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Date: Fri, 16 Oct 2015 08:50:42 -0700
From: Kees Cook <keescook@...omium.org>
To: Geliang Tang <geliangtang@....com>
Cc: Anton Vorontsov <anton@...msg.org>,
Colin Cross <ccross@...roid.com>,
Tony Luck <tony.luck@...el.com>,
LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/3] pstore: add 'rmmod ramoops' support
On Fri, Oct 16, 2015 at 8:25 AM, Geliang Tang <geliangtang@....com> wrote:
> ramoops 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) Remove try_module_get() to allow this module can be unloaded.
> 4) Unmap the memory and free it.
> 5) Set console flags, make sure it can be registered again after
> be unregistered.
>
> Signed-off-by: Geliang Tang <geliangtang@....com>
> ---
> fs/pstore/ftrace.c | 15 ++++++++++++++-
> fs/pstore/internal.h | 4 ++++
> fs/pstore/platform.c | 40 ++++++++++++++++++++++++++++++++--------
> fs/pstore/pmsg.c | 7 +++++++
> fs/pstore/ram.c | 19 ++++++++-----------
> include/linux/pstore.h | 5 +++++
> 6 files changed, 70 insertions(+), 20 deletions(-)
>
> diff --git a/fs/pstore/ftrace.c b/fs/pstore/ftrace.c
> index 76a4eeb..554c1ce 100644
> --- a/fs/pstore/ftrace.c
> +++ b/fs/pstore/ftrace.c
> @@ -104,9 +104,10 @@ static const struct file_operations pstore_knob_fops = {
> .write = pstore_ftrace_knob_write,
> };
>
> +static struct dentry *dir;
Since this is no longer a local, it should probably be renamed
something more descriptive.
> +
> void pstore_register_ftrace(void)
> {
> - struct dentry *dir;
> struct dentry *file;
>
> if (!psinfo->write_buf)
> @@ -129,3 +130,15 @@ void pstore_register_ftrace(void)
> err_file:
> debugfs_remove(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(dir);
> +}
> diff --git a/fs/pstore/internal.h b/fs/pstore/internal.h
> index c36ba2c..96253c4 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 1b11249..c474dc2 100644
> --- a/fs/pstore/platform.c
> +++ b/fs/pstore/platform.c
> @@ -237,6 +237,12 @@ static void allocate_buf_for_compression(void)
>
> }
>
> +static void free_buf_for_compression(void)
> +{
> + kfree(stream.workspace);
> + kfree(big_oops_buf);
I think both of these should be set to NULL after their kfrees.
> +}
> +
> /*
> * Called when compression fails, since the printk buffer
> * would be fetched for compression calling it again when
> @@ -358,6 +364,11 @@ 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)
> {
> @@ -387,16 +398,22 @@ static void pstore_console_write(struct console *con, const char *s, unsigned c)
> static struct console pstore_console = {
> .name = "pstore",
> .write = pstore_console_write,
> - .flags = CON_PRINTBUFFER | CON_ENABLED | CON_ANYTIME,
> .index = -1,
> };
>
> static void pstore_register_console(void)
> {
> + pstore_console.flags = CON_PRINTBUFFER | CON_ENABLED | CON_ANYTIME;
Why do these flags need to move here?
> 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,
> @@ -420,8 +437,6 @@ static int pstore_write_compat(enum pstore_type_id type,
> */
> int pstore_register(struct pstore_info *psi)
> {
> - struct module *owner = psi->owner;
> -
> if (backend && strcmp(backend, psi->name))
> return -EPERM;
>
> @@ -437,11 +452,6 @@ int pstore_register(struct pstore_info *psi)
> mutex_init(&psinfo->read_mutex);
> spin_unlock(&pstore_lock);
>
> - if (owner && !try_module_get(owner)) {
> - psinfo = NULL;
> - return -EINVAL;
> - }
Don't we still need to hold a module reference?
> -
> allocate_buf_for_compression();
>
> if (pstore_is_mounted())
> @@ -473,6 +483,20 @@ int pstore_register(struct pstore_info *psi)
> }
> EXPORT_SYMBOL_GPL(pstore_register);
>
> +void pstore_unregister(void)
> +{
> + 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 5a2f05a..7de20cd 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 6c26c4d..d938bc1 100644
> --- a/fs/pstore/ram.c
> +++ b/fs/pstore/ram.c
> @@ -580,28 +580,25 @@ fail_out:
>
> static int __exit 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);
> - cxt->max_dump_cnt = 0;
> + pstore_unregister();
>
> - /* TODO(kees): When pstore supports unregistering, call it here. */
> + cxt->max_dump_cnt = 0;
> 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 8e7a25b..34e4a6d 100644
> --- a/include/linux/pstore.h
> +++ b/include/linux/pstore.h
> @@ -77,6 +77,7 @@ struct pstore_info {
>
> #ifdef CONFIG_PSTORE
> extern int pstore_register(struct pstore_info *);
> +extern void pstore_unregister(void);
> extern bool pstore_cannot_block_path(enum kmsg_dump_reason reason);
> #else
> static inline int
> @@ -84,6 +85,10 @@ pstore_register(struct pstore_info *psi)
> {
> return -ENODEV;
> }
> +static inline void
> +pstore_unregister(void)
> +{
> +}
> static inline bool
> pstore_cannot_block_path(enum kmsg_dump_reason reason)
> {
> --
> 2.5.0
>
>
Cool! Thanks for working on the unregister logic!
-Kees
--
Kees Cook
Chrome OS Security
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