[PATCH v2 0/2] hw/nvram/fw_cfg: Let fw_cfg_add_from_generator() return boolean value

[PATCH v2 0/2] hw/nvram/fw_cfg: Let fw_cfg_add_from_generator() return boolean value

[Philippe Mathieu-Daudé]

Since v1:
- Addressed Markus review comments
- Added patch to clarify fw_cfg_add_from_generator (Markus)

Philippe Mathieu-Daudé (2):
  hw/nvram/fw_cfg: Simplify fw_cfg_add_from_generator() error
    propagation
  hw/nvram/fw_cfg: Let fw_cfg_add_from_generator() return boolean value

 include/hw/nvram/fw_cfg.h |  8 ++++++--
 hw/nvram/fw_cfg.c         | 13 +++++++------
 softmmu/vl.c              |  6 +-----
 3 files changed, 14 insertions(+), 13 deletions(-)

-- 
2.21.3

[PATCH v2 1/2] hw/nvram/fw_cfg: Simplify fw_cfg_add_from_generator() error propagation

[Philippe Mathieu-Daudé]

Document FWCfgDataGeneratorClass::get_data() return NULL
on error, and non-NULL on success. This allow us to simplify
fw_cfg_add_from_generator(). Since we don't need a local
variable to propagate the error, we can remove the ERRP_GUARD()
macro.

Suggested-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
---
 include/hw/nvram/fw_cfg.h | 4 +++-
 hw/nvram/fw_cfg.c         | 3 +--
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/include/hw/nvram/fw_cfg.h b/include/hw/nvram/fw_cfg.h
index 11feae3177..bbcf405649 100644
--- a/include/hw/nvram/fw_cfg.h
+++ b/include/hw/nvram/fw_cfg.h
@@ -32,7 +32,9 @@ typedef struct FWCfgDataGeneratorClass {
      * @obj: the object implementing this interface
      * @errp: pointer to a NULL-initialized error object
      *
-     * Returns: reference to a byte array containing the data.
+     * Returns: reference to a byte array containing the data on success,
+     *          or NULL on error.
+     *
      * The caller should release the reference when no longer
      * required.
      */
diff --git a/hw/nvram/fw_cfg.c b/hw/nvram/fw_cfg.c
index 3b1811d3bf..dfa1f2012a 100644
--- a/hw/nvram/fw_cfg.c
+++ b/hw/nvram/fw_cfg.c
@@ -1035,7 +1035,6 @@ void *fw_cfg_modify_file(FWCfgState *s, const char *filename,
 void fw_cfg_add_from_generator(FWCfgState *s, const char *filename,
                                const char *gen_id, Error **errp)
 {
-    ERRP_GUARD();
     FWCfgDataGeneratorClass *klass;
     GByteArray *array;
     Object *obj;
@@ -1053,7 +1052,7 @@ void fw_cfg_add_from_generator(FWCfgState *s, const char *filename,
     }
     klass = FW_CFG_DATA_GENERATOR_GET_CLASS(obj);
     array = klass->get_data(obj, errp);
-    if (*errp) {
+    if (!array) {
         return;
     }
     size = array->len;
-- 
2.21.3

[PATCH v2 2/2] hw/nvram/fw_cfg: Let fw_cfg_add_from_generator() return boolean value

[Philippe Mathieu-Daudé]

Commits b6d7e9b66f..a43770df5d simplified the error propagation.
Similarly to commit 6fd5bef10b "qom: Make functions taking Error**
return bool, not void", let fw_cfg_add_from_generator() return a
boolean value, not void.
This allow to simplify parse_fw_cfg() and fixes the error handling
issue reported by Coverity (CID 1430396):

  In parse_fw_cfg():

    Variable assigned once to a constant guards dead code.

    Local variable local_err is assigned only once, to a constant
    value, making it effectively constant throughout its scope.
    If this is not the intent, examine the logic to see if there
    is a missing assignment that would make local_err not remain
    constant.

It's the call of fw_cfg_add_from_generator():

        Error *local_err = NULL;

        fw_cfg_add_from_generator(fw_cfg, name, gen_id, errp);
        if (local_err) {
            error_propagate(errp, local_err);
            return -1;
        }
        return 0;

If it fails, parse_fw_cfg() sets an error and returns 0, which is
wrong. Harmless, because the only caller passes &error_fatal.

Reported-by: Peter Maydell <peter.maydell@linaro.org>
Fixes: Coverity CID 1430396: 'Constant' variable guards dead code (DEADCODE)
Fixes: 6552d87c48 ("softmmu/vl: Let -fw_cfg option take a 'gen_id' argument")
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
---
v2: Added impact assessment (Markus)
---
 include/hw/nvram/fw_cfg.h |  4 +++-
 hw/nvram/fw_cfg.c         | 10 ++++++----
 softmmu/vl.c              |  6 +-----
 3 files changed, 10 insertions(+), 10 deletions(-)

diff --git a/include/hw/nvram/fw_cfg.h b/include/hw/nvram/fw_cfg.h
index bbcf405649..f190c428e8 100644
--- a/include/hw/nvram/fw_cfg.h
+++ b/include/hw/nvram/fw_cfg.h
@@ -304,8 +304,10 @@ void *fw_cfg_modify_file(FWCfgState *s, const char *filename, void *data,
  * will be used; also, a new entry will be added to the file directory
  * structure residing at key value FW_CFG_FILE_DIR, containing the item name,
  * data size, and assigned selector key value.
+ *
+ * Returns: %true on success, %false on error.
  */
-void fw_cfg_add_from_generator(FWCfgState *s, const char *filename,
+bool fw_cfg_add_from_generator(FWCfgState *s, const char *filename,
                                const char *gen_id, Error **errp);
 
 FWCfgState *fw_cfg_init_io_dma(uint32_t iobase, uint32_t dma_iobase,
diff --git a/hw/nvram/fw_cfg.c b/hw/nvram/fw_cfg.c
index dfa1f2012a..f3a4728288 100644
--- a/hw/nvram/fw_cfg.c
+++ b/hw/nvram/fw_cfg.c
@@ -1032,7 +1032,7 @@ void *fw_cfg_modify_file(FWCfgState *s, const char *filename,
     return NULL;
 }
 
-void fw_cfg_add_from_generator(FWCfgState *s, const char *filename,
+bool fw_cfg_add_from_generator(FWCfgState *s, const char *filename,
                                const char *gen_id, Error **errp)
 {
     FWCfgDataGeneratorClass *klass;
@@ -1043,20 +1043,22 @@ void fw_cfg_add_from_generator(FWCfgState *s, const char *filename,
     obj = object_resolve_path_component(object_get_objects_root(), gen_id);
     if (!obj) {
         error_setg(errp, "Cannot find object ID '%s'", gen_id);
-        return;
+        return false;
     }
     if (!object_dynamic_cast(obj, TYPE_FW_CFG_DATA_GENERATOR_INTERFACE)) {
         error_setg(errp, "Object ID '%s' is not a '%s' subclass",
                    gen_id, TYPE_FW_CFG_DATA_GENERATOR_INTERFACE);
-        return;
+        return false;
     }
     klass = FW_CFG_DATA_GENERATOR_GET_CLASS(obj);
     array = klass->get_data(obj, errp);
     if (!array) {
-        return;
+        return false;
     }
     size = array->len;
     fw_cfg_add_file(s, filename, g_byte_array_free(array, TRUE), size);
+
+    return true;
 }
 
 static void fw_cfg_machine_reset(void *opaque)
diff --git a/softmmu/vl.c b/softmmu/vl.c
index f476ef89ed..3416241557 100644
--- a/softmmu/vl.c
+++ b/softmmu/vl.c
@@ -2070,11 +2070,7 @@ static int parse_fw_cfg(void *opaque, QemuOpts *opts, Error **errp)
         size = strlen(str); /* NUL terminator NOT included in fw_cfg blob */
         buf = g_memdup(str, size);
     } else if (nonempty_str(gen_id)) {
-        Error *local_err = NULL;
-
-        fw_cfg_add_from_generator(fw_cfg, name, gen_id, errp);
-        if (local_err) {
-            error_propagate(errp, local_err);
+        if (!fw_cfg_add_from_generator(fw_cfg, name, gen_id, errp)) {
             return -1;
         }
         return 0;
-- 
2.21.3

Re: [PATCH v2 1/2] hw/nvram/fw_cfg: Simplify fw_cfg_add_from_generator() error propagation

[Markus Armbruster]

Philippe Mathieu-Daudé <philmd@redhat.com> writes:

> Document FWCfgDataGeneratorClass::get_data() return NULL
> on error, and non-NULL on success. This allow us to simplify
> fw_cfg_add_from_generator(). Since we don't need a local
> variable to propagate the error, we can remove the ERRP_GUARD()
> macro.
>
> Suggested-by: Markus Armbruster <armbru@redhat.com>
> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> ---
>  include/hw/nvram/fw_cfg.h | 4 +++-
>  hw/nvram/fw_cfg.c         | 3 +--
>  2 files changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/include/hw/nvram/fw_cfg.h b/include/hw/nvram/fw_cfg.h
> index 11feae3177..bbcf405649 100644
> --- a/include/hw/nvram/fw_cfg.h
> +++ b/include/hw/nvram/fw_cfg.h
> @@ -32,7 +32,9 @@ typedef struct FWCfgDataGeneratorClass {
>       * @obj: the object implementing this interface
>       * @errp: pointer to a NULL-initialized error object
>       *
> -     * Returns: reference to a byte array containing the data.
> +     * Returns: reference to a byte array containing the data on success,
> +     *          or NULL on error.
> +     *
>       * The caller should release the reference when no longer
>       * required.
>       */

Thanks for clarifying the doc comment!

As far as I can tell, the only implementation is
qcrypto_tls_cipher_suites_fw_cfg_gen_data(), which is a trivial wrapper
around qcrypto_tls_cipher_suites_get_data().  I checked it conforms.

> diff --git a/hw/nvram/fw_cfg.c b/hw/nvram/fw_cfg.c
> index 3b1811d3bf..dfa1f2012a 100644
> --- a/hw/nvram/fw_cfg.c
> +++ b/hw/nvram/fw_cfg.c
> @@ -1035,7 +1035,6 @@ void *fw_cfg_modify_file(FWCfgState *s, const char *filename,
>  void fw_cfg_add_from_generator(FWCfgState *s, const char *filename,
>                                 const char *gen_id, Error **errp)
>  {
> -    ERRP_GUARD();
>      FWCfgDataGeneratorClass *klass;
>      GByteArray *array;
>      Object *obj;
> @@ -1053,7 +1052,7 @@ void fw_cfg_add_from_generator(FWCfgState *s, const char *filename,
>      }
>      klass = FW_CFG_DATA_GENERATOR_GET_CLASS(obj);
>      array = klass->get_data(obj, errp);
> -    if (*errp) {
> +    if (!array) {
>          return;
>      }
>      size = array->len;

Reviewed-by: Markus Armbruster <armbru@redhat.com>

Re: [PATCH v2 0/2] hw/nvram/fw_cfg: Let fw_cfg_add_from_generator() return boolean value

[Philippe Mathieu-Daudé]

On 7/21/20 3:19 PM, Philippe Mathieu-Daudé wrote:
> Since v1:
> - Addressed Markus review comments
> - Added patch to clarify fw_cfg_add_from_generator (Markus)
> 
> Philippe Mathieu-Daudé (2):
>   hw/nvram/fw_cfg: Simplify fw_cfg_add_from_generator() error
>     propagation
>   hw/nvram/fw_cfg: Let fw_cfg_add_from_generator() return boolean value
> 
>  include/hw/nvram/fw_cfg.h |  8 ++++++--
>  hw/nvram/fw_cfg.c         | 13 +++++++------
>  softmmu/vl.c              |  6 +-----
>  3 files changed, 14 insertions(+), 13 deletions(-)
> 

Thanks for the reviews, patches applied to fw_cfg-next tree.

Phil.