Add some more info to the libcap.so as an executable.

Mostly cause we can, but this gives a little more diagnostic
value to the libcap.so executable mode of operation.

usage: libcap.so [--help|--usage|--summary]

Signed-off-by: Andrew G. Morgan <morgan@kernel.org>

2 files changed, 49 insertions, 0 deletions

diff --git a/libcap/Makefile b/libcap/Makefile
index 967820e..05fa90d 100644
--- a/libcap/Makefile
+++ b/libcap/Makefile
@@ -135,6 +135,9 @@ cap_test: cap_test.c $(INCLS) $(CAPOBJS)
 
 libcapsotest: $(CAPLIBNAME)
 	./$(CAPLIBNAME)
+	./$(CAPLIBNAME) --usage
+	./$(CAPLIBNAME) --help
+	./$(CAPLIBNAME) --summary
 
 libpsxsotest: $(PSXLIBNAME)
 	./$(PSXLIBNAME)
diff --git a/libcap/execable.c b/libcap/execable.c
index 5e7a88f..9d3ae7f 100644
--- a/libcap/execable.c
+++ b/libcap/execable.c
@@ -1,9 +1,44 @@
 #include <stdio.h>
+#include <stdlib.h>
+#include <sys/capability.h>
+
 #include "execable.h"
 
+static void usage(int status)
+{
+    printf("\nusage: libcap.so [--help|--usage|--summary]\n");
+    exit(status);
+}
+
+static void summary(void)
+{
+    cap_value_t bits = cap_max_bits(), c;
+    cap_mode_t mode = cap_get_mode();
+
+    printf("\nCurrent mode: %s\n", cap_mode_name(mode));
+    printf("Number of cap values known to: this libcap=%d, running kernel=%d\n",
+	   CAP_LAST_CAP+1, bits);
+    if (bits > CAP_LAST_CAP+1) {
+	printf("=> Consider upgrading libcap to name:");
+	for (c = CAP_LAST_CAP+1; c < bits; c++) {
+	    printf(" %d", c);
+	}
+    } else if (bits < CAP_LAST_CAP+1) {
+	printf("=> Newer kernels also provide support for:");
+	for (c = bits; c <= CAP_LAST_CAP; c++) {
+	    char *name = cap_to_name(c);
+	    printf(" %s", name);
+	    cap_free(name);
+	}
+    }
+    printf("\n");
+}
+
 SO_MAIN(int argc, char **argv)
 {
+    int i;
     const char *cmd = "This library";
+
     if (argv != NULL && argv[0] != NULL) {
 	cmd = argv[0];
     }
@@ -12,4 +47,15 @@ SO_MAIN(int argc, char **argv)
 	   "More information on this library is available from:\n"
 	   "\n"
 	   "    https://sites.google.com/site/fullycapable/\n", cmd);
+
+    for (i = 1; i < argc; i++) {
+	if (!strcmp(argv[i], "--usage") || !strcmp(argv[i], "--help")) {
+	    usage(0);
+	}
+	if (!strcmp(argv[i], "--summary")) {
+	    summary();
+	    continue;
+	}
+	usage(1);
+    }
 }