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.
8.1: 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.
8.2: 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: intREGISTER_CONVERTIBLE (int reg)
Return non-zero if register number reg's value needs different raw
and virtual formats.
Target Macro: intREGISTER_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: intREGISTER_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.
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.
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: voidREGISTER_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.
8.3: Frame Interpretation
8.4: Inferior Call Setup
8.5: Compiler Characteristics
8.6: 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.)
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.
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.
8.7: 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 #includes `tm-arch.h' and
`config/tm-os.h'.
GDB Internals