fixes

.envrc

@@ -0,0 +1 @@
+use nix

.gitignore

@@ -2,5 +2,7 @@
 
 *.exe
 *.pdb
+*.dll
+*.dll.lib
 
 !/test/*.exe

Cargo.lock

@@ -52,6 +52,7 @@ version = "0.1.0"
 dependencies = [
  "bitflags",
  "bytemuck",
+ "libc",
  "memmap2",
  "windows",
 ]

Cargo.toml

@@ -10,3 +10,6 @@ memmap2 = "0.9.5"
 
 [target.'cfg(windows)'.dependencies]
 windows = { version = "0.59.0", features = ["Win32_System_Memory", "Win32_Security", "Win32_System_SystemInformation"] }
+
+[target.'cfg(unix)'.dependencies]
+libc = "0.2.169"

shell.nix

@@ -0,0 +1,3 @@
+{ pkgs ? import <nixpkgs> { } }: pkgs.mkShell {
+  nativeBuildInputs = with pkgs; [ lld_18 rustup ];
+}

src/lib.rs

@@ -1,7 +1,11 @@
 mod emulated;
 mod sys;
 
-use std::{ffi::CStr, fmt::Debug, path::PathBuf};
+use std::{
+    ffi::CStr,
+    fmt::Debug,
+    path::{Path, PathBuf},
+};
 
 #[derive(Clone, Copy, Debug, bytemuck::Zeroable, bytemuck::Pod)]
 #[repr(C)]
@@ -197,7 +201,7 @@ struct ImportDirectoryTableEntry {
 const IMAGE_FILE_MACHINE_AMD64: u16 = 0x8664;
 const IMAGE_FILE_MACHINE_ARM64: u16 = 0xaa64;
 
-pub fn execute(pe: &[u8]) {
+pub fn execute(pe: &[u8], executable_path: &Path) {
     let (header, after_header) = parse_header(pe);
 
     match (std::env::consts::ARCH, header.machine) {
@@ -258,14 +262,12 @@ pub fn execute(pe: &[u8]) {
 
     assert_eq!(base & (allocation_granularity - 1), 0);
 
-    let total_size = section_table.last().unwrap().virtual_address as usize;
+    let last_section = section_table.last().unwrap();
+    let total_size = (last_section.virtual_address as usize + last_section.virtual_size as usize)
+        .next_multiple_of(allocation_granularity);
 
     let a = unsafe {
-        crate::sys::anon_write_map(
-            total_size.next_multiple_of(allocation_granularity),
-            std::ptr::with_exposed_provenance(base),
-        )
-        .unwrap()
+        crate::sys::anon_write_map(total_size, std::ptr::with_exposed_provenance(base)).unwrap()
     };
 
     // allocate the sections.
@@ -273,11 +275,10 @@ pub fn execute(pe: &[u8]) {
         if section.virtual_size > section.size_of_raw_data {
             todo!("zero padding")
         }
+        eprintln!("mapping section {:?}", section.name);
 
         let section_a = &mut a[section.virtual_address as usize..];
 
-        dbg!(section);
-
         section_a[..section.size_of_raw_data as usize].copy_from_slice(
             &pe[section.pointer_to_raw_data as usize..][..section.size_of_raw_data as usize],
         );
@@ -289,19 +290,21 @@ pub fn execute(pe: &[u8]) {
     )
     .to_vec();
 
+    eprintln!("checking imports");
     for import_directory in import_directory_table {
         dbg!(import_directory);
 
         let dll_name = CStr::from_bytes_until_nul(&a[import_directory.name_rva as usize..])
             .unwrap()
             .to_owned();
+        let dll_name = dll_name.to_str().unwrap();
         if dll_name.is_empty() {
             // Trailing null import directory.
             break;
         }
-        dbg!(&dll_name);
+        eprintln!("loading dll {dll_name}");
 
-        let dll = find_dll(&dll_name);
+        let dll = find_dll(&dll_name, executable_path);
         match dll {
             Some(DllLocation::Emulated) => eprintln!("  emulating {dll_name:?}"),
             Some(DllLocation::Found(path)) => todo!("unsupported, loading dll at {path:?}"),
@@ -329,11 +332,10 @@ pub fn execute(pe: &[u8]) {
                 let func_name =
                     CStr::from_bytes_until_nul(&a[hint_name_table_rva as usize + 2..]).unwrap();
                 eprintln!(" import by name: hint={hint} name={func_name:?}");
-                let resolved_va =
-                    emulated::emulate(dll_name.to_str().unwrap(), func_name.to_str().unwrap())
-                        .unwrap_or_else(|| {
-                            panic!("could not find function {func_name:?} in dll {dll_name:?}")
-                        });
+                let resolved_va = emulated::emulate(dll_name, func_name.to_str().unwrap())
+                    .unwrap_or_else(|| {
+                        panic!("could not find function {func_name:?} in dll {dll_name:?}")
+                    });
 
                 assert_eq!(size_of::<usize>(), size_of::<u64>());
                 a[import_directory.import_address_table_rva as usize..][i * size_of::<u64>()..]
@@ -343,6 +345,7 @@ pub fn execute(pe: &[u8]) {
         }
     }
 
+    eprintln!("applying section protections");
     for section in section_table {
         let mode = if section
             .characteristics
@@ -368,13 +371,13 @@ pub fn execute(pe: &[u8]) {
         .unwrap();
     }
 
-    eprintln!("YOLO");
+    let entrypoint =
+        optional_header.image_base as usize + optional_header.address_of_entry_point as usize;
+    eprintln!("YOLO to {:#x}", entrypoint);
 
     unsafe {
-        let entrypoint = std::mem::transmute::<usize, unsafe fn() -> !>(
-            optional_header.address_of_entry_point as usize,
-        );
-        entrypoint();
+        let result = sys::call_entrypoint_via_stdcall(entrypoint);
+        eprintln!("result: {result}");
     };
 }
 
@@ -406,18 +409,39 @@ enum DllLocation {
     Found(PathBuf),
 }
 
-fn find_dll(name: &CStr) -> Option<DllLocation> {
+fn find_dll(name: &str, executable_path: &Path) -> Option<DllLocation> {
     // https://learn.microsoft.com/en-us/windows/win32/dlls/dynamic-link-library-search-order
-    let name = name.to_str().unwrap();
     if name.starts_with("api-") && emulated::supports_dll(name) {
         // This is an API set, essentially a virtual alias
         // https://learn.microsoft.com/en-us/windows/win32/apiindex/windows-apisets
         return Some(DllLocation::Emulated);
     }
-
     if emulated::supports_dll(name) {
         return Some(DllLocation::Emulated);
     }
 
+    let name_lowercase = name.to_lowercase();
+
+    let probe_path = |path: &Path| -> Option<PathBuf> {
+        std::fs::read_dir(path)
+            .ok()?
+            .find(|entry| {
+                entry
+                    .as_ref()
+                    .map(|entry| {
+                        entry
+                            .file_name()
+                            .to_str()
+                            .is_some_and(|name| name.to_lowercase() == name_lowercase)
+                    })
+                    .unwrap_or(false)
+            })
+            .map(|entry| entry.unwrap().path())
+    };
+
+    if let Some(path) = probe_path(executable_path.parent().unwrap()) {
+        return Some(DllLocation::Found(path));
+    }
+
     None
 }

src/main.rs

@@ -1,5 +1,6 @@
 #[cfg(windows)]
 use std::os::windows::fs::OpenOptionsExt;
+use std::path::Path;
 
 fn main() {
     let mut opts = std::fs::OpenOptions::new();
@@ -10,14 +11,11 @@ fn main() {
         windows::Win32::Foundation::GENERIC_EXECUTE.0 | windows::Win32::Foundation::GENERIC_READ.0,
     );
 
-    let file = opts
-        .open(
-            std::env::args()
-                .nth(1)
-                .unwrap_or_else(|| "test/example_exe.exe".into()),
-        )
-        .unwrap();
+    let path = std::env::args()
+        .nth(1)
+        .unwrap_or_else(|| "test/example_exe.exe".into());
+    let file = opts.open(&path).unwrap();
     let map = unsafe { memmap2::Mmap::map(&file).unwrap() };
 
-    portability::execute(&map);
+    portability::execute(&map, Path::new(&path));
 }

src/sys.rs

@@ -14,7 +14,8 @@ mod imp {
         Foundation::INVALID_HANDLE_VALUE,
         System::{
             Memory::{
-                FILE_MAP_EXECUTE, FILE_MAP_WRITE, PAGE_EXECUTE_READ, PAGE_EXECUTE_READWRITE, PAGE_PROTECTION_FLAGS, PAGE_READONLY, PAGE_READWRITE
+                FILE_MAP_EXECUTE, FILE_MAP_WRITE, PAGE_EXECUTE_READ, PAGE_EXECUTE_READWRITE,
+                PAGE_PROTECTION_FLAGS, PAGE_READONLY, PAGE_READWRITE,
             },
             SystemInformation::SYSTEM_INFO,
         },
@@ -51,8 +52,6 @@ mod imp {
             None,
         )?;
 
-        eprintln!("created {address:p} {size:x}");
-
         debug_assert_eq!(address.addr() & (allocation_granularity() - 1), 0);
         debug_assert_eq!(size & (allocation_granularity() - 1), 0);
 
@@ -78,7 +77,7 @@ mod imp {
 
     pub(crate) fn protect(address: *const (), size: usize, mode: Mode) -> io::Result<()> {
         debug_assert_eq!(address.addr() & (page_size() - 1), 0);
-        let mut old=  PAGE_PROTECTION_FLAGS::default();
+        let mut old = PAGE_PROTECTION_FLAGS::default();
         unsafe {
             windows::Win32::System::Memory::VirtualProtect(
                 address.cast::<c_void>(),
@@ -93,11 +92,81 @@ mod imp {
             .map_err(Into::into)
         }
     }
+
+    pub(crate) unsafe fn call_entrypoint_via_stdcall(fnptr: *const ()) -> u32 {
+        let fnptr = unsafe { std::mem::transmute::<_, unsafe extern "stdcall" fn() -> u32>(fnptr) };
+        unsafe { fnptr() }
+    }
 }
 
 #[cfg(unix)]
 mod imp {
-    compile_error!("no unix yet lol skill issue");
+    use std::io;
+
+    use super::Mode;
+
+    pub(crate) fn allocation_granularity() -> usize {
+        unsafe { libc::sysconf(libc::_SC_PAGESIZE) as usize }
+    }
+
+    pub(crate) fn page_size() -> usize {
+        allocation_granularity()
+    }
+
+    pub(crate) unsafe fn anon_write_map<'a>(
+        size: usize,
+        address: *const (),
+    ) -> io::Result<&'a mut [u8]> {
+        debug_assert_eq!(address.addr() & (allocation_granularity() - 1), 0);
+        debug_assert_eq!(size & (allocation_granularity() - 1), 0);
+
+        let ret = libc::mmap(
+            address as _,
+            size,
+            libc::PROT_READ | libc::PROT_WRITE,
+            libc::MAP_PRIVATE | libc::MAP_ANONYMOUS,
+            -1,
+            0,
+        );
+        if ret == libc::MAP_FAILED {
+            Err(io::Error::last_os_error())
+        } else if ret.addr() != address.addr() {
+            Err(io::Error::new(
+                io::ErrorKind::AlreadyExists,
+                "address already taken".to_owned(),
+            ))
+        } else {
+            Ok(std::slice::from_raw_parts_mut(
+                address.cast_mut().cast(),
+                size,
+            ))
+        }
+    }
+
+    pub(crate) fn protect(address: *const (), size: usize, mode: super::Mode) -> io::Result<()> {
+        debug_assert_eq!(address.addr() & (page_size() - 1), 0);
+        let prot = match mode {
+            Mode::Read => libc::PROT_READ,
+            Mode::Write => libc::PROT_READ | libc::PROT_WRITE,
+            Mode::Execute => libc::PROT_READ | libc::PROT_EXEC,
+        };
+        let ret = unsafe { libc::mprotect(address as _, size, prot) };
+        if ret == 0 {
+            Ok(())
+        } else {
+            Err(io::Error::last_os_error())
+        }
+    }
+
+    pub(crate) unsafe fn call_entrypoint_via_stdcall(fnptr: usize) -> u32 {
+        // todo this might be correct or not idk??? is it close enough in this case maybe?? use asm probably.
+        let fnptr = unsafe {
+            std::mem::transmute::<*const (), unsafe extern "C" fn() -> u32>(
+                std::ptr::with_exposed_provenance(fnptr),
+            )
+        };
+        unsafe { fnptr() }
+    }
 }
 
 pub(crate) use imp::*;

test/build.sh

@@ -0,0 +1,3 @@
+#!/usr/bin/env bash
+
+rustc example_exe.rs --target x86_64-pc-windows-msvc -Cpanic=abort -Clinker=lld-link -Clink-arg=/entry:my_main -Clink-arg=/NODEFAULTLIB -Cdebuginfo=0

test/example_exe.rs

@@ -1,5 +1,6 @@
 #![no_std]
 #![no_main]
+#![windows_subsystem = "console"]
 
 #[panic_handler]
 fn handle_panic(_: &core::panic::PanicInfo<'_>) -> ! {
@@ -7,4 +8,6 @@ fn handle_panic(_: &core::panic::PanicInfo<'_>) -> ! {
 }
 
 #[no_mangle]
-pub fn main() {}
+pub extern "stdcall" fn my_main() -> u32 {
+    42
+}

test/example_exe_crt.rs

@@ -0,0 +1,10 @@
+#![no_std]
+#![no_main]
+
+#[panic_handler]
+fn handle_panic(_: &core::panic::PanicInfo<'_>) -> ! {
+    loop {}
+}
+
+#[no_mangle]
+pub extern "stdcall" fn my_main() {}

test2/Makefile

@@ -0,0 +1,16 @@
+RUSTC = rustc --target x86_64-pc-windows-msvc -Cpanic=abort -Clinker=lld-link -Clink-arg=/NODEFAULTLIB -Clink-arg=/debug:none -Cdebuginfo=0
+
+build: empty_exe.exe one_dll.exe
+
+empty_exe.exe: empty_exe.rs
+	$(RUSTC) empty_exe.rs
+
+one_dll.exe: one_dll.rs small_dll.dll
+	$(RUSTC) one_dll.rs
+
+small_dll.dll: small_dll.rs
+	$(RUSTC) small_dll.rs
+
+.PHONY: clean
+clean:
+	rm *.exe *.pdb *.dll

test2/empty_exe.rs

@@ -0,0 +1,13 @@
+#![no_std]
+#![no_main]
+#![windows_subsystem = "console"]
+
+#[panic_handler]
+fn handle_panic(_: &core::panic::PanicInfo<'_>) -> ! {
+    loop {}
+}
+
+#[no_mangle]
+pub extern "stdcall" fn mainCRTStartup() -> u32 {
+    42
+}

test2/one_dll.rs

@@ -0,0 +1,18 @@
+#![no_std]
+#![no_main]
+#![windows_subsystem = "console"]
+
+#[link(name = "small_dll", kind = "raw-dylib")]
+unsafe extern "C" {
+    safe fn my_export() -> u32;
+}
+
+#[panic_handler]
+fn handle_panic(_: &core::panic::PanicInfo<'_>) -> ! {
+    loop {}
+}
+
+#[no_mangle]
+pub extern "stdcall" fn mainCRTStartup() -> u32 {
+    my_export()
+}

test2/small_dll.rs

@@ -0,0 +1,18 @@
+#![no_std]
+#![crate_type = "cdylib"]
+#![windows_subsystem = "console"]
+
+#[panic_handler]
+fn handle_panic(_: &core::panic::PanicInfo<'_>) -> ! {
+    loop {}
+}
+
+#[no_mangle]
+pub extern "C" fn my_export() -> u32 {
+    42
+}
+
+#[no_mangle]
+pub extern "stdcall" fn _DllMainCRTStartup() -> u32 {
+    0
+}