New vCtrlC packet, non-stop mode equivalent of \003

There's currently no non-stop equivalent of the all-stop ^C (\003)
"packet" that GDB sends when a ctrl-c is pressed while a foreground
command is active.  There's vCont;t, but that's defined to cause a
"signal 0" stop.

This fixes many tests that type ^C, when testing with extended-remote
with "maint set target-non-stop on".  E.g.:

 Continuing.
 talk to me baby
 PASS: gdb.base/interrupt.exp: process is alive
 a
 a
 PASS: gdb.base/interrupt.exp: child process ate our char
 ^C
 [Thread 22730.22730] #1 stopped.
 0x0000003615ee6650 in __read_nocancel () at ../sysdeps/unix/syscall-template.S:81
 81      T_PSEUDO (SYSCALL_SYMBOL, SYSCALL_NAME, SYSCALL_NARGS)
 (gdb) FAIL: gdb.base/interrupt.exp: send_gdb control C
 p func1 ()

gdb/
2015-11-30  Pedro Alves  <palves@redhat.com>

	* NEWS (New remote packets): Mention vCtrlC.
	* remote.c (PACKET_vCtrlC): New enum value.
	(async_remote_interrupt): Call target_interrupt instead of
	target_stop.
	(remote_interrupt_as): Remove 'ptid' parameter.
	(remote_interrupt_ns): New function.
	(remote_stop): Adjust.
	(remote_interrupt): If the target is in non-stop mode, try
	interrupting with vCtrlC.
	(initialize_remote): Install set remote ctrl-c packet.

gdb/doc/
2015-11-30  Pedro Alves  <palves@redhat.com>

	* gdb.texinfo (Bootstrapping): Add "interrupting remote targets"
	anchor.
	(Packets): Document vCtrlC.

gdb/gdbserver/
2015-11-30  Pedro Alves  <palves@redhat.com>

	* server.c (handle_v_requests): Handle vCtrlC.

1 files changed, 30 insertions, 4 deletions

diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index c4d8a18..972ace0 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -35090,6 +35090,24 @@ command in the @samp{vCont} packet.
 The @samp{vCont} packet is not supported.
 @end table
 
+@anchor{vCtrlC packet}
+@item vCtrlC
+@cindex @samp{vCtrlC} packet
+Interrupt remote target as if a control-C was pressed on the remote
+terminal.  This is the equivalent to reacting to the @code{^C}
+(@samp{\003}, the control-C character) character in all-stop mode
+while the target is running, except this works in non-stop mode.
+@xref{interrupting remote targets}, for more info on the all-stop
+variant.
+
+Reply:
+@table @samp
+@item E @var{nn}
+for an error
+@item OK
+for success
+@end table
+
 @item vFile:@var{operation}:@var{parameter}@dots{}
 @cindex @samp{vFile} packet
 Perform a file operation on the target system.  For details,
@@ -37857,11 +37875,12 @@ operation.
 @node Interrupts
 @section Interrupts
 @cindex interrupts (remote protocol)
+@anchor{interrupting remote targets}
 
-When a program on the remote target is running, @value{GDBN} may
-attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
-a @code{BREAK} followed by @code{g},
-control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
+In all-stop mode, when a program on the remote target is running,
+@value{GDBN} may attempt to interrupt it by sending a @samp{Ctrl-C},
+@code{BREAK} or a @code{BREAK} followed by @code{g}, control of which
+is specified via @value{GDBN}'s @samp{interrupt-sequence}.
 
 The precise meaning of @code{BREAK} is defined by the transport
 mechanism and may, in fact, be undefined.  @value{GDBN} does not
@@ -37882,6 +37901,13 @@ and does @emph{not} represent an interrupt.  E.g., an @samp{X} packet
 When Linux kernel receives this sequence from serial port,
 it stops execution and connects to gdb.
 
+In non-stop mode, because packet resumptions are asynchronous
+(@pxref{vCont packet}), @value{GDBN} is always free to send a remote
+command to the remote stub, even when the target is running.  For that
+reason, @value{GDBN} instead sends a regular packet (@pxref{vCtrlC
+packet}) with the usual packet framing instead of the single byte
+@code{0x03}.
+
 Stubs are not required to recognize these interrupt mechanisms and the
 precise meaning associated with receipt of the interrupt is
 implementation defined.  If the target supports debugging of multiple