kthd: read ELF file for exec() and relay response

Author: jewelcodes

kthd/src/exec.c

@@ -0,0 +1,75 @@
+/*
+ * luxOS - a unix-like operating system
+ * Omar Elghoul, 2024
+ * 
+ * kthd: Kernel Thread Helper Daemon
+ */
+
+#include <liblux/liblux.h>
+#include <sys/stat.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <string.h>
+#include <fnctl.h>
+#include <errno.h>
+
+void exec(ExecCommand *cmd) {
+    cmd->header.header.response = 1;
+    cmd->header.header.length = sizeof(ExecCommand);
+
+    // open the program to be executed
+    int fd = open(cmd->path, O_RDONLY);
+    if(fd < 0) {
+        cmd->header.header.status = -ENOENT;
+        luxSendLumen(cmd);
+        return;
+    }
+
+    // ensure the requesting process has execute permissions
+    struct stat st;
+    if(fstat(fd, &st)) {
+        close(fd);
+        cmd->header.header.status = -1*errno;
+        luxSendLumen(cmd);
+        return;
+    }
+
+    cmd->header.header.status = 0;
+    if(cmd->header.header.requester == st.st_uid) {
+        if(!(st.st_mode & S_IXUSR)) cmd->header.header.status = -EPERM;
+    } else {
+        if(!(st.st_mode & S_IXOTH)) cmd->header.header.status = -EPERM;
+    }
+
+    if(cmd->header.header.status) {
+        close(fd);
+        luxSendLumen(cmd);
+        return;
+    }
+
+    // now read the file into memory
+    // allocate a new buffer for this
+    ExecCommand *res = calloc(1, sizeof(ExecCommand) + st.st_size);
+    if(!res) {
+        close(fd);
+        cmd->header.header.status = -ENOMEM;
+        luxSendLumen(cmd);
+        return;
+    }
+
+    memcpy(res, cmd, sizeof(ExecCommand));
+
+    if(read(fd, res->elf, st.st_size) != st.st_size) {
+        close(fd);
+        free(res);
+        cmd->header.header.status = -1*errno;
+        luxSendLumen(cmd);
+        return;
+    }
+
+    // and relay the response
+    res->header.header.length += st.st_size;
+    res->header.header.status = 0;
+    luxSendLumen(res);
+    free(res);
+}

kthd/src/main.c

@@ -8,6 +8,8 @@
 #include <liblux/liblux.h>
 #include <stdlib.h>
 
+void exec(ExecCommand *);
+
 int main() {
     luxInit("kthd");
 
@@ -38,6 +40,7 @@ int main() {
             luxRecvLumen(msg, SERVER_MAX_SIZE, false, false);
 
             switch(msg->header.command) {
+            case COMMAND_EXEC: exec((ExecCommand *) msg); break;
             default:
                 luxLogf(KPRINT_LEVEL_WARNING, "unimplemented command 0x%04X, dropping message...\n", msg->header.command);
             }