
+
+// sysdeps/aero/include/abi-bits/stat.h
+#[repr(C)]
+#[derive(Debug, Default)]
+pub struct Stat {
+    pub st_dev: u64,
+    pub st_ino: u64,
+    pub st_mode: Mode,
+    pub st_nlink: u32,
+    pub st_uid: u32,
+    pub st_gid: u32,
+    pub st_rdev: u64,
+    pub st_size: i64,
+    pub st_atim: TimeSpec,
+    pub st_mtim: TimeSpec,
+    pub st_ctim: TimeSpec,
+    pub st_blksize: u64,
+    pub st_blocks: u64,
+}
+
+pub fn sys_stat(path: &str, stat: &mut Stat) -> Result<usize, AeroSyscallError> {
+    let value = syscall3(
+        prelude::SYS_STAT,
+        path.as_ptr() as usize,
+        path.len(),
+        stat as *mut Stat as usize,
+    );
+
+    isize_as_syscall_result(value as _)
+}