drm/i915/dmc: extract function to parse css header

Let's start splitting the parse function, making all of them return the
number of bytes parsed - different versions of the firmware header may
require different sizes for the structures.

v2: rework remaining bytes calculation on new protection for amount of
    bytes read

Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: Anusha Srivatsa <anusha.srivatsa@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190607091230.1489-5-lucas.demarchi@intel.com

diff --git a/drivers/gpu/drm/i915/intel_csr.c b/drivers/gpu/drm/i915/intel_csr.c
index 0bcda68fe44c824de35f8839c4a5a3d6bb607a68..3cf2f2bc6b5c7c2b34841b822f612ae8a83d2037 100644 (file)
--- a/drivers/gpu/drm/i915/intel_csr.c
+++ b/drivers/gpu/drm/i915/intel_csr.c
@@ -332,36 +332,22 @@ static u32 find_dmc_fw_offset(const struct intel_fw_info *fw_info,
        return dmc_offset;
 }
 
-static u32 *parse_csr_fw(struct drm_i915_private *dev_priv,
-                        const struct firmware *fw)
+/* Return number of bytes parsed or 0 on error */
+static u32 parse_csr_fw_css(struct intel_csr *csr,
+                           struct intel_css_header *css_header,
+                           size_t rem_size)
 {
-       struct intel_css_header *css_header;
-       struct intel_package_header *package_header;
-       struct intel_dmc_header *dmc_header;
-       struct intel_csr *csr = &dev_priv->csr;
-       const struct stepping_info *si = intel_get_stepping_info(dev_priv);
-       u32 dmc_offset, num_entries, max_entries, readcount = 0, nbytes;
-       u32 i;
-       u32 *dmc_payload;
-       size_t fsize;
-
-       if (!fw)
-               return NULL;
-
-       fsize = sizeof(struct intel_css_header) +
-               sizeof(struct intel_package_header) +
-               sizeof(struct intel_dmc_header);
-       if (fsize > fw->size)
-               goto error_truncated;
+       if (rem_size < sizeof(struct intel_css_header)) {
+               DRM_ERROR("Truncated DMC firmware, refusing.\n");
+               return 0;
+       }
 
-       /* Extract CSS Header information*/
-       css_header = (struct intel_css_header *)fw->data;
        if (sizeof(struct intel_css_header) !=
            (css_header->header_len * 4)) {
                DRM_ERROR("DMC firmware has wrong CSS header length "
                          "(%u bytes)\n",
                          (css_header->header_len * 4));
-               return NULL;
+               return 0;
        }
 
        if (csr->required_version &&
@@ -372,12 +358,42 @@ static u32 *parse_csr_fw(struct drm_i915_private *dev_priv,
                         CSR_VERSION_MINOR(css_header->version),
                         CSR_VERSION_MAJOR(csr->required_version),
                         CSR_VERSION_MINOR(csr->required_version));
-               return NULL;
+               return 0;
        }
 
        csr->version = css_header->version;
 
-       readcount += sizeof(struct intel_css_header);
+       return sizeof(struct intel_css_header);
+}
+
+static u32 *parse_csr_fw(struct drm_i915_private *dev_priv,
+                        const struct firmware *fw)
+{
+       struct intel_css_header *css_header;
+       struct intel_package_header *package_header;
+       struct intel_dmc_header *dmc_header;
+       struct intel_csr *csr = &dev_priv->csr;
+       const struct stepping_info *si = intel_get_stepping_info(dev_priv);
+       u32 dmc_offset, num_entries, max_entries, readcount = 0, nbytes;
+       u32 i, r;
+       u32 *dmc_payload;
+       size_t fsize;
+
+       if (!fw)
+               return NULL;
+
+       /* Extract CSS Header information */
+       css_header = (struct intel_css_header *)fw->data;
+       r = parse_csr_fw_css(csr, css_header, fw->size);
+       if (!r)
+               return NULL;
+
+       readcount += r;
+       fsize = readcount +
+               sizeof(struct intel_package_header) +
+               sizeof(struct intel_dmc_header);
+       if (fsize > fw->size)
+               goto error_truncated;
 
        /* Extract Package Header information*/
        package_header = (struct intel_package_header *)