target-xtensa: add gdb support

Specific xtensa processor overlay for GDB contains register map in
the gdb/xtensa-config.c. This description is used by the GDB to e.g.
parse 'g' response packets and it may be reused in the qemu's gdbstub
(only XTREG definitions for non-pseudoregisters are needed).

Currently mainline GDB does not support operations with privileged SRs
(see http://sourceware.org/ml/gdb/2011-07/msg00075.html). This support
may be enabled, see NUM_CORE_REGS comment in the gdbstub.c

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>

1 files changed, 96 insertions, 0 deletions

diff --git a/gdbstub.c b/gdbstub.c
index 3b87c27..9330885 100644
--- a/gdbstub.c
+++ b/gdbstub.c
@@ -1541,6 +1541,94 @@ static int cpu_gdb_write_register(CPUState *env, uint8_t *mem_buf, int n)
     }
     return 4;
 }
+#elif defined(TARGET_XTENSA)
+
+/* Use num_core_regs to see only non-privileged registers in an unmodified gdb.
+ * Use num_regs to see all registers. gdb modification is required for that:
+ * reset bit 0 in the 'flags' field of the registers definitions in the
+ * gdb/xtensa-config.c inside gdb source tree or inside gdb overlay.
+ */
+#define NUM_CORE_REGS (env->config->gdb_regmap.num_regs)
+#define num_g_regs NUM_CORE_REGS
+
+static int cpu_gdb_read_register(CPUState *env, uint8_t *mem_buf, int n)
+{
+    const XtensaGdbReg *reg = env->config->gdb_regmap.reg + n;
+
+    if (n < 0 || n >= env->config->gdb_regmap.num_regs) {
+        return 0;
+    }
+
+    switch (reg->type) {
+    case 9: /*pc*/
+        GET_REG32(env->pc);
+        break;
+
+    case 1: /*ar*/
+        xtensa_sync_phys_from_window(env);
+        GET_REG32(env->phys_regs[(reg->targno & 0xff) % env->config->nareg]);
+        break;
+
+    case 2: /*SR*/
+        GET_REG32(env->sregs[reg->targno & 0xff]);
+        break;
+
+    case 3: /*UR*/
+        GET_REG32(env->uregs[reg->targno & 0xff]);
+        break;
+
+    case 8: /*a*/
+        GET_REG32(env->regs[reg->targno & 0x0f]);
+        break;
+
+    default:
+        qemu_log("%s from reg %d of unsupported type %d\n",
+                __func__, n, reg->type);
+        return 0;
+    }
+}
+
+static int cpu_gdb_write_register(CPUState *env, uint8_t *mem_buf, int n)
+{
+    uint32_t tmp;
+    const XtensaGdbReg *reg = env->config->gdb_regmap.reg + n;
+
+    if (n < 0 || n >= env->config->gdb_regmap.num_regs) {
+        return 0;
+    }
+
+    tmp = ldl_p(mem_buf);
+
+    switch (reg->type) {
+    case 9: /*pc*/
+        env->pc = tmp;
+        break;
+
+    case 1: /*ar*/
+        env->phys_regs[(reg->targno & 0xff) % env->config->nareg] = tmp;
+        xtensa_sync_window_from_phys(env);
+        break;
+
+    case 2: /*SR*/
+        env->sregs[reg->targno & 0xff] = tmp;
+        break;
+
+    case 3: /*UR*/
+        env->uregs[reg->targno & 0xff] = tmp;
+        break;
+
+    case 8: /*a*/
+        env->regs[reg->targno & 0x0f] = tmp;
+        break;
+
+    default:
+        qemu_log("%s to reg %d of unsupported type %d\n",
+                __func__, n, reg->type);
+        return 0;
+    }
+
+    return 4;
+}
 #else
 
 #define NUM_CORE_REGS 0
@@ -1557,7 +1645,9 @@ static int cpu_gdb_write_register(CPUState *env, uint8_t *mem_buf, int n)
 
 #endif
 
+#if !defined(TARGET_XTENSA)
 static int num_g_regs = NUM_CORE_REGS;
+#endif
 
 #ifdef GDB_CORE_XML
 /* Encode data using the encoding for 'x' packets.  */
@@ -1654,6 +1744,7 @@ static int gdb_write_register(CPUState *env, uint8_t *mem_buf, int reg)
     return 0;
 }
 
+#if !defined(TARGET_XTENSA)
 /* Register a supplemental set of CPU registers.  If g_pos is nonzero it
    specifies the first register number and these registers are included in
    a standard "g" packet.  Direction is relative to gdb, i.e. get_reg is
@@ -1693,6 +1784,7 @@ void gdb_register_coprocessor(CPUState * env,
         }
     }
 }
+#endif
 
 #ifndef CONFIG_USER_ONLY
 static const int xlat_gdb_type[] = {
@@ -1818,6 +1910,8 @@ static void gdb_set_cpu_pc(GDBState *s, target_ulong pc)
     s->c_cpu->psw.addr = pc;
 #elif defined (TARGET_LM32)
     s->c_cpu->pc = pc;
+#elif defined(TARGET_XTENSA)
+    s->c_cpu->pc = pc;
 #endif
 }
 
@@ -1988,6 +2082,7 @@ static int gdb_handle_packet(GDBState *s, const char *line_buf)
         break;
     case 'g':
         cpu_synchronize_state(s->g_cpu);
+        env = s->g_cpu;
         len = 0;
         for (addr = 0; addr < num_g_regs; addr++) {
             reg_size = gdb_read_register(s->g_cpu, mem_buf + len, addr);
@@ -1998,6 +2093,7 @@ static int gdb_handle_packet(GDBState *s, const char *line_buf)
         break;
     case 'G':
         cpu_synchronize_state(s->g_cpu);
+        env = s->g_cpu;
         registers = mem_buf;
         len = strlen(p) / 2;
         hextomem((uint8_t *)registers, p, len);