[PATCH V2 5/5] Support tracepoints for ARM linux in GDBServer

Antoine Tremblay
2016-11-03T14:33:34Z

This patch adds support for tracepoints for ARM linux in GDBServer.

To enable this, this patch introduces a new :K (kind) field in the
QTDP packet to encode the breakpoint kind, this is the same kind as a z0
packet.

This is the new qSupported feature: TracepointKinds

This field is decoded by sw_breakpoint_from_kind target ops in linux-low.

Tested on Ubuntu 14.04 ARMv7 and x86 with no regression.
With gdbserver-{native,extended} / { -marm -mthumb }

gdb/ChangeLog:

* NEWS: Add news for tracepoins on ARM.

gdb/doc/ChangeLog:

* gdb.texinfo (General Query Packets): Add TracepointKinds packet.
(ARM Breakpoint Kinds): Add QTDP reference.
(Tracepoint Packets): Add kind parameter to QTDP packet.

gdb/gdbserver/ChangeLog:

* linux-arm-low.c (arm_supports_tracepoints): New function.
(struct linux_target_ops) <supports_tracepoints>: Initialize.
* mem-break.c (set_breakpoint_at_with_kind): New function.
* mem-break.h (set_breakpoint_at_with_kind): New function declaration.
* server.c (handle_query): Add TracepointsKinds feature.
* tracepoint.c (struct tracepoint) <kind>: New field.
(add_tracepoint): Initialize kind field.
(cmd_qtdp): Handle kind field 'K'.
(install_tracepoint): Use set_breakpoint_at_with_kind when kind is
present.
(cmd_qtstart): Likewise.

gdb/ChangeLog:

* remote.c (remote_supports_tracepoint_kinds): New function declaration.
(PACKET_TracepointKinds): New enum field.
(remote_protocol_features[]): New TracepointKinds element.
(remote_supports_tracepoint_kinds): New function.
(remote_download_tracepoint): Fetch the breakpoint kind and send
it as K parameter to QTDP packet.
(_initialize_remote): Add TracepointKinds packet_config_cmd.

gdb/testsuite/ChangeLog:

* gdb.trace/collection.exp (gdb_collect_return_test): Set test
unsupported for arm/aarch32 targets as it's not supported by the
arch.
* gdb.trace/trace-common.h: Add ARM fast tracepoint label to allow
tracepoints tests.
* lib/trace-support.exp: Add arm/aarch32 target support.
---
gdb/NEWS | 2 ++
gdb/doc/gdb.texinfo | 23 ++++++++++++++----
gdb/gdbserver/linux-arm-low.c | 10 +++++++-
gdb/gdbserver/mem-break.c | 13 ++++++++++
gdb/gdbserver/mem-break.h | 7 ++++++
gdb/gdbserver/server.c | 1 +
gdb/gdbserver/tracepoint.c | 43 ++++++++++++++++++++++++++++------
gdb/remote.c | 27 +++++++++++++++++++++
gdb/testsuite/gdb.trace/collection.exp | 7 +++++-
gdb/testsuite/gdb.trace/trace-common.h | 12 ++++++++--
gdb/testsuite/lib/trace-support.exp | 3 +++
11 files changed, 132 insertions(+), 16 deletions(-)

diff --git a/gdb/NEWS b/gdb/NEWS
index a6b1282..233f11e 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -3,6 +3,8 @@

*** Changes since GDB 7.12

+* Support for tracepoints on arm-linux was added in GDBServer.
+
* Building GDB and GDBserver now requires a C++11 compiler.

For example, GCC 4.8 or later.
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index df548dc..7df63ee 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -37088,6 +37088,11 @@ These are the currently defined stub features and their properties:
@tab @samp{-}
@tab No

+@item @samp{TracepointKinds}
+@tab No
+@tab @samp{-}
+@tab No
+
@end multitable

These are the currently defined stub features, in more detail:
@@ -37310,6 +37315,9 @@ The remote stub understands the @samp{QThreadEvents} packet.
@item no-resumed
The remote stub reports the @samp{N} stop reply.

+@item TracepointKinds
+The remote stub reports the @samp{:K} kind parameter for @samp{QTDP} packets.
+
@end table

@item qSymbol::
@@ -37820,7 +37828,8 @@ details of XML target descriptions for each architecture.
@subsubsection @acronym{ARM} Breakpoint Kinds
@cindex breakpoint kinds, @acronym{ARM}

-These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
+These breakpoint kinds are defined for the @samp{Z0}, @samp{Z1}
+and @samp{QTDP} packets.

@table @r

@@ -37900,7 +37909,7 @@ tracepoints (@pxref{Tracepoints}).

@table @samp

-@item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
+@item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}][:K@var{kind}]@r{[}-@r{]}
@cindex @samp{QTDP} packet
Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
@@ -37911,9 +37920,13 @@ the number of bytes that the target should copy elsewhere to make room
for the tracepoint. If an @samp{X} is present, it introduces a
tracepoint condition, which consists of a hexadecimal length, followed
by a comma and hex-encoded bytes, in a manner similar to action
-encodings as described below. If the trailing @samp{-} is present,
-further @samp{QTDP} packets will follow to specify this tracepoint's
-actions.
+encodings as described below. If a @samp{K} is present, it
+indicates a target specific breakpoint kind. The kind can be the
+length of the breakpoint. E.g., the arm and mips can insert either a
+2 or 4 byte breakpoint or have additional meaning see
+@ref{Architecture-Specific Protocol Details}. If the trailing @samp{-}
+is present, further @samp{QTDP} packets will follow to specify this
+tracepoint's actions.

Replies:
@table @samp
diff --git a/gdb/gdbserver/linux-arm-low.c b/gdb/gdbserver/linux-arm-low.c
index ed9b356..a1ca9b9 100644
--- a/gdb/gdbserver/linux-arm-low.c
+++ b/gdb/gdbserver/linux-arm-low.c
@@ -1032,6 +1032,14 @@ arm_regs_info (void)
return &regs_info_arm;
}

+/* Implementation of the linux_target_ops method "support_tracepoints". */
+
+static int
+arm_supports_tracepoints (void)
+{
+ return 1;
+}
+
struct linux_target_ops the_low_target = {
arm_arch_setup,
arm_regs_info,
@@ -1058,7 +1066,7 @@ struct linux_target_ops the_low_target = {
arm_new_fork,
arm_prepare_to_resume,
NULL, /* process_qsupported */
- NULL, /* supports_tracepoints */
+ arm_supports_tracepoints,
NULL, /* get_thread_area */
NULL, /* install_fast_tracepoint_jump_pad */
NULL, /* emit_ops */
diff --git a/gdb/gdbserver/mem-break.c b/gdb/gdbserver/mem-break.c
index bee9c30..c8fb7c9 100644
--- a/gdb/gdbserver/mem-break.c
+++ b/gdb/gdbserver/mem-break.c
@@ -870,6 +870,19 @@ set_breakpoint_at (CORE_ADDR where, int (*handler) (CORE_ADDR))
return set_breakpoint_type_at (other_breakpoint, where, handler);
}

+/* See mem-break.h */
+
+struct breakpoint *
+set_breakpoint_at_with_kind (CORE_ADDR where,
+ int (*handler) (CORE_ADDR),
+ int kind)
+{
+ int err_ignored;
+
+ return set_breakpoint (other_breakpoint, raw_bkpt_type_sw,
+ where, kind, handler,
+ &err_ignored);
+}

static int
delete_raw_breakpoint (struct process_info *proc, struct raw_breakpoint *todel)
diff --git a/gdb/gdbserver/mem-break.h b/gdb/gdbserver/mem-break.h
index 9e7ee93..07c6894 100644
--- a/gdb/gdbserver/mem-break.h
+++ b/gdb/gdbserver/mem-break.h
@@ -148,6 +148,13 @@ int gdb_breakpoint_here (CORE_ADDR where);
struct breakpoint *set_breakpoint_at (CORE_ADDR where,
int (*handler) (CORE_ADDR));

+/* Same as set_breakpoint_at but allow the kind to be specified */
+
+struct breakpoint *set_breakpoint_at_with_kind (CORE_ADDR where,
+ int (*handler)(CORE_ADDR),
+ int kind);
+
+
/* Delete a breakpoint. */

int delete_breakpoint (struct breakpoint *bkpt);
diff --git a/gdb/gdbserver/server.c b/gdb/gdbserver/server.c
index 3f9ff2b..3b3c371 100644
--- a/gdb/gdbserver/server.c
+++ b/gdb/gdbserver/server.c
@@ -2350,6 +2350,7 @@ handle_query (char *own_buf, int packet_len, int *new_packet_len_p)
strcat (own_buf, ";EnableDisableTracepoints+");
strcat (own_buf, ";QTBuffer:size+");
strcat (own_buf, ";tracenz+");
+ strcat (own_buf, ";TracepointKinds+");
}

if (target_supports_hardware_single_step ()
diff --git a/gdb/gdbserver/tracepoint.c b/gdb/gdbserver/tracepoint.c
index 7700ad1..cdb2c1d 100644
--- a/gdb/gdbserver/tracepoint.c
+++ b/gdb/gdbserver/tracepoint.c
@@ -747,6 +747,11 @@ struct tracepoint
/* Link to the next tracepoint in the list. */
struct tracepoint *next;

+ /* Optional kind of the breakpoint to be used. Note this can mean
+ different things for different archs as z0 breakpoint command.
+ Value is -1 if not persent. */
+ int32_t kind;
+
#ifndef IN_PROCESS_AGENT
/* The list of actions to take when the tracepoint triggers, in
string/packet form. */
@@ -1813,6 +1818,7 @@ add_tracepoint (int num, CORE_ADDR addr)
tpoint->compiled_cond = 0;
tpoint->handle = NULL;
tpoint->next = NULL;
+ tpoint->kind = -1;

/* Find a place to insert this tracepoint into list in order to keep
the tracepoint list still in the ascending order. There may be
@@ -2484,6 +2490,7 @@ cmd_qtdp (char *own_buf)
ULONGEST num;
ULONGEST addr;
ULONGEST count;
+ ULONGEST kind;
struct tracepoint *tpoint;
char *actparm;
char *packet = own_buf;
@@ -2550,6 +2557,12 @@ cmd_qtdp (char *own_buf)
tpoint->cond = gdb_parse_agent_expr (&actparm);
packet = actparm;
}
+ else if (*packet == 'K')
+ {
+ ++packet;
+ packet = unpack_varlen_hex (packet, &kind);
+ tpoint->kind = kind;
+ }
else if (*packet == '-')
break;
else if (*packet == '\0')
@@ -2564,11 +2577,13 @@ cmd_qtdp (char *own_buf)
}

trace_debug ("Defined %stracepoint %d at 0x%s, "
- "enabled %d step %" PRIu64 " pass %" PRIu64,
+ "enabled %d step %" PRIu64 " pass %" PRIu64
+ " kind %" PRId32,
tpoint->type == fast_tracepoint ? "fast "
: tpoint->type == static_tracepoint ? "static " : "",
tpoint->number, paddress (tpoint->address), tpoint->enabled,
- tpoint->step_count, tpoint->pass_count);
+ tpoint->step_count, tpoint->pass_count,
+ tpoint->kind);
}
else if (tpoint)
add_tracepoint_action (tpoint, packet);
@@ -3150,9 +3165,17 @@ install_tracepoint (struct tracepoint *tpoint, char *own_buf)
/* Tracepoints are installed as memory breakpoints. Just go
ahead and install the trap. The breakpoints module
handles duplicated breakpoints, and the memory read
- routine handles un-patching traps from memory reads. */
- tpoint->handle = set_breakpoint_at (tpoint->address,
- tracepoint_handler);
+ routine handles un-patching traps from memory reads.
+ If tracepoint kind is not set, use the default values
+ otherwise what was set from the gdb client will be used. */
+ if (tpoint->kind == -1)
+ tpoint->handle = set_breakpoint_at (tpoint->address,
+ tracepoint_handler);
+ else
+ tpoint->handle =
+ set_breakpoint_at_with_kind (tpoint->address,
+ tracepoint_handler,
+ tpoint->kind);
}
else if (tpoint->type == fast_tracepoint || tpoint->type == static_tracepoint)
{
@@ -3253,8 +3276,14 @@ cmd_qtstart (char *packet)
ahead and install the trap. The breakpoints module
handles duplicated breakpoints, and the memory read
routine handles un-patching traps from memory reads. */
- tpoint->handle = set_breakpoint_at (tpoint->address,
- tracepoint_handler);
+ if (tpoint->kind == -1)
+ tpoint->handle = set_breakpoint_at (tpoint->address,
+ tracepoint_handler);
+ else
+ tpoint->handle =
+ set_breakpoint_at_with_kind (tpoint->address,
+ tracepoint_handler,
+ tpoint->kind);
}
else if (tpoint->type == fast_tracepoint
|| tpoint->type == static_tracepoint)
diff --git a/gdb/remote.c b/gdb/remote.c
index 517e36d..377a6da 100644
--- a/gdb/remote.c
+++ b/gdb/remote.c
@@ -241,6 +241,8 @@ static void readahead_cache_invalidate (void);

static void remote_unpush_and_throw (void);

+static int remote_supports_tracepoint_kinds (void);
+
/* For "remote". */

static struct cmd_list_element *remote_cmdlist;
@@ -1521,6 +1523,9 @@ enum {
/* Support TARGET_WAITKIND_NO_RESUMED. */
PACKET_no_resumed,

+ /* Support target dependant tracepoint kinds. */
+ PACKET_TracepointKinds,
+
PACKET_MAX
};

@@ -4693,6 +4698,8 @@ static const struct protocol_feature remote_protocol_features[] = {
{ "vContSupported", PACKET_DISABLE, remote_supported_packet, PACKET_vContSupported },
{ "QThreadEvents", PACKET_DISABLE, remote_supported_packet, PACKET_QThreadEvents },
{ "no-resumed", PACKET_DISABLE, remote_supported_packet, PACKET_no_resumed },
+ { "TracepointKinds", PACKET_DISABLE, remote_supported_packet,
+ PACKET_TracepointKinds }
};

static char *remote_support_xml;
@@ -12197,6 +12204,12 @@ remote_can_run_breakpoint_commands (struct target_ops *self)
return packet_support (PACKET_BreakpointCommands) == PACKET_ENABLE;
}

+static int
+remote_supports_tracepoint_kinds (void)
+{
+ return packet_support (PACKET_TracepointKinds) == PACKET_ENABLE;
+}
+
static void
remote_trace_init (struct target_ops *self)
{
@@ -12285,6 +12298,7 @@ remote_download_tracepoint (struct target_ops *self, struct bp_location *loc)
char *pkt;
struct breakpoint *b = loc->owner;
struct tracepoint *t = (struct tracepoint *) b;
+ int kind;

encode_actions_rsp (loc, &tdp_actions, &stepping_actions);
old_chain = make_cleanup (free_actions_list_cleanup_wrapper,
@@ -12293,6 +12307,10 @@ remote_download_tracepoint (struct target_ops *self, struct bp_location *loc)
stepping_actions);

tpaddr = loc->address;
+
+ /* Fetch the proper tracepoint kind. */
+ gdbarch_remote_breakpoint_from_pc (target_gdbarch (), &tpaddr, &kind);
+
sprintf_vma (addrbuf, tpaddr);
xsnprintf (buf, BUF_SIZE, "QTDP:%x:%s:%c:%lx:%x", b->number,
addrbuf, /* address */
@@ -12367,6 +12385,11 @@ remote_download_tracepoint (struct target_ops *self, struct bp_location *loc)
"ignoring tp %d cond"), b->number);
}

+ /* Tracepoint Kinds are modeled after the breakpoint Z0 kind packet.
+ Send the tracepoint kind if we support it. */
+ if (remote_supports_tracepoint_kinds ())
+ xsnprintf (buf + strlen (buf), BUF_SIZE - strlen (buf), ":K%x", kind);
+
if (b->commands || *default_collect)
strcat (buf, "-");
putpkt (buf);
@@ -14333,6 +14356,10 @@ Show the maximum size of the address (in bits) in a memory packet."), NULL,
add_packet_config_cmd (&remote_protocol_packets[PACKET_no_resumed],
"N stop reply", "no-resumed-stop-reply", 0);

+ add_packet_config_cmd (&remote_protocol_packets[PACKET_TracepointKinds],
+ "TracepointKinds",
+ "tracepoint-kinds", 0);
+
/* Assert that we've registered "set remote foo-packet" commands
for all packet configs. */
{
diff --git a/gdb/testsuite/gdb.trace/collection.exp b/gdb/testsuite/gdb.trace/collection.exp
index f225429..a30234f 100644
--- a/gdb/testsuite/gdb.trace/collection.exp
+++ b/gdb/testsuite/gdb.trace/collection.exp
@@ -764,7 +764,12 @@ proc gdb_trace_collection_test {} {
gdb_collect_expression_test globals_test_func \
"globalarr\[\(l6, l7\)\]" "7" "a\[\(b, c\)\]"

- gdb_collect_return_test
+ #This architecture has no method to collect a return address.
+ if { [is_aarch32_target] } {
+ unsupported "collect \$_ret: This architecture has no method to collect a return address"
+ } else {
+ gdb_collect_return_test
+ }

gdb_collect_strings_test strings_test_func "locstr" "abcdef" "" \
"local string"
diff --git a/gdb/testsuite/gdb.trace/trace-common.h b/gdb/testsuite/gdb.trace/trace-common.h
index 60cf9e8..9d607f7 100644
--- a/gdb/testsuite/gdb.trace/trace-common.h
+++ b/gdb/testsuite/gdb.trace/trace-common.h
@@ -40,7 +40,8 @@ x86_trace_dummy ()
" call " SYMBOL(x86_trace_dummy) "\n" \
)

-#elif (defined __aarch64__) || (defined __powerpc__)
+#elif (defined __aarch64__) || (defined __powerpc__) \
+ || (defined __arm__ && !defined __thumb__)

#define FAST_TRACEPOINT_LABEL(name) \
asm (" .global " SYMBOL(name) "\n" \
@@ -48,11 +49,18 @@ x86_trace_dummy ()
" nop\n" \
)

-#elif (defined __s390__)
+#elif (defined __arm__ && defined __thumb2__)

#define FAST_TRACEPOINT_LABEL(name) \
asm (" .global " SYMBOL(name) "\n" \
SYMBOL(name) ":\n" \
+ " nop.w\n" \
+ )
+
+#elif (defined __s390__)
+#define FAST_TRACEPOINT_LABEL(name) \
+ asm (" .global " SYMBOL(name) "\n" \
+ SYMBOL(name) ":\n" \
" mvc 0(8, %r15), 0(%r15)\n" \
)

diff --git a/gdb/testsuite/lib/trace-support.exp b/gdb/testsuite/lib/trace-support.exp
index b307f3f..df0fda0 100644
--- a/gdb/testsuite/lib/trace-support.exp
+++ b/gdb/testsuite/lib/trace-support.exp
@@ -43,6 +43,9 @@ if [is_amd64_regs_target] {
} elseif { [istarget "s390*-*-*"] } {
set fpreg "r11"
set spreg "r15"
+} elseif [is_aarch32_target] {
+ set fpreg "sp"
+ set spreg "sp"
set pcreg "pc"
} else {
set fpreg "fp"
--
2.9.2