acpi: include PkgLength size only when requested

Named/Reserved{Field} definition uses PkgLength [1] encoding to specify
field length, however it doesn't include size of PkgLength field itself,
while other block objects that have explicit length of its body account
for PkgLength size while encoding it [2].
This special casing isn't mentioned in ACPI spec, but that's what 'iasl'
compiles NamedField to so add extra argument to build_prepend_pkg_length()
to allow it handle the case.

--
1. ACPI Spec 5.0, 20.2.5.2 Named Objects Encoding, page 822
2. ACPI Spec 5.0, 5.4 Definition Block Encoding

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

2 files changed, 17 insertions, 6 deletions

diff --git a/hw/acpi/aml-build.c b/hw/acpi/aml-build.c
index d7edda1..cc883cc 100644
--- a/hw/acpi/aml-build.c
+++ b/hw/acpi/aml-build.c
@@ -158,10 +158,10 @@ enum {
     PACKAGE_LENGTH_4BYTE_SHIFT = 20,
 };
 
-void build_prepend_package_length(GArray *package)
+void
+build_prepend_package_length(GArray *package, unsigned length, bool incl_self)
 {
     uint8_t byte;
-    unsigned length = package->len;
     unsigned length_bytes;
 
     if (length + 1 < (1 << PACKAGE_LENGTH_1BYTE_SHIFT)) {
@@ -174,8 +174,18 @@ void build_prepend_package_length(GArray *package)
         length_bytes = 4;
     }
 
-    /* PkgLength is the length of the inclusive length of the data. */
-    length += length_bytes;
+    /*
+     * NamedField uses PkgLength encoding but it doesn't include length
+     * of PkgLength itself.
+     */
+    if (incl_self) {
+        /*
+         * PkgLength is the length of the inclusive length of the data
+         * and PkgLength's length itself when used for terms with
+         * explitit length.
+         */
+        length += length_bytes;
+    }
 
     switch (length_bytes) {
     case 1:
@@ -208,7 +218,7 @@ void build_prepend_package_length(GArray *package)
 
 void build_package(GArray *package, uint8_t op)
 {
-    build_prepend_package_length(package);
+    build_prepend_package_length(package, package->len, true);
     build_prepend_byte(package, op);
 }
 
diff --git a/include/hw/acpi/aml-build.h b/include/hw/acpi/aml-build.h
index 298e2ef..b7f491e 100644
--- a/include/hw/acpi/aml-build.h
+++ b/include/hw/acpi/aml-build.h
@@ -99,7 +99,8 @@ void build_append_array(GArray *array, GArray *val);
 void GCC_FMT_ATTR(2, 3)
 build_append_namestring(GArray *array, const char *format, ...);
 
-void build_prepend_package_length(GArray *package);
+void
+build_prepend_package_length(GArray *package, unsigned length, bool incl_self);
 void build_package(GArray *package, uint8_t op);
 void build_append_int(GArray *table, uint64_t value);
 void build_extop_package(GArray *package, uint8_t op);