Re: [Qemu-devel] [PATCH] aml-build: don't modify child

["Michael S. Tsirkin" <mst@redhat.com>]

On Mon, Mar 09, 2015 at 10:27:15AM +0100, Igor Mammedov wrote:
> On Sat, 7 Mar 2015 20:51:33 +0100
> "Michael S. Tsirkin" <mst@redhat.com> wrote:
> 
> > this code:
> >     aml_append(foo, bar);
> > 
> > might, non-intuitively, modify bar, which means that e.g. the following
> > might not DTRT:
> > 
> >     c = ....;
> >     aml_append(a, c);
> >     aml_append(b, c);
> > 
> > to fix, simply allocate an intermediate array,
> > and always modify that.
> While at it, could 'c' be made 'const Aml*' argument of aml_append() ???

I considered this but it's mostly useless since the
buffer can still be modified.

We can think about this using a patch on top.


> > 
> > Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> > ---
> >  hw/acpi/aml-build.c | 16 ++++++++++------
> >  1 file changed, 10 insertions(+), 6 deletions(-)
> > 
> > diff --git a/hw/acpi/aml-build.c b/hw/acpi/aml-build.c
> > index 876cada..ff12b28 100644
> > --- a/hw/acpi/aml-build.c
> > +++ b/hw/acpi/aml-build.c
> > @@ -335,26 +335,29 @@ static void build_buffer(GArray *array, uint8_t op)
> >  
> >  void aml_append(Aml *parent_ctx, Aml *child)
> >  {
> > +    GArray *buf = build_alloc_array();
> > +    build_append_array(buf, child->buf);
> > +
> >      switch (child->block_flags) {
> >      case AML_OPCODE:
> >          build_append_byte(parent_ctx->buf, child->op);
> >          break;
> >      case AML_EXT_PACKAGE:
> > -        build_extop_package(child->buf, child->op);
> > +        build_extop_package(buf, child->op);
> >          break;
> >      case AML_PACKAGE:
> > -        build_package(child->buf, child->op);
> > +        build_package(buf, child->op);
> >          break;
> >      case AML_RES_TEMPLATE:
> > -        build_append_byte(child->buf, 0x79); /* EndTag */
> > +        build_append_byte(buf, 0x79); /* EndTag */
> >          /*
> >           * checksum operations are treated as succeeded if checksum
> >           * field is zero. [ACPI Spec 1.0b, 6.4.2.8 End Tag]
> >           */
> > -        build_append_byte(child->buf, 0);
> > +        build_append_byte(buf, 0);
> >          /* fall through, to pack resources in buffer */
> >      case AML_BUFFER:
> > -        build_buffer(child->buf, child->op);
> > +        build_buffer(buf, child->op);
> >          break;
> >      case AML_NO_OPCODE:
> >          break;
> > @@ -362,7 +365,8 @@ void aml_append(Aml *parent_ctx, Aml *child)
> >          assert(0);
> >          break;
> >      }
> > -    build_append_array(parent_ctx->buf, child->buf);
> > +    build_append_array(parent_ctx->buf, buf);
> > +    build_free_array(buf);
> >  }
> >  
> >  /* ACPI 1.0b: 16.2.5.1 Namespace Modifier Objects Encoding: DefScope */