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    SubjectRe: [PATCH v4] ramoops: use pstore interface
    On Sat, 7 Jan 2012 09:15:16 -0800
    Kees Cook <keescook@chromium.org> wrote:

    > Instead of using /dev/mem directly, use the common pstore infrastructure
    > to handle Oops gathering and extraction.

    um, why? This changelog provides no reason for anyone to apply the
    patch!

    >
    > ...
    >
    > -static void ramoops_do_dump(struct kmsg_dumper *dumper,
    > - enum kmsg_dump_reason reason, const char *s1, unsigned long l1,
    > - const char *s2, unsigned long l2)
    > +static int ramoops_pstore_open(struct pstore_info *psi)
    > +{
    > + struct ramoops_context *cxt = (struct ramoops_context *)psi->data;

    Unneeded and undesirable cast of void*. Multiple instances of this.

    > + cxt->read_count = 0;
    > + return 0;
    > +}
    > +
    > +static ssize_t ramoops_pstore_read(u64 *id, enum pstore_type_id *type,
    > + struct timespec *time,
    > + char **buf,
    > + struct pstore_info *psi)
    > +{
    > + ssize_t size;
    > + char *rambuf;
    > + struct ramoops_context *cxt = (struct ramoops_context *)psi->data;
    > +
    > + if (cxt->read_count >= cxt->max_count)
    > + return -EINVAL;
    > + *id = cxt->read_count++;
    > + /* Only supports dmesg output so far. */
    > + *type = PSTORE_TYPE_DMESG;
    > + /* TODO(kees): Bogus time for the moment. */

    Is this hard to fix now?

    > + time->tv_sec = 0;
    > + time->tv_nsec = 0;
    > +
    > + rambuf = cxt->virt_addr + (*id * cxt->record_size);
    > + size = strnlen(rambuf, cxt->record_size);
    > + *buf = kmalloc(size, GFP_KERNEL);
    > + if (*buf == NULL)
    > + return -ENOMEM;
    > + memcpy(*buf, rambuf, size);
    > +
    > + return size;
    > +}

    Note that pstore_get_records() will treat the -ve errno returns from
    ->read() in the same manner as EOF. IOW, your error codes will be
    dropped on the floor. This appears to be a bug in pstore_get_records().

    > +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)
    > {
    > - struct ramoops_context *cxt = container_of(dumper,
    > - struct ramoops_context, dump);
    > - unsigned long s1_start, s2_start;
    > - unsigned long l1_cpy, l2_cpy;
    > - int res, hdr_size;
    > - char *buf, *buf_orig;
    > + char *buf;
    > + size_t res;
    > struct timeval timestamp;
    > + struct ramoops_context *cxt = (struct ramoops_context *)psi->data;
    > + size_t available = cxt->record_size;
    >
    > + /* Only store dmesg dumps. */
    > + if (type != PSTORE_TYPE_DMESG)
    > + return -EINVAL;
    > +
    > + /* Only store crash dumps. */
    > if (reason != KMSG_DUMP_OOPS &&
    > - reason != KMSG_DUMP_PANIC &&
    > - reason != KMSG_DUMP_KEXEC)
    > - return;
    > + reason != KMSG_DUMP_PANIC)
    > + return -EINVAL;
    >
    > /* Only dump oopses if dump_oops is set */
    > if (reason == KMSG_DUMP_OOPS && !cxt->dump_oops)

    The above three comments describe what the code does, which was
    obvious. They failed to describe why it does this, which was
    unobvious. Sigh.

    > - return;
    > + return -EINVAL;
    > +
    > + /* Explicitly only take the first part of any new crash.
    > + * If our buffer is larger than kmsg_bytes, this can never happen,
    > + * and if our buffer is smaller than kmsg_bytes, we don't want the
    > + * report split across multiple records. */
    > + if (part != 1)
    > + return -ENOSPC;
    >
    > buf = cxt->virt_addr + (cxt->count * cxt->record_size);
    > - buf_orig = buf;
    >
    > - memset(buf, '\0', cxt->record_size);
    > res = sprintf(buf, "%s", RAMOOPS_KERNMSG_HDR);
    > buf += res;
    > + available -= res;
    > +
    > do_gettimeofday(&timestamp);
    >
    > ...
    >



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