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Re: [Qemu-devel] [PATCH v8 05/16] gdbstub: add multiprocess support to v


From: Jan Kiszka
Subject: Re: [Qemu-devel] [PATCH v8 05/16] gdbstub: add multiprocess support to vCont packets
Date: Fri, 22 Mar 2019 15:19:27 +0100
User-agent: Mozilla/5.0 (X11; U; Linux i686 (x86_64); de; rv:1.8.1.12) Gecko/20080226 SUSE/2.0.0.12-1.1 Thunderbird/2.0.0.12 Mnenhy/0.7.5.666

On 22.03.19 15:01, Luc Michel wrote:
On 3/22/19 2:29 PM, Jan Kiszka wrote:
On 07.12.18 10:01, Luc Michel wrote:
Add the gdb_first_attached_cpu() and gdb_next_attached_cpu() to iterate
over all the CPUs in currently attached processes.

Add the gdb_first_cpu_in_process() and gdb_next_cpu_in_process() to
iterate over CPUs of a given process.

Use them to add multiprocess extension support to vCont packets.

Signed-off-by: Luc Michel <address@hidden>
Reviewed-by: Philippe Mathieu-Daudé <address@hidden>
Reviewed-by: Edgar E. Iglesias <address@hidden>
Acked-by: Alistair Francis <address@hidden>
---
   gdbstub.c | 117 +++++++++++++++++++++++++++++++++++++++++++++++-------
   1 file changed, 102 insertions(+), 15 deletions(-)

diff --git a/gdbstub.c b/gdbstub.c
index 911faa225a..77b3dbb2c8 100644
--- a/gdbstub.c
+++ b/gdbstub.c
@@ -721,10 +721,40 @@ static CPUState *find_cpu(uint32_t thread_id)
       }
return NULL;
   }
+static CPUState *get_first_cpu_in_process(const GDBState *s,
+                                          GDBProcess *process)
+{
+    CPUState *cpu;
+
+    CPU_FOREACH(cpu) {
+        if (gdb_get_cpu_pid(s, cpu) == process->pid) {
+            return cpu;
+        }
+    }
+
+    return NULL;
+}
+
+static CPUState *gdb_next_cpu_in_process(const GDBState *s, CPUState *cpu)
+{
+    uint32_t pid = gdb_get_cpu_pid(s, cpu);
+    cpu = CPU_NEXT(cpu);
+
+    while (cpu) {
+        if (gdb_get_cpu_pid(s, cpu) == pid) {
+            break;
+        }
+
+        cpu = CPU_NEXT(cpu);
+    }
+
+    return cpu;
+}
+
   static CPUState *gdb_get_cpu(const GDBState *s, uint32_t pid, uint32_t tid)
   {
       GDBProcess *process;
       CPUState *cpu;
@@ -750,10 +780,41 @@ static CPUState *gdb_get_cpu(const GDBState *s, uint32_t pid, uint32_t tid)
       }
return cpu;
   }
+/* Return the cpu following @cpu, while ignoring
+ * unattached processes.
+ */
+static CPUState *gdb_next_attached_cpu(const GDBState *s, CPUState *cpu)
+{
+    cpu = CPU_NEXT(cpu);
+
+    while (cpu) {
+        if (gdb_get_cpu_process(s, cpu)->attached) {
+            break;
+        }
+
+        cpu = CPU_NEXT(cpu);
+    }
+
+    return cpu;
+}
+
+/* Return the first attached cpu */
+static CPUState *gdb_first_attached_cpu(const GDBState *s)
+{
+    CPUState *cpu = first_cpu;
+    GDBProcess *process = gdb_get_cpu_process(s, cpu);
+
+    if (!process->attached) {
+        return gdb_next_attached_cpu(s, cpu);
+    }
+
+    return cpu;
+}
+
   static const char *get_feature_xml(const char *p, const char **newp,
                                      CPUClass *cc)
   {
       size_t len;
       int i;
@@ -1088,14 +1149,16 @@ static int is_query_packet(const char *p, const char 
*query, char separator)
    * returns -ENOTSUP if a command is unsupported, -EINVAL or -ERANGE if there 
is
    *         a format error, 0 on success.
    */
   static int gdb_handle_vcont(GDBState *s, const char *p)
   {
-    int res, idx, signal = 0;
+    int res, signal = 0;
       char cur_action;
       char *newstates;
       unsigned long tmp;
+    uint32_t pid, tid;
+    GDBProcess *process;
       CPUState *cpu;
   #ifdef CONFIG_USER_ONLY
       int max_cpus = 1; /* global variable max_cpus exists only in system mode 
*/
CPU_FOREACH(cpu) {
@@ -1134,29 +1197,52 @@ static int gdb_handle_vcont(GDBState *s, const char *p)
           } else if (cur_action != 'c' && cur_action != 's') {
               /* unknown/invalid/unsupported command */
               res = -ENOTSUP;
               goto out;
           }
-        /* thread specification. special values: (none), -1 = all; 0 = any */
-        if ((p[0] == ':' && p[1] == '-' && p[2] == '1') || (p[0] != ':')) {
-            if (*p == ':') {
-                p += 3;
-            }
-            for (idx = 0; idx < max_cpus; idx++) {
-                if (newstates[idx] == 1) {
-                    newstates[idx] = cur_action;
+
+        if (*p++ != ':') {
+            res = -ENOTSUP;
+            goto out;
+        }
+
+        switch (read_thread_id(p, &p, &pid, &tid)) {
+        case GDB_READ_THREAD_ERR:
+            res = -EINVAL;
+            goto out;
+
+        case GDB_ALL_PROCESSES:
+            cpu = gdb_first_attached_cpu(s);
+            while (cpu) {
+                if (newstates[cpu->cpu_index] == 1) {
+                    newstates[cpu->cpu_index] = cur_action;
                   }
+
+                cpu = gdb_next_attached_cpu(s, cpu);
               }
-        } else if (*p == ':') {
-            p++;
-            res = qemu_strtoul(p, &p, 16, &tmp);
-            if (res) {
+            break;
+
+        case GDB_ALL_THREADS:
+            process = gdb_get_process(s, pid);
+
+            if (!process->attached) {
+                res = -EINVAL;
                   goto out;
               }
- /* 0 means any thread, so we pick the first valid CPU */
-            cpu = tmp ? find_cpu(tmp) : first_cpu;
+            cpu = get_first_cpu_in_process(s, process);
+            while (cpu) {
+                if (newstates[cpu->cpu_index] == 1) {
+                    newstates[cpu->cpu_index] = cur_action;
+                }
+
+                cpu = gdb_next_cpu_in_process(s, cpu);
+            }
+            break;
+
+        case GDB_ONE_THREAD:
+            cpu = gdb_get_cpu(s, pid, tid);
/* invalid CPU/thread specified */
               if (!cpu) {
                   res = -EINVAL;
                   goto out;
@@ -1164,10 +1250,11 @@ static int gdb_handle_vcont(GDBState *s, const char *p)
/* only use if no previous match occourred */
               if (newstates[cpu->cpu_index] == 1) {
                   newstates[cpu->cpu_index] = cur_action;
               }
+            break;
           }
       }
       s->signal = signal;
       gdb_continue_partial(s, newstates);

This breaks system-level debugging with gdb, at least with version
7.7.50 and for x86 targets.

I think it's related to
https://www.mail-archive.com/address@hidden/msg601065.html


This fixes it, indeed.

In fact, the commit I cited was probably misleading because your patch series turned out to be non-bisectable (process->attached was checked already not but yet set to true).

[snip]
Sending packet: $vCont;s:1;c#c1...Ack
Packet received: E22
warning: Remote failure reply: E22
[snip]

The vCont packet does not specifies a thread-id for the last action.
This is a valid syntax, incorrectly treated as an error by the stub.

Lucien: do you plan to send a re-roll? Otherwise I'll do it on next
Monday (25/03) because I would like this bug to be fixed before it hits 4.0.


Would be appreciated.

Thanks,
Jan

--
Siemens AG, Corporate Technology, CT RDA IOT SES-DE
Corporate Competence Center Embedded Linux



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