[Qemu-devel] [PATCH v2] gdbstub: Implement Xfer:auxv:read

[Bhushan Attarde]

Implementation of "Xfer:auxv:read" to provide auxiliary vector information
to clients which relies on it.

For example: AT_ENTRY in auxiliary vector provides the entry point information.
Client can use this information to compare it with entry point mentioned in
executable to calculate load offset and then update the load addresses
accordingly.

Signed-off-by: Bhushan Attarde <address@hidden>
---

Notes:
    Changes for v2:
        - Xfer:auxv:read and Xfer:features:read now shares the code for parsing 
out arguments rather than duplicating it.

 gdbstub.c | 71 ++++++++++++++++++++++++++++++++++++++++++++++++---------------
 1 file changed, 54 insertions(+), 17 deletions(-)

diff --git a/gdbstub.c b/gdbstub.c
index 92b2f81..a6a79dc 100644
--- a/gdbstub.c
+++ b/gdbstub.c
@@ -1150,42 +1150,73 @@ static int gdb_handle_packet(GDBState *s, const char 
*line_buf)
             if (cc->gdb_core_xml_file != NULL) {
                 pstrcat(buf, sizeof(buf), ";qXfer:features:read+");
             }
+#ifdef CONFIG_USER_ONLY
+            pstrcat(buf, sizeof(buf), ";qXfer:auxv:read+");
+#endif
             put_packet(s, buf);
             break;
         }
-        if (strncmp(p, "Xfer:features:read:", 19) == 0) {
+        if (strncmp(p, "Xfer:", 5) == 0) {
+#ifdef CONFIG_USER_ONLY
+            target_ulong auxv = 0;
+#endif
+            target_ulong total_len = 0;
+            char *ptr = NULL;
             const char *xml;
-            target_ulong total_len;
 
-            cc = CPU_GET_CLASS(first_cpu);
-            if (cc->gdb_core_xml_file == NULL) {
+            if (strncmp(p + 5, "features:read:", 14) == 0) {
+                cc = CPU_GET_CLASS(first_cpu);
+                if (cc->gdb_core_xml_file == NULL) {
+                    goto unknown_command;
+                }
+                gdb_has_xml = true;
+                p += 19;
+                xml = get_feature_xml(p, &p, cc);
+                if (!xml) {
+                    snprintf(buf, sizeof(buf), "E00");
+                    put_packet(s, buf);
+                    break;
+                }
+                total_len = strlen(xml);
+            }
+#ifdef CONFIG_USER_ONLY
+            else if (strncmp(p + 5, "auxv:read:", 10) == 0) {
+                TaskState *ts = s->c_cpu->opaque;
+                auxv = ts->info->saved_auxv;
+                total_len = ts->info->auxv_len;
+                p += 15;
+                ptr = lock_user(VERIFY_READ, auxv, total_len, 0);
+                if (ptr == NULL) {
+                    break;
+                }
+                xml = (char *) ptr;
+            }
+#endif
+            else {
                 goto unknown_command;
             }
 
-            gdb_has_xml = true;
-            p += 19;
-            xml = get_feature_xml(p, &p, cc);
-            if (!xml) {
-                snprintf(buf, sizeof(buf), "E00");
-                put_packet(s, buf);
-                break;
+            while (*p && *p != ':') {
+                p++;
             }
+            p++;
 
-            if (*p == ':')
-                p++;
             addr = strtoul(p, (char **)&p, 16);
-            if (*p == ',')
+            if (*p == ',') {
                 p++;
+            }
             len = strtoul(p, (char **)&p, 16);
 
-            total_len = strlen(xml);
-            if (addr > total_len) {
+            if ((ptr != NULL && addr > len)
+                || (ptr == NULL && addr > total_len)) {
                 snprintf(buf, sizeof(buf), "E00");
                 put_packet(s, buf);
                 break;
             }
-            if (len > (MAX_PACKET_LENGTH - 5) / 2)
+
+            if (len > (MAX_PACKET_LENGTH - 5) / 2) {
                 len = (MAX_PACKET_LENGTH - 5) / 2;
+            }
             if (len < total_len - addr) {
                 buf[0] = 'm';
                 len = memtox(buf + 1, xml + addr, len);
@@ -1194,6 +1225,12 @@ static int gdb_handle_packet(GDBState *s, const char 
*line_buf)
                 len = memtox(buf + 1, xml + addr, total_len - addr);
             }
             put_packet_binary(s, buf, len + 1);
+
+#ifdef CONFIG_USER_ONLY
+            if (ptr != NULL) {
+                unlock_user(ptr, auxv, len);
+            }
+#endif
             break;
         }
         if (is_query_packet(p, "Attached", ':')) {
-- 
2.4.4