Re: [PATCH 2/2] pstore-ram: Allow optional mapping with pgprot_noncached

From: Tony Lindgren
Date: Wed Dec 10 2014 - 16:43:07 EST

* Kees Cook <keescook@xxxxxxxxxxxx> [141210 13:18]:
> On Tue, Sep 16, 2014 at 1:50 PM, Tony Lindgren <tony@xxxxxxxxxxx> wrote:
> > From: Tony Lindgren <tony@xxxxxxxxxxx>
> > Date: Thu, 11 Sep 2014 15:02:37 -0700
> > Subject: [PATCH] pstore-ram: Allow optional mapping with pgprot_noncached
> >
> > On some ARMs the memory can be mapped pgprot_noncached() and still
> > be working for atomic operations. As pointed out by Colin Cross
> > <ccross@xxxxxxxxxxx>, in some cases you do want to use
> > pgprot_noncached() if the SoC supports it to see a debug printk
> > just before a write hanging the system.
> >
> > On ARMs, the atomic operations on strongly ordered memory are
> > implementation defined. So let's provide an optional kernel parameter
> > for configuring pgprot_noncached(), and use pgprot_writecombine() by
> > default.
> >
> > Cc: Arnd Bergmann <arnd@xxxxxxxx>
> > Cc: Rob Herring <robherring2@xxxxxxxxx>
> > Cc: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
> > Cc: Anton Vorontsov <anton@xxxxxxxxxx>
> > Cc: Colin Cross <ccross@xxxxxxxxxxx>
> > Cc: Kees Cook <keescook@xxxxxxxxxxxx>
> > Cc: Olof Johansson <olof@xxxxxxxxx>
> > Cc: Tony Luck <tony.luck@xxxxxxxxx>
> > Cc: Russell King <linux@xxxxxxxxxxxxxxxx>
> > Signed-off-by: Tony Lindgren <tony@xxxxxxxxxxx>
>
> Sorry this got missed! I think rmk's concerns were addressed in this
> v2. Tony (Luck), can you take this into your tree?
>
> Acked-by: Kees Cook <keescook@xxxxxxxxxxxx>

I take your ack covers patch 1/2 also. The first patch in this
series should be tagged cc stable when committing please.

Regards,

Tony

> Thanks!
>
> -Kees
>
> >
> > --- a/Documentation/ramoops.txt
> > +++ b/Documentation/ramoops.txt
> > @@ -14,11 +14,19 @@ survive after a restart.
> >
> > 1. Ramoops concepts
> >
> > -Ramoops uses a predefined memory area to store the dump. The start and size of
> > -the memory area are set using two variables:
> > +Ramoops uses a predefined memory area to store the dump. The start and size
> > +and type of the memory area are set using three variables:
> > * "mem_address" for the start
> > * "mem_size" for the size. The memory size will be rounded down to a
> > power of two.
> > + * "mem_type" to specifiy if the memory type (default is pgprot_writecombine).
> > +
> > +Typically the default value of mem_type=0 should be used as that sets the pstore
> > +mapping to pgprot_writecombine. Setting mem_type=1 attempts to use
> > +pgprot_noncached, which only works on some platforms. This is because pstore
> > +depends on atomic operations. At least on ARM, pgprot_noncached causes the
> > +memory to be mapped strongly ordered, and atomic operations on strongly ordered
> > +memory are implementation defined, and won't work on many ARMs such as omaps.
> >
> > The memory area is divided into "record_size" chunks (also rounded down to
> > power of two) and each oops/panic writes a "record_size" chunk of
> > @@ -55,6 +63,7 @@ Setting the ramoops parameters can be done in 2 different manners:
> > static struct ramoops_platform_data ramoops_data = {
> > .mem_size = <...>,
> > .mem_address = <...>,
> > + .mem_type = <...>,
> > .record_size = <...>,
> > .dump_oops = <...>,
> > .ecc = <...>,
> > --- a/fs/pstore/ram.c
> > +++ b/fs/pstore/ram.c
> > @@ -61,6 +61,11 @@ module_param(mem_size, ulong, 0400);
> > MODULE_PARM_DESC(mem_size,
> > "size of reserved RAM used to store oops/panic logs");
> >
> > +static unsigned int mem_type;
> > +module_param(mem_type, uint, 0600);
> > +MODULE_PARM_DESC(mem_type,
> > + "set to 1 to try to use unbuffered memory (default 0)");
> > +
> > static int dump_oops = 1;
> > module_param(dump_oops, int, 0600);
> > MODULE_PARM_DESC(dump_oops,
> > @@ -79,6 +84,7 @@ struct ramoops_context {
> > struct persistent_ram_zone *fprz;
> > phys_addr_t phys_addr;
> > unsigned long size;
> > + unsigned int memtype;
> > size_t record_size;
> > size_t console_size;
> > size_t ftrace_size;
> > @@ -358,7 +364,8 @@ static int ramoops_init_przs(struct device *dev, struct ramoops_context *cxt,
> > size_t sz = cxt->record_size;
> >
> > cxt->przs[i] = persistent_ram_new(*paddr, sz, 0,
> > - &cxt->ecc_info);
> > + &cxt->ecc_info,
> > + cxt->memtype);
> > if (IS_ERR(cxt->przs[i])) {
> > err = PTR_ERR(cxt->przs[i]);
> > dev_err(dev, "failed to request mem region (0x%zx@0x%llx): %d\n",
> > @@ -388,7 +395,7 @@ static int ramoops_init_prz(struct device *dev, struct ramoops_context *cxt,
> > return -ENOMEM;
> > }
> >
> > - *prz = persistent_ram_new(*paddr, sz, sig, &cxt->ecc_info);
> > + *prz = persistent_ram_new(*paddr, sz, sig, &cxt->ecc_info, cxt->memtype);
> > if (IS_ERR(*prz)) {
> > int err = PTR_ERR(*prz);
> >
> > @@ -435,6 +442,7 @@ static int ramoops_probe(struct platform_device *pdev)
> >
> > cxt->size = pdata->mem_size;
> > cxt->phys_addr = pdata->mem_address;
> > + cxt->memtype = pdata->mem_type;
> > cxt->record_size = pdata->record_size;
> > cxt->console_size = pdata->console_size;
> > cxt->ftrace_size = pdata->ftrace_size;
> > @@ -564,6 +572,7 @@ static void ramoops_register_dummy(void)
> >
> > dummy_data->mem_size = mem_size;
> > dummy_data->mem_address = mem_address;
> > + dummy_data->mem_type = 0;
> > dummy_data->record_size = record_size;
> > dummy_data->console_size = ramoops_console_size;
> > dummy_data->ftrace_size = ramoops_ftrace_size;
> > --- a/fs/pstore/ram_core.c
> > +++ b/fs/pstore/ram_core.c
> > @@ -380,7 +380,8 @@ void persistent_ram_zap(struct persistent_ram_zone *prz)
> > persistent_ram_update_header_ecc(prz);
> > }
> >
> > -static void *persistent_ram_vmap(phys_addr_t start, size_t size)
> > +static void *persistent_ram_vmap(phys_addr_t start, size_t size,
> > + unsigned int memtype)
> > {
> > struct page **pages;
> > phys_addr_t page_start;
> > @@ -392,7 +393,10 @@ static void *persistent_ram_vmap(phys_addr_t start, size_t size)
> > page_start = start - offset_in_page(start);
> > page_count = DIV_ROUND_UP(size + offset_in_page(start), PAGE_SIZE);
> >
> > - prot = pgprot_writecombine(PAGE_KERNEL);
> > + if (memtype)
> > + prot = pgprot_noncached(PAGE_KERNEL);
> > + else
> > + prot = pgprot_writecombine(PAGE_KERNEL);
> >
> > pages = kmalloc_array(page_count, sizeof(struct page *), GFP_KERNEL);
> > if (!pages) {
> > @@ -411,8 +415,11 @@ static void *persistent_ram_vmap(phys_addr_t start, size_t size)
> > return vaddr;
> > }
> >
> > -static void *persistent_ram_iomap(phys_addr_t start, size_t size)
> > +static void *persistent_ram_iomap(phys_addr_t start, size_t size,
> > + unsigned int memtype)
> > {
> > + void *va;
> > +
> > if (!request_mem_region(start, size, "persistent_ram")) {
> > pr_err("request mem region (0x%llx@0x%llx) failed\n",
> > (unsigned long long)size, (unsigned long long)start);
> > @@ -422,19 +429,24 @@ static void *persistent_ram_iomap(phys_addr_t start, size_t size)
> > buffer_start_add = buffer_start_add_locked;
> > buffer_size_add = buffer_size_add_locked;
> >
> > - return ioremap_wc(start, size);
> > + if (memtype)
> > + va = ioremap(start, size);
> > + else
> > + va = ioremap_wc(start, size);
> > +
> > + return va;
> > }
> >
> > static int persistent_ram_buffer_map(phys_addr_t start, phys_addr_t size,
> > - struct persistent_ram_zone *prz)
> > + struct persistent_ram_zone *prz, int memtype)
> > {
> > prz->paddr = start;
> > prz->size = size;
> >
> > if (pfn_valid(start >> PAGE_SHIFT))
> > - prz->vaddr = persistent_ram_vmap(start, size);
> > + prz->vaddr = persistent_ram_vmap(start, size, memtype);
> > else
> > - prz->vaddr = persistent_ram_iomap(start, size);
> > + prz->vaddr = persistent_ram_iomap(start, size, memtype);
> >
> > if (!prz->vaddr) {
> > pr_err("%s: Failed to map 0x%llx pages at 0x%llx\n", __func__,
> > @@ -500,7 +512,8 @@ void persistent_ram_free(struct persistent_ram_zone *prz)
> > }
> >
> > struct persistent_ram_zone *persistent_ram_new(phys_addr_t start, size_t size,
> > - u32 sig, struct persistent_ram_ecc_info *ecc_info)
> > + u32 sig, struct persistent_ram_ecc_info *ecc_info,
> > + unsigned int memtype)
> > {
> > struct persistent_ram_zone *prz;
> > int ret = -ENOMEM;
> > @@ -511,7 +524,7 @@ struct persistent_ram_zone *persistent_ram_new(phys_addr_t start, size_t size,
> > goto err;
> > }
> >
> > - ret = persistent_ram_buffer_map(start, size, prz);
> > + ret = persistent_ram_buffer_map(start, size, prz, memtype);
> > if (ret)
> > goto err;
> >
> > --- a/include/linux/pstore_ram.h
> > +++ b/include/linux/pstore_ram.h
> > @@ -53,7 +53,8 @@ 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);
> > + u32 sig, struct persistent_ram_ecc_info *ecc_info,
> > + unsigned int memtype);
> > void persistent_ram_free(struct persistent_ram_zone *prz);
> > void persistent_ram_zap(struct persistent_ram_zone *prz);
> >
> > @@ -76,6 +77,7 @@ ssize_t persistent_ram_ecc_string(struct persistent_ram_zone *prz,
> > struct ramoops_platform_data {
> > unsigned long mem_size;
> > unsigned long mem_address;
> > + unsigned int mem_type;
> > unsigned long record_size;
> > unsigned long console_size;
> > unsigned long ftrace_size;
>
>
>
> --
> Kees Cook
> Chrome OS Security
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/