modinfo: various fixes.

I came here because the new -Wno-unreachable-code-loop-increment warning
didn't like the for loop on line 86. That loop is indeed not necessary.

Use strend() to do a string suffix match.

Use memmem() to search. It's available on macOS and Android by default,
but it's behind _GNU_SOURCE for glibc, so add that to portability.h.

Output the tags in the same order as the Debian modinfo.

I've left "parmtype" in even though the Debian modinfo doesn't output it
at all.

Also fix the tests so that they work on a device that has modules for
multiple kernels installed (like my laptop) --- make sure that the two
modules we pick come from the same kernel.

3 files changed, 33 insertions, 38 deletions

diff --git a/lib/portability.h b/lib/portability.h
index d81ddead..76790f4d 100644
--- a/lib/portability.h
+++ b/lib/portability.h
@@ -103,6 +103,8 @@ char *dirname(char *path);
 char *__xpg_basename(char *path);
 static inline char *basename(char *path) { return __xpg_basename(path); }
 char *strcasestr(const char *haystack, const char *needle);
+void *memmem(const void *haystack, size_t haystack_length,
+  const void *needle, size_t needle_length);
 #endif // defined(glibc)
 
 // getopt_long(), getopt_long_only(), and struct option.
diff --git a/tests/modinfo.test b/tests/modinfo.test
index aaa7a7bd..261acfda 100644
--- a/tests/modinfo.test
+++ b/tests/modinfo.test
@@ -19,7 +19,7 @@ testcmd "missing" "missing 2>&1" "modinfo: missing: not found\n" "" ""
 # Find some modules to work with.
 MODULE_PATH1=$(find $MODULE_ROOT/lib/modules -name *.ko | head -1 2>/dev/null)
 MODULE1=$(basename -s .ko $MODULE_PATH1)
-MODULE_PATH2=$(find $MODULE_ROOT/lib/modules -name *.ko | tail -1 2>/dev/null)
+MODULE_PATH2=$(find $MODULE_ROOT/lib/modules -name *.ko | head -2 | tail -1 2>/dev/null)
 MODULE2=$(basename -s .ko $MODULE_PATH2)
 DASH_MODULE=$(basename -s .ko \
   $(find $MODULE_ROOT/lib/modules -name *-*.ko | tail -1 2>/dev/null))
diff --git a/toys/other/modinfo.c b/toys/other/modinfo.c
index 286570f1..6c1e9392 100644
--- a/toys/other/modinfo.c
+++ b/toys/other/modinfo.c
@@ -40,16 +40,16 @@ static void output_field(char *field, char *value)
 
 static void modinfo_file(char *full_name)
 {
-  int fd, len, i;
-  char *buf = 0, *pos, *modinfo_tags[] = {
-    "alias", "license", "description", "author", "firmware",
-    "vermagic", "srcversion", "intree", "depends", "parm",
-    "parmtype",
+  int fd, flen, i;
+  char *buf = 0, *end, *modinfo_tags[] = {
+    "license", "author", "description", "firmware", "alias", "srcversion",
+    "depends", "retpoline", "intree", "name", "vermagic", "parm", "parmtype",
   };
 
   if (-1 != (fd = open(full_name, O_RDONLY))) {
-    len = fdlength(fd);
-    buf = xmmap(0, len, PROT_READ, MAP_SHARED, fd, 0);
+    flen = fdlength(fd);
+    buf = xmmap(0, flen, PROT_READ, MAP_SHARED, fd, 0);
+    end = buf + flen;
     close(fd);
   }
 
@@ -61,47 +61,42 @@ static void modinfo_file(char *full_name)
   TT.count++;
   output_field("filename", full_name);
 
-  for (pos = buf; pos < buf+len; pos++) {
-    if (*pos) continue;
+  for (i=0; i<ARRAY_LEN(modinfo_tags); i++) {
+    char *field = modinfo_tags[i], *p = buf;
+    int slen = sprintf(toybuf, "%s=", field);
 
-    for (i=0; i<ARRAY_LEN(modinfo_tags); i++) {
-      char *str = modinfo_tags[i];
-      int len = strlen(str);
-
-      if (!strncmp(pos+1, str, len) && pos[len+1] == '=')
-        output_field(str, pos+len+2);
+    while (p && p < end) {
+      p = memmem(p, end-p, toybuf, slen);
+      if (p) output_field(field, p += slen);
     }
   }
 
-  munmap(buf, len);
+  munmap(buf, flen);
 }
 
 static int check_module(struct dirtree *new)
 {
-  if (!dirtree_notdotdot(new)) return 0;
+  char *s;
+  int len;
 
-  if (S_ISREG(new->st.st_mode)) {
-    char *s;
-
-    for (s = toys.optargs[TT.mod]; *s; s++) {
-      int len = 0;
+  if (!dirtree_notdotdot(new)) return 0;
 
-      // The kernel treats - and _ the same, so we should too.
-      for (len = 0; s[len]; len++) {
-        if (s[len] == '-' && new->name[len] == '_') continue;
-        if (s[len] == '_' && new->name[len] == '-') continue;
-        if (s[len] != new->name[len]) break;
-      }
-      if (s[len] || strcmp(new->name+len, ".ko")) break;
+  if (!S_ISREG(new->st.st_mode)) return DIRTREE_RECURSE;
 
-      modinfo_file(s = dirtree_path(new, 0));
-      free(s);
+  s = toys.optargs[TT.mod];
 
-      return DIRTREE_ABORT;
-    }
+  // The kernel treats - and _ the same, so we should too.
+  for (len = 0; s[len]; len++) {
+    if (s[len] == '-' && new->name[len] == '_') continue;
+    if (s[len] == '_' && new->name[len] == '-') continue;
+    if (s[len] != new->name[len]) break;
   }
+  if (s[len] || strcmp(new->name+len, ".ko")) return DIRTREE_RECURSE;
+
+  modinfo_file(s = dirtree_path(new, 0));
+  free(s);
 
-  return DIRTREE_RECURSE;
+  return DIRTREE_ABORT;
 }
 
 void modinfo_main(void)
@@ -120,9 +115,7 @@ void modinfo_main(void)
   }
 
   for (TT.mod = 0; TT.mod<toys.optc; TT.mod++) {
-    char *s = strstr(toys.optargs[TT.mod], ".ko");
-
-    if (s && !s[3]) modinfo_file(toys.optargs[TT.mod]);
+    if (strend(toys.optargs[TT.mod], ".ko")) modinfo_file(toys.optargs[TT.mod]);
     else {
       char *path = xmprintf("%s/lib/modules/%s", TT.b, TT.k);