[Qemu-devel] [PATCH] gdbstub: monitor fixes v3

[Jason Wessel]

Based on some comments in the qemu irc channel, here is a revised
implementation of gdb monitor pass through patches.

At a future time if it is truly "high value" the gdb specific monitor
commands will be migrated into the qemu monitor, OR at such time that
the user emulation begins to use the monitor.  Presently, the only
user of the gdb specific variables is a debugger and the controls
exist to alter the behavior from the debugger, even if you have to
find the debugger console window some where in a debugger UI...

I would guess the average user never uses the debugger.  Out of the
small community of users that use the debugger probably even fewer
will use these new controls. These type of controls are intended for
extremely low level debugging, hence the reason they exist in the
"Advanced Section" in the first place :-)

please apply in order:
gdb_single_step_monitor_cmd.patch
gdb_monitor_plus_qemu_monitor.patch


Thanks,
Jason.

From: Jason Wessel <address@hidden>
Subject: [PATCH] gdbstub: replace singlestep q packets with qRcmd packets

At the gdbserial protocol level, using the qRcmd packets allows gdb to
use the "monitor" command to access the controls for single stepping
behavior.  Now you can use a gdb "monitor" command instead of a gdb
"maintenance" command.

The ability to turn off single stepping entirely was removed because
it is not a useful feature.

The qemu docs were updated to reflect this change.

Signed-off-by: Jason Wessel <address@hidden>

---
 gdbstub.c     |   92 +++++++++++++++++++++++++++++++++++++++-------------------
 qemu-doc.texi |   31 ++++++-------------
 2 files changed, 74 insertions(+), 49 deletions(-)

--- a/gdbstub.c
+++ b/gdbstub.c
@@ -205,9 +205,9 @@ static void hextomem(uint8_t *mem, const
 }
 
 /* return -1 if error, 0 if OK */
-static int put_packet(GDBState *s, char *buf)
+static int put_packet_hex(GDBState *s, const char *buf, int len, int isHex)
 {
-    int len, csum, i;
+    int csum, i;
     uint8_t *p;
 
 #ifdef DEBUG_GDB
@@ -217,13 +217,19 @@ static int put_packet(GDBState *s, char 
     for(;;) {
         p = s->last_packet;
         *(p++) = '$';
-        len = strlen(buf);
-        memcpy(p, buf, len);
-        p += len;
+        if (isHex) {
+            p[0] = 'O';
+            memtohex(p + 1, buf, len);
+            len = strlen(p);
+        } else {
+            memcpy(p, buf, len);
+        }
+
         csum = 0;
         for(i = 0; i < len; i++) {
-            csum += buf[i];
+            csum += p[i];
         }
+        p += len;
         *(p++) = '#';
         *(p++) = tohex((csum >> 4) & 0xf);
         *(p++) = tohex((csum) & 0xf);
@@ -244,6 +250,24 @@ static int put_packet(GDBState *s, char 
     return 0;
 }
 
+/* return -1 if error, 0 if OK */
+static int put_packet(GDBState *s, const char *buf) {
+    return put_packet_hex(s, buf, strlen(buf), 0);
+}
+
+static void monitor_output(GDBState *s, const char *msg)
+{
+    put_packet_hex(s, msg, strlen(msg), 1);
+}
+
+static void monitor_help(GDBState *s)
+{
+    monitor_output(s, "gdbstub specific monitor commands:\n");
+    monitor_output(s, "show <sirqs|stimers> -- Show gdbstub Single Stepping 
variables\n");
+    monitor_output(s, "set sirqs <0|1> --  Single Stepping with qemu irq 
handlers enabled\n");
+    monitor_output(s, "set stimers <0|1> -- Single Stepping with qemu timers 
enabled\n");
+}
+
 #if defined(TARGET_I386)
 
 #ifdef TARGET_X86_64
@@ -948,6 +972,37 @@ static void cpu_gdb_write_registers(CPUS
 
 #endif
 
+static void gdb_rcmd(GDBState *s, const char *p, char *buf, char *mem_buf)
+{
+    int len = strlen(p);
+
+    if ((len % 2) != 0) {
+        put_packet(s, "E01");
+        return;
+    }
+    hextomem(mem_buf, p, len);
+    mem_buf[(len >> 1)] = 0;
+
+    if (!strcmp(mem_buf, "show sirqs")) {
+        sprintf(buf, "sirqs == %i\n", (sstep_flags & SSTEP_NOIRQ) == 0);
+        monitor_output(s, buf);
+    } else if (!strcmp(mem_buf, "show stimers")) {
+        sprintf(buf, "stimers == %i\n", (sstep_flags & SSTEP_NOTIMER) == 0);
+        monitor_output(s, buf);
+    } else if (!strcmp(mem_buf, "set sirqs 1")) {
+        sstep_flags &= ~SSTEP_NOIRQ;
+    } else if (!strcmp(mem_buf, "set sirqs 0")) {
+        sstep_flags |= SSTEP_NOIRQ;
+    } else if (!strcmp(mem_buf, "set stimers 1")) {
+        sstep_flags &= ~SSTEP_NOTIMER;
+    } else if (!strcmp(mem_buf, "set stimers 0")) {
+        sstep_flags |= SSTEP_NOTIMER;
+    } else if (!strcmp(mem_buf, "help") || !strcmp(mem_buf, "?")) {
+        monitor_help(s);
+    }
+    put_packet(s, "OK");
+}
+
 static int gdb_handle_packet(GDBState *s, CPUState *env, const char *line_buf)
 {
     const char *p;
@@ -1139,29 +1194,8 @@ static int gdb_handle_packet(GDBState *s
         }
         break;
     case 'q':
-    case 'Q':
-        /* parse any 'q' packets here */
-        if (!strcmp(p,"qemu.sstepbits")) {
-            /* Query Breakpoint bit definitions */
-            sprintf(buf,"ENABLE=%x,NOIRQ=%x,NOTIMER=%x",
-                    SSTEP_ENABLE,
-                    SSTEP_NOIRQ,
-                    SSTEP_NOTIMER);
-            put_packet(s, buf);
-            break;
-        } else if (strncmp(p,"qemu.sstep",10) == 0) {
-            /* Display or change the sstep_flags */
-            p += 10;
-            if (*p != '=') {
-                /* Display current setting */
-                sprintf(buf,"0x%x", sstep_flags);
-                put_packet(s, buf);
-                break;
-            }
-            p++;
-            type = strtoul(p, (char **)&p, 16);
-            sstep_flags = type;
-            put_packet(s, "OK");
+        if (!strncmp(p, "Rcmd,", 5)) {
+            gdb_rcmd(s, p + 5, buf, mem_buf);
             break;
         }
 #ifdef CONFIG_LINUX_USER
--- a/qemu-doc.texi
+++ b/qemu-doc.texi
@@ -1951,32 +1951,23 @@ Use @code{set architecture i8086} to dum
 
 Advanced debugging options:
 
-The default single stepping behavior is step with the IRQs and timer service 
routines off.  It is set this way because when gdb executes a single step it 
expects to advance beyond the current instruction.  With the IRQs and and timer 
service routines on, a single step might jump into the one of the interrupt or 
exception vectors instead of executing the current instruction. This means you 
may hit the same breakpoint a number of times before executing the instruction 
gdb wants to have executed.  Because there are rare circumstances where you 
want to single step into an interrupt vector the behavior can be controlled 
from GDB.  There are three commands you can query and set the single step 
behavior:
+The default single stepping behavior is to step with the IRQs and timer 
service routines off.  It is set this way because when gdb executes a single 
step it expects to advance beyond the current instruction.  With the IRQs and 
and timer service routines on, a single step might jump into the one of the 
interrupt or exception vectors instead of executing the current instruction. 
This means you may hit the same breakpoint a number of times before executing 
the instruction gdb wants execute.  Because there are rare circumstances where 
you want to single step into an interrupt vector the behavior can be controlled 
from GDB.  There are several commands you use to query and set the single step 
behavior while inside gdb:
 @table @code
address@hidden maintenance packet qqemu.sstepbits
address@hidden monitor show <sirqs|stimers>
 
-This will display the MASK bits used to control the single stepping IE:
+This will display the values of the single stepping controls IE:
 @example
-(gdb) maintenance packet qqemu.sstepbits
-sending: "qqemu.sstepbits"
-received: "ENABLE=1,NOIRQ=2,NOTIMER=4"
+(gdb) monitor show sirqs
+sirqs == 0
+(gdb) monitor show stimers
+stimers == 0
 @end example
address@hidden maintenance packet qqemu.sstep
address@hidden monitor set sirqs <0|1>
 
-This will display the current value of the mask used when single stepping IE:
address@hidden
-(gdb) maintenance packet qqemu.sstep
-sending: "qqemu.sstep"
-received: "0x7"
address@hidden example
address@hidden maintenance packet Qqemu.sstep=HEX_VALUE
+Turn off or on the the irq processing when single stepping, which is defaulted 
to off.
address@hidden monitor set stimers <0|1>
 
-This will change the single step mask, so if wanted to enable IRQs on the 
single step, but not timers, you would use:
address@hidden
-(gdb) maintenance packet Qqemu.sstep=0x5
-sending: "qemu.sstep=0x5"
-received: "OK"
address@hidden example
+Turn off or on the the timer processing when single stepping, which is 
defaulted to off.
 @end table
 
 @node pcsys_os_specific

From: Jason Wessel <address@hidden>
Subject: [PATCH] gdbstub: gdb pass-through qemu monitor support

This patch adds a feature to the gdbstub to allow gdb to issue monitor
commands that can pass-through to the qemu monitor.  This patch also
changes the qemu monitor such that it only sends output to a monitor
instance that sends an input.

In order to make this work, the MAX_MON (the maximum number of monitor
connections) had to get incremented by 1 to support the case when the
gdbstub is setup along with all the other connections.  A small check
was added avoid strange crashes when you allocate too many qemu
monitor connections. The mon_active variable represents the current
output channel for any output that comes from the qemu monitor.

A new exported function called monitor_handle_ext_command had to be
exported in order to allow gdbstub to pass the strings directly to the
monitor.  The gdbstub registers as an output device of the qemu
monitor such that no further changes were needed to the monitor other
than to have a global variable in the gdbstub that controls when to
transmit data from a pass through monitor command to an attached
debugger.

The qemu docs were updated to reflect this change.

Signed-off-by: Jason Wessel <address@hidden>

---
 console.h     |    1 +
 gdbstub.c     |   58 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++--
 monitor.c     |   38 +++++++++++++++++++++++---------------
 qemu-doc.texi |   11 +++++++++++
 4 files changed, 91 insertions(+), 17 deletions(-)

--- a/gdbstub.c
+++ b/gdbstub.c
@@ -33,6 +33,7 @@
 #include "qemu-char.h"
 #include "sysemu.h"
 #include "gdbstub.h"
+#include "console.h"
 #endif
 
 #include "qemu_socket.h"
@@ -71,6 +72,8 @@ typedef struct GDBState {
     int running_state;
 #else
     CharDriverState *chr;
+    CharDriverState *mon;
+    int allow_monitor;
 #endif
 } GDBState;
 
@@ -260,12 +263,21 @@ static void monitor_output(GDBState *s, 
     put_packet_hex(s, msg, strlen(msg), 1);
 }
 
+static void monitor_output_len(GDBState *s, const char *msg, int len)
+{
+    put_packet_hex(s, msg, len, 1);
+}
+
 static void monitor_help(GDBState *s)
 {
     monitor_output(s, "gdbstub specific monitor commands:\n");
     monitor_output(s, "show <sirqs|stimers> -- Show gdbstub Single Stepping 
variables\n");
     monitor_output(s, "set sirqs <0|1> --  Single Stepping with qemu irq 
handlers enabled\n");
     monitor_output(s, "set stimers <0|1> -- Single Stepping with qemu timers 
enabled\n");
+#ifndef CONFIG_USER_ONLY
+    monitor_output(s, "qemu monitor pass-through commands:\n");
+#endif
+
 }
 
 #if defined(TARGET_I386)
@@ -997,8 +1009,14 @@ static void gdb_rcmd(GDBState *s, const 
         sstep_flags &= ~SSTEP_NOTIMER;
     } else if (!strcmp(mem_buf, "set stimers 0")) {
         sstep_flags |= SSTEP_NOTIMER;
-    } else if (!strcmp(mem_buf, "help") || !strcmp(mem_buf, "?")) {
-        monitor_help(s);
+    } else {
+        if (!strcmp(mem_buf, "help") || !strcmp(mem_buf, "?"))
+            monitor_help(s);
+#ifndef CONFIG_USER_ONLY
+        s->allow_monitor = 1;
+        monitor_handle_ext_command(s->mon, mem_buf);
+        s->allow_monitor = 0;
+#endif
     }
     put_packet(s, "OK");
 }
@@ -1564,6 +1582,39 @@ static void gdb_chr_event(void *opaque, 
     }
 }
 
+static int gdb_mon_chr_write(CharDriverState *chr, const uint8_t *buf, int len)
+{
+    int max_sz;
+    const uint8_t *p = buf;
+    GDBState *s = chr->opaque;
+
+    if (s->allow_monitor) {
+        max_sz = (sizeof(s->last_packet) - 2) / 2;
+        for (;;) {
+            if (len <= max_sz) {
+                monitor_output_len(s, p, len);
+                break;
+            }
+            monitor_output_len(s, p, max_sz);
+            p += max_sz;
+            len -= max_sz;
+        }
+    }
+    return len;
+}
+
+static CharDriverState *qemu_chr_open_gdb_mon(GDBState *s)
+{
+    CharDriverState *chr;
+
+    chr = qemu_mallocz(sizeof(CharDriverState));
+    if (!chr)
+        return NULL;
+    chr->chr_write = gdb_mon_chr_write;
+    chr->opaque = s;
+    return chr;
+}
+
 int gdbserver_start(const char *port)
 {
     GDBState *s;
@@ -1596,6 +1647,9 @@ int gdbserver_start(const char *port)
     qemu_chr_add_handlers(chr, gdb_chr_can_receive, gdb_chr_receive,
                           gdb_chr_event, s);
     qemu_add_vm_stop_handler(gdb_vm_stopped, s);
+    /* Initialize a monitor port for gdb */
+    s->mon = qemu_chr_open_gdb_mon(s);
+    monitor_init(s->mon, 0);
     return 0;
 }
 #endif
--- a/monitor.c
+++ b/monitor.c
@@ -69,8 +69,9 @@ typedef struct term_cmd_t {
     const char *help;
 } term_cmd_t;
 
-#define MAX_MON 4
+#define MAX_MON 5
 static CharDriverState *monitor_hd[MAX_MON];
+static CharDriverState *mon_active;
 static int hide_banner;
 
 static term_cmd_t term_cmds[];
@@ -85,13 +86,11 @@ CPUState *mon_cpu = NULL;
 
 void term_flush(void)
 {
-    int i;
-    if (term_outbuf_index > 0) {
-        for (i = 0; i < MAX_MON; i++)
-            if (monitor_hd[i] && monitor_hd[i]->focus == 0)
-                qemu_chr_write(monitor_hd[i], term_outbuf, term_outbuf_index);
-        term_outbuf_index = 0;
-    }
+    if (term_outbuf_index <= 0)
+        return;
+    if (mon_active)
+        qemu_chr_write(mon_active, term_outbuf, term_outbuf_index);
+    term_outbuf_index = 0;
 }
 
 /* flush at every end of line or if the buffer is full */
@@ -2603,12 +2602,19 @@ static int term_can_read(void *opaque)
 static void term_read(void *opaque, const uint8_t *buf, int size)
 {
     int i;
+    mon_active = opaque;
     for(i = 0; i < size; i++)
         readline_handle_byte(buf[i]);
 }
 
 static void monitor_start_input(void);
 
+void monitor_handle_ext_command(void *opaque, const char *cmdline)
+{
+    mon_active = opaque;
+    monitor_handle_command(cmdline);
+}
+
 static void monitor_handle_command1(void *opaque, const char *cmdline)
 {
     monitor_handle_command(cmdline);
@@ -2625,6 +2631,7 @@ static void term_event(void *opaque, int
     if (event != CHR_EVENT_RESET)
        return;
 
+    mon_active = opaque;
     if (!hide_banner)
            term_printf("QEMU %s monitor - type 'help' for more information\n",
                        QEMU_VERSION);
@@ -2646,13 +2653,18 @@ void monitor_init(CharDriverState *hd, i
     for (i = 0; i < MAX_MON; i++) {
         if (monitor_hd[i] == NULL) {
             monitor_hd[i] = hd;
+            mon_active = hd;
             break;
         }
     }
+    if (i >= MAX_MON) {
+        fprintf(stderr, "ERROR too many monitor connections requested\n");
+        exit(0);
+    }
 
     hide_banner = !show_banner;
 
-    qemu_chr_add_handlers(hd, term_can_read, term_read, term_event, NULL);
+    qemu_chr_add_handlers(hd, term_can_read, term_read, term_event, hd);
 
     readline_start("", 0, monitor_handle_command1, NULL);
 }
@@ -2672,12 +2684,8 @@ static void monitor_readline_cb(void *op
 void monitor_readline(const char *prompt, int is_password,
                       char *buf, int buf_size)
 {
-    int i;
-
-    if (is_password) {
-        for (i = 0; i < MAX_MON; i++)
-            if (monitor_hd[i] && monitor_hd[i]->focus == 0)
-                qemu_chr_send_event(monitor_hd[i], CHR_EVENT_FOCUS);
+    if (is_password && mon_active) {
+        qemu_chr_send_event(mon_active, CHR_EVENT_FOCUS);
     }
     readline_start(prompt, is_password, monitor_readline_cb, NULL);
     monitor_readline_buf = buf;
--- a/console.h
+++ b/console.h
@@ -159,6 +159,7 @@ extern uint8_t _translate_keycode(const 
    does not need to include console.h  */
 /* monitor.c */
 void monitor_init(CharDriverState *hd, int show_banner);
+void monitor_handle_ext_command(void *opaque, const char *cmdline);
 void term_puts(const char *str);
 void term_vprintf(const char *fmt, va_list ap);
 void term_printf(const char *fmt, ...) __attribute__ ((__format__ (__printf__, 
1, 2)));
--- a/qemu-doc.texi
+++ b/qemu-doc.texi
@@ -1970,6 +1970,17 @@ Turn off or on the the irq processing wh
 Turn off or on the the timer processing when single stepping, which is 
defaulted to off.
 @end table
 
+You may also use gdb to send pass-through monitor commands to the qemu 
monitor.  It is easiest to start off with using just using @code{monitor help} 
to display the list of commands in available from the monitor.  Then you can 
prefix the @code{monitor} key word prior to any command.  The example below 
shows the use of the qemu monitor's @code{info pci} command.
+
address@hidden
+(gdb) monitor info pci
+  Bus  0, device   0, function 0:
+    Host bridge: PCI device 1057:4801
+  Bus  0, device   1, function 0:
+    VGA controller: PCI device 1234:1111
+      BAR0: 32 bit memory at 0xf0000000 [0xf07fffff].
address@hidden example
+
 @node pcsys_os_specific
 @section Target OS specific information