Andrew,
Only the code before InitializeDebugAgent () cannot be debugged. Most of them
are core codes and most of platform developers needn't to debug it. If they
really wants to debug the such code, they could enable debugging from SEC
instead of PEI Core. As you mentioned, some architect does not want to enable
debugging feature from SEC Core, do you know what exact reason is?
PeiCore ()
{
OldCoreData = (PEI_CORE_INSTANCE *)Data;
if (OldCoreData == NULL) {
ZeroMem (&PrivateData, sizeof (PEI_CORE_INSTANCE));
PrivateData.Signature = PEI_CORE_HANDLE_SIGNATURE;
CopyMem (&PrivateData.ServiceTableShadow, &gPs, sizeof (gPs));
} else {
// the code is this {} could be debugged.
}
PrivateData.Ps = &PrivateData.ServiceTableShadow;
ProcessLibraryConstructorList (NULL, (CONST EFI_PEI_SERVICES
**)&PrivateData.Ps);
SetPeiServicesTablePointer ((CONST EFI_PEI_SERVICES **)&PrivateData.Ps);
InitializeMemoryServices (&PrivateData, SecCoreData, OldCoreData);
InitializePpiServices (&PrivateData, OldCoreData);
InitializeDebugAgent (DEBUG_AGENT_INIT_PEI, NULL, NULL);
}
About SaveAndSetDebugTimerInterrupt (), which is designed to turn on/off the
Debug Timer interrupt only when CPU enter into some critical range to avoid
system crash or debug timer interrupt missing.
I agree with you concern on breakpoint during such critical range. Currently,
developers need to aware that the breakpoint set in such critical range may
crash the system.
If Debug Agent wants to save and disable breakpoint during such critical range,
we could think to introduce new init flag, it may just same as the one before
hand-off to OS.
Thank!
Jeff
From: Andrew Fish [mailto:[email protected]]
Sent: Wednesday, August 29, 2012 12:43 AM
To: [email protected]
Subject: Re: [edk2] DebugAgentLib question
On Aug 28, 2012, at 9:21 AM, Andrew Fish wrote:
Jeff,
The location you note is very far into PEI Core Init. In the DXE Core the
debugger is initialized right away, and in my local copy that is what I did in
the PEI Core. Initing early implies you need to use InitializeDebugAgent ()
Function callback so the debugger context can be stored on the stack. Given the
context is on the stack the 2nd call is needed to migrate the data to the stack
that ends up on moved into system memory. It kind of makes sense if you think
about it that if you want to start the debugger as early as possible in the PEI
Core you need to use a scheme that is similar to the SEC scheme.
I'm a little worried that almost every place we have a call to
SaveAndSetInterruptTimer () to disable the interrupt timer we need to also stop
the debugger. What happens if the debugger sets a port 0x80 trap and the IDT is
switched over for DXE IPL or S3 resume? Seems like you will crash in the stub
IDTs set up for these new environments. I'm thinking of making my
implementation of SaveAndSetDebugTimerInterrupt() turn off the debug registers
too, but this is not really a clean solution. We could add an InitFlag to
IntializeDebugAgent() for this, but I'm worried this will start to leak chunks
of the debugger that are not needed into various modules (DXE IPL, S3 Resume,
...).
Forgot to mention that maybe we should have a library function that is
dedicated to temporarily unhooking the debugger. So for example it disables all
the debug registers, but the content of the debug register is saved in the
debugger context, so the next call to InitializeDebugAgent() could turn them
back on if the previous context was inherited.
Andrew Fish
On Aug 27, 2012, at 10:40 PM, Fan, Jeff wrote:
Andrew,
We have defined one InitFlag DEBUG_AGENT_INIT_PEI, which could be used by one
PEI module to initialize Debug Agent. I think it also could be used by PEI Core.
For example,
It could be invoked in PEI Core at below,
//
// Initialize PEI Core Services
//
InitializeMemoryServices (&PrivateData, SecCoreData, OldCoreData);
InitializePpiServices (&PrivateData, OldCoreData);
InitializeDebugAgent (DEBUG_AGENT_INIT_PEI, NULL, NULL);
Debug Agent Library instance could initialize Debug Agent and use HOB service
to save some private contents. HOB services will be consistence before/after
physical memory is ready.
Debug Agent Library instance also could register one PPI callback function on
gEfiPeiMemoryDiscoveredPpiGuid, to send memory ready packet to HOST when memory
is ready.
Does it meet your requirement?
Now I think DEBUG_AGENT_INIT_PEI_POSTMEM is not needed. If you encountered some
issue when enabling Debug Agent in PEI Core module, we could revisit this flag
at that time.
Thanks!
Jeff
From: Andrew Fish [mailto:[email protected]]<mailto:[mailto:[email protected]]>
Sent: Tuesday, August 28, 2012 2:45 AM
To: [email protected]<mailto:[email protected]>
Subject: Re: [edk2] DebugAgentLib question
Jeff,
Since we need to add an InitFlag, can we also add DEBUG_AGENT_INIT_PEI_POSTMEM?
The code base does not seem to offer the option of having the debugger be part
of the PEI Core, which I think is a design bug. I could envision system
architectures where it is not wise to have a debugger integrated into the
SEcurity Core, but a debugger for PEI is till wanted. So I think the PEI Core
should have InitializeDebugagent() calls for DEBUG_AGENT_INIT_PEI, and
DEBUG_AGENT_INIT_PEI_POSTMEM.
Thanks,
Andrew Fish
On Aug 27, 2012, at 1:15 AM, Fan, Jeff wrote:
Andrew,
Good catch! Now, only Debug Timer interrupt was disabled before hand-off to OS.
Besides Debug Registers, we also need to think how to clear the soft break
points set by WinDbg or GDB in runtime services or in SMM code. One new
InitFlag could be introduced to help HOST debugger to clear such break points
if needed.
Jeff
From: Andrew Fish [mailto:[email protected]]<mailto:[mailto:[email protected]]>
Sent: Saturday, August 25, 2012 3:01 AM
To: [email protected]<mailto:[email protected]>
Subject: [edk2] DebugAgentLib question
#define DEBUG_AGENT_INIT_PREMEM_SEC 1
#define DEBUG_AGENT_INIT_POSTMEM_SEC 2
#define DEBUG_AGENT_INIT_DXE_CORE 3
#define DEBUG_AGENT_INIT_SMM 4
#define DEBUG_AGENT_INIT_ENTER_SMI 5
#define DEBUG_AGENT_INIT_EXIT_SMI 6
#define DEBUG_AGENT_INIT_S3 7
#define DEBUG_AGENT_INIT_DXE_AP 8
#define DEBUG_AGENT_INIT_PEI 9
#define DEBUG_AGENT_INIT_DXE_LOAD 10
#define DEBUG_AGENT_INIT_DXE_UNLOAD 11
I was looking for a InitializeDebugAgent() InitFlag to turn off the debugger on
boot? I was worried that if debug register were active when the OS boots that
may cause an issue. Is it safe to assume the OS would clear debug registers
prior to switching over the IDT? That seems to be implied by this interface?
Andrew Fish
https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2/MdeModulePkg/Include/Library/DebugAgentLib.h
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