gdb-macros

#
# Copyright 2014, General Dynamics C4 Systems
#
# SPDX-License-Identifier: GPL-2.0-only
#

#GDB macros for displaying seL4 data structures. Currently a work in progress.
#TODO: macros for examining an address space
# Note: This assumes KERNEL_OFFSET is a symbol that has the same value
# as PPTR_BASE_OFFSET


set print pretty on

define sel4
end

document sel4
  This is a set of macros to interpret sel4 data structures. Available commands:

  runqueues
  currthread 
  sched_action
  current_lookup_fault
  current_fault
  current_syscall_error
  resolve_cap
  resolve_cap_current
  currthread_cnode
  disp_cap
  disp_ep
  disp_ep_queue
  dump_cnode
  dump_currthread_cnode
  get_thread_vspace
  get_thread_cspace
  get_thread_reply_slot
  get_thread_most_recent_ipc_sender
  get_thread_ipc_buffer
  dump_thread_info

  Type help <command> for more information on a specific command
end

# Discover type of target
#
define runqueues
  set $found=0
  while($found<255)
    set $queue = ksReadyQueues[$found]
    if($queue.head != 0x0)
      set $current = $queue.head
      while($current != $queue->end)
        print *$current
        set $current = $current->tcbSchedNext
      end
      print *$current
    end
    set $found++
  end
end

document runqueues
  Print TCBs of all runnable threads
end

define runqueues_c
  set $found=0
  while($found<255)
    set $queue = ksReadyQueues[$found]
    if($queue.head != 0x0)
      set $current = $queue.head
      while($current != $queue->end)
        print_condensed_tcb $current
        set $current = $current->tcbSchedNext
      end
      print_condensed_tcb $current
    end
    set $found++
  end
end

define print_condensed_tcb
  printf "%d\n", $arg0->tcbPriority
end

define currthread
  print *ksCurThread
end

document currthread
  Print TCB of current thread
end

define sched_action
  if(ksSchedulerAction == 0x0)
    printf "ResumeCurrentThread\n"
  else 
    if (ksSchedulerAction == ~0x0)
      printf "ChooseNewThread\n"
    else
      printf "SwitchToThread:\n"
      print *ksSchedulerAction
    end
  end
end

document sched_action
  Print the next scheduler action
end

define current_lookup_fault
#print current_lookup_fault
  if((current_lookup_fault.words[0] & 0x3)==lookup_fault_invalid_root)
    printf "invalid root\n"
  else
    if((current_lookup_fault.words[0] & 0x3)==lookup_fault_missing_capability)
      printf "missing capability\n"
    else
      if ((current_lookup_fault.words[0] & 0x3)==lookup_fault_depth_mismatch)
        printf "depth mismatch\n"
      else 
        if((current_lookup_fault.words[0] & 0x3)==lookup_fault_guard_mismatch)
          printf "guard mismatch\n"
        else
          printf "unknown lookup fault\n"
        end
      end
    end
  end
end

document current_lookup_fault
  Decodes the current_lookup_fault variable to determine what went wrong with the last lookup
end

define current_fault
  print current_fault
end

document current_fault
  Prints the last fault
end

define current_syscall_error
  print current_syscall_error
end

document current_syscall_error
  Prints the last syscall error
end

define cap_type
  return ($arg1.words[0]>>28) & 0xf
end

define mask
  ((1<< $arg0)-1)
end

define currthread_cnode
  set $cnode = ((cte_t *)((unsigned int)ksCurThread&~((1<<9)-1)))
  print $cnode->cap
end

document currthread_cnode
  Prints the root CNode of the current thread
end

define cnode_for_thread
  set $cnode = ((cte_t *)((unsigned int)($arg0)&~((1<<9)-1)))
  print $cnode->cap
end

define disp_ep
  set $ep = *(endpoint_t *)$arg0
  printf "Queue head: %x\n", ($ep.words[1] & 0xfffffff0)
  printf "Queue tail: %x\n", ($ep.words[0] & 0xfffffff0)
  print ((enum endpoint_state)($ep.words[0] & 0x3))
end

document disp_ep
  Display basic information about an endpoint. arg0: pointer to an endpoint data structure in-kernel memory. This can be obtained from resolve_cap.
end

define disp_ep_queue
  set $ep = *(endpoint_t *)$arg0
  set $current = (tcb_t *)($ep.words[1] & 0xfffffff0)
  set $tail = (tcb_t *)($ep.words[0] & 0xfffffff0)
  if( $current == 0)
    printf "empty\n"
  else
    while( $current != $tail)
      print *$current
      set $current = $current->tcbEPNext
    end
    print *$current
  end
end

document disp_ep_queue
  Display all TCBs in an endpoint's queue. arg0: pointer to an endpoint data structure in kernel memory. This can be obtained from resolve_cap.
end

define disp_cap
  set $cap = $arg0
  set $type = (cap_tag_t)(($cap.words[0] >> 28) & 0xf)

  if( $type == cap_null_cap )
    printf "Type: cap_null_cap\n"
  end

  if( $type == cap_untyped_cap )
    printf "Type: cap_untyped_cap\n"
    printf "blocksize: %x\n", $cap.words[1] & 0x1f
    printf "capPtr: %x\n", ($cap.words[0]>>28) & 0xf
  end

  if( $type == cap_endpoint_cap )
    printf "Type: cap_endpoint_cap\n"
    printf "badge: %x\n", ($cap.words[1] & 0xfffffff8) >> 3
    printf "EPPtr: %x\n", ($cap.words[0] & 0xfffffff) << 4
  end

  if( $type == cap_notification_cap )
    printf "Type: cap_notification_cap\n"
    printf "badge: %x\n", ($cap.words[1] & 0xfffffff8) >> 3
    printf "AEPPtr: %x\n", ($cap.words[0] & 0xfffffff) << 4
  end

  if( $type == cap_reply_cap )
    printf "Type: cap_reply_cap\n"
  end

  if( $type == cap_cnode_cap)
    printf "Type: cap_cnode_cap\n"
    printf "Radix: %x\n", ($cap.words[1] & 0xf800000) >> 23
    printf "Guard size: %x\n", ($cap.words[1] & 0x7c0000) >> 18
    printf "Guard: %x\n", ($cap.words[1] & 0x3ffff) >> 0
    printf "CNode ptr: %x\n", ($cap.words[0] & 0x7ffffff) << 5
  end

  if( $type == cap_thread_cap)
    printf "Type: cap_thread_cap\n"
    printf "TCBPtr: %x\n", ($cap.words[0] & 0xfffffff) << 4
  end

  if( $type == cap_irq_handler_cap )
    printf "Type: cap_irq_handler_cap\n"
    printf "capIRQ: %x\n", ($cap.words[1] & 0xff) >> 0
  end

  if( $type == cap_irq_control_cap )
    printf "Type: cap_irq_control_cap\n"
    printf "not implemented\n"
  end

  if( $type == cap_zombie_cap )
    printf "Type: cap_zombie_cap\n"
  end

  if( $type == cap_subtype_cap )
    printf "Type: cap_subtype_cap\n"

    set $subtype = (subcap_tag_t)(($cap.words[0] & 0xf000000) >> 24)

    if( $subtype == subcap_asid_control_cap )
      printf "Subtype: subcap_asid_control_cap\n"
    end

    if( $subtype == subcap_asid_pool_cap )
      printf "Subtype: subcap_asid_pool_cap\n"
      printf "capASIDBase: %x\n", $cap.words[1] & 0xffff
      printf "capType: %x\n", ($cap.words[0] >> 28) & 0xf
      printf "capASIDPool %x\n", ($cap.words[0] << 12)
    end

    if( $subtype == subcap_io_port_cap )
      printf "Subtype: subcap_io_port_cap\n"
      printf "capType: %x\n", ($cap.words[0] >> 28) & 0xf
    end

    if( $subtype == subcap_io_space_cap )
      printf "Subtype: subcap_io_space_cap\n"
    end

    if( $subtype == subcap_io_page_table_cap )
      printf "Subtype: subcap_io_page_table_cap\n"
    end

  end

  if( $type == cap_frame_cap )
    printf "Type: cap_frame_cap\n"
    printf "FMappedAddress: %x\n", ($cap.words[1] & 0xfffff) << 12
    printf "FBasePtr: %x\n", ($cap.words[0] & 0xfffff) << 12
    printf "FMappedASIDLow: %x\n", ($cap.words[1] & 0x3ff00000) >> 20
    printf "FMappedASIDHigh: %x\n", ($cap.words[0] & 0xfc00000) >> 22
    printf "Frame size: %x\n", ($cap.words[1] & 0x80000000) >> 31
  end

  if( $type == cap_page_table_cap )
    printf "Type: cap_page_table_cap\n"
    printf "not implemented\n"
  end

  if( $type == cap_page_directory_cap )
    printf "Type: cap_page_directory_cap\n"
    printf "Is mapped: %x\n", ($cap.words[1] & 0x10000) >> 16
    printf "ASID: %x\n", ($cap->words[1] & 0xffff) >> 0
    printf "CapPDBasePTR: %x\n", $cap->words[1] << 12
  end

  print $cap
end

document disp_cap
  Determines the type of a cap and prints relevant information. arg0: a kernel capability data structure (not a pointer). This can be obtained from resolve_cap.
end

define get_thread_cap
  set $result = ((cte_t *)(((unsigned int) $arg0 )&~((1<<10)-1))) + $arg1
  set $result = $result->cap
end

document get_thread_cap
  Gets one of the caps associated with a TCB e.g. root CNode, VSpace, ipc_buffer. arg0: pointer to tcb struct, arg1: index of cap
end

define get_thread_cspace
  get_thread_cap $arg0 0
end

document get_thread_cspace
  Get the CTE for the root CNode of a thread. arg0: the in-kernel data structure representing the thread cap
end

define get_thread_vspace
  get_thread_cap $arg0 1
end

document get_thread_vspace
  Get the CTE for the vspace of a thread. arg0: the in-kernel data structure representing the thread cap
end

define get_thread_reply_slot
  get_thread_cap $arg0 2
end

document get_thread_reply_slot
  Get the CTE for the reply slot of a thread. arg0: the in-kernel data structure representing the thread cap
end

define get_thread_most_recent_ipc_sender
  get_thread_cap $arg0 3
end

document get_thread_most_recent_ipc_sender
  Get the CTE for the most recent IPC sender of a thread. arg0: the in-kernel data structure representing the thread cap
end

define get_thread_ipc_buffer
  get_thread_cap $arg0 4
end

document get_thread_ipc_buffer
  Get the CTE for the IPC buffer of a thread. arg0: the in-kernel data structure representing the thread cap
end

define dump_thread_info
  set $tcbptr = $arg0
  printf "\nCSpace:\n"
  get_thread_cspace $tcbptr
  disp_cap $result
  printf "\nVSpace:\n"
  get_thread_vspace $tcbptr
  disp_cap $result
  printf "\nReply slot:\n"
  get_thread_reply_slot $tcbptr
  disp_cap $result
  printf "\nMost recent IPC sender:\n"
  get_thread_most_recent_ipc_sender $tcbptr
  disp_cap $result
  printf "\nIPC buffer:\n"
  get_thread_ipc_buffer $tcbptr
  disp_cap $result
end

document dump_thread_info
  Dump the extra caps associated with a thread (root CNode, VSpace etc). arg0: the in-kernel data structure representing the thread cap
end

define pd_for_asid
  set $asid = $arg0
  set $poolPtr = x86KSASIDTable[$asid >> asidLowBits];
  set $pd = poolPtr->array[$asid & ((1<<asidLowBits)-1)];
  if( !$asid || !$poolPtr )
    printf "Something went wrong\n"
  else
    print $pd
  end
end

define resolve_cap
  set $nodeCap = $arg0
  set $capptr = (int)$arg1
  set $n_bits = (int)$arg2

  while(1) 
#printf "loop: remaining: %d\n", $n_bits
    #test cap type
    if((( $nodeCap.words[0]>>28)&0xf) != cap_cnode_cap)
      printf "Error: not a CNode\n"
      loop_break
    end
    set $radixBits = ($nodeCap.words[1] & 0xf800000) >> 23
    set $guardBits = ($nodeCap.words[1] & 0x7c0000) >> 18
    set $levelBits = $radixBits + $guardBits
    set $capGuard = ($nodeCap.words[1] & 0x3ffff) >> 0

    set $guard = ($capptr >> ($n_bits - $guardBits)) & ((1<<$guardBits)-1)
    
    if( ($guardBits > $n_bits) || ($guard != $capGuard))
      printf "levelbits: %d, radixbits: %d, guardbits: %d, n_bits: %d\n", $levelBits, $radixBits, $guardBits, $n_bits
      printf "guard: %x, capguard: %x", $guard, $capGuard
      printf "lookup fault guard mismatch\n"
      loop_break
    end

    if( $levelBits > $n_bits )
      printf "lookup fault depth mismatch\n"
      loop_break
    end

    set $offset = ($capptr >> ($n_bits - $levelBits)) & ((1<<$radixBits)-1)
    set $slot = ((cte_t *)(($nodeCap.words[0] & 0x7ffffff) << 5)) + $offset

    if( $n_bits <= $levelBits)
      disp_cap $slot->cap
      loop_break
    end

    set $n_bits -= $levelBits
    set $nodeCap = $slot->cap

    #test cap type
    if((( $nodeCap.words[0]>>28)&0xf) != cap_cnode_cap)
      printf "warning: terminating because node is not a CNode, not because all bits were resolved\n"
      disp_cap $nodeCap
      loop_break
    end

  end

end

document resolve_cap
  Resolve a capPtr and print its contents using disp_cap. arg0: CNode to start resolving at, arg1: the cap to resolve (an integer), arg2: the depth to resolve to (an integer). The currthread_cnode macro may be useful to obtain the first argument.
end

define resolve_cap_current
  currthread_cnode
  resolve_cap $cnode->cap $arg0 $arg1
end

document resolve_cap_current
  Resolve a capPtr and print its contents. Caps are resolved relative to root CNode of current thread. arg1: the cap to resolve, arg2: the depth.
end

define dump_cnode
  set $nodeCap = $arg0

  if((( $nodeCap.words[0]>>28)&0xf) != cap_cnode_cap)
    printf "Error: not a CNode\n"
  end

  set $radixBits = ($nodeCap.words[1] & 0xf800000) >> 23
  set $guardBits = ($nodeCap.words[1] & 0x7c0000) >> 18
  set $levelBits = $radixBits + $guardBits

  set $count = 0

  while( $count < (1<<$radixBits))
    set $slot = ((cte_t *)(($nodeCap.words[0] & 0x7ffffff) << 5)) + $count
    if((($slot->cap.words[0]>>28)&0xf) != cap_null_cap)
      printf "offset: %d\n", $count
      disp_cap $slot->cap 
      printf "\n"
    end
    set $count = $count+1
  end
end

document dump_cnode
  Dump the contents of a CNode. arg1: the CNode to dump
end

define dump_currthread_cnode
  printf "Top level CNode: \n"
  currthread_cnode
  printf "\n\n"
  dump_cnode $cnode->cap
end

document dump_currthread_cnode
  Dump the contents of the root CNode of the current thread. No arguments.
end

define irq_handler
  set $slot = intStateIRQNode + $arg0
  set $cap = $slot->cap
  if((cap_tag_t)(($cap.words[0] >> 28) & 0xf) != cap_notification_cap)
    printf "no handler\n"
  else
    set $cap = (async_endpoint_t *)(($cap.words[0] & 0xfffffff) << 4)
    disp_ep *$cap
    disp_ep_queue *$cap
  end
end

document irq_handler
  Print the endpoints and handling threads for an IRQ. arg0: the IRQ number
end

define finish_irq
  set $current_sel4_thread = ksCurThread
#set $current = ((struct thread_info *)per_cpu___l4_current_tinfo)->task
  tbreak *0xf012102a if (ksCurThread==$current_sel4_thread)  
  continue
  stepi
end

document finish_irq
  Run until the end of the IRQ handler. This is useful if you are stepping through userland code and an interrupt occurs and control moves to the kernel. As far as I know there is no way to disable interrupts in qemu to avoid this.
end

define n2
  next
  if $eip>(unsigned long)&KERNEL_OFFSET
    printf "IRQ happened\n"
    finish_irq
  end
end

document n2
  Like next but if it detects that an IRQ happens it executes that and returns.
end

define vtd_root
  print x86KSvtdRootTable
end

define decode_vtd_root_entry
  set $vtd_root_entry = (vtd_rte_t)$arg0
  set $vtd_re_ctp = ($vtd_root_entry.words[0] & 0xfffff000)
  set $vtd_re_present = ($vtd_root_entry.words[0] & 0x1)
end

document decode_vtd_root_entry
  "Decodes the vtd root entry into its component parts"
end

define print_vtd_root_entry
  printf "ctp: %x\n", $vtd_re_ctp
  printf "present: %x\n", $vtd_re_present
end

document print_vtd_root_entry
  "Print the fields of an earlier decoded vtd root entry"
end

define print_vtd_root_table 
  set $vtd_root_entry_ptr = x86KSvtdRootTable
  set $count = 0
  while($count < 256)
    decode_vtd_root_entry $vtd_root_entry_ptr[$count] 
    if($vtd_re_present)
      printf "Index: %x\n", $count
      print_vtd_root_entry 
    end
    set $count++
  end
end

document print_vtd_root_table
  "Prints all of the entries in the vtd root table. There is one entry for each PCI bus"
end

define decode_vtd_context_entry
  set $vtd_context_entry = (vtd_cte_t)$arg0
  set $vtd_ce_did = ($vtd_context_entry.words[2] & 0xffff00) >> 8
  set $vtd_ce_aw = ($vtd_context_entry.words[2] & 0x7)
  set $vtd_ce_asr = ($vtd_context_entry.words[0] & 0xfffff000)
  set $vtd_ce_present = ($vtd_context_entry.words[0] & 0x1)
end

document decode_vtd_context_entry
  "Decodes a vtd context entry into its component parts. arg0: pointer to the entry"
end

define print_vtd_context_entry
  printf "did: %x\n", $vtd_ce_did
  printf "aw: %x\n", $vtd_ce_aw
  printf "asr: %x\n", $vtd_ce_asr
  printf "present: %x\n", $vtd_ce_present
end

document print_vtd_context_entry 
  "Print the fields of an earlier decoded vtd context entry"
end

define print_vtd_context_table
  set $vtd_context_entry_ptr = (vtd_cte_t *)$arg0
  set $count = 0
  while($count < 256)
    decode_vtd_context_entry $vtd_context_entry_ptr[$count]
    if($vtd_ce_present)
      printf "index %x\n", $count
      print_vtd_context_entry
    end
    set $count++
  end
end

document print_vtd_context_table
  "Prints all of the fields in a vtd context table. There is one entry for each (dev, fn) in the bus. arg0: a pointer to the context table"
end

define decode_vtd_page_table_entry
  set $vtd_page_table_entry = (vtd_pte_t)$arg0
  set $vtd_pte_addr =  ($vtd_page_table_entry.words[0] & 0xfffff000)
  set $vtd_pte_write = ($vtd_page_table_entry.words[0] & 0x2) >> 1
  set $vtd_pte_read = ($vtd_page_table_entry.words[0] & 0x1)
end

document decode_vtd_page_table_entry
  "Decodes a vtd PTE info its component parts. arg0: pointer to the entry"
end

define print_vtd_page_table_entry
  printf "addr: %x\n", $vtd_pte_addr
  printf "write: %x\n", $vtd_pte_write
  printf "read: %x\n", $vtd_pte_read
end

document print_vtd_page_table_entry 
  "Print the fields of an earlier decoded vtd page table entry"
end

define print_vtd_page_table
  set $vtd_pte_ptr = (vtd_pte_t *)$arg0
  set $count = 0
  while($count < 256)
    decode_vtd_page_table_entry $vtd_pte_ptr[$count]
    if($vtd_pte_read || $vtd_pte_write)
      printf "index: %x\n", $count
      print_vtd_page_table_entry 
    end
    set $count++
  end
end

document print_vtd_page_table
  "Prints all of the fields in a vtd page table. arg0: a pointer to the page table"
end


define paddr_to_vaddr
  set $var = (unsigned long)$arg0
  set $vaddr = ($var + (unsigned long)&KERNEL_OFFSET)
end

document paddr_to_vaddr
  "Convert a physical address to the locaction to which it is mapped in the kernel"
end

define vaddr_to_paddr
  set $paddr = ($arg0 - (unsigned long)&KERNEL_OFFSET)
end

document vaddr_to_paddr
  "Convert a virtual address in the kernel to a physical address"
end

define lookup_vtd_address
  set $bus = $arg0
  set $devfn = $arg1
  set $address = $arg2

  set $vtd_root_entry_ptr = x86KSvtdRootTable
  decode_vtd_root_entry $vtd_root_entry_ptr[$bus]
  if($vtd_re_present)
    printf "Root entry: \n"
    print_vtd_root_entry
    paddr_to_vaddr $vtd_re_ctp
    print/x $vaddr
    set $vtd_context_entry_ptr = (vtd_cte_t *)$vaddr
    paddr_to_vaddr $vtd_context_entry_ptr[$devfn]
    decode_vtd_context_entry $vaddr
    if($vtd_ce_present)
      printf "Context entry: \n"
      print_vtd_context_entry
      walk_vtd_pgtables $vtd_ce_asr $address
    else
      printf "Error: context entry not present\n"
    end
  else
    printf "Error: root entry not present\n"
  end
end

document lookup_vtd_address
  "Looks up an address in the address space of a given PCI device. arg0: PCI bus number, arg1: PCI devfn number, arg2: virtual address to look up"
end

define walk_vtd_pgtables
  set $pg_tab = (vtd_pte_t *)$arg0
  set $address = (unsigned long long int)$arg1
  set $count=0
  if(($address & 0xffffff8000000000) == 0x0)
    set $address = $address << 25
    while(1)
      set $index = ($address & 0xff80000000000000) >> (64-9)
      printf "index: %x\n", $index
      set $address = ($address << 9)
      paddr_to_vaddr $pg_tab
      set $pg_tab = (vtd_pte_t *)$vaddr
      decode_vtd_page_table_entry $pg_tab[$index]
      if($vtd_pte_read || $vtd_pte_write)
        printf "Page table entry: \n"
        print_vtd_page_table_entry
#TODO check for superpages
        set $count++
        if($count==3)
          printf "Translation complete. Physical address: %llx\n", $vtd_pte_addr 
          loop_break
        else
          set $pg_tab = (vtd_pte_t *)$vtd_pte_addr
        end
      else 
        printf "Error: Page table entry not present\n"
        printf "Page table: "
        print_vtd_page_table_entry 
        loop_break
      end
    end
  else
    printf "Error: bits 63:39 must be 0\n"
  end
end

document walk_vtd_pgtables
  "Walks the IOMMU page table to resolve a virtual address starting at the given page table. arg0: pointer to page table (in seL4 virtual memory), arg1: virtual address to resolve"
end

define decode_pte
  set $pte_addr = $arg0 & 0xfffff000
  set $pte_present = $arg0 & 1
  set $pte_rw = ($arg0 >> 1) & 1
  set $pte_usr = ($arg0 >> 2) & 1
  set $pte_pwt = ($arg0 >> 3) & 1
  set $pte_pcd = ($arg0 >> 4) & 1
  set $pte_accessed = ($arg0 >> 5) & 1
  set $pte_dirty = ($arg0 >> 6) & 1
  set $pte_pse = ($arg0 >> 7) & 1
  set $pte_pat = ($arg0 >> 12) & 1
  set $pte_avl = ($arg0 >> 9) & 7
  set $pte_global = ($arg0 >> 8) & 1
end

document decode_pte
 Decode an X86 page table leaf entry into its component parts.
 If the PRESENT bit is 0 then the rest of the bits can be anything
 (OSs typically reuse them for swap housekeeping)
end

define maybe_print
  if $arg0
    printf $arg1
  else
    printf $arg2
  end
end

document maybe_print
 If arg0 is non-zero print arg1 otherwise print arg2.
end

# Can't use the obvious printf formulation for this because gdb tries
# to call malloc in the target --- which doesn't work in SeL4
define print_pte
  printf "Address 0x%x ", $pte_addr
  printf "  attributes: "
  maybe_print $pte_present "P" "-"
  maybe_print $pte_rw  "w"  "r"
  maybe_print $pte_usr  "U"  "S"
  maybe_print $pte_pwt " WT "  " WB "
  maybe_print $pte_pcd "NC "  "C "
  maybe_print $pte_accessed  "A"  "-"
  maybe_print $pte_dirty  "d"  "-"
  maybe_print $pte_pse  "4M"  "4k"
  maybe_print $pte_pat " PAT " ""
  maybe_print $pte_global "g" ""

  printf "AVL%x\n", $pte_avl
end

document print_pte
  Print the PTE parts split out by decode_pte.
  You must invoke decode_pte before invoking this function.
end

define pgd
  set $idx = 0
  set $pgdptr = $arg0
  while ($idx < 1024)
    set $pte = *(long *)$pgdptr
#printf "PGD@0x%x is 0x%x\n", $pgdptr, $pte
    decode_pte $pte
    set $mapped_addr =  $idx * (4 * 1024 * 1024)
    set $idx = $idx + 1
    set $pgdptr = $pgdptr + 4
    if (! $pte_present)
       loop_continue
    end
    if $pte_pse
       printf "HUGE (4G) V 0x%x ", $mapped_addr
       print_pte
    else
      set $pteptr = (long)$pte_addr + 0xe0000000
      set $n = 0
      while ($n < 1024)
        set $pte = *(long *)$pteptr
        decode_pte $pte
        if $pte_present
          printf  "V:%08x ", $mapped_addr
          print_pte
        end
        set $pteptr = $pteptr + 4
        set $mapped_addr = $mapped_addr + 4096
        set $n = $n + 1
      end
    end
  end
end

document pgd
  Print a page table, starting at the page global directory.
  Assumes 2-level (non-PAE) page tables,
end