* Maintenance Commands:: Maintenance Commands
* Remote Protocol:: GDB Remote Serial Protocol
* Agent Expressions:: The GDB Agent Expression Mechanism
+* Target Descriptions:: How targets can describe themselves to
+ @value{GDBN}
* Copying:: GNU General Public License says
how you can copy and share GDB
* GNU Free Documentation License:: The license for this documentation
@item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
@cindex pass signals to inferior, remote request
@cindex @samp{QPassSignals} packet
+@anchor{QPassSignals}
Each listed @var{signal} should be passed directly to the inferior process.
Signals are numbered identically to continue packets and stop replies
(@pxref{Stop Reply Packets}). Each @var{signal} list item should be
@tab @samp{-}
@tab Yes
+@item @samp{qXfer:features:read}
+@tab No
+@tab @samp{-}
+@tab Yes
+
@item @samp{qXfer:memory-map:read}
@tab No
@tab @samp{-}
The remote stub understands the @samp{qXfer:auxv:read} packet
(@pxref{qXfer auxiliary vector read}).
+@item qXfer:features:read
+The remote stub understands the @samp{qXfer:features:read} packet
+(@pxref{qXfer target description read}).
+
+@item qXfer:memory-map:read
+The remote stub understands the @samp{qXfer:memory-map:read} packet
+(@pxref{qXfer memory map read}).
+
+@item QPassSignals
+The remote stub understands the @samp{QPassSignals} packet
+(@pxref{QPassSignals}).
+
@end table
@item qSymbol::
This packet is not probed by default; the remote stub must request it,
by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
-@end table
-@table @samp
+@item qXfer:features:read:@var{annex}:@var{offset},@var{length}
+@anchor{qXfer target description read}
+Access the @dfn{target description}. @xref{Target Descriptions}. The
+annex specifies which XML document to access. The main description is
+always loaded from the @samp{target.xml} annex.
+
+This packet is not probed by default; the remote stub must request it,
+by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
+
@item qXfer:memory-map:read::@var{offset},@var{length}
@anchor{qXfer memory map read}
Access the target's @dfn{memory-map}. @xref{Memory map format}. The
@include agentexpr.texi
+@node Target Descriptions
+@appendix Target Descriptions
+@cindex target descriptions
+
+@strong{Warning:} target descriptions are still under active development,
+and the contents and format may change between @value{GDBN} releases.
+The format is expected to stabilize in the future.
+
+One of the challenges of using @value{GDBN} to debug embedded systems
+is that there are so many minor variants of each processor
+architecture in use. It is common practice for vendors to start with
+a standard processor core --- ARM, PowerPC, or MIPS, for example ---
+and then make changes to adapt it to a particular market niche. Some
+architectures have hundreds of variants, available from dozens of
+vendors. This leads to a number of problems:
+
+@itemize @bullet
+@item
+With so many different customized processors, it is difficult for
+the @value{GDBN} maintainers to keep up with the changes.
+@item
+Since individual variants may have short lifetimes or limited
+audiences, it may not be worthwhile to carry information about every
+variant in the @value{GDBN} source tree.
+@item
+When @value{GDBN} does support the architecture of the embedded system
+at hand, the task of finding the correct architecture name to give the
+@command{set architecture} command can be error-prone.
+@end itemize
+
+To address these problems, the @value{GDBN} remote protocol allows a
+target system to not only identify itself to @value{GDBN}, but to
+actually describe its own features. This lets @value{GDBN} support
+processor variants it has never seen before --- to the extent that the
+descriptions are accurate, and that @value{GDBN} understands them.
+
+@menu
+* Retrieving Descriptions:: How descriptions are fetched from a target.
+* Target Description Format:: The contents of a target description.
+@end menu
+
+@node Retrieving Descriptions
+@section Retrieving Descriptions
+
+Target descriptions can be read from the target automatically, or
+specified by the user manually. The default behavior is to read the
+description from the target. @value{GDBN} retrieves it via the remote
+protocol using @samp{qXfer} requests (@pxref{General Query Packets,
+qXfer}). The @var{annex} in the @samp{qXfer} packet will be
+@samp{target.xml}. The contents of the @samp{target.xml} annex are an
+XML document, of the form described in @ref{Target Description
+Format}.
+
+Alternatively, you can specify a file to read for the target description.
+If a file is set, the target will not be queried. The commands to
+specify a file are:
+
+@table @code
+@cindex set tdesc filename
+@item set tdesc filename @var{path}
+Read the target description from @var{path}.
+
+@cindex unset tdesc filename
+@item unset tdesc filename
+Do not read the XML target description from a file. @value{GDBN}
+will use the description supplied by the current target.
+
+@cindex show tdesc filename
+@item show tdesc filename
+Show the filename to read for a target description, if any.
+@end table
+
+
+@node Target Description Format
+@section Target Description Format
+@cindex target descriptions, XML format
+
+A target description annex is an @uref{http://www.w3.org/XML/, XML}
+document which complies with the Document Type Definition provided in
+the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
+means you can use generally available tools like @command{xmllint} to
+check that your feature descriptions are well-formed and valid.
+However, to help people unfamiliar with XML write descriptions for
+their targets, we also describe the grammar here.
+
+At the moment, target descriptions can only provide minimal information
+about the architecture of the remote target. @value{GDBN} can use this
+information to autoconfigure, or to warn you if you connect to an
+unsupported target.
+
+Here is a simple target description:
+
+@example
+<target>
+ <architecture>i386:x86-64</architecture>
+</target>
+@end example
+
+@noindent
+This minimal description only says that the target uses
+the x86-64 architecture.
+
+A target description has the overall form:
+
+@example
+<?xml version="1.0"?>
+<!DOCTYPE target SYSTEM "gdb-target.dtd">
+<target>
+ <architecture>@var{arch name}</architecture>
+</target>
+@end example
+
+@noindent
+The description is generally insensitive to whitespace and line
+breaks, under the usual common-sense rules. The XML version
+declaration and document type declaration can generally be omitted
+(@value{GDBN} does not require them), but specifying them may be
+useful for XML validation tools.
+
+The content of the @samp{<architecture>} element is an architecture
+name, from the same selection accepted by @code{set architecture}
+(@pxref{Targets, ,Specifying a Debugging Target}).
+
+
@include gpl.texi
@raisesections
projects / deliverable / binutils-gdb.git / blobdiff