[PATCH v10 07/10] btrace, gdbserver: Add ptwrite to btrace_config_pt.

Felix Willgerodt via Gdb-patches
2023-07-18T11:58:59Z

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

Reviewed-By: Eli Zaretskii <eliz@gnu.org>
---
gdb/btrace.c | 8 +++++++-
gdb/doc/gdb.texinfo | 21 +++++++++++++++++++++
gdb/features/btrace-conf.dtd | 1 +
gdb/remote.c | 33 +++++++++++++++++++++++++++++++++
gdbserver/linux-low.cc | 3 +++
gdbserver/server.cc | 18 ++++++++++++++++++
gdbsupport/btrace-common.h | 6 ++++++
7 files changed, 89 insertions(+), 1 deletion(-)

diff --git a/gdb/btrace.c b/gdb/btrace.c
index 2c20763b570..6cbb53b01f1 100644
--- a/gdb/btrace.c
+++ b/gdb/btrace.c
@@ -2273,7 +2273,7 @@ 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;
@@ -2282,10 +2282,16 @@ 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 != nullptr)
+ 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_enum,
+ gdb_xml_enums_boolean },
{ NULL, GDB_XML_AF_NONE, NULL, NULL }
};

diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index 2cd0a6c49e7..fa2ad1123ac 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -43943,6 +43943,11 @@ 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{-}
@@ -44254,6 +44259,9 @@ 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.
@@ -44761,6 +44769,18 @@ The ring buffer size has been set.
A badly formed request or an error was encountered.
@end table

+@item Qbtrace-conf:pt:ptwrite=@var{(yes|no)}
+Indicate support for @code{PTWRITE} packets. This allows 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
@@ -47409,6 +47429,7 @@ The formal DTD for the branch trace configuration format is given below:

<!ELEMENT pt EMPTY>
<!ATTLIST pt size CDATA #IMPLIED>
+<!ATTLIST pt ptwrite (yes | no) #IMPLIED>
@end smallexample

@include agentexpr.texi
diff --git a/gdb/features/btrace-conf.dtd b/gdb/features/btrace-conf.dtd
index 3fbe3a4dc32..7aeaa4695e1 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 (yes | no) #IMPLIED>
diff --git a/gdb/remote.c b/gdb/remote.c
index 7e3d6adfe4f..095aa630236 100644
--- a/gdb/remote.c
+++ b/gdb/remote.c
@@ -286,6 +286,9 @@ 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,

@@ -5597,6 +5600,8 @@ 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 },
@@ -14211,6 +14216,31 @@ remote_target::btrace_sync_conf (const btrace_config *conf)

rs->btrace_config.pt.size = conf->pt.size;
}
+
+ if ((m_features.packet_support (PACKET_Qbtrace_conf_pt_ptwrite)
+ == PACKET_ENABLE)
+ && conf->pt.ptwrite != rs->btrace_config.pt.ptwrite)
+ {
+ pos = buf;
+ const char *ptw = conf->pt.ptwrite ? "yes" : "no";
+ const char *name
+ = packets_descriptions[PACKET_Qbtrace_conf_pt_ptwrite].name;
+ pos += xsnprintf (pos, endbuf - pos, "%s=\"%s\"", name, ptw);
+
+ putpkt (buf);
+ getpkt (&rs->buf, 0);
+
+ if (m_features.packet_ok (buf, PACKET_Qbtrace_conf_pt_ptwrite)
+ == 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 TP's btrace configuration from the target and store it into CONF. */
@@ -15390,6 +15420,9 @@ Show the maximum size of the address (in bits) in a memory packet."), NULL,
add_packet_config_cmd (PACKET_Qbtrace_conf_pt_size, "Qbtrace-conf:pt:size",
"btrace-conf-pt-size", 0);

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

diff --git a/gdbserver/linux-low.cc b/gdbserver/linux-low.cc
index 651f219b738..a4f48b1e4bf 100644
--- a/gdbserver/linux-low.cc
+++ b/gdbserver/linux-low.cc
@@ -6881,6 +6881,9 @@ linux_process_target::read_btrace_conf (const btrace_target_info *tinfo,
string_xml_appendf (*buffer, "<pt");
string_xml_appendf (*buffer, " size=\"0x%x\"", conf->pt.size);
string_xml_appendf (*buffer, "/>\n");
+ string_xml_appendf (*buffer, " ptwrite=\"%s\"",
+ conf->pt.ptwrite ? "yes" : "no");
+ string_xml_appendf (*buffer, "/>\n");
break;
}
}
diff --git a/gdbserver/server.cc b/gdbserver/server.cc
index c57270175b4..f54095b9a37 100644
--- a/gdbserver/server.cc
+++ b/gdbserver/server.cc
@@ -547,6 +547,23 @@ 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)
+ {
+ bool ptwrite;
+
+ op += strlen ("pt:ptwrite=");
+ if (strncmp (op, "\"yes\"", strlen ("\"yes\"")) == 0)
+ ptwrite = true;
+ else if (strncmp (op, "\"no\"", strlen ("\"no\"")) == 0)
+ ptwrite = false;
+ else
+ {
+ strcpy (own_buf, "E.Bad ptwrite value.");
+ return -1;
+ }
+
+ current_btrace_conf.pt.ptwrite = ptwrite;
+ }
else
{
strcpy (own_buf, "E.Bad Qbtrace configuration option.");
@@ -2146,6 +2163,7 @@ 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 e287c93a6c1..03cc60648e9 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 both gdb and gdbserver support this, gdb will try to enable ptwrite
+ packets when tracing is started. */
+ bool ptwrite;
};

/* A branch tracing configuration.
--
2.34.1