On Wed, Jul 06, 2011, Olivier Martin wrote:
> Anyway, these are the build instructions to build the Tianocore project
> (UEFI Open Source implementation) and to test on qEmu:
> http://edk2.svn.sourceforge.net/viewvc/edk2/trunk/edk2/BeagleBoardPkg/readme
> .txt?revision=11997
I had started following these, but ran into some issues with my setup;
I will try with the alternate build-next.sh approach too, to see
whether I get other issues or not.
The two classes of issues I ran into was:
a) variables being written to, but never read
b) conditions being always true
I indeed had to apply the patch you mention; what's the state of that
patch? Are these things which will get merged soonish? Without the
patch, my toolchain wouldn't be properly picked up (it'd try running
c:/program files/ stuff and calling a CS toolchain) and I had some
error conditions like '-(' in linker invocations due to missing '\'
escapes. These go away with the patch and my toolchain is picked up
and works.
I'm running Ubuntu oneiric (which will become 11.10) and the toolchain
I've used is our packaged Linaro GCC based cross-compiler
(arm-linux-gnueabi-gcc from the gcc-arm-linux-gnueabi package).
a) variables being written to, but never read
This is stuff like:
--- a/edk2/BaseTools/Source/C/EfiLdrImage/EfiLdrImage.c
+++ b/edk2/BaseTools/Source/C/EfiLdrImage/EfiLdrImage.c
@@ -181,7 +181,7 @@ Returns:
CHAR8* OutputFileName = NULL;
CHAR8* InputFileNames[MAX_PE_IMAGES + 1];
UINT8 InputFileCount = 0;
- BOOLEAN QuietFlag = FALSE;
+ //BOOLEAN QuietFlag = FALSE;
UINT64 DebugLevel = 0;
UINT64 VerboseLevel = 0;
EFI_STATUS Status = EFI_SUCCESS;
@@ -220,7 +220,7 @@ Returns:
}
if ((stricmp (argv[0], "-q") == 0) || (stricmp (argv[0], "--quiet") == 0)) {
- QuietFlag = TRUE;
+ //QuietFlag = TRUE;
argc --;
argv ++;
continue;
QuietFlag is never used (read), newer gccs detect this and report it as
a fatal warning by default (not sure where this warning is configured
as a fatal one, whether it's in UEFI or in the toolchain config).
There are many such cases, but some are a bit more worrying, like
variables holding the return values of fread of fwrite not being
checked:
--- a/edk2/BaseTools/Source/C/GenVtf/GenVtf.c
+++ b/edk2/BaseTools/Source/C/GenVtf/GenVtf.c
@@ -1141,7 +1141,7 @@ Returns:
EFI_STATUS Status;
UINT64 CompStartAddress;
UINT64 FileSize;
- UINT64 NumByteRead;
+ //UINT64 NumByteRead;
UINT64 NumAdjustByte;
UINT8 *Buffer;
FILE *Fp;
@@ -1189,7 +1189,7 @@ Returns:
//
// Read first 64 bytes of PAL header and use it to find version info
//
- NumByteRead = fread (Buffer, sizeof (UINT8), SIZE_OF_PAL_HEADER, Fp);
+ /* NumByteRead = */fread (Buffer, sizeof (UINT8), SIZE_OF_PAL_HEADER, Fp);
//
// PAL header contains the version info. Currently, we will use the header
@@ -1200,7 +1200,7 @@ Returns:
}
}
- NumByteRead = fread (Buffer, sizeof (UINT8), (UINTN) FileSize, Fp);
+ /* NumByteRead = */fread (Buffer, sizeof (UINT8), (UINTN) FileSize, Fp);
fclose (Fp);
//
I just quickly hacked the source to get it to build, but we should fix
the code to loop until all bytes have been read or to raise an error.
The last such cases is a conditional piece of code:
--- a/edk2/BaseTools/Source/C/LzmaCompress/Sdk/C/LzmaEnc.c
+++ b/edk2/BaseTools/Source/C/LzmaCompress/Sdk/C/LzmaEnc.c
@@ -1919,11 +1919,13 @@ static SRes LzmaEnc_CodeOneBlock(CLzmaEnc *p, Bool useLimits, UInt32 maxPackSize
static SRes LzmaEnc_Alloc(CLzmaEnc *p, UInt32 keepWindowSize, ISzAlloc *alloc, ISzAlloc *allocBig)
{
UInt32 beforeSize = kNumOpts;
+ #ifdef COMPRESS_MF_MT
Bool btMode;
+ #endif
if (!RangeEnc_Alloc(&p->rc, alloc))
return SZ_ERROR_MEM;
- btMode = (p->matchFinderBase.btMode != 0);
#ifdef COMPRESS_MF_MT
+ btMode = (p->matchFinderBase.btMode != 0);
p->mtMode = (p->multiThread && !p->fastMode && btMode);
#endif
b) conditions being always true
A bunch of asserts trigger a warning in newer GCCs, essentially the
ASSERT macros in question are doing multiple things:
- testing whether the object is null
- testing some other condition on the object, like some state being
correct
but the objects are guaranteed to never be null from GCC PoV, so it
raises a fatal warning; as a workaround I just commented the asserts
out, but I guess what we should do is review whether any of the
ASSERT_LOCKED() users has a chance of getting a NULL pointer, and
either drop the NULL check or replace the macro with two.
--- a/edk2/MdeModulePkg/Core/Dxe/Event/Event.c
+++ b/edk2/MdeModulePkg/Core/Dxe/Event/Event.c
@@ -225,7 +225,7 @@ CoreNotifyEvent (
//
// Event database must be locked
//
- ASSERT_LOCKED (&gEventQueueLock);
+ //ASSERT_LOCKED (&gEventQueueLock);
//
// If the event is queued somewhere, remove it
I got this for a bunch of ASSERT_LOCKED(),
ASSERT_PROTOCOL_ALREADY_INSTALLED(), and ASSERT_VOLUME_LOCKED()
These are all issues in edk2, except the ASSERT_VOLUME_LOCKED() macro
issue which is the only issue in FatPkg and only there.
A cleaner workaround would be to make this warnings non-fatal for now
for this toolchain, but the code should also be fixed not to trigger
them. What's the best way to address this? Is there some bug tracker
I should report these issues at?
To try the resulting image, I just did:
qemu-system-arm -mtdblock \
../Build/BeagleBoard/DEBUG_ARMGCC/FV/BeagleBoard_EFI_flashboot.fd \
-nographic -M beagle
which sent this on the serial port:
UART Enabled
Magic delay to disable watchdog timers properly.
ASSERT_EFI_ERROR (Status = Unsupported)
ASSERT /home/lool/git/edk2/edk2/edk2/EmbeddedPkg/Library/PrePiLib/PrePiLib.c(73): !EFI_ERROR (Status)
I didn't actually look into this issue yet.
I tried passing a barebox based SD image I had built earlier (see other
message) with -sd sd.img, but that didn't change the output.
--
Loïc Minier
Okay, minutes from the last meeting are posted to the wiki, and the
next meeting is scheduled for tomorrow, 3 hours earlier to accommodate
Jean in China (0600MDT, 0800EDT, 1200UTC). Email me if you want to
attend and I'll add you to the invite.
g.
On Thu, Jun 23, 2011 at 10:47 PM, Grant Likely
<grant.likely(a)secretlab.ca> wrote:
> Hi all,
>
> here are the notes from today's meeting. Please look over it an make
> sure all of it is okay by you for posting on the public wiki. If
> there is anything sensitive that should not be published, then let me
> know right away so that I can edit it out.
>
> Cheers,
> g.
>
>
>
> Meeting notes from ARM Boot Architecture Meeting, June 23, 2011
>
> https://wiki.linaro.org/OfficeofCTO/BootArchitecture/2011-06-23
>
> == Attendees ==
>
> Loïc Minier
> Grant Likely
> Olivier Martin
> Jean-Christophe PLAGNIOL-VILLARD
> Jon Masters
> Andrew Pickard
>
>
> == Minutes ==
>
> * Need to think about what do we actually care about and write it down
> * Should be careful to consider non-Linux OSes
> * Want to get to a standard ARM platform
>
> * Time to market also an important consideration
>
>
> Notes on process:
> - We are not a standards body - need to be agile and try to base on
> existing standards
> - We need to be congnisent of other operating systems and other architectures
>
> Other Topics (maybe to put on the backburner):
> * How to we boot multiple CPUs of heterogeneous architectures
> * How does the boot architecture define how to start other CPUs, and
> other scenarii like kexec or virtualization? security / secure boot
> also impact the boot architecture subtly
>
> Licensing: GPL might be a problem for some specific pieces of code,
> e.g. touching CPU initialization
> * Specifications should remain as abstract of the licensing as
> possible though
> * Eveything we discuss should be public and avaiable free of charge
>
> Bootloader consolidation: we agree that there wont be consolidation on
> a single bootloader, instead a variety of bootloaders have to be
> supported
>
> Skeleton of boot architecture plan at
> https://wiki.linaro.org/OfficeofCTO/BootArchitecture/
> * Not clear whether we want to specify UI though
>
> What's the output?
> * Standard?
> * Wiki page? web site?
> * Need to work dynamically in the beginning, then freeze a version 1
> or something of the recommendations
> * Deliverable of some kind at the August Linaro meeting
>
> Dealing with legacy?
> * Could provide old-world boot media chainloading into new-world boot
> architecture media
> * Hard to implement security architecture in this mode
> * Don't care about legacy beyond a point (why care with product lifecycles?)
>
> Another output is one or more reference implementation(s) which can be
> deployed in production (be it UEFI, Barebox or whatever)
>
> Need to make sure we document the things which are NOT covered in our
> outputs/documents
>
> Should add definitions for terms; particuarly in the case of secure
> boot terminology.
>
> Need to handle booting secondary "bootloaders" like GRUB. Need to
> handle bits beyond just kernel, including initramfs, and other data
> images that need to be loaded by the bootloader.
>
>
> Power Management & PM handoff to the kernel.
>
> Plan agenda ahead of calls and assign time slots
>
> Suggest having a whole day/half day to advance (bootstrap!) this effort
>
> Topics raised after meeting:
> Privacy: The goal is to have everything open and public, but anybody
> can request for a conversation on the mailing list to be kept private
> in the interest of open communication.
>
> Minimal "run time" service type of interface for example to allow
> second stage bootloader to retrieve "files". However, this should not
> be massive overkill.
>
>
>
>
> --
> Grant Likely, B.Sc., P.Eng.
> Secret Lab Technologies Ltd.
>
--
Grant Likely, B.Sc., P.Eng.
Secret Lab Technologies Ltd.
On Wed, Jul 06, 2011, Olivier Martin wrote:
> UEFI Device Path
> ----------------
> UEFI has the concept of 'Device Path'. Every hardware devices supported by
> the UEFI firmware on the platform have a representation that defined the
> hardware path to access to this device and their properties.
I had a couple of questions on this:
* is the definition ARM specific or across all arches?
* is there a registry of GUID and allowed interfaces?
--
Loïc Minier
Hi,
one of the big issue on the device tree will be to update it at
runtime from the bootloader
As example the same board have 2 version with only one difference the
Main Oscilator. So to support it easly without having 2 DT will want
to update the default DT with the proper Osc value from the
bootlaoder.
But as the bootloader will not be able to be udpate in the futur on
production board, we will have to never change to format of the DT
otherwise the bootloder will not be able to work on never kernel.
This is one of issue that nearly all of the PowerPC kernel dev meet
ofen with the couple u-boot + kernel + DT
To avoid this we may use a script to update the DT and then specify
how we get the information from the bootloader. So in this case, the
script we will manage the dependency of the current format version of
the DT.
Best Regards,
J.
HI,
Barebox flow basecly the linux kernel architecture
We use as linux a file system (devfs) to manage the device
such as NOR, NAND, SPI Flash, Memory, phy, SD etc...
As have a pseudo POSIX API to implement command application
such as ls, rm, mount, boot etc...
You can see barebox as "Small Linux like" bootlader
To extend it's fonctionality at runtime we use modules (same as in the
kernel).
We do not support yet ABI Application
With start from anywhere and they relocate our self at the right
addres in DDR after have init the soc and the board. Which include the
DDR.
After we use the initcall to init:
1: the core
Usualy clock and pio
2: console
uart
3: core device
using the device / driver model of the kernel
4: Filesystem
register filesytem
5: device
using the device / driver model of the kernel
as Frambuffer, and other
Then we mount a ramfs and devfs and execute a script /env/bin/init
all the boot sequence is manage by script based on Hush from busybox
we have a default scripting implementation to boot but you are free to
manage it how you want
we an boot from any media and from tftp, nfs with uImage or zImage or
Image
You can manage your boot loader configuration and boot from via a Menu
which can be manage in C or in shell
Over uart and soon over Framebuffer
Best Regards,
J.
I have tried tonight on my personal computer with the latest revision of Tianocore (rev1199).
Actually, there is two versions of the BeagleBoard UFEI upstream. There is the original version.
And the version we are working on which reuses most of the framework we have introduces for our development platform to avoid code duplication and flexibilty.
This is the version I have tested, to build it you must use './build-next.sh' instead of './build.sh'
Unfortunately, there are two patches you will need to apply. These patches are pending and wait to be approved by the maintainers of their respective packages.
One of the patch in the source tree and the other one is attached to this email.
Configuration:
--------------
- ARM GCC CodeSourcery arm-none-eabi-2010q3
- qEmu-linaro:
commit 2d601b5fb663bb2876b85bec255d73bba01e38e6
Author: Peter Maydell <peter.maydell(a)linaro.org>
Date: Wed Jun 15 15:08:48 2011 +0000
- Tianocore EDK2: revision 11999
Build process:
--------------
svn co https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2 edk2 --username guest -r 11999
cd edk2
svn co https://edk2-fatdriver2.svn.sourceforge.net/svnroot/edk2-fatdriver2/trunk/F… FatPkg --username guest
patch -p1 < ArmPlatformPkg/Documentation/patches/BaseTools-Pending-Patches.patch
patch -p1 < 0001-MdeModulePkg-DxeCore-Fix-the-loop-to-find-the-highes.patch
cd BeagleBoardPkg
I add to fix 2 easy warnings to make it build
./build-next.sh RELEASE
To test on qEmu:
----------------
./qemu-system-arm -M beagle -mtdblock ~/dev/edk2/Build/BeagleBoard/RELEASE_ARMGCC/FV/BeagleBoard_EFI_flashboot.fd -serial stdio -sd ~/dev/linaro-image-tools-0.4.8/beagle_sd.img
Log: starting an ATAG kernel from UEFI (after editing its filepath):
------------------------------------------------------------------------------
VNC server running on `127.0.0.1:5900'
The default boot selection will start in 8 seconds
[1] Linux from SD
[2] EBL
[3] Boot Manager
Start: 1
ERROR: Did not find Linux kernel.
[1] Linux from SD
[2] EBL
[3] Boot Manager
Start: 3
[1] Add Boot Device Entry
[2] Update Boot Device Entry
[3] Remove Boot Device Entry
[4] Return to main menu
Choice: 2
[1] Linux from SD
Update entry: 1
File path of the EFI Application or the kernel: zImage-atag
Has FDT support? [y/n] n
Arguments to pass to the binary:
Description for this new Entry: Linux from SD
[1] Add Boot Device Entry
[2] Update Boot Device Entry
[3] Remove Boot Device Entry
[4] Return to main menu
Choice: 4
[1] Linux from SD
[2] EBL
[3] Boot Manager
Start: 1
PEI 160 ms
DXE 622 ms
BDS 22922 ms
BDS 1418980260529 ms
Total Time = 1418980284234 ms
Uncompressing Linux... done, booting the kernel.
[ 0.000000] Linux version 2.6.38.7 (olivier@olivier-laptop) (gcc version 4.5.1 (Sourcery G++ Lite 2010.09-51) ) #1 Sun Jul 3 15:42:26 BST 2011
[ 0.000000] CPU: ARMv7 Processor [412fc083] revision 3 (ARMv7), cr=10c53c7f
[ 0.000000] CPU: VIPT nonaliasing data cache, VIPT nonaliasing instruction cache
[ 0.000000] Machine: OMAP3 Beagle Board
[ 0.000000] Reserving 33554432 bytes SDRAM for VRAM
[ 0.000000] Memory policy: ECC disabled, Data cache writeback
[ 0.000000] OMAP3430/3530 ES3.1 (iva sgx neon isp )
[ 0.000000] SRAM: Mapped pa 0x40200000 to va 0xfe400000 size: 0x10000
[ 0.000000] Clocking rate (Crystal/Core/MPU): 26.0/332/500 MHz
[ 0.000000] Reprogramming SDRC clock to 332000000 Hz
[ 0.000000] Built 1 zonelists in Zone order, mobility grouping on. Total pages: 24320
[ 0.000000] Kernel command line: root=/dev/mmcblk0p2 rootwait console=ttyO2,115200
[ 0.000000] PID hash table entries: 512 (order: -1, 2048 bytes)
[ 0.000000] Dentry cache hash table entries: 16384 (order: 4, 65536 bytes)
[ 0.000000] Inode-cache hash table entries: 8192 (order: 3, 32768 bytes)
[ 0.000000] Memory: 96MB = 96MB total
(...)
Log: Boot from a FDT kernel added to the Boot Menu:
-----------------------------------------------------------------
UEFI firmware built at 23:09:40 on Jul 6 2011
omap_badwidth_read32: 32-bit register 0x00000000
The default boot selection will start in 8 seconds
[1] Linux from SD
[2] EBL
[3] Boot Manager
Start: 3
[1] Add Boot Device Entry
[2] Update Boot Device Entry
[3] Remove Boot Device Entry
[4] Return to main menu
Choice: 1
[1] SemihostFs (0 MB)
[2] boot (51 MB)
[3] VenHw(4D00EF14-C4E0-426B-81B7-30A00A14AAD6)
Select the Boot Device: 2
File path of the EFI Application or the kernel: zImage-fdt
Has FDT support? [y/n] y
Arguments to pass to the binary:
Description for this new Entry: FDT Kernel from SD
[1] Add Boot Device Entry
[2] Update Boot Device Entry
[3] Remove Boot Device Entry
[4] Return to main menu
Choice: 4
[1] Linux from SD
[2] FDT Kernel from SD
[3] EBL
[4] Boot Manager
Start: 2
PEI 149 ms
DXE 609 ms
BDS 222 ms
Total Time = 981 ms
omap2_inth_read: Bad register 0x00000020
[ 0.000000] Linux version 2.6.39.1 (cosgor01@cam-vm-424) (gcc version 4.5.1 (Sourcery G++ Lite 2010.09-51) ) #2 SMP Thu Jun 30 18:55:24 BST 2011
[ 0.000000] CPU: ARMv7 Processor [412fc083] revision 3 (ARMv7), cr=10c53c7f
[ 0.000000] CPU: VIPT nonaliasing data cache, VIPT nonaliasing instruction cache
[ 0.000000] Machine: OMAP3 Beagle Board, model: TI OMAP3 BeagleBoard
[ 0.000000] Memory policy: ECC disabled, Data cache writeback
[ 0.000000] OMAP3430/3530 ES3.1 (iva sgx neon isp )
[ 0.000000] SRAM: Mapped pa 0x40200000 to va 0xfe400000 size: 0x10000
[ 0.000000] Clocking rate (Crystal/Core/MPU): 26.0/332/500 MHz
[ 0.000000] Reprogramming SDRC clock to 332000000 Hz
[ 0.000000] PERCPU: Embedded 7 pages/cpu @c0cc7000 s8160 r8192 d12320 u32768
[ 0.000000] Built 1 zonelists in Zone order, mobility grouping on. Total pages: 32512
[ 0.000000] Kernel command line: root=/dev/mmcblk0p2 rootwait console=ttyO2,115200n8
[ 0.000000] PID hash table entries: 512 (order: -1, 2048 bytes)
[ 0.000000] Dentry cache hash table entries: 16384 (order: 4, 65536 bytes)
[ 0.000000] Inode-cache hash table entries: 8192 (order: 3, 32768 bytes)
(...)
-- IMPORTANT NOTICE: The contents of this email and any attachments are confidential and may also be privileged. If you are not the intended recipient, please notify the sender immediately and do not disclose the contents to any other person, use it for any purpose, or store or copy the information in any medium. Thank you.
To be frank, I spent most of my time since the last meeting to get Tianocore
working on qEmu.
Unfortunately, I have not been able to reproduce a consistent stable
firmware on qEmu.
It seems to work fine on my computer at home. I can boot Linux with ATAG
support or FDT support from UEFI on qEmu.
Booting UEFI from NOR Flash works. I also successfully 'hacked' a SD card
created with the linaro-media-create to replace u-boot by UEFI to get the
following boot stage ROM -> x-loader -> UEFI -> Linux.
I am using ARM GCC with the latest qEmu-linaro tree.
But on my machines at work with the same configuration, qEmu crashes during
the UEFI boot up with a 'Segmentation Fault'. It is the first time I work
with qEmu, I do not know if an 'Exception Fault' could be expected in case
of bug in the emulated binary or a problem in qEmu itself. I have not enough
element yet to report the issue to the qEmu team.
Anyway, these are the build instructions to build the Tianocore project
(UEFI Open Source implementation) and to test on qEmu:
http://edk2.svn.sourceforge.net/viewvc/edk2/trunk/edk2/BeagleBoardPkg/readme
.txt?revision=11997
Olivier
I forgot to mention but Tianocore and other UEFI Open Source projects have implemented shells for UEFI firmwares.
Some people are even working on porting Python to UEFI.
Feel free to ask questions or clarifications about this overview.
Mainly if you had thoughts about the way UEFI works which does not correspond to the big picture I gave.
Olivier
-----Original Message-----
From: boot-architecture-bounces(a)lists.linaro.org [mailto:boot-architecture-bounces@lists.linaro.org] On Behalf Of Olivier Martin
Sent: 06 July 2011 20:29
To: boot-architecture(a)lists.linaro.org
Subject: UEFI Overview
This email describes the way UEFI Tianocore implementation works. I limit
the scope to the UEFI drivers and the 'boot manager'. The implementation and
the platform specific bits are skipped.
Boot sequence:
--------------
1) After the platform modules (part of the PI (Platform Initialization)
phase) have finished the bringup initialization, the DXE (Driver Execution
Environment) Core is loaded.
2) The DXE core scans the different firmwares available on the platform and
calls the entrypoint of all the drivers that are expected to start (either
they request to be initialized during this sequence or they have their
dependencies solved).
Following the recommendation of the UEFI specification, the drivers should
do not touch the hardware controllers during this phase. They should only
declares their protocols (UEFI name for 'interfaces') to the DXE core.
3) Once all the drivers are dispatched, the DXE core passes its control to
the driver that exports the Boot Device Selection (BDS) interface.
This BDS driver should implement the 'Boot Manager' of the UEFI firmware
defined by the Chapter 3 of the UEFI spec.
This chapter defines non volatile variables that define among other things:
- The Boot Device entries ('Boot###' variables) (Name, location of the OS
loader, arguments) and their order ('BootOrder' variable)
- The devices responsible for the Console Input/Output
- The 'Timeout' before the BDS starts the default boot selection
- if defined, 'BootNext' defines the OS loader/EFI application to start the
next boot only (the variable is erased at the next boot)
4) Following the non variables values, the BDS will either automatically
starts the boot device (case 'BootNext' is defined or 'TimeOut' reached 0)
or displays the boot menu (with the Boot Device entries defined by
'Boot###' listed in the order defined by 'BootOrder'). Then the user chooses
in this menu which entry he/she wants to start.
5) With our implementation of the Boot Manager, we currently defines 3 types
of boot devices. The boot device can be either an EFI application (eg: an OS
loader) or a ATAG or FDT Linux kernel image. In case the BDS starts a Linux
kernel images, our BDS will automatically fills the required ATAG or loads
the Device Tree blob.
Note: One of our partner has been asking us to provide a reference EFI
Application to boot Linux. It is expecting some platforms will have their
own BDS and will use an EFI application to load the Linux kernel.
Actually, we are waiting the output of the Boot Architecture 'forum' to
provide such 'reference' EFI application.
UEFI Device Path
----------------
UEFI has the concept of 'Device Path'. Every hardware devices supported by
the UEFI firmware on the platform have a representation that defined the
hardware path to access to this device and their properties.
Some examples:
# Device path for a kernel on PCI SATA Hard Drive:
PciRoot(0)/Pci(0|0)/Pci(0|0)/Pci(5|0)/Pci(0|0)/Sata(0,0,0)/HD(2,MBR,0x000767
30,0x1F21BF,0x1F21BF)\boot\zImage
- PciRoot(0) define the first PCI Root complex.
- PCI(5|0) = PCI controller with Device = 5 and Function = 0
- HD(Partition,Type,Signature,Start, Size) = hard disk partition
- \boot\zImage : filepath on the partition
# Device path for a Linux kernel on the first partition of the SD card:
VenHw(B615F1F5-5088-43CD-809C-A16E52487D00)/HD(1,MBR,0x00000000,0x3F,0x19FC0
)/zImage
- VenHw(guid) is used when the device path node is not defined by the UEFI
specification (generally memory mapped controllers)
The Device Path allows to describe hardware devices or media even if they
have been initialized. When hardware drivers are started they can declare
the device path(s) of the hardware they support.
The advantage is if we do not need some specific hardwares during the UEFI
boot up, we could skip their initialization in UEFI.
This device path complexity can be hidden by the Boot Manager. We have
implemented our own interactive boot menu to help us to define the boot
devices.
_______________________________________________
boot-architecture mailing list
boot-architecture(a)lists.linaro.org
http://lists.linaro.org/mailman/listinfo/boot-architecture
-- IMPORTANT NOTICE: The contents of this email and any attachments are confidential and may also be privileged. If you are not the intended recipient, please notify the sender immediately and do not disclose the contents to any other person, use it for any purpose, or store or copy the information in any medium. Thank you.
This email describes the way UEFI Tianocore implementation works. I limit
the scope to the UEFI drivers and the 'boot manager'. The implementation and
the platform specific bits are skipped.
Boot sequence:
--------------
1) After the platform modules (part of the PI (Platform Initialization)
phase) have finished the bringup initialization, the DXE (Driver Execution
Environment) Core is loaded.
2) The DXE core scans the different firmwares available on the platform and
calls the entrypoint of all the drivers that are expected to start (either
they request to be initialized during this sequence or they have their
dependencies solved).
Following the recommendation of the UEFI specification, the drivers should
do not touch the hardware controllers during this phase. They should only
declares their protocols (UEFI name for 'interfaces') to the DXE core.
3) Once all the drivers are dispatched, the DXE core passes its control to
the driver that exports the Boot Device Selection (BDS) interface.
This BDS driver should implement the 'Boot Manager' of the UEFI firmware
defined by the Chapter 3 of the UEFI spec.
This chapter defines non volatile variables that define among other things:
- The Boot Device entries ('Boot###' variables) (Name, location of the OS
loader, arguments) and their order ('BootOrder' variable)
- The devices responsible for the Console Input/Output
- The 'Timeout' before the BDS starts the default boot selection
- if defined, 'BootNext' defines the OS loader/EFI application to start the
next boot only (the variable is erased at the next boot)
4) Following the non variables values, the BDS will either automatically
starts the boot device (case 'BootNext' is defined or 'TimeOut' reached 0)
or displays the boot menu (with the Boot Device entries defined by
'Boot###' listed in the order defined by 'BootOrder'). Then the user chooses
in this menu which entry he/she wants to start.
5) With our implementation of the Boot Manager, we currently defines 3 types
of boot devices. The boot device can be either an EFI application (eg: an OS
loader) or a ATAG or FDT Linux kernel image. In case the BDS starts a Linux
kernel images, our BDS will automatically fills the required ATAG or loads
the Device Tree blob.
Note: One of our partner has been asking us to provide a reference EFI
Application to boot Linux. It is expecting some platforms will have their
own BDS and will use an EFI application to load the Linux kernel.
Actually, we are waiting the output of the Boot Architecture 'forum' to
provide such 'reference' EFI application.
UEFI Device Path
----------------
UEFI has the concept of 'Device Path'. Every hardware devices supported by
the UEFI firmware on the platform have a representation that defined the
hardware path to access to this device and their properties.
Some examples:
# Device path for a kernel on PCI SATA Hard Drive:
PciRoot(0)/Pci(0|0)/Pci(0|0)/Pci(5|0)/Pci(0|0)/Sata(0,0,0)/HD(2,MBR,0x000767
30,0x1F21BF,0x1F21BF)\boot\zImage
- PciRoot(0) define the first PCI Root complex.
- PCI(5|0) = PCI controller with Device = 5 and Function = 0
- HD(Partition,Type,Signature,Start, Size) = hard disk partition
- \boot\zImage : filepath on the partition
# Device path for a Linux kernel on the first partition of the SD card:
VenHw(B615F1F5-5088-43CD-809C-A16E52487D00)/HD(1,MBR,0x00000000,0x3F,0x19FC0
)/zImage
- VenHw(guid) is used when the device path node is not defined by the UEFI
specification (generally memory mapped controllers)
The Device Path allows to describe hardware devices or media even if they
have been initialized. When hardware drivers are started they can declare
the device path(s) of the hardware they support.
The advantage is if we do not need some specific hardwares during the UEFI
boot up, we could skip their initialization in UEFI.
This device path complexity can be hidden by the Boot Manager. We have
implemented our own interactive boot menu to help us to define the boot
devices.
