Re: [PATCH] pstore/ram: Clarify resource reservation labels

[Dan Williams]

On Wed, Oct 17, 2018 at 5:29 PM Kees Cook <keescook@xxxxxxxxxxxx> wrote:
>
> When ramoops reserved a memory region in the kernel, it had an unhelpful
> label of "persistent_memory". When reading /proc/iomem, it would be
> repeated many times, did not hint that it was ramoops in particular,
> and didn't clarify very much about what each was used for:
>
> 400000000-407ffffff : Persistent Memory (legacy)
>   400000000-400000fff : persistent_memory
>   400001000-400001fff : persistent_memory
> ...
>   4000ff000-4000fffff : persistent_memory
>
> Instead, this adds meaningful labels for how the various regions are
> being used:
>
> 400000000-407ffffff : Persistent Memory (legacy)
>   400000000-400000fff : ramoops:dump(0/252)
>   400001000-400001fff : ramoops:dump(1/252)
> ...
>   4000fc000-4000fcfff : ramoops:dump(252/252)
>   4000fd000-4000fdfff : ramoops:console
>   4000fe000-4000fe3ff : ramoops:ftrace(0/3)
>   4000fe400-4000fe7ff : ramoops:ftrace(1/3)
>   4000fe800-4000febff : ramoops:ftrace(2/3)
>   4000fec00-4000fefff : ramoops:ftrace(3/3)
>   4000ff000-4000fffff : ramoops:pmsg

Hopefully ramoops is doing request_region() before trying to do
anything with its ranges, because it's going to collide with the pmem
driver doing a request_region(). If we want to have pstore use pmem as
a backing store that's a new drivers/nvdimm/ namespace personality
driver to turn around and register a persistent memory range with
pstore rather than the pmem block-device driver.
>
> Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
> ---
>  fs/pstore/ram.c            | 16 +++++++++++++---
>  fs/pstore/ram_core.c       | 11 +++++++----
>  include/linux/pstore_ram.h |  3 ++-
>  3 files changed, 22 insertions(+), 8 deletions(-)
>
> diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
> index 6ea9cd801044..ffcff6516e89 100644
> --- a/fs/pstore/ram.c
> +++ b/fs/pstore/ram.c
> @@ -587,9 +587,16 @@ static int ramoops_init_przs(const char *name,
>                 goto fail;
>
>         for (i = 0; i < *cnt; i++) {
> +               char *label;
> +
> +               if (*cnt == 1)
> +                       label = kasprintf(GFP_KERNEL, "ramoops:%s", name);
> +               else
> +                       label = kasprintf(GFP_KERNEL, "ramoops:%s(%d/%d)",
> +                                         name, i, *cnt - 1);
>                 prz_ar[i] = persistent_ram_new(*paddr, zone_sz, sig,
> -                                                 &cxt->ecc_info,
> -                                                 cxt->memtype, flags);
> +                                              &cxt->ecc_info,
> +                                              cxt->memtype, flags, label);
>                 if (IS_ERR(prz_ar[i])) {
>                         err = PTR_ERR(prz_ar[i]);
>                         dev_err(dev, "failed to request %s mem region (0x%zx@0x%llx): %d\n",
> @@ -619,6 +626,8 @@ static int ramoops_init_prz(const char *name,
>                             struct persistent_ram_zone **prz,
>                             phys_addr_t *paddr, size_t sz, u32 sig)
>  {
> +       char *label;
> +
>         if (!sz)
>                 return 0;
>
> @@ -629,8 +638,9 @@ static int ramoops_init_prz(const char *name,
>                 return -ENOMEM;
>         }
>
> +       label = kasprintf(GFP_KERNEL, "ramoops:%s", name);
>         *prz = persistent_ram_new(*paddr, sz, sig, &cxt->ecc_info,
> -                                 cxt->memtype, 0);
> +                                 cxt->memtype, 0, label);
>         if (IS_ERR(*prz)) {
>                 int err = PTR_ERR(*prz);
>
> diff --git a/fs/pstore/ram_core.c b/fs/pstore/ram_core.c
> index 0792595ebcfb..12e21f789194 100644
> --- a/fs/pstore/ram_core.c
> +++ b/fs/pstore/ram_core.c
> @@ -438,11 +438,11 @@ static void *persistent_ram_vmap(phys_addr_t start, size_t size,
>  }
>
>  static void *persistent_ram_iomap(phys_addr_t start, size_t size,
> -               unsigned int memtype)
> +               unsigned int memtype, char *label)
>  {
>         void *va;
>
> -       if (!request_mem_region(start, size, "persistent_ram")) {
> +       if (!request_mem_region(start, size, label ?: "ramoops")) {
>                 pr_err("request mem region (0x%llx@0x%llx) failed\n",
>                         (unsigned long long)size, (unsigned long long)start);
>                 return NULL;
> @@ -470,7 +470,8 @@ static int persistent_ram_buffer_map(phys_addr_t start, phys_addr_t size,
>         if (pfn_valid(start >> PAGE_SHIFT))
>                 prz->vaddr = persistent_ram_vmap(start, size, memtype);
>         else
> -               prz->vaddr = persistent_ram_iomap(start, size, memtype);
> +               prz->vaddr = persistent_ram_iomap(start, size, memtype,
> +                                                 prz->label);
>
>         if (!prz->vaddr) {
>                 pr_err("%s: Failed to map 0x%llx pages at 0x%llx\n", __func__,
> @@ -541,12 +542,13 @@ void persistent_ram_free(struct persistent_ram_zone *prz)
>         prz->ecc_info.par = NULL;
>
>         persistent_ram_free_old(prz);
> +       kfree(prz->label);
>         kfree(prz);
>  }
>
>  struct persistent_ram_zone *persistent_ram_new(phys_addr_t start, size_t size,
>                         u32 sig, struct persistent_ram_ecc_info *ecc_info,
> -                       unsigned int memtype, u32 flags)
> +                       unsigned int memtype, u32 flags, char *label)
>  {
>         struct persistent_ram_zone *prz;
>         int ret = -ENOMEM;
> @@ -560,6 +562,7 @@ struct persistent_ram_zone *persistent_ram_new(phys_addr_t start, size_t size,
>         /* Initialize general buffer state. */
>         raw_spin_lock_init(&prz->buffer_lock);
>         prz->flags = flags;
> +       prz->label = label;
>
>         ret = persistent_ram_buffer_map(start, size, prz, memtype);
>         if (ret)
> diff --git a/include/linux/pstore_ram.h b/include/linux/pstore_ram.h
> index e6d226464838..602d64725222 100644
> --- a/include/linux/pstore_ram.h
> +++ b/include/linux/pstore_ram.h
> @@ -46,6 +46,7 @@ struct persistent_ram_zone {
>         phys_addr_t paddr;
>         size_t size;
>         void *vaddr;
> +       char *label;
>         struct persistent_ram_buffer *buffer;
>         size_t buffer_size;
>         u32 flags;
> @@ -65,7 +66,7 @@ struct persistent_ram_zone {
>
>  struct persistent_ram_zone *persistent_ram_new(phys_addr_t start, size_t size,
>                         u32 sig, struct persistent_ram_ecc_info *ecc_info,
> -                       unsigned int memtype, u32 flags);
> +                       unsigned int memtype, u32 flags, char *label);
>  void persistent_ram_free(struct persistent_ram_zone *prz);
>  void persistent_ram_zap(struct persistent_ram_zone *prz);
>
> --
> 2.17.1
>
>
> --
> Kees Cook
> Pixel Security