Leif,
Yes. Typecasts are used by the caller if the type does not match. Here is an
example from the PciCfg2.c that you referenced.
IN OUT VOID *Buffer
//
// Aligned Pci address access
//
WriteUnaligned16 (((UINT16 *) Buffer), PciRead16 (PciLibAddress));
Since Buffer is type VOID *, a typecast to UINT16 * is made. That is valid C
code. One use case where making these APIs type specific is when a data
structure
is used that is either byte packed or the start of the structure is not aligned
(e.g.
network packet processing). In these cases, the fields may have explicit types
such
as UINT16, UINT32, UINT64, and the compiler does type checking when a pointer
to the
field is passed into the unaligned access functions.
By changing the APIs to be VOID* instead of UINT16*, UINT32*, or UINT64*, some
type
checking is lost. The APIs as they are defines now have worked for IPF. What
is
different about ARM and AArch64? Are you wanting to remove the requirement for
the
explicit typecast by the caller?
You are correct. PatchCheck.py does not check EDK II C style. The ECC tool
can be
used for that. We have discussed adding ECC to PatchCheck.py, but have not
done that
yet.
Thanks,
Mike
> -----Original Message-----
> From: Leif Lindholm [mailto:[email protected]]
> Sent: Thursday, May 12, 2016 3:49 PM
> To: Kinney, Michael D <[email protected]>
> Cc: [email protected]; Gao, Liming <[email protected]>; Ard
> Biesheuvel
> <[email protected]>
> Subject: Re: [RFC] MdePkg: BaseLib: don't use aligned pointers for unaligned
> accessors
>
> On Thu, May 12, 2016 at 10:29:34PM +0000, Kinney, Michael D wrote:
> > Leif,
> >
> > Why does the current definition strictly require alignment?
> >
> > I know we have used this for a long time with many compilers passing in
> > unaligned pointers to UINT16, UINT32, UINT64 values without any compiler
> > warnings/errors.
>
> Sure, but that does not make it valid C.
>
> Specifying an input argument to be a UINT32 * at least in ARM, AArch64
> and IPF land means that the programmer provides an explicit guarantee
> that the pointer references a naturally aligned location.
>
> Also, the reason that edk2 compiles without warnings is that code in
> the tree makes (also invalid) casts at the call sites to these
> functions in order to get rid of said warnings. See for example
> MdeModulePkg/Universal/PcatSingleSegmentPciCfg2Pei/PciCfg2.c
>
> (A naive grep throws up 129 instances of explicit casts on lines
> calling a ReadUnaligned function and 211 instances of ones calling a
> WriteUnaligned function.)
>
> > Also, the patch contains locals that are initialized in the declaration
> > of the local. We prefer locals to be initialized in the body of the
> > function.
>
> Understood - PatchCheck.py didn't warn me about that :)
>
> Regards,
>
> Leif
>
> > Thanks,
> >
> > Mike
> >
> > > -----Original Message-----
> > > From: Leif Lindholm [mailto:[email protected]]
> > > Sent: Thursday, May 12, 2016 3:22 PM
> > > To: [email protected]
> > > Cc: Kinney, Michael D <[email protected]>; Gao, Liming
> > > <[email protected]>; Ard Biesheuvel <[email protected]>
> > > Subject: [RFC] MdePkg: BaseLib: don't use aligned pointers for unaligned
> accessors
> > >
> > > The ReadUnaligned##/WriteUnaligned## functions provide a portable way of
> > > accessing potentially unaligned locations, but the prototypes in
> > > BaseLib.h all specify strictly aligned pointers.
> > >
> > > Change the prototypes as well as the implementations across Ia32/X64,
> > > ARM/AArch64 and IPF to use VOID * pointers instead.
> > >
> > > Contributed-under: TianoCore Contribution Agreement 1.0
> > > Signed-off-by: Leif Lindholm <[email protected]>
> > > ---
> > >
> > > Built and tested for ArmVirtPkg for AArch64/ARM DEBUG/RELEASE.
> > > Build tested only for OvmfPkg for Ia32/X64 DEBUG/RELEASE.
> > > Not tested at all for IPF.
> > >
> > > I am not entirely convinced by the BitFieldWrite32 logic in
> > > WriteUnaligned24, but this patch is not the place to fix this.
> > >
> > > I am also not convinced there is much point in keeping separate
> > > implementations for IPF and ARM* - the optimization issues mentioned
> > > in the git log could even have been affected by the incorrect
> > > pointer types.
> > >
> > > This is the first patch triggered by my CLANG -Weverything exercises
> > > earlier this year. More to come.
> > >
> > > MdePkg/Include/Library/BaseLib.h | 16 ++++++------
> > > MdePkg/Library/BaseLib/Arm/Unaligned.c | 16 ++++++------
> > > MdePkg/Library/BaseLib/Ipf/Unaligned.c | 16 ++++++------
> > > MdePkg/Library/BaseLib/Unaligned.c | 48
> > > ++++++++++++++++++++++------------
> > > 4 files changed, 56 insertions(+), 40 deletions(-)
> > >
> > > diff --git a/MdePkg/Include/Library/BaseLib.h
> > > b/MdePkg/Include/Library/BaseLib.h
> > > index c41fa78..133656a 100644
> > > --- a/MdePkg/Include/Library/BaseLib.h
> > > +++ b/MdePkg/Include/Library/BaseLib.h
> > > @@ -2549,7 +2549,7 @@ DivS64x64Remainder (
> > > UINT16
> > > EFIAPI
> > > ReadUnaligned16 (
> > > - IN CONST UINT16 *Buffer
> > > + IN CONST VOID *Buffer
> > > );
> > >
> > >
> > > @@ -2571,7 +2571,7 @@ ReadUnaligned16 (
> > > UINT16
> > > EFIAPI
> > > WriteUnaligned16 (
> > > - OUT UINT16 *Buffer,
> > > + OUT VOID *Buffer,
> > > IN UINT16 Value
> > > );
> > >
> > > @@ -2592,7 +2592,7 @@ WriteUnaligned16 (
> > > UINT32
> > > EFIAPI
> > > ReadUnaligned24 (
> > > - IN CONST UINT32 *Buffer
> > > + IN CONST VOID *Buffer
> > > );
> > >
> > >
> > > @@ -2614,7 +2614,7 @@ ReadUnaligned24 (
> > > UINT32
> > > EFIAPI
> > > WriteUnaligned24 (
> > > - OUT UINT32 *Buffer,
> > > + OUT VOID *Buffer,
> > > IN UINT32 Value
> > > );
> > >
> > > @@ -2635,7 +2635,7 @@ WriteUnaligned24 (
> > > UINT32
> > > EFIAPI
> > > ReadUnaligned32 (
> > > - IN CONST UINT32 *Buffer
> > > + IN CONST VOID *Buffer
> > > );
> > >
> > >
> > > @@ -2657,7 +2657,7 @@ ReadUnaligned32 (
> > > UINT32
> > > EFIAPI
> > > WriteUnaligned32 (
> > > - OUT UINT32 *Buffer,
> > > + OUT VOID *Buffer,
> > > IN UINT32 Value
> > > );
> > >
> > > @@ -2678,7 +2678,7 @@ WriteUnaligned32 (
> > > UINT64
> > > EFIAPI
> > > ReadUnaligned64 (
> > > - IN CONST UINT64 *Buffer
> > > + IN CONST VOID *Buffer
> > > );
> > >
> > >
> > > @@ -2700,7 +2700,7 @@ ReadUnaligned64 (
> > > UINT64
> > > EFIAPI
> > > WriteUnaligned64 (
> > > - OUT UINT64 *Buffer,
> > > + OUT VOID *Buffer,
> > > IN UINT64 Value
> > > );
> > >
> > > diff --git a/MdePkg/Library/BaseLib/Arm/Unaligned.c
> > > b/MdePkg/Library/BaseLib/Arm/Unaligned.c
> > > index 34f1732..ef9efbc 100644
> > > --- a/MdePkg/Library/BaseLib/Arm/Unaligned.c
> > > +++ b/MdePkg/Library/BaseLib/Arm/Unaligned.c
> > > @@ -33,7 +33,7 @@
> > > UINT16
> > > EFIAPI
> > > ReadUnaligned16 (
> > > - IN CONST UINT16 *Buffer
> > > + IN CONST VOID *Buffer
> > > )
> > > {
> > > volatile UINT8 LowerByte;
> > > @@ -65,7 +65,7 @@ ReadUnaligned16 (
> > > UINT16
> > > EFIAPI
> > > WriteUnaligned16 (
> > > - OUT UINT16 *Buffer,
> > > + OUT VOID *Buffer,
> > > IN UINT16 Value
> > > )
> > > {
> > > @@ -93,7 +93,7 @@ WriteUnaligned16 (
> > > UINT32
> > > EFIAPI
> > > ReadUnaligned24 (
> > > - IN CONST UINT32 *Buffer
> > > + IN CONST VOID *Buffer
> > > )
> > > {
> > > ASSERT (Buffer != NULL);
> > > @@ -122,7 +122,7 @@ ReadUnaligned24 (
> > > UINT32
> > > EFIAPI
> > > WriteUnaligned24 (
> > > - OUT UINT32 *Buffer,
> > > + OUT VOID *Buffer,
> > > IN UINT32 Value
> > > )
> > > {
> > > @@ -149,7 +149,7 @@ WriteUnaligned24 (
> > > UINT32
> > > EFIAPI
> > > ReadUnaligned32 (
> > > - IN CONST UINT32 *Buffer
> > > + IN CONST VOID *Buffer
> > > )
> > > {
> > > UINT16 LowerBytes;
> > > @@ -181,7 +181,7 @@ ReadUnaligned32 (
> > > UINT32
> > > EFIAPI
> > > WriteUnaligned32 (
> > > - OUT UINT32 *Buffer,
> > > + OUT VOID *Buffer,
> > > IN UINT32 Value
> > > )
> > > {
> > > @@ -208,7 +208,7 @@ WriteUnaligned32 (
> > > UINT64
> > > EFIAPI
> > > ReadUnaligned64 (
> > > - IN CONST UINT64 *Buffer
> > > + IN CONST VOID *Buffer
> > > )
> > > {
> > > UINT32 LowerBytes;
> > > @@ -240,7 +240,7 @@ ReadUnaligned64 (
> > > UINT64
> > > EFIAPI
> > > WriteUnaligned64 (
> > > - OUT UINT64 *Buffer,
> > > + OUT VOID *Buffer,
> > > IN UINT64 Value
> > > )
> > > {
> > > diff --git a/MdePkg/Library/BaseLib/Ipf/Unaligned.c
> > > b/MdePkg/Library/BaseLib/Ipf/Unaligned.c
> > > index 7d0d8dd..5ba8029 100644
> > > --- a/MdePkg/Library/BaseLib/Ipf/Unaligned.c
> > > +++ b/MdePkg/Library/BaseLib/Ipf/Unaligned.c
> > > @@ -30,7 +30,7 @@
> > > UINT16
> > > EFIAPI
> > > ReadUnaligned16 (
> > > - IN CONST UINT16 *Buffer
> > > + IN CONST VOID *Buffer
> > > )
> > > {
> > > ASSERT (Buffer != NULL);
> > > @@ -56,7 +56,7 @@ ReadUnaligned16 (
> > > UINT16
> > > EFIAPI
> > > WriteUnaligned16 (
> > > - OUT UINT16 *Buffer,
> > > + OUT VOID *Buffer,
> > > IN UINT16 Value
> > > )
> > > {
> > > @@ -84,7 +84,7 @@ WriteUnaligned16 (
> > > UINT32
> > > EFIAPI
> > > ReadUnaligned24 (
> > > - IN CONST UINT32 *Buffer
> > > + IN CONST VOID *Buffer
> > > )
> > > {
> > > ASSERT (Buffer != NULL);
> > > @@ -113,7 +113,7 @@ ReadUnaligned24 (
> > > UINT32
> > > EFIAPI
> > > WriteUnaligned24 (
> > > - OUT UINT32 *Buffer,
> > > + OUT VOID *Buffer,
> > > IN UINT32 Value
> > > )
> > > {
> > > @@ -140,7 +140,7 @@ WriteUnaligned24 (
> > > UINT32
> > > EFIAPI
> > > ReadUnaligned32 (
> > > - IN CONST UINT32 *Buffer
> > > + IN CONST VOID *Buffer
> > > )
> > > {
> > > UINT16 LowerBytes;
> > > @@ -172,7 +172,7 @@ ReadUnaligned32 (
> > > UINT32
> > > EFIAPI
> > > WriteUnaligned32 (
> > > - OUT UINT32 *Buffer,
> > > + OUT VOID *Buffer,
> > > IN UINT32 Value
> > > )
> > > {
> > > @@ -199,7 +199,7 @@ WriteUnaligned32 (
> > > UINT64
> > > EFIAPI
> > > ReadUnaligned64 (
> > > - IN CONST UINT64 *Buffer
> > > + IN CONST VOID *Buffer
> > > )
> > > {
> > > UINT32 LowerBytes;
> > > @@ -231,7 +231,7 @@ ReadUnaligned64 (
> > > UINT64
> > > EFIAPI
> > > WriteUnaligned64 (
> > > - OUT UINT64 *Buffer,
> > > + OUT VOID *Buffer,
> > > IN UINT64 Value
> > > )
> > > {
> > > diff --git a/MdePkg/Library/BaseLib/Unaligned.c
> b/MdePkg/Library/BaseLib/Unaligned.c
> > > index 68dafa6..ed58861 100644
> > > --- a/MdePkg/Library/BaseLib/Unaligned.c
> > > +++ b/MdePkg/Library/BaseLib/Unaligned.c
> > > @@ -32,12 +32,14 @@
> > > UINT16
> > > EFIAPI
> > > ReadUnaligned16 (
> > > - IN CONST UINT16 *Buffer
> > > + IN CONST VOID *Buffer
> > > )
> > > {
> > > + CONST UINT16 *Input = Buffer;
> > > +
> > > ASSERT (Buffer != NULL);
> > >
> > > - return *Buffer;
> > > + return *Input;
> > > }
> > >
> > > /**
> > > @@ -58,13 +60,15 @@ ReadUnaligned16 (
> > > UINT16
> > > EFIAPI
> > > WriteUnaligned16 (
> > > - OUT UINT16 *Buffer,
> > > + OUT VOID *Buffer,
> > > IN UINT16 Value
> > > )
> > > {
> > > + UINT16 *Output = Buffer;
> > > +
> > > ASSERT (Buffer != NULL);
> > >
> > > - return *Buffer = Value;
> > > + return *Output = Value;
> > > }
> > >
> > > /**
> > > @@ -83,12 +87,14 @@ WriteUnaligned16 (
> > > UINT32
> > > EFIAPI
> > > ReadUnaligned24 (
> > > - IN CONST UINT32 *Buffer
> > > + IN CONST VOID *Buffer
> > > )
> > > {
> > > + CONST UINT32 *Input = Buffer;
> > > +
> > > ASSERT (Buffer != NULL);
> > >
> > > - return *Buffer & 0xffffff;
> > > + return *Input & 0xffffff;
> > > }
> > >
> > > /**
> > > @@ -109,13 +115,15 @@ ReadUnaligned24 (
> > > UINT32
> > > EFIAPI
> > > WriteUnaligned24 (
> > > - OUT UINT32 *Buffer,
> > > + OUT VOID *Buffer,
> > > IN UINT32 Value
> > > )
> > > {
> > > + UINT32 *Output = Buffer;
> > > +
> > > ASSERT (Buffer != NULL);
> > >
> > > - *Buffer = BitFieldWrite32 (*Buffer, 0, 23, Value);
> > > + *Output = BitFieldWrite32 (*Output, 0, 23, Value);
> > > return Value;
> > > }
> > >
> > > @@ -135,12 +143,14 @@ WriteUnaligned24 (
> > > UINT32
> > > EFIAPI
> > > ReadUnaligned32 (
> > > - IN CONST UINT32 *Buffer
> > > + IN CONST VOID *Buffer
> > > )
> > > {
> > > + CONST UINT32 *Input = Buffer;
> > > +
> > > ASSERT (Buffer != NULL);
> > >
> > > - return *Buffer;
> > > + return *Input;
> > > }
> > >
> > > /**
> > > @@ -161,13 +171,15 @@ ReadUnaligned32 (
> > > UINT32
> > > EFIAPI
> > > WriteUnaligned32 (
> > > - OUT UINT32 *Buffer,
> > > + OUT VOID *Buffer,
> > > IN UINT32 Value
> > > )
> > > {
> > > + UINT32 *Output = Buffer;
> > > +
> > > ASSERT (Buffer != NULL);
> > >
> > > - return *Buffer = Value;
> > > + return *Output = Value;
> > > }
> > >
> > > /**
> > > @@ -186,12 +198,14 @@ WriteUnaligned32 (
> > > UINT64
> > > EFIAPI
> > > ReadUnaligned64 (
> > > - IN CONST UINT64 *Buffer
> > > + IN CONST VOID *Buffer
> > > )
> > > {
> > > + CONST UINT64 *Input = Buffer;
> > > +
> > > ASSERT (Buffer != NULL);
> > >
> > > - return *Buffer;
> > > + return *Input;
> > > }
> > >
> > > /**
> > > @@ -212,11 +226,13 @@ ReadUnaligned64 (
> > > UINT64
> > > EFIAPI
> > > WriteUnaligned64 (
> > > - OUT UINT64 *Buffer,
> > > + OUT VOID *Buffer,
> > > IN UINT64 Value
> > > )
> > > {
> > > + UINT64 *Output = Buffer;
> > > +
> > > ASSERT (Buffer != NULL);
> > >
> > > - return *Buffer = Value;
> > > + return *Output = Value;
> > > }
> > > --
> > > 2.1.4
> >
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