Re: DEBUG() macros in DXE driver: can’t make it work in QEMU

[Laszlo Ersek <lersek@redhat.com>]

On 02/14/17 23:06, Nikolay Bodunov wrote:
> Thank you for the suggestions.
> 
> I tried to use them:
> 
>> (1) Please always terminate the debug message with a newline ("\n")
> Done. No changes. Of course, I usually do it, but in that case all I
> needed was to have any string on output. Sorry for bad programming style.
> 
>> (2) Please use DEBUG_ERROR as the symbolic constant for the error mask
> Done. I think you meant in DEBUG() macros. No changes. Question about
> style, too.
> 
>> (3) DEBUG output from OVMF is by default not written to the serial port
> and
>> add -D DEBUG_ON_SERIAL_PORT
> Done. Recompiled OVMF with that option. I have now file "debug.log"
> 74415 bytes size that contains everything, include EFI Shell output, but
> except my debug messages
> 
> BTW, QEMU option "-debugcon file:debug.log -global
> isa-debugcon.iobase=0x402", recommended in OVMF README, did nothing -
> "debug.log was empty.

I think you have it mixed up a little. The README covers this, but it
might not be very approachable.

So: if you do *not* specify -D DEBUG_ON_SERIAL_PORT when you build OVMF,
then the debug messages will go to the QEMU debug port. And, if you want
to capture the QEMU debug port in a file, then you should pass
"-debugcon file:debug.log -global isa-debugcon.iobase=0x402" on the QEMU
command line.

Conversely, if you *do* specify -D DEBUG_ON_SERIAL_PORT when building
OVMF, then debug messages will go to the emulated serial port (and
they'll be intermixed with any serial terminal output, which is why this
setting is not the default). In this case, the -debugcon etc. settings
are useless, because the QEMU debug port is not used.

> 
> Based on results, I suppose that the problem is not on OVMF side.
> Hope you propose something else to try. Maybe I got something in a wrong
> way.

Are you sure that when you build your module, it links against the right
DebugLib instance?

If you pass -D DEBUG_ON_SERIAL_PORT when you build OVMF, that switches
the library class resolution for DebugLib from the default

  DebugLib|OvmfPkg/Library/PlatformDebugLibIoPort/PlatformDebugLibIoPort.inf

to

  DebugLib|MdePkg/Library/BaseDebugLibSerialPort/BaseDebugLibSerialPort.inf

for all module types. However, for this library class resolution to take
effect for your own module as well, you should either add your module
directly to OvmfPkg*.dsc, or else implement the exact same library
resolution for your module (in the external DSC file where your module
is listed). Library instances are statically linked into driver and
application modules in edk2.

In other words, if you *separately* build your driver or application
module with a DebugLib class resolution that points to, say, the

  MdePkg/Library/BaseDebugLibNull/BaseDebugLibNull.inf

library instance, then you won't see any DEBUG output whatsoever,
regardless of how you build OVMF (*separately* again), and how you
configure QEMU. At that point, a "null" DebugLib instance will have been
statically linked into your driver or application, and it will produce
no output.

Thanks
Laszlo

> 
> Nikolay
> 
> 2017-02-14 21:28 GMT+03:00 Kinney, Michael D <michael.d.kinney@intel.com
> <mailto:michael.d.kinney@intel.com>>:
> 
>     If you prefer debug messages on a serial port, you can
>     add -D DEBUG_ON_SERIAL_PORT
> 
>     Mike
> 
>     > -----Original Message-----
>     > From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org
>     <mailto:edk2-devel-bounces@lists.01.org>] On Behalf Of Laszlo Ersek
>     > Sent: Tuesday, February 14, 2017 10:17 AM
>     > To: Nikolay Bodunov <nikolay.bodunov@gmail.com
>     <mailto:nikolay.bodunov@gmail.com>>; edk2-devel@ml01.01.org
>     <mailto:edk2-devel@ml01.01.org>
>     > Subject: Re: [edk2] DEBUG() macros in DXE driver: can’t make it
>     work in QEMU
>     >
>     > Hi Nikolay,
>     >
>     > On 02/14/17 18:55, Nikolay Bodunov wrote:
>     > > Hello
>     > >
>     > >
>     > > I compiled DXE Driver, in DEBUG_GCC49 mode, but I can’t print
>     any debug
>     > > message.
>     > > DEBUG((-1, “Print test”))  does nothing.  Exactly as
>     > > DebugPrint(EFI_D_ERROR, “Print Test);
>     >
>     > (1) Please always terminate the debug message with a newline
>     ("\n") once
>     > you are done with it. (It's okay to format a single message with
>     several
>     > DEBUG calls of course, and terminate only the last DEBUG with a
>     newline.)
>     >
>     > (2) Please use DEBUG_ERROR as the symbolic constant for the error
>     mask.
>     >
>     > >
>     > > However, I see “Print Test” string in my *.efi binary.
>     > > I use QEMU + OMVF (OVMF was also recompliled in DEBUG_GCC49
>     mode, to be
>     > > sure). Serial port output is redirected to a file:
>     > > qemu-system-x86_64 -L . --bios /…/FV/OVMF.fd -hda hdd.img -serial
>     > > file:./serial_file
>     >
>     > (3) DEBUG output from OVMF is by default not written to the serial
>     port,
>     > it is written to the QEMU debug port. Please consult
>     OvmfPkg/README for
>     > specifics, namely under "Capturing OVMF debug messages on qemu".
>     >
>     > Hope this helps,
>     > Laszlo
>     >
>     > >
>     > > All I see in output file is EFI shell output messages, include
>     one that my
>     > > driver was succesfully loaded. But no messages from DEBUG().
>     > >
>     > >
>     > > My conditions:
>     > >
>     > > MODULE_TYPE    = DXE_DRIVER
>     > >
>     > >
>     > > Debug Print Library:
>     > >
>     > >
>     DebugLib|MdePkg/Library/BaseDebugLibSerialPort/BaseDebugLibSerialPort.inf
>     > >
>     > > (BaseDebugLibNull.inf is commented, of course)
>     > >
>     > >
>     > > DebugPrintEnabled() returns TRUE
>     > >
>     > >
>     > > I also tried to set some key options manually in MdeModulePkg.dsc
>     > > afterwards, but result didn’t change:
>     > >
>     > >
>     > > [Components]
>     > >
>     > >
>     > >   MdeModulePkg/CrScreenshotDxe/CrScreenshotDxe.inf  {
>     > >
>     > >
>     > >     <PcdsFixedAtBuild>
>     > >
>     > >
>     > >
>     gEfiMdePkgTokenSpaceGuid.gEfiMdePkgTokenSpaceGuid.PcdDebugPrintErrorLevel|0x07
>     > >
>     > >       gEfiMdePkgTokenSpaceGuid.PcdDebugPropertyMask|0x2F
>     > >
>     > >       gEfiMdePkgTokenSpaceGuid.PcdDebugPrintErrorLevel|0x80000042
>     > >
>     > >
>     > >
>     > >    <LibraryClasses>
>     > >
>     > >
>     > >
>     DebugLib|MdePkg/Library/BaseDebugLibSerialPort/BaseDebugLibSerialPort.inf
>     > >
>     > >
>     > >    <BuildOptions>
>     > >
>     > >       GCC:*_*_*_CC_FLAGS             = -UMDEPKG_NDEBUG
>     > >
>     > > }
>     > >
>     > >
>     > > Code (I used it as a base):
>     https://github.com/LongSoft/CrScreenshotDxe
>     <https://github.com/LongSoft/CrScreenshotDxe>
>     > >
>     > > Where I got wrong and what else could I try to make it work?
>     > >
>     >
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> 
> 
> 
> 
> -- 
> With best regards,
> Nikolay Bodunov