[PATCH 4/4] Support tracepoints for ARM linux in GDBServer

Antoine Tremblay
2016-01-07T17:45:14Z

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.

A note about tests :

New tests passing: All of gdb.trace except below tests.

Failing tests:

new FAIL: gdb.trace/unavailable.exp: unavailable locals:
register locals: tfile: info locals
new FAIL: gdb.trace/unavailable.exp: unavailable locals:
register locals: tfile: print locd
new FAIL: gdb.trace/unavailable.exp: unavailable locals:
register locals: tfile: print locf

These tests are failing since we would need the proper gdbarch containing
the vfp registers when trying to read pseudo-registers. However, we would
need to have an inferior running to have this and since we don't, the tests
fail.

Should these be set as expected fail ?

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 | 22 +++++++++++++----
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 | 10 +++++++-
gdb/testsuite/lib/trace-support.exp | 4 ++++
11 files changed, 131 insertions(+), 15 deletions(-)

diff --git a/gdb/NEWS b/gdb/NEWS
index 484d98d..28110cc 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -3,6 +3,8 @@

*** Changes since GDB 7.10

+* Support for tracepoints on arm-linux was added in GDBServer.
+
* Record btrace now supports non-stop mode.

* Support for tracepoints on aarch64-linux was added in GDBserver.
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index 0778383..cffad48 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -36633,6 +36633,11 @@ 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:
@@ -36851,6 +36856,9 @@ 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::
@@ -37361,7 +37369,8 @@ 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

@@ -37441,7 +37450,7 @@ 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
@@ -37452,9 +37461,12 @@ 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 length. E.g., the arm and mips
+can insert either a 2 or 4 byte breakpoint. Some architectures have
+additional meanings for kind 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 d967e58..76d0e32 100644
--- a/gdb/gdbserver/linux-arm-low.c
+++ b/gdb/gdbserver/linux-arm-low.c
@@ -1005,6 +1005,14 @@ 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,
@@ -1031,7 +1039,7 @@ 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 2e220b8..3a9a816 100644
--- a/gdb/gdbserver/mem-break.c
+++ b/gdb/gdbserver/mem-break.c
@@ -791,6 +791,19 @@ set_breakpoint_at (CORE_ADDR where, int (*handler) (CORE_ADDR))
&err_ignored);
}

+/* 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 4d9a76c..02a1038 100644
--- a/gdb/gdbserver/mem-break.h
+++ b/gdb/gdbserver/mem-break.h
@@ -146,6 +146,13 @@ 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 fe7195d..059a373 100644
--- a/gdb/gdbserver/server.c
+++ b/gdb/gdbserver/server.c
@@ -2269,6 +2269,7 @@ 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 40d0da9..3a50f47 100644
--- a/gdb/gdbserver/tracepoint.c
+++ b/gdb/gdbserver/tracepoint.c
@@ -754,6 +754,11 @@ 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. */
@@ -1820,6 +1825,7 @@ 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
@@ -2495,6 +2501,7 @@ cmd_qtdp (char *own_buf)
ULONGEST num;
ULONGEST addr;
ULONGEST count;
+ ULONGEST kind;
struct tracepoint *tpoint;
char *actparm;
char *packet = own_buf;
@@ -2561,6 +2568,12 @@ 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')
@@ -2575,11 +2588,13 @@ 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);
@@ -3153,9 +3168,17 @@ 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)
{
@@ -3248,8 +3271,14 @@ 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 528d863..17581e2 100644
--- a/gdb/remote.c
+++ b/gdb/remote.c
@@ -241,6 +241,8 @@ static int stop_reply_queue_length (void);

static void readahead_cache_invalidate (void);

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

static struct cmd_list_element *remote_cmdlist;
@@ -1491,6 +1493,9 @@ enum {
/* Support TARGET_WAITKIND_NO_RESUMED. */
PACKET_no_resumed,

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

@@ -4534,6 +4539,8 @@ 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;
@@ -11692,6 +11699,12 @@ 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)
{
@@ -11780,6 +11793,7 @@ 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,
@@ -11788,6 +11802,10 @@ 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 */
@@ -11862,6 +11880,11 @@ 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);
@@ -13767,6 +13790,10 @@ 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 eceb182..4f05423 100644
--- a/gdb/testsuite/gdb.trace/trace-common.h
+++ b/gdb/testsuite/gdb.trace/trace-common.h
@@ -40,7 +40,7 @@ x86_trace_dummy ()
" call " SYMBOL(x86_trace_dummy) "\n" \
)

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

#define FAST_TRACEPOINT_LABEL(name) \
asm (" .global " SYMBOL(name) "\n" \
@@ -48,6 +48,14 @@ x86_trace_dummy ()
" nop\n" \
)

+#elif (defined __arm__ && defined __thumb2__)
+
+#define FAST_TRACEPOINT_LABEL(name) \
+ asm (" .global " SYMBOL(name) "\n" \
+ SYMBOL(name) ":\n" \
+ " nop.w\n" \
+ )
+
#else

#error "unsupported architecture for trace tests"
diff --git a/gdb/testsuite/lib/trace-support.exp b/gdb/testsuite/lib/trace-support.exp
index f593c43..ef63f7a 100644
--- a/gdb/testsuite/lib/trace-support.exp
+++ b/gdb/testsuite/lib/trace-support.exp
@@ -36,6 +36,10 @@ if [is_amd64_regs_target] {
set fpreg "x29"
set spreg "sp"
set pcreg "pc"
+} elseif [is_aarch32_target] {
+ set fpreg "sp"
+ set spreg "sp"
+ set pcreg "pc"
} else {
set fpreg "fp"
set spreg "sp"
--
2.6.4