linux: ensure bytes are valid before patching

We use sed to replace original bytes by patched ones, but unfortunately
sed doesn't report any errors when this substitution fails.

Now, before actually running sed, we check if these bytes that are soon
to be replaced, actually exist in the driver file.

patch-fbc.sh

@@ -381,6 +381,20 @@ patch_common () {
 
 }
 
+ensure_bytes_are_valid () {
+    driver_file="$driver_dir/$object.$driver_version"
+    original_bytes=$(awk -F / '$2 { print $2 }' <<< "$patch")
+    patched_bytes=$(awk -F / '$3 { print $3 }' <<< "$patch")
+    if LC_ALL=C grep -qaP "$original_bytes" "$driver_file"; then
+        return 0 # file is ready to be patched
+    fi
+    if LC_ALL=C grep -qaP "$patched_bytes" "$driver_file"; then
+        return 0 # file is likely patched already
+    fi
+    echo "Error: Could not find bytes '$original_bytes' to patch in '$driver_file'."
+    exit 1
+}
+
 rollback () {
     patch_common
     if [[ -f "$backup_path/$object.$driver_version$backup_suffix" ]]; then
@@ -395,6 +409,7 @@ rollback () {
 
 patch () {
     patch_common
+    ensure_bytes_are_valid
     if [[ -f "$backup_path/$object.$driver_version$backup_suffix" ]]; then
         bkp_hash="$(sha1sum "$backup_path/$object.$driver_version$backup_suffix" | cut -f1 -d\ )"
         drv_hash="$(sha1sum "$driver_dir/$object.$driver_version" | cut -f1 -d\ )"

patch.sh

@@ -457,6 +457,20 @@ patch_common () {
 
 }
 
+ensure_bytes_are_valid () {
+    driver_file="$driver_dir/$object.$driver_version"
+    original_bytes=$(awk -F / '$2 { print $2 }' <<< "$patch")
+    patched_bytes=$(awk -F / '$3 { print $3 }' <<< "$patch")
+    if LC_ALL=C grep -qaP "$original_bytes" "$driver_file"; then
+        return 0 # file is ready to be patched
+    fi
+    if LC_ALL=C grep -qaP "$patched_bytes" "$driver_file"; then
+        return 0 # file is likely patched already
+    fi
+    echo "Error: Could not find bytes '$original_bytes' to patch in '$driver_file'."
+    exit 1
+}
+
 rollback () {
     patch_common
     if [[ -f "$backup_path/$object.$driver_version$backup_suffix" ]]; then
@@ -471,6 +485,7 @@ rollback () {
 
 patch () {
     patch_common
+    ensure_bytes_are_valid
     if [[ -f "$backup_path/$object.$driver_version$backup_suffix" ]]; then
         bkp_hash="$(sha1sum "$backup_path/$object.$driver_version$backup_suffix" | cut -f1 -d\ )"
         drv_hash="$(sha1sum "$driver_dir/$object.$driver_version" | cut -f1 -d\ )"