[PATCH v2 07/12] btrace, gdbserver: Add ptwrite to btrace_config_pt.

Felix Willgerodt via Gdb-patches
2021-06-14T15:05:58Z

This enables gdb and gdbserver to communicate about ptwrite support. If
ptwrite support would be enabled unconditionally, GDBs with older libipt
versions would break.

gdb/ChangeLog:
2021-06-14 Felix Willgerodt <felix.willgerodt@intel.com>

* btrace.c (parse_xml_btrace_conf_pt): Add ptwrite to pt.conf.
(btrace_conf_pt_attributes): Add ptwrite.

gdb/doc/ChangeLog:
2021-06-14 Felix Willgerodt <felix.willgerodt@intel.com>

* gdb.texinfo (General Query Packets): Document Qbtrace-conf:pt:ptwrite.
(Branch Trace Configuration Format): Document ptwrite in btrace-conf.

gdbserver/ChangeLog:
2021-06-14 Felix Willgerodt <felix.willgerodt@intel.com>

* linux-low.cc (linux_process_target::read_btrace_conf): Add ptwrite.
* server.cc (handle_btrace_conf_general_set): Handle pt:ptwrite.
(supported_btrace_packets): Add Qbtrace-conf:pt:ptwrite.

gdbsupport/ChangeLog:
2021-06-14 Felix Willgerodt <felix.willgerodt@intel.com>

* btrace-common.h (btrace_config_pt): Add ptwrite.
---
gdb/btrace.c | 7 ++++++-
gdb/doc/gdb.texinfo | 21 +++++++++++++++++++++
gdb/features/btrace-conf.dtd | 1 +
gdb/remote.c | 30 ++++++++++++++++++++++++++++++
gdbserver/linux-low.cc | 1 +
gdbserver/server.cc | 16 ++++++++++++++++
gdbsupport/btrace-common.h | 6 ++++++
7 files changed, 81 insertions(+), 1 deletion(-)

diff --git a/gdb/btrace.c b/gdb/btrace.c
index 9f117a5e90d..2c4f3f67c6b 100644
--- a/gdb/btrace.c
+++ b/gdb/btrace.c
@@ -2261,7 +2261,7 @@ parse_xml_btrace_conf_pt (struct gdb_xml_parser *parser,
std::vector<gdb_xml_value> &attributes)
{
struct btrace_config *conf;
- struct gdb_xml_value *size;
+ struct gdb_xml_value *size, *ptwrite;

conf = (struct btrace_config *) user_data;
conf->format = BTRACE_FORMAT_PT;
@@ -2270,10 +2270,15 @@ parse_xml_btrace_conf_pt (struct gdb_xml_parser *parser,
size = xml_find_attribute (attributes, "size");
if (size != NULL)
conf->pt.size = (unsigned int) *(ULONGEST *) size->value.get ();
+
+ ptwrite = xml_find_attribute (attributes, "ptwrite");
+ if (ptwrite != NULL)
+ conf->pt.ptwrite = (bool) *(ULONGEST *) ptwrite->value.get ();
}

static const struct gdb_xml_attribute btrace_conf_pt_attributes[] = {
{ "size", GDB_XML_AF_OPTIONAL, gdb_xml_parse_attr_ulongest, NULL },
+ { "ptwrite", GDB_XML_AF_OPTIONAL, gdb_xml_parse_attr_ulongest, NULL },
{ NULL, GDB_XML_AF_NONE, NULL, NULL }
};

diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index 5e4f8e73b7d..60c1340d31d 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -41906,6 +41906,11 @@ These are the currently defined stub features and their properties:
@tab @samp{-}
@tab Yes

+@item @samp{Qbtrace-conf:pt:ptwrite}
+@tab Yes
+@tab @samp{-}
+@tab Yes
+
@item @samp{QNonStop}
@tab No
@tab @samp{-}
@@ -42217,6 +42222,9 @@ The remote stub understands the @samp{Qbtrace-conf:bts:size} packet.
@item Qbtrace-conf:pt:size
The remote stub understands the @samp{Qbtrace-conf:pt:size} packet.

+@item Qbtrace-conf:pt:ptwrite
+The remote stub understands the @samp{Qbtrace-conf:pt:ptwrite} packet.
+
@item swbreak
The remote stub reports the @samp{swbreak} stop reason for memory
breakpoints.
@@ -42717,6 +42725,18 @@ The ring buffer size has been set.
A badly formed request or an error was encountered.
@end table

+@item Qbtrace-conf:pt:ptwrite=@var{value}
+Control recording of ptwrite packets. This was added for backwards-
+compatibility.
+
+Reply:
+@table @samp
+@item OK
+The ptwrite config parameter has been set.
+@item E.errtext
+A badly formed request or an error was encountered.
+@end table
+
@end table

@node Architecture-Specific Protocol Details
@@ -45359,6 +45379,7 @@ The formal DTD for the branch trace configuration format is given below:

<!ELEMENT pt EMPTY>
<!ATTLIST pt size CDATA #IMPLIED>
+<!ATTLIST pt ptwrite CDATA #IMPLIED>
@end smallexample

@include agentexpr.texi
diff --git a/gdb/features/btrace-conf.dtd b/gdb/features/btrace-conf.dtd
index 4b060bb408c..339ce4a4966 100644
--- a/gdb/features/btrace-conf.dtd
+++ b/gdb/features/btrace-conf.dtd
@@ -12,3 +12,4 @@

<!ELEMENT pt EMPTY>
<!ATTLIST pt size CDATA #IMPLIED>
+<!ATTLIST pt ptwrite CDATA #IMPLIED>
diff --git a/gdb/remote.c b/gdb/remote.c
index 22933eeaeec..554dbbf107b 100644
--- a/gdb/remote.c
+++ b/gdb/remote.c
@@ -2168,6 +2168,9 @@ enum {
/* Support for the Qbtrace-conf:pt:size packet. */
PACKET_Qbtrace_conf_pt_size,

+ /* Support for the Qbtrace-conf:pt:ptwrite packet. */
+ PACKET_Qbtrace_conf_pt_ptwrite,
+
/* Support for exec events. */
PACKET_exec_event_feature,

@@ -5328,6 +5331,8 @@ static const struct protocol_feature remote_protocol_features[] = {
PACKET_exec_event_feature },
{ "Qbtrace-conf:pt:size", PACKET_DISABLE, remote_supported_packet,
PACKET_Qbtrace_conf_pt_size },
+ { "Qbtrace-conf:pt:ptwrite", PACKET_DISABLE, remote_supported_packet,
+ PACKET_Qbtrace_conf_pt_ptwrite },
{ "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 },
@@ -14028,6 +14033,28 @@ remote_target::btrace_sync_conf (const btrace_config *conf)

rs->btrace_config.pt.size = conf->pt.size;
}
+
+ packet = &remote_protocol_packets[PACKET_Qbtrace_conf_pt_ptwrite];
+ if (packet_config_support (packet) == PACKET_ENABLE
+ && conf->pt.ptwrite != rs->btrace_config.pt.ptwrite)
+ {
+ pos = buf;
+ pos += xsnprintf (pos, endbuf - pos, "%s=%d", packet->name,
+ conf->pt.ptwrite);
+
+ putpkt (buf);
+ getpkt (&rs->buf, 0);
+
+ if (packet_ok (buf, packet) == PACKET_ERROR)
+ {
+ if (buf[0] == 'E' && buf[1] == '.')
+ error (_("Failed to sync ptwrite config: %s"), buf + 2);
+ else
+ error (_("Failed to sync ptwrite config."));
+ }
+
+ rs->btrace_config.pt.ptwrite = conf->pt.ptwrite;
+ }
}

/* Read the current thread's btrace configuration from the target and
@@ -15230,6 +15257,9 @@ Show the maximum size of the address (in bits) in a memory packet."), NULL,
add_packet_config_cmd (&remote_protocol_packets[PACKET_Qbtrace_conf_pt_size],
"Qbtrace-conf:pt:size", "btrace-conf-pt-size", 0);

+ add_packet_config_cmd (&remote_protocol_packets[PACKET_Qbtrace_conf_pt_ptwrite],
+ "Qbtrace-conf:pt:ptwrite", "btrace-conf-pt-ptwrite", 0);
+
add_packet_config_cmd (&remote_protocol_packets[PACKET_vContSupported],
"vContSupported", "verbose-resume-supported", 0);

diff --git a/gdbserver/linux-low.cc b/gdbserver/linux-low.cc
index 5c6191d941c..6554e9766ab 100644
--- a/gdbserver/linux-low.cc
+++ b/gdbserver/linux-low.cc
@@ -7096,6 +7096,7 @@ linux_process_target::read_btrace_conf (const btrace_target_info *tinfo,
case BTRACE_FORMAT_PT:
buffer_xml_printf (buffer, "<pt");
buffer_xml_printf (buffer, " size=\"0x%x\"", conf->pt.size);
+ buffer_xml_printf (buffer, " ptwrite=\"%d\"", conf->pt.ptwrite);
buffer_xml_printf (buffer, "/>\n");
break;
}
diff --git a/gdbserver/server.cc b/gdbserver/server.cc
index 32dcc05924e..b899f50db35 100644
--- a/gdbserver/server.cc
+++ b/gdbserver/server.cc
@@ -546,6 +546,21 @@ handle_btrace_conf_general_set (char *own_buf)

current_btrace_conf.pt.size = (unsigned int) size;
}
+ else if (strncmp (op, "pt:ptwrite=", strlen ("pt:ptwrite=")) == 0)
+ {
+ int ptwrite;
+ char *endp = NULL;
+
+ errno = 0;
+ ptwrite = strtoul (op + strlen ("pt:ptwrite="), &endp, 16);
+ if (endp == NULL || *endp != 0 || errno != 0 || ptwrite > 1)
+ {
+ strcpy (own_buf, "E.Bad ptwrite value.");
+ return -1;
+ }
+
+ current_btrace_conf.pt.ptwrite = (bool) ptwrite;
+ }
else
{
strcpy (own_buf, "E.Bad Qbtrace configuration option.");
@@ -2189,6 +2204,7 @@ supported_btrace_packets (char *buf)
strcat (buf, ";Qbtrace-conf:bts:size+");
strcat (buf, ";Qbtrace:pt+");
strcat (buf, ";Qbtrace-conf:pt:size+");
+ strcat (buf, ";Qbtrace-conf:pt:ptwrite+");
strcat (buf, ";Qbtrace:off+");
strcat (buf, ";qXfer:btrace:read+");
strcat (buf, ";qXfer:btrace-conf:read+");
diff --git a/gdbsupport/btrace-common.h b/gdbsupport/btrace-common.h
index 26d26ec957f..ccdf2fc25af 100644
--- a/gdbsupport/btrace-common.h
+++ b/gdbsupport/btrace-common.h
@@ -117,6 +117,12 @@ struct btrace_config_pt
This is unsigned int and not size_t since it is registered as
control variable for "set record btrace pt buffer-size". */
unsigned int size;
+
+ /* Configuration bit for ptwrite packets.
+
+ If this is set, gdb will try to enable ptwrite packets if the OS
+ supports this. */
+ bool ptwrite;
};

/* A branch tracing configuration.