gdbstub: Implement qemu physical memory mode

Add a new query/set which changes the memory GDB sees to physical memory
only.

gdb> maint packet qqemu.PhyMemMode
will reply the current phy_mem_mode state (1 for enabled, 0 for disabled)
gdb> maint packet Qqemu.PhyMemMode:1
Will make GDB read/write only to physical memory, set to 0 to disable

Signed-off-by: Jon Doron <arilou@gmail.com>
Message-Id: <20190529064148.19856-21-arilou@gmail.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>

1 files changed, 60 insertions, 2 deletions

diff --git a/gdbstub.c b/gdbstub.c
index 4af94d8f78..d614a1f3c0 100644
--- a/gdbstub.c
+++ b/gdbstub.c
@@ -50,11 +50,27 @@
 #define GDB_ATTACHED "1"
 #endif
 
+#ifndef CONFIG_USER_ONLY
+static int phy_memory_mode;
+#endif
+
 static inline int target_memory_rw_debug(CPUState *cpu, target_ulong addr,
                                          uint8_t *buf, int len, bool is_write)
 {
-    CPUClass *cc = CPU_GET_CLASS(cpu);
+    CPUClass *cc;
 
+#ifndef CONFIG_USER_ONLY
+    if (phy_memory_mode) {
+        if (is_write) {
+            cpu_physical_memory_write(addr, buf, len);
+        } else {
+            cpu_physical_memory_read(addr, buf, len);
+        }
+        return 0;
+    }
+#endif
+
+    cc = CPU_GET_CLASS(cpu);
     if (cc->memory_rw_debug) {
         return cc->memory_rw_debug(cpu, addr, buf, len, is_write);
     }
@@ -2136,8 +2152,36 @@ static void handle_query_attached(GdbCmdContext *gdb_ctx, void *user_ctx)
 
 static void handle_query_qemu_supported(GdbCmdContext *gdb_ctx, void *user_ctx)
 {
-    put_packet(gdb_ctx->s, "sstepbits;sstep");
+    snprintf(gdb_ctx->str_buf, sizeof(gdb_ctx->str_buf), "sstepbits;sstep");
+#ifndef CONFIG_USER_ONLY
+    pstrcat(gdb_ctx->str_buf, sizeof(gdb_ctx->str_buf), ";PhyMemMode");
+#endif
+    put_packet(gdb_ctx->s, gdb_ctx->str_buf);
+}
+
+#ifndef CONFIG_USER_ONLY
+static void handle_query_qemu_phy_mem_mode(GdbCmdContext *gdb_ctx,
+                                           void *user_ctx)
+{
+    snprintf(gdb_ctx->str_buf, sizeof(gdb_ctx->str_buf), "%d", phy_memory_mode);
+    put_packet(gdb_ctx->s, gdb_ctx->str_buf);
+}
+
+static void handle_set_qemu_phy_mem_mode(GdbCmdContext *gdb_ctx, void *user_ctx)
+{
+    if (!gdb_ctx->num_params) {
+        put_packet(gdb_ctx->s, "E22");
+        return;
+    }
+
+    if (!gdb_ctx->params[0].val_ul) {
+        phy_memory_mode = 0;
+    } else {
+        phy_memory_mode = 1;
+    }
+    put_packet(gdb_ctx->s, "OK");
 }
+#endif
 
 static GdbCmdParseEntry gdb_gen_query_set_common_table[] = {
     /* Order is important if has same prefix */
@@ -2219,6 +2263,12 @@ static GdbCmdParseEntry gdb_gen_query_table[] = {
         .handler = handle_query_qemu_supported,
         .cmd = "qemu.Supported",
     },
+#ifndef CONFIG_USER_ONLY
+    {
+        .handler = handle_query_qemu_phy_mem_mode,
+        .cmd = "qemu.PhyMemMode",
+    },
+#endif
 };
 
 static GdbCmdParseEntry gdb_gen_set_table[] = {
@@ -2229,6 +2279,14 @@ static GdbCmdParseEntry gdb_gen_set_table[] = {
         .cmd_startswith = 1,
         .schema = "l0"
     },
+#ifndef CONFIG_USER_ONLY
+    {
+        .handler = handle_set_qemu_phy_mem_mode,
+        .cmd = "qemu.PhyMemMode:",
+        .cmd_startswith = 1,
+        .schema = "l0"
+    },
+#endif
 };
 
 static void handle_gen_query(GdbCmdContext *gdb_ctx, void *user_ctx)