(gdbint.info) Target Architecture Definition
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Target Architecture Definition
******************************
GDB's target architecture defines what sort of machine-language
programs GDB can work with, and how it works with them.
At present, the target architecture definition consists of a number
of C macros.
Registers and Memory
====================
GDB's model of the target machine is rather simple. GDB assumes the
machine includes a bank of registers and a block of memory. Each
register may have a different size.
GDB does not have a magical way to match up with the compiler's idea
of which registers are which; however, it is critical that they do
match up accurately. The only way to make this work is to get accurate
information about the order that the compiler uses, and to reflect that
in the `REGISTER_NAME' and related macros.
GDB can handle big-endian, little-endian, and bi-endian
architectures.
Using Different Register and Memory Data Representations
========================================================
Some architectures use one representation for a value when it lives
in a register, but use a different representation when it lives in
memory. In GDB's terminology, the "raw" representation is the one used
in the target registers, and the "virtual" representation is the one
used in memory, and within GDB `struct value' objects.
For almost all data types on almost all architectures, the virtual
and raw representations are identical, and no special handling is
needed. However, they do occasionally differ. For example:
* The x86 architecture supports an 80-bit long double type.
However, when we store those values in memory, they occupy twelve
bytes: the floating-point number occupies the first ten, and the
final two bytes are unused. This keeps the values aligned on
four-byte boundaries, allowing more efficient access. Thus, the
x86 80-bit floating-point type is the raw representation, and the
twelve-byte loosely-packed arrangement is the virtual
representation.
* Some 64-bit MIPS targets present 32-bit registers to GDB as 64-bit
registers, with garbage in their upper bits. GDB ignores the top
32 bits. Thus, the 64-bit form, with garbage in the upper 32
bits, is the raw representation, and the trimmed 32-bit
representation is the virtual representation.
In general, the raw representation is determined by the
architecture, or GDB's interface to the architecture, while the virtual
representation can be chosen for GDB's convenience. GDB's register
file, `registers', holds the register contents in raw format, and the
GDB remote protocol transmits register values in raw format.
Your architecture may define the following macros to request raw /
virtual conversions:
- Target Macro: int REGISTER_CONVERTIBLE (int REG)
Return non-zero if register number REG's value needs different raw
and virtual formats.
- Target Macro: int REGISTER_RAW_SIZE (int REG)
The size of register number REG's raw value. This is the number
of bytes the register will occupy in `registers', or in a GDB
remote protocol packet.
- Target Macro: int REGISTER_VIRTUAL_SIZE (int REG)
The size of register number REG's value, in its virtual format.
This is the size a `struct value''s buffer will have, holding that
register's value.
- Target Macro: struct type *REGISTER_VIRTUAL_TYPE (int REG)
This is the type of the virtual representation of register number
REG. Note that there is no need for a macro giving a type for the
register's raw form; once the register's value has been obtained,
GDB always uses the virtual form.
- Target Macro: void REGISTER_CONVERT_TO_VIRTUAL (int REG, struct type
*TYPE, char *FROM, char *TO)
Convert the value of register number REG to TYPE, which should
always be `REGISTER_VIRTUAL_TYPE (REG)'. The buffer at FROM holds
the register's value in raw format; the macro should convert the
value to virtual format, and place it at TO.
Note that REGISTER_CONVERT_TO_VIRTUAL and REGISTER_CONVERT_TO_RAW
take their REG and TYPE arguments in different orders.
- Target Macro: void REGISTER_CONVERT_TO_RAW (struct type *TYPE, int
REG, char *FROM, char *TO)
Convert the value of register number REG to TYPE, which should
always be `REGISTER_VIRTUAL_TYPE (REG)'. The buffer at FROM holds
the register's value in raw format; the macro should convert the
value to virtual format, and place it at TO.
Note that REGISTER_CONVERT_TO_VIRTUAL and REGISTER_CONVERT_TO_RAW
take their REG and TYPE arguments in different orders.
Frame Interpretation
====================
Inferior Call Setup
===================
Compiler Characteristics
========================
Target Conditionals
===================
This section describes the macros that you can use to define the
target machine.
`ADDITIONAL_OPTIONS'
`ADDITIONAL_OPTION_CASES'
`ADDITIONAL_OPTION_HANDLER'
`ADDITIONAL_OPTION_HELP'
These are a set of macros that allow the addition of additional
command line options to GDB. They are currently used only for the
unsupported i960 Nindy target, and should not be used in any other
configuration.
`ADDR_BITS_REMOVE (addr)'
If a raw machine instruction address includes any bits that are not
really part of the address, then define this macro to expand into
an expression that zeros those bits in ADDR. This is only used for
addresses of instructions, and even then not in all contexts.
For example, the two low-order bits of the PC on the
Hewlett-Packard PA 2.0 architecture contain the privilege level of
the corresponding instruction. Since instructions must always be
aligned on four-byte boundaries, the processor masks out these
bits to generate the actual address of the instruction.
ADDR_BITS_REMOVE should filter out these bits with an expression
such as `((addr) & ~3)'.
`BEFORE_MAIN_LOOP_HOOK'
Define this to expand into any code that you want to execute
before the main loop starts. Although this is not, strictly
speaking, a target conditional, that is how it is currently being
used. Note that if a configuration were to define it one way for
a host and a different way for the target, GDB will probably not
compile, let alone run correctly. This is currently used only for
the unsupported i960 Nindy target, and should not be used in any
other configuration.
`BELIEVE_PCC_PROMOTION'
Define if the compiler promotes a short or char parameter to an
int, but still reports the parameter as its original type, rather
than the promoted type.
`BELIEVE_PCC_PROMOTION_TYPE'
Define this if GDB should believe the type of a short argument when
compiled by pcc, but look within a full int space to get its value.
Only defined for Sun-3 at present.
`BITS_BIG_ENDIAN'
Define this if the numbering of bits in the targets does *not*
match the endianness of the target byte order. A value of 1 means
that the bits are numbered in a big-endian order, 0 means
little-endian.
`BREAKPOINT'
This is the character array initializer for the bit pattern to put
into memory where a breakpoint is set. Although it's common to
use a trap instruction for a breakpoint, it's not required; for
instance, the bit pattern could be an invalid instruction. The
breakpoint must be no longer than the shortest instruction of the
architecture.
BREAKPOINT has been deprecated in favour of BREAKPOINT_FROM_PC.
`BIG_BREAKPOINT'
`LITTLE_BREAKPOINT'
Similar to BREAKPOINT, but used for bi-endian targets.
BIG_BREAKPOINT and LITTLE_BREAKPOINT have been deprecated in
favour of BREAKPOINT_FROM_PC.
`REMOTE_BREAKPOINT'
`LITTLE_REMOTE_BREAKPOINT'
`BIG_REMOTE_BREAKPOINT'
Similar to BREAKPOINT, but used for remote targets.
BIG_REMOTE_BREAKPOINT and LITTLE_REMOTE_BREAKPOINT have been
deprecated in favour of BREAKPOINT_FROM_PC.
`BREAKPOINT_FROM_PC (pcptr, lenptr)'
Use the program counter to determine the contents and size of a
breakpoint instruction. It returns a pointer to a string of bytes
that encode a breakpoint instruction, stores the length of the
string to *lenptr, and adjusts pc (if necessary) to point to the
actual memory location where the breakpoint should be inserted.
Although it is common to use a trap instruction for a breakpoint,
it's not required; for instance, the bit pattern could be an
invalid instruction. The breakpoint must be no longer than the
shortest instruction of the architecture.
Replaces all the other BREAKPOINT macros.
`MEMORY_INSERT_BREAKPOINT (addr, contents_cache)'
`MEMORY_REMOVE_BREAKPOINT (addr, contents_cache)'
Insert or remove memory based breakpoints. Reasonable defaults
(`default_memory_insert_breakpoint' and
`default_memory_remove_breakpoint' respectively) have been
provided so that it is not necessary to define these for most
architectures. Architectures which may want to define
MEMORY_INSERT_BREAKPOINT and MEMORY_REMOVE_BREAKPOINT will likely
have instructions that are oddly sized or are not stored in a
conventional manner.
It may also be desirable (from an efficiency standpoint) to define
custom breakpoint insertion and removal routines if
BREAKPOINT_FROM_PC needs to read the target's memory for some
reason.
`CALL_DUMMY_P'
A C expresson that is non-zero when the target suports inferior
function calls.
`CALL_DUMMY_WORDS'
Pointer to an array of LONGEST words of data containing
host-byte-ordered REGISTER_BYTES sized values that partially
specify the sequence of instructions needed for an inferior
function call.
Should be deprecated in favour of a macro that uses
target-byte-ordered data.
`SIZEOF_CALL_DUMMY_WORDS'
The size of CALL_DUMMY_WORDS. When CALL_DUMMY_P this must return
a positive value. See also CALL_DUMMY_LENGTH.
`CALL_DUMMY'
A static initializer for CALL_DUMMY_WORDS. Deprecated.
`CALL_DUMMY_LOCATION'
inferior.h
`CALL_DUMMY_STACK_ADJUST'
Stack adjustment needed when performing an inferior function call.
Should be deprecated in favor of something like STACK_ALIGN.
`CALL_DUMMY_STACK_ADJUST_P'
Predicate for use of CALL_DUMMY_STACK_ADJUST.
Should be deprecated in favor of something like STACK_ALIGN.
`CANNOT_FETCH_REGISTER (regno)'
A C expression that should be nonzero if REGNO cannot be fetched
from an inferior process. This is only relevant if
`FETCH_INFERIOR_REGISTERS' is not defined.
`CANNOT_STORE_REGISTER (regno)'
A C expression that should be nonzero if REGNO should not be
written to the target. This is often the case for program
counters, status words, and other special registers. If this is
not defined, GDB will assume that all registers may be written.
`DO_DEFERRED_STORES'
`CLEAR_DEFERRED_STORES'
Define this to execute any deferred stores of registers into the
inferior, and to cancel any deferred stores.
Currently only implemented correctly for native Sparc
configurations?
`COERCE_FLOAT_TO_DOUBLE (FORMAL, ACTUAL)'
If we are calling a function by hand, and the function was declared
(according to the debug info) without a prototype, should we
automatically promote floats to doubles? This macro must evaluate
to non-zero if we should, or zero if we should leave the value
alone.
The argument ACTUAL is the type of the value we want to pass to
the function. The argument FORMAL is the type of this argument,
as it appears in the function's definition. Note that FORMAL may
be zero if we have no debugging information for the function, or if
we're passing more arguments than are officially declared (for
example, varargs). This macro is never invoked if the function
definitely has a prototype.
The default behavior is to promote only when we have no type
information for the formal parameter. This is different from the
obvious behavior, which would be to promote whenever we have no
prototype, just as the compiler does. It's annoying, but some
older targets rely on this. If you want GDB to follow the typical
compiler behavior -- to always promote when there is no prototype
in scope -- your gdbarch init function can call
`set_gdbarch_coerce_float_to_double' and select the
`standard_coerce_float_to_double' function.
`CPLUS_MARKER'
Define this to expand into the character that G++ uses to
distinguish compiler-generated identifiers from
programmer-specified identifiers. By default, this expands into
`'$''. Most System V targets should define this to `'.''.
`DBX_PARM_SYMBOL_CLASS'
Hook for the `SYMBOL_CLASS' of a parameter when decoding DBX symbol
information. In the i960, parameters can be stored as locals or as
args, depending on the type of the debug record.
`DECR_PC_AFTER_BREAK'
Define this to be the amount by which to decrement the PC after the
program encounters a breakpoint. This is often the number of
bytes in BREAKPOINT, though not always. For most targets this
value will be 0.
`DECR_PC_AFTER_HW_BREAK'
Similarly, for hardware breakpoints.
`DISABLE_UNSETTABLE_BREAK addr'
If defined, this should evaluate to 1 if ADDR is in a shared
library in which breakpoints cannot be set and so should be
disabled.
`DO_REGISTERS_INFO'
If defined, use this to print the value of a register or all
registers.
`END_OF_TEXT_DEFAULT'
This is an expression that should designate the end of the text
section (? FIXME ?)
`EXTRACT_RETURN_VALUE(type,regbuf,valbuf)'
Define this to extract a function's return value of type TYPE from
the raw register state REGBUF and copy that, in virtual format,
into VALBUF.
`EXTRACT_STRUCT_VALUE_ADDRESS(regbuf)'
When EXTRACT_STRUCT_VALUE_ADDRESS_P this is used to to extract
from an array REGBUF (containing the raw register state) the
address in which a function should return its structure value, as a
CORE_ADDR (or an expression that can be used as one).
`EXTRACT_STRUCT_VALUE_ADDRESS_P'
Predicate for EXTRACT_STRUCT_VALUE_ADDRESS.
`FLOAT_INFO'
If defined, then the `info float' command will print information
about the processor's floating point unit.
`FP_REGNUM'
If the virtual frame pointer is kept in a register, then define
this macro to be the number (greater than or equal to zero) of
that register.
This should only need to be defined if `TARGET_READ_FP' and
`TARGET_WRITE_FP' are not defined.
`FRAMELESS_FUNCTION_INVOCATION(fi)'
Define this to an expression that returns 1 if the function
invocation represented by FI does not have a stack frame
associated with it. Otherwise return 0.
`FRAME_ARGS_ADDRESS_CORRECT'
stack.c
`FRAME_CHAIN(frame)'
Given FRAME, return a pointer to the calling frame.
`FRAME_CHAIN_COMBINE(chain,frame)'
Define this to take the frame chain pointer and the frame's nominal
address and produce the nominal address of the caller's frame.
Presently only defined for HP PA.
`FRAME_CHAIN_VALID(chain,thisframe)'
Define this to be an expression that returns zero if the given
frame is an outermost frame, with no caller, and nonzero
otherwise. Several common definitions are available.
`file_frame_chain_valid' is nonzero if the chain pointer is nonzero
and given frame's PC is not inside the startup file (such as
`crt0.o'). `func_frame_chain_valid' is nonzero if the chain
pointer is nonzero and the given frame's PC is not in `main()' or a
known entry point function (such as `_start()').
`generic_file_frame_chain_valid' and
`generic_func_frame_chain_valid' are equivalent implementations for
targets using generic dummy frames.
`FRAME_INIT_SAVED_REGS(frame)'
See `frame.h'. Determines the address of all registers in the
current stack frame storing each in `frame->saved_regs'. Space for
`frame->saved_regs' shall be allocated by `FRAME_INIT_SAVED_REGS'
using either `frame_saved_regs_zalloc' or `frame_obstack_alloc'.
FRAME_FIND_SAVED_REGS and EXTRA_FRAME_INFO are deprecated.
`FRAME_NUM_ARGS (fi)'
For the frame described by FI return the number of arguments that
are being passed. If the number of arguments is not known, return
`-1'.
`FRAME_SAVED_PC(frame)'
Given FRAME, return the pc saved there. That is, the return
address.
`FUNCTION_EPILOGUE_SIZE'
For some COFF targets, the `x_sym.x_misc.x_fsize' field of the
function end symbol is 0. For such targets, you must define
`FUNCTION_EPILOGUE_SIZE' to expand into the standard size of a
function's epilogue.
`FUNCTION_START_OFFSET'
An integer, giving the offset in bytes from a function's address
(as used in the values of symbols, function pointers, etc.), and
the function's first genuine instruction.
This is zero on almost all machines: the function's address is
usually the address of its first instruction. However, on the
VAX, for example, each function starts with two bytes containing a
bitmask indicating which registers to save upon entry to the
function. The VAX `call' instructions check this value, and save
the appropriate registers automatically. Thus, since the offset
from the function's address to its first instruction is two bytes,
`FUNCTION_START_OFFSET' would be 2 on the VAX.
`GCC_COMPILED_FLAG_SYMBOL'
`GCC2_COMPILED_FLAG_SYMBOL'
If defined, these are the names of the symbols that GDB will look
for to detect that GCC compiled the file. The default symbols are
`gcc_compiled.' and `gcc2_compiled.', respectively. (Currently
only defined for the Delta 68.)
`GDB_MULTI_ARCH'
If defined and non-zero, enables suport for multiple architectures
within GDB.
The support can be enabled at two levels. At level one, only
definitions for previously undefined macros are provided; at level
two, a multi-arch definition of all architecture dependant macros
will be defined.
`GDB_TARGET_IS_HPPA'
This determines whether horrible kludge code in dbxread.c and
partial-stab.h is used to mangle multiple-symbol-table files from
HPPA's. This should all be ripped out, and a scheme like elfread.c
used.
`GET_LONGJMP_TARGET'
For most machines, this is a target-dependent parameter. On the
DECstation and the Iris, this is a native-dependent parameter,
since <setjmp.h> is needed to define it.
This macro determines the target PC address that longjmp() will
jump to, assuming that we have just stopped at a longjmp
breakpoint. It takes a CORE_ADDR * as argument, and stores the
target PC value through this pointer. It examines the current
state of the machine as needed.
`GET_SAVED_REGISTER'
Define this if you need to supply your own definition for the
function `get_saved_register'.
`HAVE_REGISTER_WINDOWS'
Define this if the target has register windows.
`REGISTER_IN_WINDOW_P (regnum)'
Define this to be an expression that is 1 if the given register is
in the window.
`IBM6000_TARGET'
Shows that we are configured for an IBM RS/6000 target. This
conditional should be eliminated (FIXME) and replaced by
feature-specific macros. It was introduced in haste and we are
repenting at leisure.
`SYMBOLS_CAN_START_WITH_DOLLAR'
Some systems have routines whose names start with `$'. Giving this
macro a non-zero value tells GDB's expression parser to check for
such routines when parsing tokens that begin with `$'.
On HP-UX, certain system routines (millicode) have names beginning
with `$' or `$$'. For example, `$$dyncall' is a millicode routine
that handles inter-space procedure calls on PA-RISC.
`IEEE_FLOAT'
Define this if the target system uses IEEE-format floating point
numbers.
`INIT_EXTRA_FRAME_INFO (fromleaf, frame)'
If additional information about the frame is required this should
be stored in `frame->extra_info'. Space for `frame->extra_info'
is allocated using `frame_obstack_alloc'.
`INIT_FRAME_PC (fromleaf, prev)'
This is a C statement that sets the pc of the frame pointed to by
PREV. [By default...]
`INNER_THAN (lhs,rhs)'
Returns non-zero if stack address LHS is inner than (nearer to the
stack top) stack address RHS. Define this as `lhs < rhs' if the
target's stack grows downward in memory, or `lhs > rsh' if the
stack grows upward.
`IN_SIGTRAMP (pc, name)'
Define this to return true if the given PC and/or NAME indicates
that the current function is a sigtramp.
`SIGTRAMP_START (pc)'
`SIGTRAMP_END (pc)'
Define these to be the start and end address of the sigtramp for
the given PC. On machines where the address is just a compile time
constant, the macro expansion will typically just ignore the
supplied PC.
`IN_SOLIB_CALL_TRAMPOLINE pc name'
Define this to evaluate to nonzero if the program is stopped in the
trampoline that connects to a shared library.
`IN_SOLIB_RETURN_TRAMPOLINE pc name'
Define this to evaluate to nonzero if the program is stopped in the
trampoline that returns from a shared library.
`IN_SOLIB_DYNSYM_RESOLVE_CODE pc'
Define this to evaluate to nonzero if the program is stopped in the
dynamic linker.
`SKIP_SOLIB_RESOLVER pc'
Define this to evaluate to the (nonzero) address at which execution
should continue to get past the dynamic linker's symbol resolution
function. A zero value indicates that it is not important or
necessary to set a breakpoint to get through the dynamic linker
and that single stepping will suffice.
`IS_TRAPPED_INTERNALVAR (name)'
This is an ugly hook to allow the specification of special actions
that should occur as a side-effect of setting the value of a
variable internal to GDB. Currently only used by the h8500. Note
that this could be either a host or target conditional.
`NEED_TEXT_START_END'
Define this if GDB should determine the start and end addresses of
the text section. (Seems dubious.)
`NO_HIF_SUPPORT'
(Specific to the a29k.)
`REGISTER_CONVERTIBLE (REG)'
Return non-zero if REG uses different raw and virtual formats.
Using Different Register and Memory Data Representations
Target Architecture Definition.
`REGISTER_RAW_SIZE (REG)'
Return the raw size of REG. Using Different Register and
Memory Data Representations Target Architecture Definition.
`REGISTER_VIRTUAL_SIZE (REG)'
Return the virtual size of REG. Using Different Register
and Memory Data Representations Target Architecture Definition.
`REGISTER_VIRTUAL_TYPE (REG)'
Return the virtual type of REG. Using Different Register
and Memory Data Representations Target Architecture Definition.
`REGISTER_CONVERT_TO_VIRTUAL(REG, TYPE, FROM, TO)'
Convert the value of register REG from its raw form to its virtual
form. Using Different Register and Memory Data
Representations Target Architecture Definition.
`REGISTER_CONVERT_TO_RAW(TYPE, REG, FROM, TO)'
Convert the value of register REG from its virtual form to its raw
form. Using Different Register and Memory Data
Representations Target Architecture Definition.
`SOFTWARE_SINGLE_STEP_P'
Define this as 1 if the target does not have a hardware single-step
mechanism. The macro `SOFTWARE_SINGLE_STEP' must also be defined.
`SOFTWARE_SINGLE_STEP(signal,insert_breapoints_p)'
A function that inserts or removes (dependant on
INSERT_BREAPOINTS_P) breakpoints at each possible destinations of
the next instruction. See `sparc-tdep.c' and `rs6000-tdep.c' for
examples.
`SOFUN_ADDRESS_MAYBE_MISSING'
Somebody clever observed that, the more actual addresses you have
in the debug information, the more time the linker has to spend
relocating them. So whenever there's some other way the debugger
could find the address it needs, you should omit it from the debug
info, to make linking faster.
`SOFUN_ADDRESS_MAYBE_MISSING' indicates that a particular set of
hacks of this sort are in use, affecting `N_SO' and `N_FUN'
entries in stabs-format debugging information. `N_SO' stabs mark
the beginning and ending addresses of compilation units in the text
segment. `N_FUN' stabs mark the starts and ends of functions.
`SOFUN_ADDRESS_MAYBE_MISSING' means two things:
* `N_FUN' stabs have an address of zero. Instead, you should
find the addresses where the function starts by taking the
function name from the stab, and then looking that up in the
minsyms (the linker/ assembler symbol table). In other
words, the stab has the name, and the linker / assembler
symbol table is the only place that carries the address.
* `N_SO' stabs have an address of zero, too. You just look at
the `N_FUN' stabs that appear before and after the `N_SO'
stab, and guess the starting and ending addresses of the
compilation unit from them.
`PCC_SOL_BROKEN'
(Used only in the Convex target.)
`PC_IN_CALL_DUMMY'
inferior.h
`PC_LOAD_SEGMENT'
If defined, print information about the load segment for the
program counter. (Defined only for the RS/6000.)
`PC_REGNUM'
If the program counter is kept in a register, then define this
macro to be the number (greater than or equal to zero) of that
register.
This should only need to be defined if `TARGET_READ_PC' and
`TARGET_WRITE_PC' are not defined.
`NPC_REGNUM'
The number of the "next program counter" register, if defined.
`NNPC_REGNUM'
The number of the "next next program counter" register, if defined.
Currently, this is only defined for the Motorola 88K.
`PARM_BOUNDARY'
If non-zero, round arguments to a boundary of this many bits before
pushing them on the stack.
`PRINT_REGISTER_HOOK (regno)'
If defined, this must be a function that prints the contents of the
given register to standard output.
`PRINT_TYPELESS_INTEGER'
This is an obscure substitute for `print_longest' that seems to
have been defined for the Convex target.
`PROCESS_LINENUMBER_HOOK'
A hook defined for XCOFF reading.
`PROLOGUE_FIRSTLINE_OVERLAP'
(Only used in unsupported Convex configuration.)
`PS_REGNUM'
If defined, this is the number of the processor status register.
(This definition is only used in generic code when parsing "$ps".)
`POP_FRAME'
Used in `call_function_by_hand' to remove an artificial stack
frame.
`PUSH_ARGUMENTS (nargs, args, sp, struct_return, struct_addr)'
Define this to push arguments onto the stack for inferior function
call. Return the updated stack pointer value.
`PUSH_DUMMY_FRAME'
Used in `call_function_by_hand' to create an artificial stack
frame.
`REGISTER_BYTES'
The total amount of space needed to store GDB's copy of the
machine's register state.
`REGISTER_NAME(i)'
Return the name of register I as a string. May return NULL or NUL
to indicate that register I is not valid.
`REGISTER_NAMES'
Deprecated in favor of REGISTER_NAME.
`REG_STRUCT_HAS_ADDR (gcc_p, type)'
Define this to return 1 if the given type will be passed by pointer
rather than directly.
`SAVE_DUMMY_FRAME_TOS (sp)'
Used in `call_function_by_hand' to notify the target dependent code
of the top-of-stack value that will be passed to the the inferior
code. This is the value of the SP after both the dummy frame and
space for parameters/results have been allocated on the stack.
`SDB_REG_TO_REGNUM'
Define this to convert sdb register numbers into GDB regnums. If
not defined, no conversion will be done.
`SHIFT_INST_REGS'
(Only used for m88k targets.)
`SKIP_PERMANENT_BREAKPOINT'
Advance the inferior's PC past a permanent breakpoint. GDB
normally steps over a breakpoint by removing it, stepping one
instruction, and re-inserting the breakpoint. However, permanent
breakpoints are hardwired into the inferior, and can't be removed,
so this strategy doesn't work. Calling SKIP_PERMANENT_BREAKPOINT
adjusts the processor's state so that execution will resume just
after the breakpoint. This macro does the right thing even when
the breakpoint is in the delay slot of a branch or jump.
`SKIP_PROLOGUE (pc)'
A C expression that returns the address of the "real" code beyond
the function entry prologue found at PC.
`SKIP_PROLOGUE_FRAMELESS_P'
A C expression that should behave similarly, but that can stop as
soon as the function is known to have a frame. If not defined,
`SKIP_PROLOGUE' will be used instead.
`SKIP_TRAMPOLINE_CODE (pc)'
If the target machine has trampoline code that sits between
callers and the functions being called, then define this macro to
return a new PC that is at the start of the real function.
`SP_REGNUM'
If the stack-pointer is kept in a register, then define this macro
to be the number (greater than or equal to zero) of that register.
This should only need to be defined if `TARGET_WRITE_SP' and
`TARGET_WRITE_SP' are not defined.
`STAB_REG_TO_REGNUM'
Define this to convert stab register numbers (as gotten from `r'
declarations) into GDB regnums. If not defined, no conversion
will be done.
`STACK_ALIGN (addr)'
Define this to adjust the address to the alignment required for the
processor's stack.
`STEP_SKIPS_DELAY (addr)'
Define this to return true if the address is of an instruction
with a delay slot. If a breakpoint has been placed in the
instruction's delay slot, GDB will single-step over that
instruction before resuming normally. Currently only defined for
the Mips.
`STORE_RETURN_VALUE (type, valbuf)'
A C expression that stores a function return value of type TYPE,
where VALBUF is the address of the value to be stored.
`SUN_FIXED_LBRAC_BUG'
(Used only for Sun-3 and Sun-4 targets.)
`SYMBOL_RELOADING_DEFAULT'
The default value of the `symbol-reloading' variable. (Never
defined in current sources.)
`TARGET_BYTE_ORDER_DEFAULT'
The ordering of bytes in the target. This must be either
`BIG_ENDIAN' or `LITTLE_ENDIAN'. This macro replaces
TARGET_BYTE_ORDER which is deprecated.
`TARGET_BYTE_ORDER_SELECTABLE_P'
Non-zero if the target has both `BIG_ENDIAN' and `LITTLE_ENDIAN'
variants. This macro replaces TARGET_BYTE_ORDER_SELECTABLE which
is deprecated.
`TARGET_CHAR_BIT'
Number of bits in a char; defaults to 8.
`TARGET_COMPLEX_BIT'
Number of bits in a complex number; defaults to `2 *
TARGET_FLOAT_BIT'.
At present this macro is not used.
`TARGET_DOUBLE_BIT'
Number of bits in a double float; defaults to `8 *
TARGET_CHAR_BIT'.
`TARGET_DOUBLE_COMPLEX_BIT'
Number of bits in a double complex; defaults to `2 *
TARGET_DOUBLE_BIT'.
At present this macro is not used.
`TARGET_FLOAT_BIT'
Number of bits in a float; defaults to `4 * TARGET_CHAR_BIT'.
`TARGET_INT_BIT'
Number of bits in an integer; defaults to `4 * TARGET_CHAR_BIT'.
`TARGET_LONG_BIT'
Number of bits in a long integer; defaults to `4 *
TARGET_CHAR_BIT'.
`TARGET_LONG_DOUBLE_BIT'
Number of bits in a long double float; defaults to `2 *
TARGET_DOUBLE_BIT'.
`TARGET_LONG_LONG_BIT'
Number of bits in a long long integer; defaults to `2 *
TARGET_LONG_BIT'.
`TARGET_PTR_BIT'
Number of bits in a pointer; defaults to `TARGET_INT_BIT'.
`TARGET_SHORT_BIT'
Number of bits in a short integer; defaults to `2 *
TARGET_CHAR_BIT'.
`TARGET_READ_PC'
`TARGET_WRITE_PC (val, pid)'
`TARGET_READ_SP'
`TARGET_WRITE_SP'
`TARGET_READ_FP'
`TARGET_WRITE_FP'
These change the behavior of `read_pc', `write_pc', `read_sp',
`write_sp', `read_fp' and `write_fp'. For most targets, these may
be left undefined. GDB will call the read and write register
functions with the relevant `_REGNUM' argument.
These macros are useful when a target keeps one of these registers
in a hard to get at place; for example, part in a segment register
and part in an ordinary register.
`TARGET_VIRTUAL_FRAME_POINTER(pc,regp,offsetp)'
Returns a `(register, offset)' pair representing the virtual frame
pointer in use at the code address `"pc"'. If virtual frame
pointers are not used, a default definition simply returns
`FP_REGNUM', with an offset of zero.
`USE_STRUCT_CONVENTION (gcc_p, type)'
If defined, this must be an expression that is nonzero if a value
of the given TYPE being returned from a function must have space
allocated for it on the stack. GCC_P is true if the function
being considered is known to have been compiled by GCC; this is
helpful for systems where GCC is known to use different calling
convention than other compilers.
`VARIABLES_INSIDE_BLOCK (desc, gcc_p)'
For dbx-style debugging information, if the compiler puts variable
declarations inside LBRAC/RBRAC blocks, this should be defined to
be nonzero. DESC is the value of `n_desc' from the `N_RBRAC'
symbol, and GCC_P is true if GDB has noticed the presence of
either the `GCC_COMPILED_SYMBOL' or the `GCC2_COMPILED_SYMBOL'.
By default, this is 0.
`OS9K_VARIABLES_INSIDE_BLOCK (desc, gcc_p)'
Similarly, for OS/9000. Defaults to 1.
Motorola M68K target conditionals.
`BPT_VECTOR'
Define this to be the 4-bit location of the breakpoint trap
vector. If not defined, it will default to `0xf'.
`REMOTE_BPT_VECTOR'
Defaults to `1'.
Adding a New Target
===================
The following files define a target to GDB:
`gdb/config/ARCH/TTT.mt'
Contains a Makefile fragment specific to this target. Specifies
what object files are needed for target TTT, by defining
`TDEPFILES=...' and `TDEPLIBS=...'. Also specifies the header
file which describes TTT, by defining `TM_FILE= tm-TTT.h'.
You can also define `TM_CFLAGS', `TM_CLIBS', `TM_CDEPS', but these
are now deprecated, replaced by autoconf, and may go away in
future versions of GDB.
`gdb/config/ARCH/tm-TTT.h'
(`tm.h' is a link to this file, created by configure). Contains
macro definitions about the target machine's registers, stack frame
format and instructions.
`gdb/TTT-tdep.c'
Contains any miscellaneous code required for this target machine.
On some machines it doesn't exist at all. Sometimes the macros in
`tm-TTT.h' become very complicated, so they are implemented as
functions here instead, and the macro is simply defined to call the
function. This is vastly preferable, since it is easier to
understand and debug.
`gdb/config/ARCH/tm-ARCH.h'
This often exists to describe the basic layout of the target
machine's processor chip (registers, stack, etc). If used, it is
included by `tm-TTT.h'. It can be shared among many targets that
use the same processor.
`gdb/ARCH-tdep.c'
Similarly, there are often common subroutines that are shared by
all target machines that use this particular architecture.
If you are adding a new operating system for an existing CPU chip,
add a `config/tm-OS.h' file that describes the operating system
facilities that are unusual (extra symbol table info; the breakpoint
instruction needed; etc). Then write a `ARCH/tm-OS.h' that just
`#include's `tm-ARCH.h' and `config/tm-OS.h'.
Info Catalog
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