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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.
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.
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.)
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
.
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'.
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