pstore: add pstore unregister

pstore doesn't support unregistering yet. It was marked as TODO.
This patch adds some code to fix it:
 1) Add functions to unregister kmsg/console/ftrace/pmsg.
 2) Add a function to free compression buffer.
 3) Unmap the memory and free it.
 4) Add a function to unregister pstore filesystem.

Signed-off-by: Geliang Tang <geliangtang@163.com>
Acked-by: Kees Cook <keescook@chromium.org>
[Removed __exit annotation from ramoops_remove(). Reported by Arnd Bergmann]
Signed-off-by: Tony Luck <tony.luck@intel.com>

10 files changed, 88 insertions, 34 deletions

diff --git a/fs/pstore/Kconfig b/fs/pstore/Kconfig
index 916b8e23d968..360ae43f590c 100644
--- a/fs/pstore/Kconfig
+++ b/fs/pstore/Kconfig
@@ -1,5 +1,5 @@
 config PSTORE
-        bool "Persistent store support"
+        tristate "Persistent store support"
         default n
         select ZLIB_DEFLATE
         select ZLIB_INFLATE
diff --git a/fs/pstore/Makefile b/fs/pstore/Makefile
index e647d8e81712..b8803cc07fce 100644
--- a/fs/pstore/Makefile
+++ b/fs/pstore/Makefile
@@ -2,12 +2,12 @@
 # Makefile for the linux pstorefs routines.
 #
 
-obj-y += pstore.o
+obj-$(CONFIG_PSTORE) += pstore.o
 
 pstore-objs += inode.o platform.o
-obj-$(CONFIG_PSTORE_FTRACE)     += ftrace.o
+pstore-$(CONFIG_PSTORE_FTRACE)  += ftrace.o
 
-obj-$(CONFIG_PSTORE_PMSG)       += pmsg.o
+pstore-$(CONFIG_PSTORE_PMSG)    += pmsg.o
 
 ramoops-objs += ram.o ram_core.o
 obj-$(CONFIG_PSTORE_RAM)        += ramoops.o
diff --git a/fs/pstore/ftrace.c b/fs/pstore/ftrace.c
index 76a4eeb92982..d4887705bb61 100644
--- a/fs/pstore/ftrace.c
+++ b/fs/pstore/ftrace.c
@@ -104,22 +104,23 @@ static const struct file_operations pstore_knob_fops = {
         .write  = pstore_ftrace_knob_write,
 };
 
+static struct dentry *pstore_ftrace_dir;
+
 void pstore_register_ftrace(void)
 {
-        struct dentry *dir;
         struct dentry *file;
 
         if (!psinfo->write_buf)
                 return;
 
-        dir = debugfs_create_dir("pstore", NULL);
-        if (!dir) {
+        pstore_ftrace_dir = debugfs_create_dir("pstore", NULL);
+        if (!pstore_ftrace_dir) {
                 pr_err("%s: unable to create pstore directory\n", __func__);
                 return;
         }
 
-        file = debugfs_create_file("record_ftrace", 0600, dir, NULL,
-                                   &pstore_knob_fops);
+        file = debugfs_create_file("record_ftrace", 0600, pstore_ftrace_dir,
+                                   NULL, &pstore_knob_fops);
         if (!file) {
                 pr_err("%s: unable to create record_ftrace file\n", __func__);
                 goto err_file;
@@ -127,5 +128,17 @@ void pstore_register_ftrace(void)
 
         return;
 err_file:
-        debugfs_remove(dir);
+        debugfs_remove(pstore_ftrace_dir);
+}
+
+void pstore_unregister_ftrace(void)
+{
+        mutex_lock(&pstore_ftrace_lock);
+        if (pstore_ftrace_enabled) {
+                unregister_ftrace_function(&pstore_ftrace_ops);
+                pstore_ftrace_enabled = 0;
+        }
+        mutex_unlock(&pstore_ftrace_lock);
+
+        debugfs_remove_recursive(pstore_ftrace_dir);
 }
diff --git a/fs/pstore/inode.c b/fs/pstore/inode.c
index 3adcc4669fac..3586491f26ba 100644
--- a/fs/pstore/inode.c
+++ b/fs/pstore/inode.c
@@ -178,6 +178,7 @@ static loff_t pstore_file_llseek(struct file *file, loff_t off, int whence)
 }
 
 static const struct file_operations pstore_file_operations = {
+        .owner          = THIS_MODULE,
         .open           = pstore_file_open,
         .read           = pstore_file_read,
         .llseek         = pstore_file_llseek,
@@ -456,6 +457,7 @@ static void pstore_kill_sb(struct super_block *sb)
 }
 
 static struct file_system_type pstore_fs_type = {
+        .owner          = THIS_MODULE,
         .name           = "pstore",
         .mount          = pstore_mount,
         .kill_sb        = pstore_kill_sb,
@@ -479,5 +481,12 @@ out:
 }
 module_init(init_pstore_fs)
 
+static void __exit exit_pstore_fs(void)
+{
+        unregister_filesystem(&pstore_fs_type);
+        sysfs_remove_mount_point(fs_kobj, "pstore");
+}
+module_exit(exit_pstore_fs)
+
 MODULE_AUTHOR("Tony Luck <tony.luck@intel.com>");
 MODULE_LICENSE("GPL");
diff --git a/fs/pstore/internal.h b/fs/pstore/internal.h
index c36ba2cd0b5d..96253c474ea5 100644
--- a/fs/pstore/internal.h
+++ b/fs/pstore/internal.h
@@ -41,14 +41,18 @@ pstore_ftrace_decode_cpu(struct pstore_ftrace_record *rec)
 
 #ifdef CONFIG_PSTORE_FTRACE
 extern void pstore_register_ftrace(void);
+extern void pstore_unregister_ftrace(void);
 #else
 static inline void pstore_register_ftrace(void) {}
+static inline void pstore_unregister_ftrace(void) {}
 #endif
 
 #ifdef CONFIG_PSTORE_PMSG
 extern void pstore_register_pmsg(void);
+extern void pstore_unregister_pmsg(void);
 #else
 static inline void pstore_register_pmsg(void) {}
+static inline void pstore_unregister_pmsg(void) {}
 #endif
 
 extern struct pstore_info *psinfo;
diff --git a/fs/pstore/platform.c b/fs/pstore/platform.c
index 1b1124942b4e..0aab920efff7 100644
--- a/fs/pstore/platform.c
+++ b/fs/pstore/platform.c
@@ -237,6 +237,14 @@ static void allocate_buf_for_compression(void)
 
 }
 
+static void free_buf_for_compression(void)
+{
+        kfree(stream.workspace);
+        stream.workspace = NULL;
+        kfree(big_oops_buf);
+        big_oops_buf = NULL;
+}
+
 /*
  * Called when compression fails, since the printk buffer
  * would be fetched for compression calling it again when
@@ -358,6 +366,11 @@ static void pstore_register_kmsg(void)
         kmsg_dump_register(&pstore_dumper);
 }
 
+static void pstore_unregister_kmsg(void)
+{
+        kmsg_dump_unregister(&pstore_dumper);
+}
+
 #ifdef CONFIG_PSTORE_CONSOLE
 static void pstore_console_write(struct console *con, const char *s, unsigned c)
 {
@@ -395,8 +408,14 @@ static void pstore_register_console(void)
 {
         register_console(&pstore_console);
 }
+
+static void pstore_unregister_console(void)
+{
+        unregister_console(&pstore_console);
+}
 #else
 static void pstore_register_console(void) {}
+static void pstore_unregister_console(void) {}
 #endif
 
 static int pstore_write_compat(enum pstore_type_id type,
@@ -467,12 +486,28 @@ int pstore_register(struct pstore_info *psi)
          */
         backend = psi->name;
 
+        module_put(owner);
+
         pr_info("Registered %s as persistent store backend\n", psi->name);
 
         return 0;
 }
 EXPORT_SYMBOL_GPL(pstore_register);
 
+void pstore_unregister(struct pstore_info *psi)
+{
+        pstore_unregister_pmsg();
+        pstore_unregister_ftrace();
+        pstore_unregister_console();
+        pstore_unregister_kmsg();
+
+        free_buf_for_compression();
+
+        psinfo = NULL;
+        backend = NULL;
+}
+EXPORT_SYMBOL_GPL(pstore_unregister);
+
 /*
  * Read all the records from the persistent store. Create
  * files in our filesystem.  Don't warn about -EEXIST errors
diff --git a/fs/pstore/pmsg.c b/fs/pstore/pmsg.c
index 5a2f05a16c1e..7de20cd3797f 100644
--- a/fs/pstore/pmsg.c
+++ b/fs/pstore/pmsg.c
@@ -114,3 +114,10 @@ err_class:
 err:
         return;
 }
+
+void pstore_unregister_pmsg(void)
+{
+        device_destroy(pmsg_class, MKDEV(pmsg_major, 0));
+        class_destroy(pmsg_class);
+        unregister_chrdev(pmsg_major, PMSG_NAME);
+}
diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
index 6c26c4daaec9..319c3a60cfa5 100644
--- a/fs/pstore/ram.c
+++ b/fs/pstore/ram.c
@@ -578,30 +578,27 @@ fail_out:
         return err;
 }
 
-static int __exit ramoops_remove(struct platform_device *pdev)
+static int ramoops_remove(struct platform_device *pdev)
 {
-#if 0
-        /* TODO(kees): We cannot unload ramoops since pstore doesn't support
-         * unregistering yet.
-         */
         struct ramoops_context *cxt = &oops_cxt;
 
-        iounmap(cxt->virt_addr);
-        release_mem_region(cxt->phys_addr, cxt->size);
+        pstore_unregister(&cxt->pstore);
         cxt->max_dump_cnt = 0;
 
-        /* TODO(kees): When pstore supports unregistering, call it here. */
         kfree(cxt->pstore.buf);
         cxt->pstore.bufsize = 0;
 
+        persistent_ram_free(cxt->mprz);
+        persistent_ram_free(cxt->fprz);
+        persistent_ram_free(cxt->cprz);
+        ramoops_free_przs(cxt);
+
         return 0;
-#endif
-        return -EBUSY;
 }
 
 static struct platform_driver ramoops_driver = {
         .probe          = ramoops_probe,
-        .remove         = __exit_p(ramoops_remove),
+        .remove         = ramoops_remove,
         .driver         = {
                 .name   = "ramoops",
         },
diff --git a/include/linux/pstore.h b/include/linux/pstore.h
index 8e7a25b068b0..831479f8df8f 100644
--- a/include/linux/pstore.h
+++ b/include/linux/pstore.h
@@ -75,20 +75,8 @@ struct pstore_info {
 
 #define PSTORE_FLAGS_FRAGILE    1
 
-#ifdef CONFIG_PSTORE
 extern int pstore_register(struct pstore_info *);
+extern void pstore_unregister(struct pstore_info *);
 extern bool pstore_cannot_block_path(enum kmsg_dump_reason reason);
-#else
-static inline int
-pstore_register(struct pstore_info *psi)
-{
-        return -ENODEV;
-}
-static inline bool
-pstore_cannot_block_path(enum kmsg_dump_reason reason)
-{
-        return false;
-}
-#endif
 
 #endif /*_LINUX_PSTORE_H*/
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 8f0324ef72ab..b16f35487b67 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -517,6 +517,7 @@ int check_syslog_permissions(int type, int source)
 ok:
         return security_syslog(type);
 }
+EXPORT_SYMBOL_GPL(check_syslog_permissions);
 
 static void append_char(char **pp, char *e, char c)
 {