How to get BBS_BBS_DEVICE_PATH from BOOTXXXX variable

How to get BBS_BBS_DEVICE_PATH from BOOTXXXX variable

[Saqib Khan]

Hi,
I can not find structure of BOOTXXXX variable, Can any one help how to
extract device path from BOOTXXXX variable.

here is code  i have attempt (rEFind)

*UINT8 *Value;*












*Status = gRT->GetVariable ((CHAR16 *)Name, &gEfiGlobalVariableGuid, NULL,
&BootVariableSize, Value);        //print attribute        /*Check if
device boot variable is legacy*/                  Ptr = Value;         Ptr
+= sizeof (UINT32);         DevPathLen = *(UINT16 *) Ptr;         Ptr +=
sizeof (UINT16);         Ptr += StrSize ((UINT16 *) Ptr);
 DevicePath = (EFI_DEVICE_PATH_PROTOCOL *) Ptr;          Print (L"Paths:
%s\n",ConvertDevicePathToText (DevicePath,TRUE,TRUE));*


-- 
Regards
Saqib

Re: How to get BBS_BBS_DEVICE_PATH from BOOTXXXX variable

[Laszlo Ersek]

On 10/18/16 19:18, Saqib Khan wrote:
> Hi,
> I can not find structure of BOOTXXXX variable, Can any one help how to
> extract device path from BOOTXXXX variable.

In UEFI-related questions, the UEFI specification has a fair chance to
provide useful information.

Please refer to "3.1.3 Load Options" in the UEFI v2.6 spec, available
for download from <http://www.uefi.org/specifications>.

Locating the matching structure definition in the edk2 tree is left as
an exercise to the reader ;)

Laszlo

Re: How to get BBS_BBS_DEVICE_PATH from BOOTXXXX variable

[Andrew Fish]

> On Oct 18, 2016, at 10:40 AM, Laszlo Ersek <lersek@redhat.com> wrote:
> 
> On 10/18/16 19:18, Saqib Khan wrote:
>> Hi,
>> I can not find structure of BOOTXXXX variable, Can any one help how to
>> extract device path from BOOTXXXX variable.
> 
> In UEFI-related questions, the UEFI specification has a fair chance to
> provide useful information.
> 
> Please refer to "3.1.3 Load Options" in the UEFI v2.6 spec, available
> for download from <http://www.uefi.org/specifications>.
> 
> Locating the matching structure definition in the edk2 tree is left as
> an exercise to the reader ;)
> 

Chapter 3 Boot Manager. 

The structure is EFI_LOAD_OPTION but some of the fields are variable length so you have to do math to figure stuff out. 

Thanks,

Andrew Fish


> Laszlo
> 
> _______________________________________________
> edk2-devel mailing list
> edk2-devel@lists.01.org
> https://lists.01.org/mailman/listinfo/edk2-devel

Re: How to get BBS_BBS_DEVICE_PATH from BOOTXXXX variable

[Saqib Khan]

Hi, so i have parsed the structure as follow :







*BootVariable = mGetVariable(Name, &gEfiGlobalVariableGuid,
&BootVariableSize, NULL);LDAttr = BootVariable[0];FilePathListLength =
(BootVariable+2);Ptr = (BootVariable+3); // for description *



*for FilePathList[] Ptr+= StrSize((CHAR16 *)Ptr);         CopyMem (Ptr,
DevicePath, *FilePathListLength);*


I am able to get LDAttr ,FilePathListLength and description but

when i try to check DevicePath->Type it always return 0x01( Hardware Device
Path) for each device .


I have hard drive with legacy OS(BBS_DEVICE_PATH). So it should not always
return 0x01 .What i am doing wrong in parsing ?

Thanks

On Tue, Oct 18, 2016 at 11:37 PM, Andrew Fish <afish@apple.com> wrote:

>
> > On Oct 18, 2016, at 10:40 AM, Laszlo Ersek <lersek@redhat.com> wrote:
> >
> > On 10/18/16 19:18, Saqib Khan wrote:
> >> Hi,
> >> I can not find structure of BOOTXXXX variable, Can any one help how to
> >> extract device path from BOOTXXXX variable.
> >
> > In UEFI-related questions, the UEFI specification has a fair chance to
> > provide useful information.
> >
> > Please refer to "3.1.3 Load Options" in the UEFI v2.6 spec, available
> > for download from <http://www.uefi.org/specifications>.
> >
> > Locating the matching structure definition in the edk2 tree is left as
> > an exercise to the reader ;)
> >
>
> Chapter 3 Boot Manager.
>
> The structure is EFI_LOAD_OPTION but some of the fields are variable
> length so you have to do math to figure stuff out.
>
> Thanks,
>
> Andrew Fish
>
>
> > Laszlo
> >
> > _______________________________________________
> > edk2-devel mailing list
> > edk2-devel@lists.01.org
> > https://lists.01.org/mailman/listinfo/edk2-devel
>
>


-- 
Regards
Saqib Ahmed Khanzada

Re: How to get BBS_BBS_DEVICE_PATH from BOOTXXXX variable

[Carsey, Jaben]

Have you examined the BCFG command in the UEFI Shell?  

It does this exact behavior and the code is at: ShellPkg\Library\UefiBcfgCommandLib\bcfg.c.

-Jaben

> -----Original Message-----
> From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf Of
> Saqib Khan
> Sent: Wednesday, October 19, 2016 11:18 AM
> To: Andrew Fish <afish@apple.com>
> Cc: edk2-devel@ml01.01.org; Laszlo Ersek <lersek@redhat.com>
> Subject: Re: [edk2] How to get BBS_BBS_DEVICE_PATH from BOOTXXXX
> variable
> 
> Hi, so i have parsed the structure as follow :
> 
> 
> 
> 
> 
> 
> 
> *BootVariable = mGetVariable(Name, &gEfiGlobalVariableGuid,
> &BootVariableSize, NULL);LDAttr = BootVariable[0];FilePathListLength =
> (BootVariable+2);Ptr = (BootVariable+3); // for description *
> 
> 
> 
> *for FilePathList[] Ptr+= StrSize((CHAR16 *)Ptr);         CopyMem (Ptr,
> DevicePath, *FilePathListLength);*
> 
> 
> I am able to get LDAttr ,FilePathListLength and description but
> 
> when i try to check DevicePath->Type it always return 0x01( Hardware Device
> Path) for each device .
> 
> 
> I have hard drive with legacy OS(BBS_DEVICE_PATH). So it should not always
> return 0x01 .What i am doing wrong in parsing ?
> 
> Thanks
> 
> On Tue, Oct 18, 2016 at 11:37 PM, Andrew Fish <afish@apple.com> wrote:
> 
> >
> > > On Oct 18, 2016, at 10:40 AM, Laszlo Ersek <lersek@redhat.com> wrote:
> > >
> > > On 10/18/16 19:18, Saqib Khan wrote:
> > >> Hi,
> > >> I can not find structure of BOOTXXXX variable, Can any one help how to
> > >> extract device path from BOOTXXXX variable.
> > >
> > > In UEFI-related questions, the UEFI specification has a fair chance to
> > > provide useful information.
> > >
> > > Please refer to "3.1.3 Load Options" in the UEFI v2.6 spec, available
> > > for download from <http://www.uefi.org/specifications>.
> > >
> > > Locating the matching structure definition in the edk2 tree is left as
> > > an exercise to the reader ;)
> > >
> >
> > Chapter 3 Boot Manager.
> >
> > The structure is EFI_LOAD_OPTION but some of the fields are variable
> > length so you have to do math to figure stuff out.
> >
> > Thanks,
> >
> > Andrew Fish
> >
> >
> > > Laszlo
> > >
> > > _______________________________________________
> > > edk2-devel mailing list
> > > edk2-devel@lists.01.org
> > > https://lists.01.org/mailman/listinfo/edk2-devel
> >
> >
> 
> 
> --
> Regards
> Saqib Ahmed Khanzada
> _______________________________________________
> edk2-devel mailing list
> edk2-devel@lists.01.org
> https://lists.01.org/mailman/listinfo/edk2-devel

Re: How to get BBS_BBS_DEVICE_PATH from BOOTXXXX variable

[Saqib Khan]

*BootVariable = mGetVariable(Name, &gEfiGlobalVariableGuid,
&BootVariableSize, NULL);Ptr = (BootVariable+3);         Print(L"
%s",(CHAR16 *)(Ptr));         DevicePath =AllocateZeroPool
(*FilePathListLength)     ;         Ptr+= StrSize((CHAR16 *)Ptr);
 CopyMem (DevicePath, Ptr, *FilePathListLength);*
As Carsey suggested i used the same Math in order to get DevicePath but in
my case it is not working

As documentation this data structure is not aligned so i am assuming that
just after description there should be
FilePathList ,so if i CopyMem * (**FilePathListLength) bytes to DevicePath
i should get the right value but i am getting garbage.

On Thu, Oct 20, 2016 at 1:41 AM, Carsey, Jaben <jaben.carsey@intel.com>
wrote:

> Have you examined the BCFG command in the UEFI Shell?
>
> It does this exact behavior and the code is at: ShellPkg\Library\
> UefiBcfgCommandLib\bcfg.c.
>
> -Jaben
>
> > -----Original Message-----
> > From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf Of
> > Saqib Khan
> > Sent: Wednesday, October 19, 2016 11:18 AM
> > To: Andrew Fish <afish@apple.com>
> > Cc: edk2-devel@ml01.01.org; Laszlo Ersek <lersek@redhat.com>
> > Subject: Re: [edk2] How to get BBS_BBS_DEVICE_PATH from BOOTXXXX
> > variable
> >
> > Hi, so i have parsed the structure as follow :
> >
> >
> >
> >
> >
> >
> >
> > *BootVariable = mGetVariable(Name, &gEfiGlobalVariableGuid,
> > &BootVariableSize, NULL);LDAttr = BootVariable[0];FilePathListLength =
> > (BootVariable+2);Ptr = (BootVariable+3); // for description *
> >
> >
> >
> > *for FilePathList[] Ptr+= StrSize((CHAR16 *)Ptr);         CopyMem (Ptr,
> > DevicePath, *FilePathListLength);*
> >
> >
> > I am able to get LDAttr ,FilePathListLength and description but
> >
> > when i try to check DevicePath->Type it always return 0x01( Hardware
> Device
> > Path) for each device .
> >
> >
> > I have hard drive with legacy OS(BBS_DEVICE_PATH). So it should not
> always
> > return 0x01 .What i am doing wrong in parsing ?
> >
> > Thanks
> >
> > On Tue, Oct 18, 2016 at 11:37 PM, Andrew Fish <afish@apple.com> wrote:
> >
> > >
> > > > On Oct 18, 2016, at 10:40 AM, Laszlo Ersek <lersek@redhat.com>
> wrote:
> > > >
> > > > On 10/18/16 19:18, Saqib Khan wrote:
> > > >> Hi,
> > > >> I can not find structure of BOOTXXXX variable, Can any one help how
> to
> > > >> extract device path from BOOTXXXX variable.
> > > >
> > > > In UEFI-related questions, the UEFI specification has a fair chance
> to
> > > > provide useful information.
> > > >
> > > > Please refer to "3.1.3 Load Options" in the UEFI v2.6 spec, available
> > > > for download from <http://www.uefi.org/specifications>.
> > > >
> > > > Locating the matching structure definition in the edk2 tree is left
> as
> > > > an exercise to the reader ;)
> > > >
> > >
> > > Chapter 3 Boot Manager.
> > >
> > > The structure is EFI_LOAD_OPTION but some of the fields are variable
> > > length so you have to do math to figure stuff out.
> > >
> > > Thanks,
> > >
> > > Andrew Fish
> > >
> > >
> > > > Laszlo
> > > >
> > > > _______________________________________________
> > > > edk2-devel mailing list
> > > > edk2-devel@lists.01.org
> > > > https://lists.01.org/mailman/listinfo/edk2-devel
> > >
> > >
> >
> >
> > --
> > Regards
> > Saqib Ahmed Khanzada
> > _______________________________________________
> > edk2-devel mailing list
> > edk2-devel@lists.01.org
> > https://lists.01.org/mailman/listinfo/edk2-devel
>



-- 
Regards
Saqib Ahmed Khanzada

Re: How to get BBS_BBS_DEVICE_PATH from BOOTXXXX variable

[Carsey, Jaben]

Have you examined the structure EFI_LOAD_OPTION from UefiSpec.h?

I think that you are traversing the structure incorrectly.  I cannot be sure since I am not certain what this mGetVariable function does specifically.

I start by getting the correct size (BufferSize is zero at this first call):
    Status = gRT->GetVariable(
        VariableName,
        (EFI_GUID*)&gEfiGlobalVariableGuid,
        NULL,
        &BufferSize,
        Buffer);
    if (Status == EFI_BUFFER_TOO_SMALL) {
      Buffer = AllocateZeroPool(BufferSize);
      Status = gRT->GetVariable(
          VariableName,
          (EFI_GUID*)&gEfiGlobalVariableGuid,
          NULL,
          &BufferSize,
          Buffer);
    }

To parse the structure I divide it up using the structure.  I think your +3 may be causing lots of issues.

    LoadOption      = (EFI_LOAD_OPTION *)Buffer;
    Description     = (CHAR16*)(Buffer + sizeof (EFI_LOAD_OPTION));
    DescriptionSize = StrSize (Description);
    if (LoadOption->FilePathListLength != 0) {
      FilePathList = (UINT8 *)Description + DescriptionSize;
   }

After this we can calculate the location of optional data.
    OptionalDataOffset = sizeof *LoadOption + DescriptionSize +
                         LoadOption->FilePathListLength;
The optional data would be found at:
    Buffer + OptionalDataOffset

Note that all the pointer math is based on using UINT8* or the raw Buffer variable which is a UINT8*.  Otherwise the size in bytes will not work out.

-Jaben


From: Saqib Khan [mailto:saqib.khan2011@gmail.com]
Sent: Thursday, October 20, 2016 12:30 AM
To: Carsey, Jaben <jaben.carsey@intel.com>
Cc: Andrew Fish <afish@apple.com>; edk2-devel@ml01.01.org; Laszlo Ersek <lersek@redhat.com>
Subject: Re: [edk2] How to get BBS_BBS_DEVICE_PATH from BOOTXXXX variable
Importance: High

BootVariable = mGetVariable(Name, &gEfiGlobalVariableGuid, &BootVariableSize, NULL);
Ptr = (BootVariable+3);
         Print(L" %s",(CHAR16 *)(Ptr));
         DevicePath =AllocateZeroPool     (*FilePathListLength)     ;
         Ptr+= StrSize((CHAR16 *)Ptr);
         CopyMem (DevicePath, Ptr, *FilePathListLength);
As Carsey suggested i used the same Math in order to get DevicePath but in my case it is not working
As documentation this data structure is not aligned so i am assuming that just after description there should be
FilePathList ,so if i CopyMem (*FilePathListLength) bytes to DevicePath i should get the right value but i am getting garbage.

On Thu, Oct 20, 2016 at 1:41 AM, Carsey, Jaben <jaben.carsey@intel.com<mailto:jaben.carsey@intel.com>> wrote:
Have you examined the BCFG command in the UEFI Shell?

It does this exact behavior and the code is at: ShellPkg\Library\UefiBcfgCommandLib\bcfg.c.

-Jaben

> -----Original Message-----
> From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org<mailto:edk2-devel-bounces@lists.01.org>] On Behalf Of
> Saqib Khan
> Sent: Wednesday, October 19, 2016 11:18 AM
> To: Andrew Fish <afish@apple.com<mailto:afish@apple.com>>
> Cc: edk2-devel@ml01.01.org<mailto:edk2-devel@ml01.01.org>; Laszlo Ersek <lersek@redhat.com<mailto:lersek@redhat.com>>
> Subject: Re: [edk2] How to get BBS_BBS_DEVICE_PATH from BOOTXXXX
> variable
>
> Hi, so i have parsed the structure as follow :
>
>
>
>
>
>
>
> *BootVariable = mGetVariable(Name, &gEfiGlobalVariableGuid,
> &BootVariableSize, NULL);LDAttr = BootVariable[0];FilePathListLength =
> (BootVariable+2);Ptr = (BootVariable+3); // for description *
>
>
>
> *for FilePathList[] Ptr+= StrSize((CHAR16 *)Ptr);         CopyMem (Ptr,
> DevicePath, *FilePathListLength);*
>
>
> I am able to get LDAttr ,FilePathListLength and description but
>
> when i try to check DevicePath->Type it always return 0x01( Hardware Device
> Path) for each device .
>
>
> I have hard drive with legacy OS(BBS_DEVICE_PATH). So it should not always
> return 0x01 .What i am doing wrong in parsing ?
>
> Thanks
>
> On Tue, Oct 18, 2016 at 11:37 PM, Andrew Fish <afish@apple.com<mailto:afish@apple.com>> wrote:
>
> >
> > > On Oct 18, 2016, at 10:40 AM, Laszlo Ersek <lersek@redhat.com<mailto:lersek@redhat.com>> wrote:
> > >
> > > On 10/18/16 19:18, Saqib Khan wrote:
> > >> Hi,
> > >> I can not find structure of BOOTXXXX variable, Can any one help how to
> > >> extract device path from BOOTXXXX variable.
> > >
> > > In UEFI-related questions, the UEFI specification has a fair chance to
> > > provide useful information.
> > >
> > > Please refer to "3.1.3 Load Options" in the UEFI v2.6 spec, available
> > > for download from <http://www.uefi.org/specifications>.
> > >
> > > Locating the matching structure definition in the edk2 tree is left as
> > > an exercise to the reader ;)
> > >
> >
> > Chapter 3 Boot Manager.
> >
> > The structure is EFI_LOAD_OPTION but some of the fields are variable
> > length so you have to do math to figure stuff out.
> >
> > Thanks,
> >
> > Andrew Fish
> >
> >
> > > Laszlo
> > >
> > > _______________________________________________
> > > edk2-devel mailing list
> > > edk2-devel@lists.01.org<mailto:edk2-devel@lists.01.org>
> > > https://lists.01.org/mailman/listinfo/edk2-devel
> >
> >
>
>
> --
> Regards
> Saqib Ahmed Khanzada
> _______________________________________________
> edk2-devel mailing list
> edk2-devel@lists.01.org<mailto:edk2-devel@lists.01.org>
> https://lists.01.org/mailman/listinfo/edk2-devel



--
Regards
Saqib Ahmed Khanzada