Re: [PATCH 10/11] pstore/ram: Switch to persistent_ram routines
From: Kees Cook
Date: Mon May 14 2012 - 18:21:15 EST
On Fri, May 11, 2012 at 5:18 PM, Anton Vorontsov
<anton.vorontsov@xxxxxxxxxx> wrote:
> The patch switches pstore RAM backend to use persistent_ram routines,
> one step closer to the ECC support.
>
> Signed-off-by: Anton Vorontsov <anton.vorontsov@xxxxxxxxxx>
As mentioned, I'm all for this consolidation. That said, some notes below...
> ---
> fs/pstore/ram.c | 109 ++++++++++++++++++++++++++++++-------------------------
> 1 file changed, 60 insertions(+), 49 deletions(-)
>
> diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
> index b26b58e..cf0ad92 100644
> --- a/fs/pstore/ram.c
> +++ b/fs/pstore/ram.c
> @@ -62,7 +62,7 @@ MODULE_PARM_DESC(dump_oops,
> "set to 1 to dump oopses, 0 to only dump panics (default 1)");
>
> struct ramoops_context {
> - void *virt_addr;
> + struct persistent_ram_zone **przs;
> phys_addr_t phys_addr;
> unsigned long size;
> size_t record_size;
> @@ -90,39 +90,56 @@ static ssize_t ramoops_pstore_read(u64 *id, enum pstore_type_id *type,
> struct pstore_info *psi)
> {
> ssize_t size;
> - char *rambuf;
> struct ramoops_context *cxt = psi->data;
> + struct persistent_ram_zone *prz;
>
> if (cxt->read_count >= cxt->max_count)
> return -EINVAL;
> +
> *id = cxt->read_count++;
> + prz = cxt->przs[*id];
> +
> /* Only supports dmesg output so far. */
> *type = PSTORE_TYPE_DMESG;
> /* TODO(kees): Bogus time for the moment. */
> time->tv_sec = 0;
> time->tv_nsec = 0;
>
> - rambuf = cxt->virt_addr + (*id * cxt->record_size);
> - size = strnlen(rambuf, cxt->record_size);
> + size = persistent_ram_old_size(prz);
> *buf = kmalloc(size, GFP_KERNEL);
> if (*buf == NULL)
> return -ENOMEM;
> - memcpy(*buf, rambuf, size);
> + memcpy(*buf, persistent_ram_old(prz), size);
>
> return size;
> }
>
> +static size_t ramoops_write_kmsg_hdr(struct persistent_ram_zone *prz)
> +{
> + char *hdr;
> + struct timeval timestamp;
> + size_t len;
> +
> + do_gettimeofday(×tamp);
> + hdr = kasprintf(GFP_ATOMIC, RAMOOPS_KERNMSG_HDR "%lu.%lu\n",
> + (long)timestamp.tv_sec, (long)timestamp.tv_usec);
> + WARN_ON_ONCE(!hdr);
> + len = hdr ? strlen(hdr) : 0;
> + persistent_ram_write(prz, hdr, len);
> + kfree(hdr);
> +
> + return len;
> +}
> +
> static int ramoops_pstore_write(enum pstore_type_id type,
> enum kmsg_dump_reason reason,
> u64 *id,
> unsigned int part,
> size_t size, struct pstore_info *psi)
> {
> - char *buf;
> - size_t res;
> - struct timeval timestamp;
> struct ramoops_context *cxt = psi->data;
> - size_t available = cxt->record_size;
> + struct persistent_ram_zone *prz = cxt->przs[cxt->count];
> + size_t hlen;
>
> /* Currently ramoops is designed to only store dmesg dumps. */
> if (type != PSTORE_TYPE_DMESG)
> @@ -147,22 +164,10 @@ static int ramoops_pstore_write(enum pstore_type_id type,
> if (part != 1)
> return -ENOSPC;
>
> - buf = cxt->virt_addr + (cxt->count * cxt->record_size);
> -
> - res = sprintf(buf, "%s", RAMOOPS_KERNMSG_HDR);
> - buf += res;
> - available -= res;
> -
> - do_gettimeofday(×tamp);
> - res = sprintf(buf, "%lu.%lu\n", (long)timestamp.tv_sec, (long)timestamp.tv_usec);
> - buf += res;
> - available -= res;
> -
> - if (size > available)
> - size = available;
> -
> - memcpy(buf, cxt->pstore.buf, size);
> - memset(buf + size, '\0', available - size);
> + hlen = ramoops_write_kmsg_hdr(prz);
> + if (size + hlen > prz->buffer_size)
> + size = prz->buffer_size - hlen;
> + persistent_ram_write(prz, cxt->pstore.buf, size);
>
> cxt->count = (cxt->count + 1) % cxt->max_count;
>
> @@ -172,14 +177,12 @@ static int ramoops_pstore_write(enum pstore_type_id type,
> static int ramoops_pstore_erase(enum pstore_type_id type, u64 id,
> struct pstore_info *psi)
> {
> - char *buf;
> struct ramoops_context *cxt = psi->data;
>
> if (id >= cxt->max_count)
> return -EINVAL;
>
> - buf = cxt->virt_addr + (id * cxt->record_size);
> - memset(buf, '\0', cxt->record_size);
> + persistent_ram_free_old(cxt->przs[id]);
Hm, I don't think persistent_ram_free_old() is what's wanted here.
That appears to entirely release the region? I want to make sure the
memory is cleared first. And will this area come back on a write, or
does it stay released?
>
> return 0;
> }
> @@ -200,6 +203,7 @@ static int __init ramoops_probe(struct platform_device *pdev)
> struct ramoops_platform_data *pdata = pdev->dev.platform_data;
> struct ramoops_context *cxt = &oops_cxt;
> int err = -EINVAL;
> + int i;
>
> /* Only a single ramoops area allowed at a time, so fail extra
> * probes.
> @@ -237,32 +241,37 @@ static int __init ramoops_probe(struct platform_device *pdev)
> cxt->record_size = pdata->record_size;
> cxt->dump_oops = pdata->dump_oops;
>
> + cxt->przs = kzalloc(sizeof(*cxt->przs) * cxt->max_count, GFP_KERNEL);
> + if (!cxt->przs) {
> + pr_err("failed to initialize a prz array\n");
> + goto fail_przs;
This should be fail_out.
> + }
> +
> + for (i = 0; i < cxt->max_count; i++) {
> + size_t sz = cxt->record_size;
> + phys_addr_t start = cxt->phys_addr + sz * i;
> +
> + cxt->przs[i] = persistent_ram_new(start, sz, 0);
persistent_ram_new() is marked as __init, so this is unsafe to call if
built as a module. I think persistent_ram_new() will need to lose the
__init marking, or I'm misunderstanding something.
> + if (IS_ERR(cxt->przs[i])) {
> + err = PTR_ERR(cxt->przs[i]);
> + pr_err("failed to initialize a prz\n");
Since neither persistent_ram_new() nor persistent_ram_buffer_map()
report the location of the failure, I'd like to keep the error report
(removed below "pr_err("request mem region (0x%lx@0x%llx)
failed\n",...") for failures, so there is something actionable in
dmesg when the platform data is mismatched for the hardware.
> + goto fail_prz;
This should be fail_przs.
> + }
> + }
> +
> cxt->pstore.data = cxt;
> - cxt->pstore.bufsize = cxt->record_size;
> - cxt->pstore.buf = kmalloc(cxt->pstore.bufsize, GFP_KERNEL);
> spin_lock_init(&cxt->pstore.buf_lock);
> + cxt->pstore.bufsize = cxt->przs[0]->buffer_size;
> + cxt->pstore.buf = kmalloc(cxt->pstore.bufsize, GFP_KERNEL);
I don't see a reason to re-order these (nothing can use buf yet
because we haven't registered it with pstore yet).
> if (!cxt->pstore.buf) {
> pr_err("cannot allocate pstore buffer\n");
> goto fail_clear;
> }
>
> - if (!request_mem_region(cxt->phys_addr, cxt->size, "ramoops")) {
> - pr_err("request mem region (0x%lx@0x%llx) failed\n",
> - cxt->size, (unsigned long long)cxt->phys_addr);
> - err = -EINVAL;
> - goto fail_buf;
> - }
> -
> - cxt->virt_addr = ioremap(cxt->phys_addr, cxt->size);
> - if (!cxt->virt_addr) {
> - pr_err("ioremap failed\n");
> - goto fail_mem_region;
> - }
> -
> err = pstore_register(&cxt->pstore);
> if (err) {
> pr_err("registering with pstore failed\n");
> - goto fail_iounmap;
> + goto fail_pstore;
This should be fail_buf.
> }
>
> /*
> @@ -280,15 +289,17 @@ static int __init ramoops_probe(struct platform_device *pdev)
>
> return 0;
>
> -fail_iounmap:
> - iounmap(cxt->virt_addr);
> -fail_mem_region:
> - release_mem_region(cxt->phys_addr, cxt->size);
> -fail_buf:
> +fail_pstore:
No reason to rename this from "fail_buf".
> kfree(cxt->pstore.buf);
> fail_clear:
> cxt->pstore.bufsize = 0;
> cxt->max_count = 0;
> +fail_przs:
> + for (i = 0; cxt->przs[i]; i++)
> + persistent_ram_free(cxt->przs[i]);
This can lead to a BUG, since persistent_ram_free() doesn't handle
NULL arguments.
> + kfree(cxt->przs);
> +fail_prz:
> + kfree(cxt->pstore.buf);
This target (fail_prz) should be removed, and the kfree is redundant
to fail_buf above.
> fail_out:
> return err;
> }
> --
> 1.7.9.2
>
-Kees
--
Kees Cook
Chrome OS Security
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