Add support for "/proc/[pid]/comm" and fix "/proc/[pid]/cmdline"

src/libos/src/fs/procfs/pid_inode.rs

@@ -1,6 +1,6 @@
 use super::*;
 use crate::process::table::get_process;
-use crate::process::ProcessRef;
+use crate::process::{ProcessRef, ProcessStatus};
 
 pub struct LockedPidDirINode(RwLock<PidDirINode>);
 
@@ -41,7 +41,9 @@ impl LockedPidDirINode {
         // root
         let root_inode = ProcRootSymINode::new(&file.process_ref);
         file.entries.insert(String::from("root"), root_inode);
-
+        // comm
+        let comm_inode = ProcCommINode::new(&file.process_ref);
+        file.entries.insert(String::from("comm"), comm_inode);
         Ok(())
     }
 }
@@ -136,7 +138,15 @@ impl ProcCmdlineINode {
 
 impl ProcINode for ProcCmdlineINode {
     fn generate_data_in_bytes(&self) -> vfs::Result<Vec<u8>> {
-        Ok(self.0.exec_path().to_owned().into_bytes())
+        let cmdline = if let ProcessStatus::Zombie = self.0.status() {
+            Vec::new()
+        } else {
+            // Null-terminated bytes
+            std::ffi::CString::new(self.0.exec_path())
+                .expect("failed to new CString")
+                .into_bytes_with_nul()
+        };
+        Ok(cmdline)
     }
 }
 
@@ -186,6 +196,24 @@ impl ProcINode for ProcRootSymINode {
     }
 }
 
+pub struct ProcCommINode(ProcessRef);
+
+impl ProcCommINode {
+    pub fn new(process_ref: &ProcessRef) -> Arc<dyn INode> {
+        Arc::new(File::new(Self(Arc::clone(process_ref))))
+    }
+}
+
+impl ProcINode for ProcCommINode {
+    fn generate_data_in_bytes(&self) -> vfs::Result<Vec<u8>> {
+        let main_thread = self.0.main_thread().ok_or(FsError::EntryNotFound)?;
+        let mut comm = main_thread.name().as_c_str().to_bytes().to_vec();
+        // Add '\n' at the end to make the result same with Linux
+        comm.push(b'\n');
+        Ok(comm)
+    }
+}
+
 pub struct FdSymINode(FileRef);
 
 impl FdSymINode {

test/procfs/main.c

@@ -1,3 +1,4 @@
+#define _GNU_SOURCE
 #include <sys/types.h>
 #include <sys/vfs.h>
 #include <fcntl.h>
@@ -10,7 +11,8 @@
 // Helper variable and function
 // ============================================================================
 
-const char **g_argv;
+// Contains the name that was used to invoke the calling program
+extern char *program_invocation_short_name;
 
 static int test_readlink_from_procfs(const char *proc_inode, char *buf, int buf_size,
                                      const char *expected_target) {
@@ -36,7 +38,8 @@ static int test_readlink_from_proc_self_exe() {
     char absolute_path[PATH_MAX] = { 0 };
     const char *proc_exe = "/proc/self/exe";
 
-    int n = snprintf(absolute_path, sizeof(absolute_path), "/bin/%s", *g_argv);
+    int n = snprintf(absolute_path, sizeof(absolute_path), "/bin/%s",
+                     program_invocation_short_name);
     if (n < 0) {
         THROW_ERROR("failed to call snprintf");
     }
@@ -94,13 +97,41 @@ static int test_read_from_proc_self_cmdline() {
     char absolute_path[PATH_MAX] = { 0 };
     const char *proc_cmdline = "/proc/self/cmdline";
 
-    int n = snprintf(absolute_path, sizeof(absolute_path), "/bin/%s", *g_argv);
+    int n = snprintf(absolute_path, sizeof(absolute_path), "/bin/%s",
+                     program_invocation_short_name);
     if (n < 0) {
         THROW_ERROR("failed to call snprintf");
     }
-    if (fs_check_file_content(proc_cmdline, absolute_path) < 0) {
+    char read_buf[PATH_MAX] = { 0 };
+    int fd = open(proc_cmdline, O_RDONLY);
+    size_t len = read(fd, read_buf, sizeof(read_buf));
+    if (len != strlen(absolute_path) + 1) {
+        THROW_ERROR("failed check the return value of reading from %s", proc_cmdline);
+    }
+    if (read_buf[strlen(absolute_path)] != '\0') {
+        THROW_ERROR("failed check the buffer of reading from %s", proc_cmdline);
+    }
+    if (strcmp(absolute_path, read_buf) != 0) {
         THROW_ERROR("failed to check result in %s", proc_cmdline);
     }
+    close(fd);
+    return 0;
+}
+
+static int test_read_from_proc_self_comm() {
+    // The name can be up to 16 bytes long, including the terminating null byte.
+    char comm_name[16] = { 0 };
+    const char *proc_comm = "/proc/self/comm";
+
+    if (snprintf(comm_name, sizeof(comm_name), "%s", program_invocation_short_name) < 0) {
+        THROW_ERROR("failed to call snprintf");
+    }
+    // The last byte shoud be '\n'
+    int end_idx = strlen(comm_name);
+    comm_name[end_idx] = '\n';
+    if (fs_check_file_content(proc_comm, comm_name) < 0) {
+        THROW_ERROR("failed to check result in %s", proc_comm);
+    }
 
     return 0;
 }
@@ -169,12 +200,12 @@ static test_case_t test_cases[] = {
     TEST_CASE(test_readlink_from_proc_self_root),
     TEST_CASE(test_create_and_unlink_file_from_proc_self_root),
     TEST_CASE(test_read_from_proc_self_cmdline),
+    TEST_CASE(test_read_from_proc_self_comm),
     TEST_CASE(test_read_from_proc_meminfo),
     TEST_CASE(test_read_from_proc_cpuinfo),
     TEST_CASE(test_statfs),
 };
 
 int main(int argc, const char *argv[]) {
-    g_argv = argv;
     return test_suite_run(test_cases, ARRAY_SIZE(test_cases));
 }