Add shebang handling

arch/amd64/binfmt_elf.c

@@ -105,6 +105,13 @@ static int elf_bzero(mm_space_t space, uintptr_t vma_dst, size_t size) {
     return 0;
 }
 
+int binfmt_is_elf(const char *ident, size_t len) {
+    if (len < 4) {
+        return 0;
+    }
+    return !strncmp(ident, "\x7F""ELF", 4);
+}
+
 int elf_load(struct process *proc, struct vfs_ioctx *ctx, struct ofile *fd, uintptr_t *entry) {
     int res;
     ssize_t bread;

include/sys/binfmt_elf.h

@@ -5,3 +5,4 @@ struct process;
 struct ofile;
 
 int elf_load(struct process *proc, struct vfs_ioctx *ctx, struct ofile *fd, uintptr_t *entry);
+int binfmt_is_elf(const char *guess, size_t len);

sys/execve.c

@@ -120,6 +120,7 @@ int sys_execve(const char *path, const char **argv, const char **envp) {
     _assert(thr);
     struct process *proc = thr->proc;
     _assert(proc);
+    char shebang[128];
 
     if (proc->thread_count > 1) {
         panic("XXX: execve() in multithreaded process\n");
@@ -136,6 +137,47 @@ int sys_execve(const char *path, const char **argv, const char **envp) {
         return res;
     }
 
+    if ((res = vfs_open(&proc->ioctx, &fd, path, O_RDONLY, 0)) != 0) {
+        kerror("%s: %s\n", path, kstrerror(res));
+        return res;
+    }
+
+    if ((res = vfs_read(&proc->ioctx, &fd, shebang, sizeof(shebang))) <= 0) {
+        kerror("%s: %s\n", path, kstrerror(res));
+        return res;
+    }
+
+    if (!binfmt_is_elf(shebang, res)) {
+        // Try checking for shebang line
+        if (shebang[0] == '#' && shebang[1] == '!') {
+            char *e = strchr(shebang, '\n');
+            if (!e) {
+                vfs_close(&proc->ioctx, &fd);
+                return -EINVAL;
+            }
+            *e = 0;
+
+            int argc;
+            for (argc = 0; argv[argc]; ++argc);
+            // For interpreter
+            ++argc;
+            // Sanity check
+            _assert(argc <= 32);
+            const char *argv_new[argc + 1];
+            argv_new[0] = shebang + 2;
+            for (int i = 1; i < argc; ++i) {
+                argv_new[i] = argv[i - 1];
+            }
+            argv_new[argc] = NULL;
+
+            for (int i = 0; i < argc; ++i) {
+                kdebug("[%d]: %s\n", i, argv_new[i]);
+            }
+
+            return sys_execve(shebang + 2, argv_new, envp);
+        }
+    }
+
     const char *e = strrchr(path, '/');
     const char *name = e + 1;
     if (!e) {
@@ -162,11 +204,6 @@ int sys_execve(const char *path, const char **argv, const char **envp) {
         panic("Failed to copy argp/envp to new process\n");
     }
 
-    if ((res = vfs_open(&proc->ioctx, &fd, path, O_RDONLY, 0)) != 0) {
-        kerror("%s: %s\n", path, kstrerror(res));
-        return res;
-    }
-
     if (proc->space == mm_kernel) {
         // Have to allocate a new PID for kernel -> userspace transition
         proc->pid = process_alloc_pid(1); //thread_alloc_pid(1);