intercept: make execvpe optional (macos does not have)

Author: rizsotto

intercept-preload/src/c/shim.c

@@ -58,6 +58,7 @@ extern void rust_session_init(char *const *envp);
 // Exec family functions
 extern int rust_execve(const char *path, char *const argv[], char *const envp[]);
 extern int rust_execvpe(const char *file, char *const argv[], char *const envp[]);
+extern int rust_execvp(const char *file, char *const argv[]);
 extern int rust_execvP(const char *file, const char *search_path, char *const argv[]);
 extern int rust_exect(const char *path, char *const argv[], char *const envp[]);
 extern int rust_posix_spawn(pid_t *pid, const char *path,
@@ -163,7 +164,11 @@ EXPORT int execlp(const char *file, const char *arg0, ...)
 
     va_end(ap);
 
+#if defined(has_symbol_execvpe)
     return rust_execvpe(file, argv, get_environ());
+#else
+    return rust_execvp(file, argv);
+#endif
 }
 #endif
 
@@ -226,7 +231,11 @@ EXPORT int execve(const char *path, char *const argv[], char *const envp[])
 #if defined(has_symbol_execvp)
 EXPORT int execvp(const char *file, char *const argv[])
 {
+#if defined(has_symbol_execvpe)
     return rust_execvpe(file, argv, get_environ());
+#else
+    return rust_execvp(file, argv);
+#endif
 }
 #endif
 

intercept-preload/src/implementation.rs

@@ -49,6 +49,12 @@ static REAL_EXECVPE: AtomicPtr<libc::c_void> = {
     AtomicPtr::new(ptr)
 };
 
+#[ctor]
+static REAL_EXECVP: AtomicPtr<libc::c_void> = {
+    let ptr = unsafe { libc::dlsym(RTLD_NEXT, c"execvp".as_ptr() as *const _) };
+    AtomicPtr::new(ptr)
+};
+
 #[ctor]
 static REAL_EXECVP_OPENBSD: AtomicPtr<libc::c_void> = {
     let ptr = unsafe { libc::dlsym(RTLD_NEXT, c"execvP".as_ptr() as *const _) };
@@ -180,7 +186,8 @@ pub unsafe extern "C" fn rust_execve(
 
 /// Rust implementation of execvpe (GNU extension)
 ///
-/// Called from C shim for: execvpe, execvp, execlp
+/// Called from C shim for: execvpe
+/// On platforms where execvpe is available, execlp and execvp are also routed here.
 ///
 /// # Safety
 /// This function is unsafe because it:
@@ -226,6 +233,52 @@ pub unsafe extern "C" fn rust_execvpe(
     }
 }
 
+/// Rust implementation of execvp
+///
+/// Called from C shim for: execvp, execlp (on platforms where execvpe is not available)
+///
+/// Unlike `rust_execvpe`, this function does not take an explicit `envp` argument.
+/// The real `execvp` uses the process's `environ`, so no environment doctoring is
+/// performed here (same approach as `popen` and `system`).
+///
+/// # Safety
+/// This function is unsafe because it:
+/// - Dereferences raw pointers
+/// - Calls the real execvp function
+#[cfg(has_symbol_execvp)]
+#[unsafe(no_mangle)]
+pub unsafe extern "C" fn rust_execvp(
+    file: *const c_char,
+    argv: *const *const c_char,
+) -> c_int {
+    type ExecvpFunc = unsafe extern "C" fn(
+        file: *const c_char,
+        argv: *const *const c_char,
+    ) -> c_int;
+
+    unsafe {
+        report(|| {
+            let result = Execution {
+                executable: as_path_buf(file)?,
+                arguments: as_string_vec(argv)?,
+                working_dir: working_dir()?,
+                environment: std::env::vars().collect(),
+            };
+            Ok(result)
+        });
+
+        let func_ptr = REAL_EXECVP.load(Ordering::SeqCst);
+        if !func_ptr.is_null() {
+            let real_func_ptr: ExecvpFunc = std::mem::transmute(func_ptr);
+            real_func_ptr(file, argv)
+        } else {
+            log::error!("Real execvp function not found");
+            set_errno(libc::ENOSYS);
+            -1
+        }
+    }
+}
+
 /// Rust implementation of execvP (BSD extension)
 ///
 /// Called from C shim for: execvP

intercept-preload/src/session.rs

@@ -15,7 +15,9 @@ use std::ffi::{CStr, CString};
 use std::net::SocketAddr;
 use std::sync::OnceLock;
 
-use bear::environment::{KEY_INTERCEPT_STATE, KEY_OS__PRELOAD_PATH};
+use bear::environment::KEY_INTERCEPT_STATE;
+#[cfg(not(target_os = "macos"))]
+use bear::environment::KEY_OS__PRELOAD_PATH;
 #[cfg(target_os = "macos")]
 use bear::environment::{KEY_OS__MACOS_FLAT_NAMESPACE, KEY_OS__MACOS_PRELOAD_PATH};
 use bear::intercept::environment::{PreloadState, insert_to_path};