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Document host/native/target split.

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John Gilmore 1992-10-21 10:45:11 +00:00
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@ -71,6 +71,7 @@ GDB as you discover it (or as you design changes to GDB).
* New Architectures:: Defining a New Host or Target Architecture
* Config:: Adding a New Configuration
* Host:: Adding a New Host
* Native:: Adding a New Native Configuration
* Target:: Adding a New Target
* Languages:: Defining New Source Languages
* Releases:: Configuring GDB for Release
@ -110,34 +111,72 @@ and targets.
@dfn{Host} refers to attributes of the system where GDB runs.
@dfn{Target} refers to the system where the program being debugged
executes. In most cases they are the same machine; unfortunately, that
means you must add @emph{both} host and target support for new machines
in this category.
The @file{config/mh-*}, @file{xm-*.h} and @file{*-xdep.c} files are for
host support. Similarly, the @file{config/mt-*}, @file{tm-*.h} and
@file{*-tdep.c} files are for target support. The question is, what
features or aspects of a debugging or cross-debugging environment are
considered to be ``host'' support?
executes. In most cases they are the same machine, in which case
a third type of @dfn{Native} attributes come into play.
Defines and include files needed to build on the host are host support.
Examples are tty support, system defined types, host byte order, host
float format.
Unix child process support is considered an aspect of the host. Since
when you fork on the host you are still on the host, the various macros
needed for finding the registers in the upage, running @code{ptrace}, and such
are all in the host-dependent files.
Defines and information needed to handle the target format are target
dependent. Examples are the stack frame format, instruction set,
breakpoint instruction, registers, and how to set up and tear down the stack
to call a function.
@c FIXME so what kinds of things are target support?
Information that is only needed when the host and target are the same,
is native dependent. One example is Unix child process support; if the
host and target are not the same, doing a fork to start the target
process is a bad idea. The various macros needed for finding the
registers in the @code{upage}, running @code{ptrace}, and such are all in the
native-dependent files.
This is still somewhat of a grey area; I (John Gilmore) didn't do the
@file{xm-*} and @file{tm-*} split for gdb (it was done by Jim Kingdon)
so I have had to figure out the grounds on which it was split, and make
my own choices as I evolve it. I have moved many things out of the xdep
files actually, partly as a result of BFD and partly by removing
duplicated code.
Another example of native-dependent code is support for features
that are really part of the target environment, but which require
@code{#include} files that are only available on the host system.
Core file handling and @code{setjmp} handling are two common cases.
When you want to make GDB work ``native'' on a particular
machine, you have to include all three kinds of information.
The dependent information in GDB is organized into files by naming
conventions.
Host-Dependent Files
@table @file
@item config/*.mh
Sets Makefile parameters
@item xm-*.h
Global #include's and #define's and definitions
@item *-xdep.c
Global variables and functions
@end table
Native-Dependent Files
@table @file
@item config/*.mh
Sets Makefile parameters (for @emph{both} host and native)
@item nm-*.h
#include's and #define's and definitions. This file
is only included by the small number of modules that need it,
so beware of doing feature-test #define's from its macros.
@item *-nat.c
global variables and functions
@end table
Target-Dependent Files
@table @file
@item config/*.mt
Sets Makefile parameters
@item tm-*.h
Global #include's and #define's and definitions
@item *-tdep.c
Global variables and functions
@end table
At this writing, most supported hosts have had their host and native
dependencies sorted out properly. There are a few stragglers, which
can be recognized by the absence of NATDEPFILES lines in their
@file{config/*.mh}.
@node Config
@chapter Adding a New Configuration
@ -173,21 +212,23 @@ Now, go to the @file{bfd} directory and
create a new file @file{bfd/hosts/h-@var{xxx}.h}. Examine the
other @file{h-*.h} files as templates, and create one that brings in the
right include files for your system, and defines any host-specific
macros needed by GDB.
macros needed by BFD, the Binutils, GNU LD, or the Opcodes directories.
(They all share the bfd @file{hosts} directory and the @file{configure.host}
file.)
Then edit @file{bfd/configure.in}. Add shell script code to recognize your
Then edit @file{bfd/configure.host}. Add a line to recognize your
@code{@var{xarch}-@var{xvend}-@var{xos}} configuration, and set
@code{my_host} to @var{xxx} when you recognize it. This will cause your
file @file{h-@var{xxx}.h} to be linked to @file{sysdep.h} at configuration
time.
time. When creating the line that recognizes your configuration,
only match the fields that you really need to match; e.g. don't match
match the architecture or manufacturer if the OS is sufficient
to distinguish the configuration that your @file{h-@var{xxx}.h} file supports.
Don't match the manufacturer name unless you really need to.
This should make future ports easier.
Also, if this host requires any changes to the Makefile, create a file
@file{bfd/config/mh-@var{xxx}}, which includes the required lines.
(If you have the binary utilities and/or GNU ld in the same tree,
you'll also have to edit @file{binutils/configure.in} or
@file{ld/configure.in} to match what you've done in the @file{bfd}
directory.)
@file{bfd/config/@var{xxx}.mh}, which includes the required lines.
It's possible that the @file{libiberty} and @file{readline} directories
won't need any changes for your configuration, but if they do, you can
@ -195,6 +236,9 @@ change the @file{configure.in} file there to recognize your system and
map to an @file{mh-@var{xxx}} file. Then add @file{mh-@var{xxx}}
to the @file{config/} subdirectory, to set any makefile variables you
need. The only current options in there are things like @samp{-DSYSV}.
(This @file{mh-@var{xxx}} naming convention differs from elsewhere
in GDB, by historical accident. It should be cleaned up so that all
such files are called @file{@var{xxx}.mh}.)
Aha! Now to configure GDB itself! Edit
@file{gdb/configure.in} to recognize your system and set @code{gdb_host}
@ -206,7 +250,7 @@ per-target}.
@c Would it be simpler to just use different per-host and per-target
@c *scripts*, and call them from {configure} ?
Finally, you'll need to specify and define GDB's host- and
Finally, you'll need to specify and define GDB's host-, native-, and
target-dependent @file{.h} and @file{.c} files used for your
configuration; the next two chapters discuss those.
@ -215,7 +259,7 @@ configuration; the next two chapters discuss those.
@chapter Adding a New Host
Once you have specified a new configuration for your host
(@pxref{Config,,Adding a New Configuration}), there are two remaining
(@pxref{Config,,Adding a New Configuration}), there are three remaining
pieces to making GDB work on a new machine. First, you have to make it
host on the new machine (compile there, handle that machine's terminals
properly, etc). If you will be cross-debugging to some other kind of
@ -223,7 +267,8 @@ system that's already supported, you are done.
If you want to use GDB to debug programs that run on the new machine,
you have to get it to understand the machine's object files, symbol
files, and interfaces to processes. @pxref{Target,,Adding a New Target}
files, and interfaces to processes; @pxref{Target,,Adding a New Target}
and @pxref{Native,,Adding a New Native Configuration}
Several files control GDB's configuration for host systems:
@ -247,11 +292,15 @@ to create a new one.
@item gdb/@var{xxx}-xdep.c
Contains any miscellaneous C code required for this machine
as a host. On some machines it doesn't exist at all.
as a host. On many machines it doesn't exist at all. If it does
exist, put @file{@var{xxx}-xdep.o} into the @code{XDEPFILES} line
in @file{gdb/config/mh-@var{xxx}}.
@end table
@subheading Generic Host Support Files
There are some ``generic'' versions of routines that can be used by
various host systems. These can be customized in various ways by macros
various systems. These can be customized in various ways by macros
defined in your @file{xm-@var{xxx}.h} file. If these routines work for
the @var{xxx} host, you can just include the generic file's name (with
@samp{.o}, not @samp{.c}) in @code{XDEPFILES}.
@ -259,51 +308,22 @@ the @var{xxx} host, you can just include the generic file's name (with
Otherwise, if your machine needs custom support routines, you will need
to write routines that perform the same functions as the generic file.
Put them into @code{@var{xxx}-xdep.c}, and put @code{@var{xxx}-xdep.o}
into @code{XDEPFILES}.
@subheading Generic Host Support Files
into @code{XDEPFILES}.
@table @file
@item ser-bsd.c
This contains serial line support for Berkeley-derived Unix systems.
@item infptrace.c
This is the low level interface to inferior processes for systems
using the Unix @code{ptrace} call in a vanilla way.
@item ser-go32.c
This contains serial line support for 32-bit programs running under DOS
using the GO32 execution environment.
@item coredep.c::fetch_core_registers()
Support for reading registers out of a core file. This routine calls
@code{register_addr()}, see below.
Now that BFD is used to read core files, virtually all machines should
use @code{coredep.c}, and should just provide @code{fetch_core_registers} in
@code{@var{xxx}-xdep.c} (or @code{REGISTER_U_ADDR} in @code{xm-@var{xxx}.h}).
@item coredep.c::register_addr()
If your @code{xm-@var{xxx}.h} file defines the macro
@code{REGISTER_U_ADDR(addr, blockend, regno)}, it should be defined to
set @code{addr} to the offset within the @samp{user}
struct of GDB register number @code{regno}. @code{blockend} is the
offset within the ``upage'' of @code{u.u_ar0}.
If @code{REGISTER_U_ADDR} is defined,
@file{coredep.c} will define the @code{register_addr()} function and use
the macro in it. If you do not define @code{REGISTER_U_ADDR}, but you
are using the standard @code{fetch_core_registers()}, you will need to
define your own version of @code{register_addr()}, put it into your
@code{@var{xxx}-xdep.c} file, and be sure @code{@var{xxx}-xdep.o} is in
the @code{XDEPFILES} list. If you have your own
@code{fetch_core_registers()}, you may not need a separate
@code{register_addr()}. Many custom @code{fetch_core_registers()}
implementations simply locate the registers themselves.@refill
@item ser-termios.c
This contains serial line support for System V-derived Unix systems.
@end table
Object files needed when the target system is an @var{xxx} are listed
in the file @file{config/mt-@var{xxx}}, in the makefile macro
@samp{TDEPFILES = }@dots{}. The header file that defines the target
system should be called @file{tm-@var{xxx}.h}, and should be specified
as the value of @samp{TM_FILE} in @file{config/mt-@var{xxx}}. You can
also define @samp{TM_CFLAGS}, @samp{TM_CLIBS}, and @samp{TM_CDEPS} in
there; see @file{Makefile.in}.
Now, you are now ready to try configuring GDB to compile for your system.
From the top level (above @file{bfd}, @file{gdb}, etc), do:
Now, you are now ready to try configuring GDB to compile using your system
as its host. From the top level (above @file{bfd}, @file{gdb}, etc), do:
@example
./configure @var{xxx} +target=vxworks960
@ -320,10 +340,104 @@ If this succeeds, you can try building it all with:
make
@end example
Repeat until the program configures, compiles, links, and runs.
When run, it won't be able to do much (unless you have a VxWorks/960
board on your network) but you will know that the host support is
pretty well done.
Good luck! Comments and suggestions about this section are particularly
welcome; send them to @samp{bug-gdb@@prep.ai.mit.edu}.
When hosting GDB on a new operating system, to make it possible to debug
@node Native
@chapter Adding a New Native Configuration
If you are making GDB run native on the @var{xxx} machine, you have
plenty more work to do. Several files control GDB's configuration for
native support:
@table @file
@item gdb/config/@var{xxx}.mh
Specifies Makefile fragments needed when hosting @emph{or native}
on machine @var{xxx}.
In particular, this lists the required native-dependent object files,
by defining @samp{NATDEPFILES=@dots{}}. Also
specifies the header file which describes native support on @var{xxx},
by defining @samp{NM_FILE= nm-@var{xxx}.h}.
You can also define @samp{NAT_CFLAGS},
@samp{NAT_ADD_FILES}, @samp{NAT_CLIBS}, @samp{NAT_CDEPS},
etc.; see @file{Makefile.in}.
@item gdb/nm-@var{xxx}.h
(@file{nm.h} is a link to this file, created by configure).
Contains C macro definitions describing the native system environment,
such as child process control and core file support.
Crib from existing @file{nm-*.h} files to create a new one.
Code that needs these definitions will have to @code{#include "nm.h"}
explicitly, since it is not included by @file{defs.h}.
@item gdb/@var{xxx}-nat.c
Contains any miscellaneous C code required for this native support
of this machine. On some machines it doesn't exist at all.
@end table
@subheading Generic Native Support Files
There are some ``generic'' versions of routines that can be used by
various systems. These can be customized in various ways by macros
defined in your @file{nm-@var{xxx}.h} file. If these routines work for
the @var{xxx} host, you can just include the generic file's name (with
@samp{.o}, not @samp{.c}) in @code{NATDEPFILES}.
Otherwise, if your machine needs custom support routines, you will need
to write routines that perform the same functions as the generic file.
Put them into @code{@var{xxx}-nat.c}, and put @code{@var{xxx}-nat.o}
into @code{NATDEPFILES}.
@table @file
@item inftarg.c
This contains the @emph{target_ops vector} that supports Unix child
processes on systems which use ptrace and wait to control the child.
@item procfs.c
This contains the @emph{target_ops vector} that supports Unix child
processes on systems which use /proc to control the child.
@item fork-child.c
This does the low-level grunge that uses Unix system calls
to do a "fork and exec" to start up a child process.
@item infptrace.c
This is the low level interface to inferior processes for systems
using the Unix @code{ptrace} call in a vanilla way.
@item coredep.c::fetch_core_registers()
Support for reading registers out of a core file. This routine calls
@code{register_addr()}, see below.
Now that BFD is used to read core files, virtually all machines should
use @code{coredep.c}, and should just provide @code{fetch_core_registers} in
@code{@var{xxx}-nat.c} (or @code{REGISTER_U_ADDR} in @code{nm-@var{xxx}.h}).
@item coredep.c::register_addr()
If your @code{nm-@var{xxx}.h} file defines the macro
@code{REGISTER_U_ADDR(addr, blockend, regno)}, it should be defined to
set @code{addr} to the offset within the @samp{user}
struct of GDB register number @code{regno}. @code{blockend} is the
offset within the ``upage'' of @code{u.u_ar0}.
If @code{REGISTER_U_ADDR} is defined,
@file{coredep.c} will define the @code{register_addr()} function and use
the macro in it. If you do not define @code{REGISTER_U_ADDR}, but you
are using the standard @code{fetch_core_registers()}, you will need to
define your own version of @code{register_addr()}, put it into your
@code{@var{xxx}-nat.c} file, and be sure @code{@var{xxx}-nat.o} is in
the @code{NATDEPFILES} list. If you have your own
@code{fetch_core_registers()}, you may not need a separate
@code{register_addr()}. Many custom @code{fetch_core_registers()}
implementations simply locate the registers themselves.@refill
@end table
When making GDB run native on a new operating system,
to make it possible to debug
core files, you will need to either write specific code for parsing your
OS's core files, or customize @file{bfd/trad-core.c}. First, use
whatever @code{#include} files your machine uses to define the struct of
@ -341,7 +455,7 @@ around in.
Then back in GDB, you need a matching routine called
@code{fetch_core_registers()}. If you can use the generic one, it's in
@file{core-dep.c}; if not, it's in your @file{@var{xxx}-xdep.c} file.
@file{coredep.c}; if not, it's in your @file{@var{xxx}-nat.c} file.
It will be passed a char pointer to the entire ``registers'' segment,
its length, and a zero; or a char pointer to the entire ``regs2''
segment, its length, and a 2. The routine should suck out the supplied
@ -349,6 +463,9 @@ register values and install them into GDB's ``registers'' array.
(@xref{New Architectures,,Defining a New Host or Target Architecture},
for more info about this.)
If your system uses @file{/proc} to control processes, and uses ELF
format core files, then you may be able to use the same routines
for reading the registers out of processes and out of core files.
@node Target
@chapter Adding a New Target
@ -360,12 +477,13 @@ target is the same as your new host, you've probably already done that.
A variety of files specify attributes of the GDB target environment:
@table @file
@item gdb/config/mt-@var{ttt}
@item gdb/config/@var{ttt}.mt
Contains a Makefile fragment specific to this target.
Specifies what object files are needed for target @var{ttt}, by
defining @samp{TDEPFILES=@dots{}}.
Also specifies the header file which describes @var{ttt}, by defining
@samp{TM_FILE= tm-@var{ttt}.h}. You can also define @samp{TM_CFLAGS},
@samp{TM_CLIBS}, @samp{TM_CDEPS},
and other Makefile variables here; see @file{Makefile.in}.
@item gdb/tm-@var{ttt}.h