a quick C cat

README.adoc

@@ -17108,6 +17108,7 @@ Good sanity check for user mode: <<qemu-user-mode-getting-started>>
 *** link:userland/c/stderr.c[]
 *** File IO
 **** link:userland/c/file_write_read.c[]
+***** link:userland/c/cat.c[]: a quick and dirty `cat` implementation for interactive <<user-mode-simulation>> tests
 **** link:userland/linux/open_o_tmpfile.c[]: https://stackoverflow.com/questions/4508998/what-is-an-anonymous-inode-in-linux/44388030#44388030
 ** `time.h`
 *** link:userland/c/timespec_get.c[] `timespec_get` is a C11 for `clock_gettime` http://stackoverflow.com/questions/361363/how-to-measure-time-in-milliseconds-using-ansi-c/36095407#36095407

lkmc/file_io.h

@@ -0,0 +1,66 @@
+#ifndef LKMC_FILE_IO_H
+#define LKMC_FILE_IO_H
+
+/* Returns the size of the given open `FILE*`.
+ *
+ * If an error occurs, returns `-1L`.
+ *
+ * Does not work for pipes.
+ */
+long lkmc_fget_file_size(FILE *fp) {
+    long oldpos;
+    long return_value;
+    oldpos = ftell(fp);
+    if (oldpos == -1L) {
+        return -1L;
+    }
+    if (fseek(fp, 0, SEEK_END) != 0) {
+        return -1L;
+    }
+    return_value = ftell(fp);
+    if (return_value == -1L) {
+        return -1L;
+    }
+    /* Restore the old position. */
+    if (fseek(fp, oldpos , SEEK_SET) != 0) {
+        return -1L;
+    }
+    return return_value;
+}
+
+/* Read the entire file to a char[] dynamically allocated inside this function.
+ *
+ * Returns a pointer to the start of that array.
+ *
+ * In case of any error, returns NULL.
+ *
+ * http://stackoverflow.com/questions/174531/easiest-way-to-get-files-contents-in-c
+ */
+char *lkmc_file_read(char *path) {
+    FILE *fp;
+    char *buffer;
+    long fsize;
+
+    fp = fopen(path , "rb");
+    if (fp == NULL) {
+        return NULL;
+    }
+    fsize = lkmc_fget_file_size(fp);
+    if (fsize < 0){
+        fprintf(stderr, "could not determine lenght of:\n%s\n", path);
+        return NULL;
+    }
+    buffer = (char*)malloc(fsize);
+    if (buffer == NULL) {
+        return NULL;
+    }
+    if (fread(buffer, 1, fsize, fp) != (size_t)fsize) {
+        return NULL;
+    }
+    if (fclose(fp) == EOF){
+        return NULL;
+    }
+    return buffer;
+}
+
+#endif

path_properties.py

@@ -67,7 +67,6 @@ class PathProperties:
         'no_build': False,
         # The path does not generate an executable in itself, e.g.
         # it only generates intermediate object files. Therefore it
-        # should not be run while testing.
         'no_executable': False,
         'qemu_unimplemented_instruction': False,
         # The script requires a non-trivial to determine argument to be passed to run properly.
@@ -655,8 +654,8 @@ path_properties_tuples = (
                             'test_run_args': {'cpus': 3},
                         },
                         'assert_fail.c': {'signal_received': signal.Signals.SIGABRT},
-                        # This has complex failure modes, too hard to assert.
-                        'smash_stack.c': {'skip_run_unclassified': True},
+                        # Not sure which argument to pass.
+                        'cat.c': {'skip_run_unclassified': True},
                         'exit1.c': {'exit_status': 1},
                         'exit2.c': {'exit_status': 2},
                         'false.c': {'exit_status': 1},
@@ -666,6 +665,8 @@ path_properties_tuples = (
                         'm5ops.c': {'allowed_emulators': {'gem5'}},
                         'return1.c': {'exit_status': 1},
                         'return2.c': {'exit_status': 2},
+                        # This has complex failure modes, too hard to assert.
+                        'smash_stack.c': {'skip_run_unclassified': True},
                         # Wrapper not defined by newlib.
                         'timespec_get.c': {'baremetal': False},
                     }

userland/c/cat.c

@@ -0,0 +1,13 @@
+#include <assert.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#include <lkmc/file_io.h>
+
+int main(int argc, char **argv) {
+    assert(argc == 2);
+    char *s = lkmc_file_read(argv[1]);
+    puts(s);
+    free(s);
+    return EXIT_SUCCESS;
+}

userland/c/file_write_read.c

@@ -1,38 +1,12 @@
 /* https://cirosantilli.com/linux-kernel-module-cheat#c */
 
 #include <lkmc.h>
+#include <lkmc/file_io.h>
 
 #include <assert.h>
 #include <string.h>
 #include <stdio.h>
 
-/* Returns the size of the given open `FILE*`.
- *
- * If an error occurs, returns `-1L`.
- *
- * Does not work for pipes.
- */
-long fget_file_size(FILE *fp) {
-    long oldpos;
-    long return_value;
-    oldpos = ftell(fp);
-    if (oldpos == -1L) {
-        return -1L;
-    }
-    if (fseek(fp, 0, SEEK_END) != 0) {
-        return -1L;
-    }
-    return_value = ftell(fp);
-    if (return_value == -1L) {
-        return -1L;
-    }
-    /* Restore the old position. */
-    if (fseek(fp, oldpos , SEEK_SET) != 0) {
-        return -1L;
-    }
-    return return_value;
-}
-
 /* Same as `file_size`, but takes the path instead of a `FILE*`. */
 long file_size(char *path) {
     FILE *fp;
@@ -41,48 +15,13 @@ long file_size(char *path) {
     if (fp == NULL) {
         return -1L;
     }
-    return_value = fget_file_size(fp);
+    return_value = lkmc_fget_file_size(fp);
     if (fclose(fp) == EOF) {
         return -1L;
     }
     return return_value;
 }
 
-/* Read the entire file to a char[] dynamically allocated inside this function.
- *
- * Returns a pointer to the start of that array.
- *
- * In case of any error, returns NULL.
- *
- * http://stackoverflow.com/questions/174531/easiest-way-to-get-files-contents-in-c
- */
-char *file_read(char *path) {
-    FILE *fp;
-    char *buffer;
-    long fsize;
-
-    fp = fopen(path , "rb");
-    if (fp == NULL) {
-        return NULL;
-    }
-    fsize = fget_file_size(fp);
-    if (fsize < 0){
-        fprintf(stderr, "could not determine lenght of:\n%s\n", path);
-        return NULL;
-    }
-    buffer = (char*)malloc(fsize);
-    if (buffer == NULL) {
-        return NULL;
-    }
-    if (fread(buffer, 1, fsize, fp) != (size_t)fsize) {
-        return NULL;
-    }
-    if (fclose(fp) == EOF){
-        return NULL;
-    }
-    return buffer;
-}
-
 /* Write a null terminated string to file
  *
  * Return -1 on failure, 0 on success.
@@ -117,9 +56,9 @@ int main(void) {
 
     /* Read entire file at once to a string. */
     {
-        char *output = file_read(path);
+        char *output = lkmc_file_read(path);
         if (output == NULL) {
-            LKMC_IO_ERROR("file_read", path);
+            LKMC_IO_ERROR("lkmc_file_read", path);
         }
         assert(strcmp(data, output) == 0);
         free(output);