* Bytecode Descriptions:: What each one does.
* Using Agent Expressions:: How agent expressions fit into the big picture.
* Varying Target Capabilities:: How to discover what the target can do.
-* Tracing on Symmetrix:: Special info for implementation on EMC's
- boxes.
* Rationale:: Why we did it this way.
@end menu
GDB agent, running on the debugging target.
@item
-The agent arranges to be notified when a trace point is hit. Note that,
-on some systems, the target operating system is completely responsible
-for collecting the data; see @ref{Tracing on Symmetrix}.
+The agent arranges to be notified when a trace point is hit.
@item
When execution on the target reaches a trace point, the agent evaluates
@end itemize
-
-
-@node Tracing on Symmetrix
-@section Tracing on Symmetrix
-
-This section documents the API used by the GDB agent to collect data on
-Symmetrix systems.
-
-Cygnus originally implemented these tracing features to help EMC
-Corporation debug their Symmetrix high-availability disk drives. The
-Symmetrix application code already includes substantial tracing
-facilities; the GDB agent for the Symmetrix system uses those facilities
-for its own data collection, via the API described here.
-
-@deftypefn Function DTC_RESPONSE adbg_find_memory_in_frame (FRAME_DEF *@var{frame}, char *@var{address}, char **@var{buffer}, unsigned int *@var{size})
-Search the trace frame @var{frame} for memory saved from @var{address}.
-If the memory is available, provide the address of the buffer holding
-it; otherwise, provide the address of the next saved area.
-
-@itemize @bullet
-
-@item
-If the memory at @var{address} was saved in @var{frame}, set
-@code{*@var{buffer}} to point to the buffer in which that memory was
-saved, set @code{*@var{size}} to the number of bytes from @var{address}
-that are saved at @code{*@var{buffer}}, and return
-@code{OK_TARGET_RESPONSE}. (Clearly, in this case, the function will
-always set @code{*@var{size}} to a value greater than zero.)
-
-@item
-If @var{frame} does not record any memory at @var{address}, set
-@code{*@var{size}} to the distance from @var{address} to the start of
-the saved region with the lowest address higher than @var{address}. If
-there is no memory saved from any higher address, set @code{*@var{size}}
-to zero. Return @code{NOT_FOUND_TARGET_RESPONSE}.
-@end itemize
-
-These two possibilities allow the caller to either retrieve the data, or
-walk the address space to the next saved area.
-@end deftypefn
-
-This function allows the GDB agent to map the regions of memory saved in
-a particular frame, and retrieve their contents efficiently.
-
-This function also provides a clean interface between the GDB agent and
-the Symmetrix tracing structures, making it easier to adapt the GDB
-agent to future versions of the Symmetrix system, and vice versa. This
-function searches all data saved in @var{frame}, whether the data is
-there at the request of a bytecode expression, or because it falls in
-one of the format's memory ranges, or because it was saved from the top
-of the stack. EMC can arbitrarily change and enhance the tracing
-mechanism, but as long as this function works properly, all collected
-memory is visible to GDB.
-
-The function itself is straightforward to implement. A single pass over
-the trace frame's stack area, memory ranges, and expression blocks can
-yield the address of the buffer (if the requested address was saved),
-and also note the address of the next higher range of memory, to be
-returned when the search fails.
-
-As an example, suppose the trace frame @code{f} has saved sixteen bytes
-from address @code{0x8000} in a buffer at @code{0x1000}, and thirty-two
-bytes from address @code{0xc000} in a buffer at @code{0x1010}. Here are
-some sample calls, and the effect each would have:
-
-@table @code
-
-@item adbg_find_memory_in_frame (f, (char*) 0x8000, &buffer, &size)
-This would set @code{buffer} to @code{0x1000}, set @code{size} to
-sixteen, and return @code{OK_TARGET_RESPONSE}, since @code{f} saves
-sixteen bytes from @code{0x8000} at @code{0x1000}.
-
-@item adbg_find_memory_in_frame (f, (char *) 0x8004, &buffer, &size)
-This would set @code{buffer} to @code{0x1004}, set @code{size} to
-twelve, and return @code{OK_TARGET_RESPONSE}, since @file{f} saves the
-twelve bytes from @code{0x8004} starting four bytes into the buffer at
-@code{0x1000}. This shows that request addresses may fall in the middle
-of saved areas; the function should return the address and size of the
-remainder of the buffer.
-
-@item adbg_find_memory_in_frame (f, (char *) 0x8100, &buffer, &size)
-This would set @code{size} to @code{0x3f00} and return
-@code{NOT_FOUND_TARGET_RESPONSE}, since there is no memory saved in
-@code{f} from the address @code{0x8100}, and the next memory available
-is at @code{0x8100 + 0x3f00}, or @code{0xc000}. This shows that request
-addresses may fall outside of all saved memory ranges; the function
-should indicate the next saved area, if any.
-
-@item adbg_find_memory_in_frame (f, (char *) 0x7000, &buffer, &size)
-This would set @code{size} to @code{0x1000} and return
-@code{NOT_FOUND_TARGET_RESPONSE}, since the next saved memory is at
-@code{0x7000 + 0x1000}, or @code{0x8000}.
-
-@item adbg_find_memory_in_frame (f, (char *) 0xf000, &buffer, &size)
-This would set @code{size} to zero, and return
-@code{NOT_FOUND_TARGET_RESPONSE}. This shows how the function tells the
-caller that no further memory ranges have been saved.
-
-@end table
-
-As another example, here is a function which will print out the
-addresses of all memory saved in the trace frame @code{frame} on the
-Symmetrix INLINES console:
-@example
-void
-print_frame_addresses (FRAME_DEF *frame)
-@{
- char *addr;
- char *buffer;
- unsigned long size;
-
- addr = 0;
- for (;;)
- @{
- /* Either find out how much memory we have here, or discover
- where the next saved region is. */
- if (adbg_find_memory_in_frame (frame, addr, &buffer, &size)
- == OK_TARGET_RESPONSE)
- printp ("saved %x to %x\n", addr, addr + size);
- if (size == 0)
- break;
- addr += size;
- @}
-@}
-@end example
-
-Note that there is not necessarily any connection between the order in
-which the data is saved in the trace frame, and the order in which
-@code{adbg_find_memory_in_frame} will return those memory ranges. The
-code above will always print the saved memory regions in order of
-increasing address, while the underlying frame structure might store the
-data in a random order.
-
-[[This section should cover the rest of the Symmetrix functions the stub
-relies upon, too.]]
-
@node Rationale
@section Rationale
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