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System Dump Analyzer
SHOW CALL_FRAME
SHOW CALL_FRAME
Displays the locations and contents of the longwords representing a procedure
call frame.
Format
SHOW CALL_FRAME [starting-address | /NEXT_FP]
Parameter
starting-address
Expression representing the starting address of the procedure call frame to be
displayed. The default starting-address is the longword contained in the FP
register of the SDA current process.
Qualifier
/NEXT_FP
Displays the procedure call frame starting at the address stored in the FP
longword of the last call frame displayed by this command. You must have issued
a SHOW CALL_FRAME command previously in the current SDA session to use
the /NEXT_FP qualifier to the command.
Description
Whenever a procedure is called using CALLG or CALLS instructions, information
is stored on the stack of the calling routine in the form of a procedure call frame.
Figure SDA–5 illustrates the format of a call frame.
6
The SHOW CALL_FRAME command interprets the contents of the designated
call frame and displays whether the call frame was generated by a CALLG or
CALLS instruction. If it locates nonzero bits in the portion of the second longword
that represents the upper byte of the processor status word (PSW), it presents a
message that indicates the fault or trap in effect. For example:
Nonzero PSW Bits (15:8) => Reserved Operand Fault on RET
SHOW_CALL_FRAME then produces four columns of information:
• The components of the call frame.
• The virtual addresses that are part of the call frame.
• The contents of the longwords at these addresses.
• A symbolic representation of the contents of each longword, if possible. SDA
does not attempt to symbolize the second longword in the call frame (mask-
PSW longword), which contains the register save mask and the processor
status word (PSW).
6
In Figure SDA–5, the second longword contains the stack pointer alignment (SPA) bits,
which indicate the zero to three bytes needed to align the frame to a longword boundary.
The S bit is set if the frame resulted from a CALLS instruction; it is clear if it resulted
from a CALLG instruction.
SDA–82