Support vendor boot unpack/repack

Fix #6460, close #6620

native/src/base/cxx_extern.rs

@@ -7,6 +7,7 @@ use cfg_if::cfg_if;
 use cxx::private::c_char;
 use libc::mode_t;
 
+use crate::files::map_file_at;
 pub(crate) use crate::xwrap::*;
 use crate::{
     clone_attr, cstr, fclone_attr, fd_path, map_fd, map_file, slice_from_ptr, CxxResultExt,
@@ -61,6 +62,14 @@ pub(crate) fn map_file_for_cxx(path: &Utf8CStr, rw: bool) -> &'static mut [u8] {
     map_file(path, rw).log_cxx().unwrap_or(&mut [])
 }
 
+pub(crate) fn map_file_at_for_cxx(fd: RawFd, path: &Utf8CStr, rw: bool) -> &'static mut [u8] {
+    unsafe {
+        map_file_at(BorrowedFd::borrow_raw(fd), path, rw)
+            .log_cxx()
+            .unwrap_or(&mut [])
+    }
+}
+
 pub(crate) fn map_fd_for_cxx(fd: RawFd, sz: usize, rw: bool) -> &'static mut [u8] {
     unsafe {
         map_fd(BorrowedFd::borrow_raw(fd), sz, rw)

native/src/base/files.cpp

@@ -117,6 +117,14 @@ mmap_data::mmap_data(const char *name, bool rw) {
     }
 }
 
+mmap_data::mmap_data(int dirfd, const char *name, bool rw) {
+    auto slice = rust::map_file_at(dirfd, name, rw);
+    if (!slice.empty()) {
+        _buf = slice.data();
+        _sz = slice.size();
+    }
+}
+
 mmap_data::mmap_data(int fd, size_t sz, bool rw) {
     auto slice = rust::map_fd(fd, sz, rw);
     if (!slice.empty()) {

native/src/base/files.hpp

@@ -26,6 +26,7 @@ struct mmap_data : public byte_data {
     ALLOW_MOVE_ONLY(mmap_data)
 
     explicit mmap_data(const char *name, bool rw = false);
+    mmap_data(int dirfd, const char *name, bool rw = false);
     mmap_data(int fd, size_t sz, bool rw = false);
     ~mmap_data();
 };

native/src/base/files.rs

@@ -856,6 +856,14 @@ impl MappedFile {
         Ok(MappedFile(map_file(path, true)?))
     }
 
+    pub fn openat<T: AsFd>(dir: &T, path: &Utf8CStr) -> io::Result<MappedFile> {
+        Ok(MappedFile(map_file_at(dir.as_fd(), path, false)?))
+    }
+
+    pub fn openat_rw<T: AsFd>(dir: &T, path: &Utf8CStr) -> io::Result<MappedFile> {
+        Ok(MappedFile(map_file_at(dir.as_fd(), path, true)?))
+    }
+
     pub fn create(fd: BorrowedFd, sz: usize, rw: bool) -> io::Result<MappedFile> {
         Ok(MappedFile(map_fd(fd, sz, rw)?))
     }
@@ -888,6 +896,14 @@ extern "C" {
 
 // We mark the returned slice static because it is valid until explicitly unmapped
 pub(crate) fn map_file(path: &Utf8CStr, rw: bool) -> io::Result<&'static mut [u8]> {
+    unsafe { map_file_at(BorrowedFd::borrow_raw(libc::AT_FDCWD), path, rw) }
+}
+
+pub(crate) fn map_file_at(
+    dirfd: BorrowedFd,
+    path: &Utf8CStr,
+    rw: bool,
+) -> io::Result<&'static mut [u8]> {
     #[cfg(target_pointer_width = "64")]
     const BLKGETSIZE64: u32 = 0x80081272;
 
@@ -895,18 +911,22 @@ pub(crate) fn map_file(path: &Utf8CStr, rw: bool) -> io::Result<&'static mut [u8
     const BLKGETSIZE64: u32 = 0x80041272;
 
     let flag = if rw { O_RDWR } else { O_RDONLY };
-    let file = FsPath::from(path).open(flag | O_CLOEXEC)?;
+    let fd = unsafe {
+        OwnedFd::from_raw_fd(
+            libc::openat(dirfd.as_raw_fd(), path.as_ptr(), flag | O_CLOEXEC).check_os_err()?,
+        )
+    };
 
-    let attr = fd_get_attr(file.as_raw_fd())?;
+    let attr = fd_get_attr(fd.as_raw_fd())?;
     let sz = if attr.is_block_device() {
         let mut sz = 0_u64;
-        unsafe { ioctl(file.as_raw_fd(), BLKGETSIZE64, &mut sz) }.as_os_err()?;
+        unsafe { ioctl(fd.as_raw_fd(), BLKGETSIZE64, &mut sz) }.as_os_err()?;
         sz
     } else {
         attr.st.st_size as u64
     };
 
-    map_fd(file.as_fd(), sz as usize, rw)
+    map_fd(fd.as_fd(), sz as usize, rw)
 }
 
 pub(crate) fn map_fd(fd: BorrowedFd, sz: usize, rw: bool) -> io::Result<&'static mut [u8]> {

native/src/base/lib.rs

@@ -61,6 +61,8 @@ pub mod ffi {
         fn fd_path_for_cxx(fd: i32, buf: &mut [u8]) -> isize;
         #[cxx_name = "map_file"]
         fn map_file_for_cxx(path: Utf8CStrRef, rw: bool) -> &'static mut [u8];
+        #[cxx_name = "map_file_at"]
+        fn map_file_at_for_cxx(fd: i32, path: Utf8CStrRef, rw: bool) -> &'static mut [u8];
         #[cxx_name = "map_fd"]
         fn map_fd_for_cxx(fd: i32, sz: usize, rw: bool) -> &'static mut [u8];
     }