Re: [RFC v2 1/3] UefiCpuPkg/CpuExceptionHandlerLib/X64: Add stack trace support

["Paulo Alcantara" <pcacjr@zytor.com>]

Hi Brijan,

On Thu, November 16, 2017 1:43 pm, Brian J. Johnson
>
> (These comments apply to patch 3/3 as well.)
>
> Typo:  UnwondStacksCount should be UnwoundStacksCount

Fixed in v3. Thanks!

>
> It's good to check the alignment of the stack, as you're doing.  But
> I'll reiterate that you absolutely need some better sanity checking of
> the stack and IP addresses before you dereference them.  Remember that
> they could be absolutely *anything* at the entry to this code.
> Something caused an error, and it may have been one of those registers.

Yes - you're absolutely right. I currently have no idea how to validate
those values as well as didn't have time to do so. Sorry. I hope to get to
it ASAP or someone could help me with that.

>
> Also, if the code was built with a compiler which isn't using RBP as a
> base pointer, RBP is unlikely to contain a stack address.  That will
> cause issues if you use it for unwinding without a sanity check.

Yes. I haven't figured out how to do that yet. It's also in my TODO list.

Thank you very much for the suggestions!

Paulo

>
> Thanks,
> Brian
>
>> ---
>>   UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/ArchExceptionHandler.c |
>> 369 +++++++++++++++++++-
>>   1 file changed, 367 insertions(+), 2 deletions(-)
>>
>> diff --git
>> a/UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/ArchExceptionHandler.c
>> b/UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/ArchExceptionHandler.c
>> index 65f0cff680..11cd7c9e1c 100644
>> ---
>> a/UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/ArchExceptionHandler.c
>> +++
>> b/UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/ArchExceptionHandler.c
>> @@ -14,6 +14,11 @@
>>
>>   #include "CpuExceptionCommon.h"
>>
>> +//
>> +// Unknown PDB file name
>> +//
>> +GLOBAL_REMOVE_IF_UNREFERENCED CONST CHAR8 *mUnknownPdbFileName =
>> "????";
>> +
>>   /**
>>     Return address map of exception handler template so that C code can
>> generate
>>     exception tables.
>> @@ -242,6 +247,350 @@ DumpCpuContext (
>>       );
>>   }
>>
>> +/**
>> +  Get absolute path and file name of PDB file in PE/COFF image.
>> +
>> +  @param[in]  ImageBase            Base address of PE/COFF image.
>> +  @param[out] PdbAbsoluteFilePath  Absolute path of PDB file.
>> +  @param[out] PdbFileName          File name of PDB file.
>> +**/
>> +STATIC
>> +VOID
>> +GetPdbFileName (
>> +  IN  UINTN    ImageBase,
>> +  OUT CHAR8    **PdbAbsoluteFilePath,
>> +  OUT CHAR8    **PdbFileName
>> +  )
>> +{
>> +  VOID   *PdbPointer;
>> +  CHAR8  *Str;
>> +
>> +  //
>> +  // Get PDB file name from PE/COFF image
>> +  //
>> +  PdbPointer = PeCoffLoaderGetPdbPointer ((VOID *)ImageBase);
>> +  if (PdbPointer == NULL) {
>> +    //
>> +    // No PDB file name found. Set it to an unknown file name.
>> +    //
>> +    *PdbFileName = (CHAR8 *)mUnknownPdbFileName;
>> +    if (PdbAbsoluteFilePath != NULL) {
>> +      *PdbAbsoluteFilePath = NULL;
>> +    }
>> +  } else {
>> +    //
>> +    // Get file name portion out of PDB file in PE/COFF image
>> +    //
>> +    Str = (CHAR8 *)((UINTN)PdbPointer +
>> +                    AsciiStrLen ((CHAR8 *)PdbPointer) - sizeof *Str);
>> +    for (; *Str != '/' && *Str != '\\'; Str--) {
>> +      ;
>> +    }
>> +
>> +    //
>> +    // Set PDB file name (also skip trailing path separator: '/' or
>> '\\')
>> +    //
>> +    *PdbFileName = Str + 1;
>> +
>> +    if (PdbAbsoluteFilePath != NULL) {
>> +      //
>> +      // Set absolute file path of PDB file
>> +      //
>> +      *PdbAbsoluteFilePath = PdbPointer;
>> +    }
>> +  }
>> +}
>> +
>> +/**
>> +  Dump stack contents.
>> +
>> +  @param[in]  CurrentRsp         Current stack pointer address.
>> +  @param[in]  UnwondStacksCount  Count of unwond stack frames.
>> +**/
>> +STATIC
>> +VOID
>> +DumpStackContents (
>> +  IN UINT64  CurrentRsp,
>> +  IN INTN    UnwondStacksCount
>> +  )
>> +{
>> +  //
>> +  // Check for proper stack pointer alignment
>> +  //
>> +  if (((UINTN)CurrentRsp & (CPU_STACK_ALIGNMENT - 1)) != 0) {
>> +    InternalPrintMessage ("!!!! Unaligned stack pointer. !!!!\n");
>> +    return;
>> +  }
>> +
>> +  //
>> +  // Dump out stack contents
>> +  //
>> +  InternalPrintMessage ("\nStack dump:\n");
>> +  while (UnwondStacksCount-- > 0) {
>> +    InternalPrintMessage (
>> +      "0x%016lx: %016lx %016lx\n",
>> +      CurrentRsp,
>> +      *(UINT64 *)CurrentRsp,
>> +      *(UINT64 *)((UINTN)CurrentRsp + 8)
>> +      );
>> +
>> +    //
>> +    // Point to next stack
>> +    //
>> +    CurrentRsp += CPU_STACK_ALIGNMENT;
>> +  }
>> +}
>> +
>> +/**
>> +  Dump all image module names from call stack.
>> +
>> +  @param[in]  SystemContext  Pointer to EFI_SYSTEM_CONTEXT.
>> +**/
>> +STATIC
>> +VOID
>> +DumpImageModuleNames (
>> +  IN EFI_SYSTEM_CONTEXT   SystemContext
>> +  )
>> +{
>> +  EFI_STATUS  Status;
>> +  UINT64      Rip;
>> +  UINTN       ImageBase;
>> +  VOID        *EntryPoint;
>> +  CHAR8       *PdbAbsoluteFilePath;
>> +  CHAR8       *PdbFileName;
>> +  UINT64      Rbp;
>> +
>> +  //
>> +  // Set current RIP address
>> +  //
>> +  Rip = SystemContext.SystemContextX64->Rip;
>> +
>> +  //
>> +  // Set current frame pointer address
>> +  //
>> +  Rbp = SystemContext.SystemContextX64->Rbp;
>> +
>> +  //
>> +  // Check for proper frame pointer alignment
>> +  //
>> +  if (((UINTN)Rbp & (CPU_STACK_ALIGNMENT - 1)) != 0) {
>> +    InternalPrintMessage ("!!!! Unaligned frame pointer. !!!!\n");
>> +    return;
>> +  }
>> +
>> +  //
>> +  // Get initial PE/COFF image base address from current RIP
>> +  //
>> +  ImageBase = PeCoffSearchImageBase (Rip);
>> +  if (ImageBase == 0) {
>> +    InternalPrintMessage ("!!!! Could not find image module names.
>> !!!!");
>> +    return;
>> +  }
>> +
>> +  //
>> +  // Get initial PE/COFF image's entry point
>> +  //
>> +  Status = PeCoffLoaderGetEntryPoint ((VOID *)ImageBase, &EntryPoint);
>> +  if (EFI_ERROR (Status)) {
>> +    EntryPoint = NULL;
>> +  }
>> +
>> +  //
>> +  // Get file name and absolute path of initial PDB file
>> +  //
>> +  GetPdbFileName (ImageBase, &PdbAbsoluteFilePath, &PdbFileName);
>> +
>> +  //
>> +  // Print out initial image module name (if any)
>> +  //
>> +  if (PdbAbsoluteFilePath != NULL) {
>> +    InternalPrintMessage (
>> +      "\n%a (ImageBase=0x%016lx, EntryPoint=0x%016lx):\n",
>> +      PdbFileName,
>> +      ImageBase,
>> +      (UINTN)EntryPoint
>> +      );
>> +    InternalPrintMessage ("%a\n", PdbAbsoluteFilePath);
>> +  }
>> +
>> +  //
>> +  // Walk through call stack and find next module names
>> +  //
>> +  for (;;) {
>> +    //
>> +    // Set RIP with return address from current stack frame
>> +    //
>> +    Rip = *(UINT64 *)((UINTN)Rbp + 8);
>> +
>> +    //
>> +    // If RIP is zero, then stop unwinding the stack
>> +    //
>> +    if (Rip == 0) {
>> +      break;
>> +    }
>> +
>> +    //
>> +    // Check if RIP is within another PE/COFF image base address
>> +    //
>> +    if (Rip < ImageBase) {
>> +      //
>> +      // Search for the respective PE/COFF image based on RIP
>> +      //
>> +      ImageBase = PeCoffSearchImageBase (Rip);
>> +      if (ImageBase == 0) {
>> +        //
>> +        // Stop stack trace
>> +        //
>> +        break;
>> +      }
>> +
>> +      //
>> +      // Get PE/COFF image's entry point
>> +      //
>> +      Status = PeCoffLoaderGetEntryPoint ((VOID *)ImageBase,
>> &EntryPoint);
>> +      if (EFI_ERROR (Status)) {
>> +        EntryPoint = NULL;
>> +      }
>> +
>> +      //
>> +      // Get file name and absolute path of PDB file
>> +      //
>> +      GetPdbFileName (ImageBase, &PdbAbsoluteFilePath, &PdbFileName);
>> +
>> +      //
>> +      // Print out image module name (if any)
>> +      //
>> +      if (PdbAbsoluteFilePath != NULL) {
>> +        InternalPrintMessage (
>> +          "%a (ImageBase=0x%016lx, EntryPoint=0x%016lx):\n",
>> +          PdbFileName,
>> +          ImageBase,
>> +          (UINTN)EntryPoint
>> +          );
>> +        InternalPrintMessage ("%a\n", PdbAbsoluteFilePath);
>> +      }
>> +    }
>> +
>> +    //
>> +    // Unwind the stack
>> +    //
>> +    Rbp = *(UINT64 *)(UINTN)Rbp;
>> +  }
>> +}
>> +
>> +/**
>> +  Dump stack trace.
>> +
>> +  @param[in]  SystemContext      Pointer to EFI_SYSTEM_CONTEXT.
>> +  @param[out] UnwondStacksCount  Count of unwond stack frames.
>> +**/
>> +STATIC
>> +VOID
>> +DumpStackTrace (
>> +  IN  EFI_SYSTEM_CONTEXT   SystemContext,
>> +  OUT INTN                 *UnwondStacksCount
>> +  )
>> +{
>> +  UINT64  Rip;
>> +  UINT64  Rbp;
>> +  UINTN   ImageBase;
>> +  CHAR8   *PdbFileName;
>> +
>> +  //
>> +  // Set current RIP address
>> +  //
>> +  Rip = SystemContext.SystemContextX64->Rip;
>> +
>> +  //
>> +  // Set current frame pointer address
>> +  //
>> +  Rbp = SystemContext.SystemContextX64->Rbp;
>> +
>> +  //
>> +  // Get initial PE/COFF image base address from current RIP
>> +  //
>> +  ImageBase = PeCoffSearchImageBase (Rip);
>> +  if (ImageBase == 0) {
>> +    InternalPrintMessage ("!!!! Could not find backtrace information.
>> !!!!");
>> +    return;
>> +  }
>> +
>> +  //
>> +  // Get PDB file name from initial PE/COFF image
>> +  //
>> +  GetPdbFileName (ImageBase, NULL, &PdbFileName);
>> +
>> +  //
>> +  // Initialize count of unwond stacks
>> +  //
>> +  *UnwondStacksCount = 1;
>> +
>> +  //
>> +  // Print out back trace
>> +  //
>> +  InternalPrintMessage ("\nCall trace:\n");
>> +
>> +  for (;;) {
>> +    //
>> +    // Print stack frame in the following format:
>> +    //
>> +    // # <RIP> @ <ImageBase>+<RelOffset> (RBP) in [<ModuleName> | ????]
>> +    //
>> +    InternalPrintMessage (
>> +      "%d 0x%016lx @ 0x%016lx+0x%x (0x%016lx) in %a\n",
>> +      *UnwondStacksCount - 1,
>> +      Rip,
>> +      ImageBase,
>> +      Rip - ImageBase - 1,
>> +      Rbp,
>> +      PdbFileName
>> +      );
>> +
>> +    //
>> +    // Set RIP with return address from current stack frame
>> +    //
>> +    Rip = *(UINT64 *)((UINTN)Rbp + 8);
>> +
>> +    //
>> +    // If RIP is zero, then stop unwinding the stack
>> +    //
>> +    if (Rip == 0) {
>> +      break;
>> +    }
>> +
>> +    //
>> +    // Check if RIP is within another PE/COFF image base address
>> +    //
>> +    if (Rip < ImageBase) {
>> +      //
>> +      // Search for the respective PE/COFF image based on RIP
>> +      //
>> +      ImageBase = PeCoffSearchImageBase (Rip);
>> +      if (ImageBase == 0) {
>> +        //
>> +        // Stop stack trace
>> +        //
>> +        break;
>> +      }
>> +
>> +      //
>> +      // Get PDB file name
>> +      //
>> +      GetPdbFileName (ImageBase, NULL, &PdbFileName);
>> +    }
>> +
>> +    //
>> +    // Unwind the stack
>> +    //
>> +    Rbp = *(UINT64 *)(UINTN)Rbp;
>> +
>> +    //
>> +    // Increment count of unwond stacks
>> +    //
>> +    (*UnwondStacksCount)++;
>> +  }
>> +}
>> +
>>   /**
>>     Display CPU information.
>>
>> @@ -254,9 +603,25 @@ DumpImageAndCpuContent (
>>     IN EFI_SYSTEM_CONTEXT   SystemContext
>>     )
>>   {
>> +  INTN UnwondStacksCount;
>> +
>> +  //
>> +  // Dump CPU context
>> +  //
>>     DumpCpuContext (ExceptionType, SystemContext);
>> +
>> +  //
>> +  // Dump stack trace
>> +  //
>> +  DumpStackTrace (SystemContext, &UnwondStacksCount);
>> +
>> +  //
>> +  // Dump image module names
>> +  //
>> +  DumpImageModuleNames (SystemContext);
>> +
>>     //
>> -  // Dump module image base and module entry point by RIP
>> +  // Dump stack contents
>>     //
>> -  DumpModuleImageInfo (SystemContext.SystemContextX64->Rip);
>> +  DumpStackContents (SystemContext.SystemContextX64->Rsp,
>> UnwondStacksCount);
>>   }
>>
>
>
> --
> Brian J. Johnson
> Enterprise X86 Lab
>
> Hewlett Packard Enterprise
>
> brian.johnson@hpe.com
>
> _______________________________________________
> edk2-devel mailing list
> edk2-devel@lists.01.org
> https://lists.01.org/mailman/listinfo/edk2-devel
>


-- 
Paulo Alcantara, HP Inc.
Speaking for myself only.