[Libguestfs] [PATCH 3/3] febootstrap/helper: Major change to kernel module handling code
Hilko Bengen
bengen at hilluzination.de
Sat Jun 4 23:02:50 UTC 2011
The previous implementation had two problems: (I) Not all needed
kernel modules were copied to the initrd. (II) If a kernel module
depended on more than one other module, only the first dependency was
considered for the load order. Using 2.6.39-1-amd64 (Debian/unstable)
ext2.ko was not loaded and therefore the root FS could not be mounted.
The use of tsort(1) has been replaced with a set of functions that
build a DAG in memory and use that to calculate the list of modules to
be copied into the initrd and the order in which to laod them.
---
helper/ext2initrd.c | 222 ++++++++++++++++++++++++++-------------------------
1 files changed, 113 insertions(+), 109 deletions(-)
diff --git a/helper/ext2initrd.c b/helper/ext2initrd.c
index 17af3bd..19ac8b3 100644
--- a/helper/ext2initrd.c
+++ b/helper/ext2initrd.c
@@ -27,6 +27,7 @@
#include <dirent.h>
#include <errno.h>
#include <assert.h>
+#include <fnmatch.h>
#include "error.h"
#include "full-write.h"
@@ -38,7 +39,10 @@
static void read_module_deps (const char *modpath);
static void free_module_deps (void);
-static const char *get_module_dep (const char *);
+static void add_module_dep (const char *name, const char *dep);
+static struct module * add_module (const char *name);
+static struct module * find_module (const char *name);
+static void print_module_load_order (FILE *f, FILE *pp, struct module *m);
/* The init binary. */
extern char _binary_init_start, _binary_init_end, _binary_init_size;
@@ -65,6 +69,20 @@ static const char *kmods[] = {
NULL
};
+/* Module dependencies. */
+struct module {
+ struct module *next;
+ struct moddep *deps;
+ char *name;
+ int visited;
+};
+struct module *modules = NULL;
+
+struct moddep {
+ struct moddep *next;
+ struct module *dep;
+};
+
void
ext2_make_initrd (const char *modpath, const char *initrd)
{
@@ -72,85 +90,39 @@ ext2_make_initrd (const char *modpath, const char *initrd)
if (mkdtemp (dir) == NULL)
error (EXIT_FAILURE, errno, "mkdtemp");
- char *cmd;
- int r;
-
- /* Copy kernel modules into tmpdir. */
- size_t n = strlen (modpath) + strlen (dir) + 64;
- size_t i;
- for (i = 0; kmods[i] != NULL; ++i)
- n += strlen (kmods[i]) + 16;
- cmd = malloc (n);
- /* "cd /" here is for virt-v2v. It's cwd might not be accessible by
- * the current user (because it sometimes sets its own uid) and the
- * "find" command works by changing directory then changing back to
- * the cwd. This results in a warning:
- *
- * find: failed to restore initial working directory: Permission denied
- *
- * Note this only works because "modpath" and temporary "dir" are
- * currently guaranteed to be absolute paths, hence assertion.
- */
- assert (modpath[0] == '/');
- sprintf (cmd, "cd / ; find '%s' ", modpath);
- for (i = 0; kmods[i] != NULL; ++i) {
- if (i > 0) strcat (cmd, "-o ");
- strcat (cmd, "-name '");
- strcat (cmd, kmods[i]);
- strcat (cmd, "' ");
- }
- strcat (cmd, "| xargs cp -t ");
- strcat (cmd, dir);
- if (verbose >= 2) fprintf (stderr, "%s\n", cmd);
- r = system (cmd);
- if (r == -1 || WEXITSTATUS (r) != 0)
- error (EXIT_FAILURE, 0, "ext2_make_initrd: copy kmods failed");
- free (cmd);
-
- /* The above command effectively gives us the final list of modules.
- * Calculate dependencies from modpath/modules.dep and write that
- * into the output.
- */
read_module_deps (modpath);
-
- cmd = xasprintf ("tsort > %s/modules", dir);
- if (verbose >= 2) fprintf (stderr, "%s\n", cmd);
- FILE *pp = popen (cmd, "w");
- if (pp == NULL)
- error (EXIT_FAILURE, errno, "tsort: failed to create modules list");
-
- DIR *dr = opendir (dir);
- if (dr == NULL)
- error (EXIT_FAILURE, errno, "opendir: %s", dir);
-
- struct dirent *d;
- while ((errno = 0, d = readdir (dr)) != NULL) {
- size_t n = strlen (d->d_name);
- if (n >= 3 &&
- d->d_name[n-3] == '.' &&
- d->d_name[n-2] == 'k' &&
- d->d_name[n-1] == 'o') {
- const char *dep = get_module_dep (d->d_name);
- if (dep)
- /* Reversed so that tsort will print the final list in the
- * order that it has to be loaded.
- */
- fprintf (pp, "%s %s\n", dep, d->d_name);
+ add_module ("");
+ for (int i = 0; kmods[i] != NULL; ++i) {
+ for (struct module *m = modules; m; m = m->next) {
+ char *n = strrchr (m->name, '/');
+ if (n)
+ n += 1;
else
- /* No dependencies, just make it depend on itself so that
- * tsort prints it.
- */
- fprintf (pp, "%s %s\n", d->d_name, d->d_name);
+ n = m->name;
+ if (fnmatch (kmods[i], n, FNM_PATHNAME) == 0) {
+ if (verbose >= 2)
+ fprintf (stderr, "Adding top-level dependency %s (%s)\n", m->name, kmods[i]);
+ add_module_dep ("", m->name);
+ }
}
}
- if (errno)
- error (EXIT_FAILURE, errno, "readdir: %s", dir);
-
- if (closedir (dr) == -1)
- error (EXIT_FAILURE, errno, "closedir: %s", dir);
+
+ char *cmd = xasprintf ("cd %s; xargs cp -t %s", modpath, dir);
+ char *outfile = xasprintf ("%s/modules", dir);
+ if (verbose >= 2) fprintf (stderr, "writing to %s\n", cmd);
+
+ FILE *f = fopen (outfile, "w");
+ if (f == NULL)
+ error (EXIT_FAILURE, errno, "failed to create modules list (%s)", outfile);
+ FILE *pp = popen (cmd, "w");
+ if (pp == NULL)
+ error (EXIT_FAILURE, errno, "failed to create pipe (%s)", cmd);
- if (pclose (pp) == -1)
- error (EXIT_FAILURE, errno, "pclose: %s", cmd);
+ /* The "pseudo" module depends on all modules matched by the contents of kmods */
+ struct module *pseudo = find_module ("");
+ print_module_load_order (pp, f, pseudo);
+ fclose (pp);
+ pclose (f);
free (cmd);
free_module_deps ();
@@ -161,7 +133,7 @@ ext2_make_initrd (const char *modpath, const char *initrd)
if (fd == -1)
error (EXIT_FAILURE, errno, "open: %s", init);
- n = (size_t) &_binary_init_size;
+ size_t n = (size_t) &_binary_init_size;
if (full_write (fd, &_binary_init_start, n) != n)
error (EXIT_FAILURE, errno, "write: %s", init);
@@ -175,7 +147,7 @@ ext2_make_initrd (const char *modpath, const char *initrd)
" | cpio --quiet -o -H newc) > '%s'",
dir, initrd);
if (verbose >= 2) fprintf (stderr, "%s\n", cmd);
- r = system (cmd);
+ int r = system (cmd);
if (r == -1 || WEXITSTATUS (r) != 0)
error (EXIT_FAILURE, 0, "ext2_make_initrd: cpio failed");
free (cmd);
@@ -187,21 +159,11 @@ ext2_make_initrd (const char *modpath, const char *initrd)
free (cmd);
}
-/* Module dependencies. */
-struct moddep {
- struct moddep *next;
- char *name;
- char *dep;
-};
-struct moddep *moddeps = NULL;
-
-static void add_module_dep (const char *name, const char *dep);
-
static void
free_module_deps (void)
{
/* Short-lived program, don't bother to free it. */
- moddeps = NULL;
+ modules = NULL;
}
/* Read modules.dep into internal structure. */
@@ -225,15 +187,9 @@ read_module_deps (const char *modpath)
char *name = strtok (line, ": ");
if (!name) continue;
- /* Only want the module basename, but keep the ".ko" extension. */
- char *p = strrchr (name, '/');
- if (p) name = p+1;
-
+ add_module (name);
char *dep;
while ((dep = strtok (NULL, " ")) != NULL) {
- p = strrchr (dep, '/');
- if (p) dep = p+1;
-
add_module_dep (name, dep);
}
}
@@ -242,25 +198,73 @@ read_module_deps (const char *modpath)
fclose (fp);
}
-/* Module 'name' requires 'dep' to be loaded first. */
-static void
-add_module_dep (const char *name, const char *dep)
+static struct module *
+add_module (const char *name)
{
- struct moddep *m = xmalloc (sizeof *m);
- m->next = moddeps;
- moddeps = m;
+ struct module *m = find_module (name);
+ if (m)
+ return m;
+ m = xmalloc (sizeof *m);
m->name = xstrdup (name);
- m->dep = xstrdup (dep);
+ m->deps = NULL;
+ m->next = modules;
+ m->visited = 0;
+ modules = m;
+ return m;
}
-static const char *
-get_module_dep (const char *name)
+static struct module *
+find_module (const char *name)
{
- struct moddep *m;
+ struct module *m;
+ for (m = modules; m; m = m->next) {
+ if (strcmp (name, m->name) == 0)
+ break;
+ }
+ return m;
+}
- for (m = moddeps; m; m = m->next)
- if (strcmp (m->name, name) == 0)
- return m->dep;
+/* Module 'name' requires 'dep' to be loaded first. */
+static void
+add_module_dep (const char *name, const char *dep)
+{
+ if (verbose >= 2) fprintf (stderr, "add_module_dep %s: %s\n", name, dep);
+ struct module *m1 = add_module (name);
+ struct module *m2 = add_module (dep);
+ struct moddep *d;
+ for (d = m1->deps; d; d = d->next) {
+ if (d->dep == m2)
+ return;
+ }
+ d = xmalloc (sizeof *d);
+ d->next = m1->deps;
+ d->dep = m2;
+ m1->deps = d;
+ return;
+}
- return NULL;
+/* DFS on the dependency graph */
+static void
+print_module_load_order (FILE *pipe, FILE *list, struct module *m)
+{
+ if (m->visited)
+ return;
+
+ for (struct moddep *d = m->deps; d; d = d->next)
+ print_module_load_order (pipe, list, d->dep);
+
+ if (m->name[0] == 0)
+ return;
+
+ char *basename = strrchr (m->name, '/');
+ if (basename)
+ ++basename;
+ else
+ basename = m->name;
+
+ fputs (m->name, pipe);
+ fputc ('\n', pipe);
+ fputs (basename, list);
+ fputc ('\n', list);
+ m->visited = 1;
}
--
1.7.5.3
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