Re: How to open a file by it's full path in UEFI

["Jarlstrom, Laurie" <laurie.jarlstrom@intel.com>]

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Keshava,
Attached Sample code  is an example that will open a file name passed through the command line using the Shell.


thanks,
Laurie
 
laurie.jarlstrom@intel.com

Intel SSG/STO/EBP
(503) 712-9395



-----Original Message-----
From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf Of GN Keshava
Sent: Tuesday, September 27, 2016 4:52 AM
To: Laszlo Ersek
Cc: edk2-devel@lists.01.org
Subject: Re: [edk2] How to open a file by it's full path in UEFI

Thank you Laszlo.

I'll check it out. :)

Thanks again.
Regards,
Keshava

On Tue, 27 Sep 2016 at 16:47 Laszlo Ersek <lersek@redhat.com> wrote:

> On 09/27/16 12:46, GN Keshava wrote:
> > Hi Laszlo,
> >
> > Thank you for the answer. It was helpful.
> >
> > Considering option #1, can you give some more details (a small 
> > example or any reference link would be helpful), how I can use Shell 
> > APIs in my C file (which will compile to my .efi app)?
>
> Hmmm, I don't have hands-on experience with this, but you might want 
> to try the ShellOpenFileByName() function, from 
> "ShellPkg/Include/Library/ShellLib.h".
>
> You can find examples for UEFI applications that use the Shell library
> with:
>
>   git grep -w ShellLib -- '*inf'
>
> or just grep the tree for ShellOpenFileByName().
>
> See also "AppPkg/ReadMe.txt".
>
> > Considering option #2, How I can find device path programatically 
> > from my C file?
>
> The EFI_SHELL_PROTOCOL.GetDevicePathFromMap() member function seems 
> relevant -- it is specified in the UEFI Shell spec --, but I would 
> definitely try ShellOpenFileByName() first.
>
> Thanks
> Laszlo
>
> > Thanks again for the help. :)
> > With regards,
> > Keshava
> >
> > On Tue, 27 Sep 2016 at 15:19 Laszlo Ersek <lersek@redhat.com 
> > <mailto:lersek@redhat.com>> wrote:
> >
> >     On 09/27/16 11:25, GN Keshava wrote:
> >     > Hi Laszlo,
> >     >
> >     > Thanks for the reply. I meant I have complete file path. I 
> > believe
> the
> >     > "device path" is different. Is it possible to obtain DevicePath
> >     using my
> >     > full file path?
> >
> >     The pathname you seem to have (as "complete") is specific to a given
> >     simple FS, so system-wide it cannot be considered complete 
> > (there
> can be
> >     multiple filesystems).
> >
> >     In your original email I missed that you started with "FS1:".
> Andrew's
> >     answer covers that case.
> >
> >     In summary, you can do three things:
> >     - have a pathname that starts with FSx: (which is a shell-specific
> >     mapping), and use Andrew's recommendation,
> >     - have a complete UEFI device path, and then use what I recommended,
> >     - have no information for selecting the filesystem (from the many
> >     possible), and use your current iteration.
> >
> >     Options #1 and #2 actually correspond to each other, considering
> >     "expressive power" / information content (as long as you are in the
> >     shell); please see the MAP shell command.
> >
> >     Thanks
> >     Laszlo
> >
> >     > On Tue, 27 Sep 2016 at 14:46 Laszlo Ersek <lersek@redhat.com
> >     <mailto:lersek@redhat.com>
> >     > <mailto:lersek@redhat.com <mailto:lersek@redhat.com>>> wrote:
> >     >
> >     >     On 09/27/16 11:03, GN Keshava wrote:
> >     >     > Hi all,
> >     >     >
> >     >     >
> >     >     > I'm trying to open a file from my UEFI application. The path
> of
> >     >     file is
> >     >     >
> >     >     > fs1:/myfolder/myfile.txt
> >     >     >
> >     >     > The code :
> >     >     >
> >     >     > efiStatus = bs->LocateHandleBuffer(ByProtocol,
> >     >     >                                    &sfspGuid,
> >     >     >                                    NULL,
> >     >     >                                    &handleCount,
> >     >     >                                    &handles);
> >     >     >
> >     >     > for (index = 0; index < (int)handleCount; ++ index)
> >     >     > {
> >     >     >     EFI_SIMPLE_FILE_SYSTEM_PROTOCOL* fs = NULL;
> >     >     >
> >     >     >     efiStatus = bs->HandleProtocol(
> >     >     >         handles[index],
> >     >     >         &sfspGuid,
> >     >     >         (void**)&fs);
> >     >     >
> >     >     >     EFI_FILE_PROTOCOL* root = NULL;
> >     >     >     ...
> >     >     >     efiStatus = fs->OpenVolume(fs, &root);
> >     >     >
> >     >     >     EFI_FILE_PROTOCOL* token = NULL;
> >     >     >
> >     >     >     efiStatus = root->Open(
> >     >     >         root,
> >     >     >         &token,
> >     >     >         L"myfolder\\myfile.txt",
> >     >     >         EFI_FILE_MODE_READ,
> >     >     >         EFI_FILE_READ_ONLY | EFI_FILE_HIDDEN |
> EFI_FILE_SYSTEM);
> >     >     > }
> >     >     >
> >     >     > But using this method, I can only go through all the file
> system
> >     >     handles
> >     >     > and open each volume and try opening my file.
> >     >     >
> >     >     > But I want to give full path to my file and open it in it's
> >     volume.
> >     >     >
> >     >     > How can I acheive this?
> >     >     > Thanks.
> >     >
> >     >     If you have a complete device path, you can use
> >     gBS->LocateDevicePath()
> >     >     with gEfiSimpleFileSystemProtocolGuid, to locate the handle
> >     with the
> >     >     most specific device path (--> the longest device path prefix)
> >     with the
> >     >     simple FS protocol installed on it. Then you can check if the
> >     remaining
> >     >     device path (returned by the service) consist of nothing but
> >     one File
> >     >     Path Media Device Path node. If so, you can open the simple FS
> >     protocol
> >     >     on the handle found, then use that to open the file by
> pathname.
> >     >
> >     >     Laszlo
> >     >
> >
>
>
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[-- Attachment #2: SFA.inf.txt --]
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#/** @file
#  Sample UEFI Application Reference EDKII Module
#
#  This is a simple shell application
#
#  Copyright (c) 2009, Intel Corporation.
#
#  All rights reserved. This program and the accompanying materials
#  are licensed and made available under the terms and conditions of the BSD License
#  which accompanies this distribution. The full text of the license may be found at
#  http://opensource.org/licenses/bsd-license.php
#  THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
#  WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
#
#
#**/

[Defines]
  INF_VERSION                    = 0x00010005
  BASE_NAME                      = SampleFileA
  FILE_GUID                      = 10C75C00-3052-4467-9ED8-7196CAAF610F
  MODULE_TYPE                    = UEFI_APPLICATION
  VERSION_STRING                 = 1.0
  ENTRY_POINT                    = UefiMain

#
# The following information is for reference only and not required by the build tools.
#
#  VALID_ARCHITECTURES           = IA32 X64 IPF EBC
#

[Sources]
  SampleFileA.c

[Packages]
  MdePkg/MdePkg.dec
  ShellPkg/ShellPkg.dec

[LibraryClasses]
  UefiApplicationEntryPoint
  UefiLib
  ShellLib
  
[Guids]

[Ppis]

[Protocols]

[FeaturePcd]

[Pcd]

[-- Attachment #3: SFA.c.txt --]
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/** @file
  This is a simple shell application

  Copyright (c) 2008, Intel Corporation                                                         
  All rights reserved. This program and the accompanying materials                          
  are licensed and made available under the terms and conditions of the BSD License         
  which accompanies this distribution.  The full text of the license may be found at        
  http://opensource.org/licenses/bsd-license.php                                            

  THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,                     
  WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.             

**/

#include <Base.h>
#include <Uefi.h>

#include <Library/DebugLib.h>

#include <Library/UefiApplicationEntryPoint.h>
#include <Library/UefiLib.h>
#include <Library/UefiBootServicesTableLib.h>

#include <Library/ShellLib.h>  // uses Shell globals gSP and gSPP
//#include <Protocol/EfiShellParameters.h>



/**
  as the real entry point for the application.

  @param[in] ImageHandle    The firmware allocated handle for the EFI image.  
  @param[in] SystemTable    A pointer to the EFI System Table.
  
  @retval EFI_SUCCESS       The entry point is executed successfully.
  @retval other             Some error occurs when executing this entry point.

**/
EFI_STATUS
EFIAPI
UefiMain (
  IN EFI_HANDLE        ImageHandle,
  IN EFI_SYSTEM_TABLE  *SystemTable
  )
{

    EFI_STATUS      Status;
    UINTN			Argc;
	CHAR16			**Argv;
    SHELL_FILE_HANDLE Handle;

	if (gSPP != NULL) {
      //
      // use shell 2.0 interface
      //
        Argc = gSPP->Argc;
        Argv = gSPP->Argv;

	}else { // error out if shell interface not supported NOTE only UEFI Shell 2.0 supported here
		Print(L"Argc / Argv not supported with this application on EFI Shell 1.0\n Please use UEFI Shell 2.0\n");
	    return (EFI_UNSUPPORTED);
	}

	if (Argc <= 1){
		Print(L"No file name to open\n");
		return (EFI_UNSUPPORTED);  //need to have at least one parameter
	}

	Print(L"File to open is: %s\n", Argv[1]);

	Status = gSP->OpenFileByName (Argv[1], &Handle, 
		EFI_FILE_MODE_READ | EFI_FILE_MODE_WRITE | EFI_FILE_MODE_CREATE);

	if (EFI_ERROR(Status)) {
		Print(L"\nFile Open did not work %s\n", Argv[1]);
		return (Status);
	}else{
        Print(L"\nFile Open worked %s\n", Argv[1]);
	    gSP->CloseFile(Handle);
	}

	return EFI_SUCCESS;
}