drm/amd/display: Check BIOS images before it is used

BIOS images may fail to load and null checks are added before they are
used.

This fixes 6 NULL_RETURNS issues reported by Coverity.
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Acked-by: Hamza Mahfooz <hamza.mahfooz@amd.com>
Signed-off-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/bios/bios_parser.c

@@ -665,6 +665,9 @@ static enum bp_result get_ss_info_v3_1(
 	ss_table_header_include = ((ATOM_ASIC_INTERNAL_SS_INFO_V3 *) bios_get_image(&bp->base,
 				DATA_TABLES(ASIC_InternalSS_Info),
 				struct_size(ss_table_header_include, asSpreadSpectrum, 1)));
+	if (!ss_table_header_include)
+		return BP_RESULT_UNSUPPORTED;
+
 	table_size =
 		(le16_to_cpu(ss_table_header_include->sHeader.usStructureSize)
 				- sizeof(ATOM_COMMON_TABLE_HEADER))
@@ -1034,6 +1037,8 @@ static enum bp_result get_ss_info_from_internal_ss_info_tbl_V2_1(
 				&bp->base,
 				DATA_TABLES(ASIC_InternalSS_Info),
 				struct_size(header, asSpreadSpectrum, 1)));
+	if (!header)
+		return result;
 
 	memset(info, 0, sizeof(struct spread_spectrum_info));
 
@@ -1107,6 +1112,8 @@ static enum bp_result get_ss_info_from_ss_info_table(
 	get_atom_data_table_revision(header, &revision);
 
 	tbl = GET_IMAGE(ATOM_SPREAD_SPECTRUM_INFO, DATA_TABLES(SS_Info));
+	if (!tbl)
+		return result;
 
 	if (1 != revision.major || 2 > revision.minor)
 		return result;
@@ -1634,6 +1641,8 @@ static uint32_t get_ss_entry_number_from_ss_info_tbl(
 
 	tbl = GET_IMAGE(ATOM_SPREAD_SPECTRUM_INFO,
 			DATA_TABLES(SS_Info));
+	if (!tbl)
+		return number;
 
 	if (1 != revision.major || 2 > revision.minor)
 		return number;
@@ -1716,6 +1725,8 @@ static uint32_t get_ss_entry_number_from_internal_ss_info_tbl_v2_1(
 				&bp->base,
 				DATA_TABLES(ASIC_InternalSS_Info),
 				struct_size(header_include, asSpreadSpectrum, 1)));
+	if (!header_include)
+		return 0;
 
 	size = (le16_to_cpu(header_include->sHeader.usStructureSize)
 			- sizeof(ATOM_COMMON_TABLE_HEADER))
@@ -1755,6 +1766,9 @@ static uint32_t get_ss_entry_number_from_internal_ss_info_tbl_V3_1(
 	header_include = ((ATOM_ASIC_INTERNAL_SS_INFO_V3 *) bios_get_image(&bp->base,
 				DATA_TABLES(ASIC_InternalSS_Info),
 				struct_size(header_include, asSpreadSpectrum, 1)));
+	if (!header_include)
+		return number;
+
 	size = (le16_to_cpu(header_include->sHeader.usStructureSize) -
 			sizeof(ATOM_COMMON_TABLE_HEADER)) /
 					sizeof(ATOM_ASIC_SS_ASSIGNMENT_V3);