riscv: Use the XML target descriptions to report 3 system registers

The $status, $badaddr, and $cause registers belong to the thread context,
so KGDB can obtain their contents from pt_regs in each trap. However, the
sequential number of these registers in the gdb register list is far from
the general-purpose registers. If riscv port uses the existing method to
report these three registers, many trivial registers with sequence numbers
in the middle of them will also be packaged to the reply packets. To solve
this problem, the riscv port wants to introduce the GDB target description
mechanism to customize the reported register list. By the list, the KGDB
can ignore the intermediate registers and just reports the general-purpose
registers and these three system registers.

Signed-off-by: Vincent Chen <vincent.chen@sifive.com>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

2 files changed, 124 insertions, 1 deletions

diff --git a/arch/riscv/include/asm/gdb_xml.h b/arch/riscv/include/asm/gdb_xml.h
new file mode 100644
index 000000000000..041b45f5b997
--- /dev/null
+++ b/arch/riscv/include/asm/gdb_xml.h
@@ -0,0 +1,117 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#ifndef __ASM_GDB_XML_H_
+#define __ASM_GDB_XML_H_
+
+#define kgdb_arch_gdb_stub_feature riscv_gdb_stub_feature
+static const char riscv_gdb_stub_feature[64] =
+			"PacketSize=800;qXfer:features:read+;";
+
+static const char gdb_xfer_read_target[31] = "qXfer:features:read:target.xml:";
+
+#ifdef CONFIG_64BIT
+static const char gdb_xfer_read_cpuxml[39] =
+			"qXfer:features:read:riscv-64bit-cpu.xml";
+
+static const char riscv_gdb_stub_target_desc[256] =
+"l<?xml version=\"1.0\"?>"
+"<!DOCTYPE target SYSTEM \"gdb-target.dtd\">"
+"<target>"
+"<xi:include href=\"riscv-64bit-cpu.xml\"/>"
+"</target>";
+
+static const char riscv_gdb_stub_cpuxml[2048] =
+"l<?xml version=\"1.0\"?>"
+"<!DOCTYPE feature SYSTEM \"gdb-target.dtd\">"
+"<feature name=\"org.gnu.gdb.riscv.cpu\">"
+"<reg name=\""DBG_REG_ZERO"\" bitsize=\"64\" type=\"int\" regnum=\"0\"/>"
+"<reg name=\""DBG_REG_RA"\" bitsize=\"64\" type=\"code_ptr\"/>"
+"<reg name=\""DBG_REG_SP"\" bitsize=\"64\" type=\"data_ptr\"/>"
+"<reg name=\""DBG_REG_GP"\" bitsize=\"64\" type=\"data_ptr\"/>"
+"<reg name=\""DBG_REG_TP"\" bitsize=\"64\" type=\"data_ptr\"/>"
+"<reg name=\""DBG_REG_T0"\" bitsize=\"64\" type=\"int\"/>"
+"<reg name=\""DBG_REG_T1"\" bitsize=\"64\" type=\"int\"/>"
+"<reg name=\""DBG_REG_T2"\" bitsize=\"64\" type=\"int\"/>"
+"<reg name=\""DBG_REG_FP"\" bitsize=\"64\" type=\"data_ptr\"/>"
+"<reg name=\""DBG_REG_S1"\" bitsize=\"64\" type=\"int\"/>"
+"<reg name=\""DBG_REG_A0"\" bitsize=\"64\" type=\"int\"/>"
+"<reg name=\""DBG_REG_A1"\" bitsize=\"64\" type=\"int\"/>"
+"<reg name=\""DBG_REG_A2"\" bitsize=\"64\" type=\"int\"/>"
+"<reg name=\""DBG_REG_A3"\" bitsize=\"64\" type=\"int\"/>"
+"<reg name=\""DBG_REG_A4"\" bitsize=\"64\" type=\"int\"/>"
+"<reg name=\""DBG_REG_A5"\" bitsize=\"64\" type=\"int\"/>"
+"<reg name=\""DBG_REG_A6"\" bitsize=\"64\" type=\"int\"/>"
+"<reg name=\""DBG_REG_A7"\" bitsize=\"64\" type=\"int\"/>"
+"<reg name=\""DBG_REG_S2"\" bitsize=\"64\" type=\"int\"/>"
+"<reg name=\""DBG_REG_S3"\" bitsize=\"64\" type=\"int\"/>"
+"<reg name=\""DBG_REG_S4"\" bitsize=\"64\" type=\"int\"/>"
+"<reg name=\""DBG_REG_S5"\" bitsize=\"64\" type=\"int\"/>"
+"<reg name=\""DBG_REG_S6"\" bitsize=\"64\" type=\"int\"/>"
+"<reg name=\""DBG_REG_S7"\" bitsize=\"64\" type=\"int\"/>"
+"<reg name=\""DBG_REG_S8"\" bitsize=\"64\" type=\"int\"/>"
+"<reg name=\""DBG_REG_S9"\" bitsize=\"64\" type=\"int\"/>"
+"<reg name=\""DBG_REG_S10"\" bitsize=\"64\" type=\"int\"/>"
+"<reg name=\""DBG_REG_S11"\" bitsize=\"64\" type=\"int\"/>"
+"<reg name=\""DBG_REG_T3"\" bitsize=\"64\" type=\"int\"/>"
+"<reg name=\""DBG_REG_T4"\" bitsize=\"64\" type=\"int\"/>"
+"<reg name=\""DBG_REG_T5"\" bitsize=\"64\" type=\"int\"/>"
+"<reg name=\""DBG_REG_T6"\" bitsize=\"64\" type=\"int\"/>"
+"<reg name=\""DBG_REG_EPC"\" bitsize=\"64\" type=\"code_ptr\"/>"
+"<reg name=\""DBG_REG_STATUS"\" bitsize=\"64\" type=\"int\"/>"
+"<reg name=\""DBG_REG_BADADDR"\" bitsize=\"64\" type=\"int\"/>"
+"<reg name=\""DBG_REG_CAUSE"\" bitsize=\"64\" type=\"int\"/>"
+"</feature>";
+#else
+static const char gdb_xfer_read_cpuxml[39] =
+			"qXfer:features:read:riscv-32bit-cpu.xml";
+
+static const char riscv_gdb_stub_target_desc[256] =
+"l<?xml version=\"1.0\"?>"
+"<!DOCTYPE target SYSTEM \"gdb-target.dtd\">"
+"<target>"
+"<xi:include href=\"riscv-32bit-cpu.xml\"/>"
+"</target>";
+
+static const char riscv_gdb_stub_cpuxml[2048] =
+"l<?xml version=\"1.0\"?>"
+"<!DOCTYPE feature SYSTEM \"gdb-target.dtd\">"
+"<feature name=\"org.gnu.gdb.riscv.cpu\">"
+"<reg name=\""DBG_REG_ZERO"\" bitsize=\"32\" type=\"int\" regnum=\"0\"/>"
+"<reg name=\""DBG_REG_RA"\" bitsize=\"32\" type=\"code_ptr\"/>"
+"<reg name=\""DBG_REG_SP"\" bitsize=\"32\" type=\"data_ptr\"/>"
+"<reg name=\""DBG_REG_GP"\" bitsize=\"32\" type=\"data_ptr\"/>"
+"<reg name=\""DBG_REG_TP"\" bitsize=\"32\" type=\"data_ptr\"/>"
+"<reg name=\""DBG_REG_T0"\" bitsize=\"32\" type=\"int\"/>"
+"<reg name=\""DBG_REG_T1"\" bitsize=\"32\" type=\"int\"/>"
+"<reg name=\""DBG_REG_T2"\" bitsize=\"32\" type=\"int\"/>"
+"<reg name=\""DBG_REG_FP"\" bitsize=\"32\" type=\"data_ptr\"/>"
+"<reg name=\""DBG_REG_S1"\" bitsize=\"32\" type=\"int\"/>"
+"<reg name=\""DBG_REG_A0"\" bitsize=\"32\" type=\"int\"/>"
+"<reg name=\""DBG_REG_A1"\" bitsize=\"32\" type=\"int\"/>"
+"<reg name=\""DBG_REG_A2"\" bitsize=\"32\" type=\"int\"/>"
+"<reg name=\""DBG_REG_A3"\" bitsize=\"32\" type=\"int\"/>"
+"<reg name=\""DBG_REG_A4"\" bitsize=\"32\" type=\"int\"/>"
+"<reg name=\""DBG_REG_A5"\" bitsize=\"32\" type=\"int\"/>"
+"<reg name=\""DBG_REG_A6"\" bitsize=\"32\" type=\"int\"/>"
+"<reg name=\""DBG_REG_A7"\" bitsize=\"32\" type=\"int\"/>"
+"<reg name=\""DBG_REG_S2"\" bitsize=\"32\" type=\"int\"/>"
+"<reg name=\""DBG_REG_S3"\" bitsize=\"32\" type=\"int\"/>"
+"<reg name=\""DBG_REG_S4"\" bitsize=\"32\" type=\"int\"/>"
+"<reg name=\""DBG_REG_S5"\" bitsize=\"32\" type=\"int\"/>"
+"<reg name=\""DBG_REG_S6"\" bitsize=\"32\" type=\"int\"/>"
+"<reg name=\""DBG_REG_S7"\" bitsize=\"32\" type=\"int\"/>"
+"<reg name=\""DBG_REG_S8"\" bitsize=\"32\" type=\"int\"/>"
+"<reg name=\""DBG_REG_S9"\" bitsize=\"32\" type=\"int\"/>"
+"<reg name=\""DBG_REG_S10"\" bitsize=\"32\" type=\"int\"/>"
+"<reg name=\""DBG_REG_S11"\" bitsize=\"32\" type=\"int\"/>"
+"<reg name=\""DBG_REG_T3"\" bitsize=\"32\" type=\"int\"/>"
+"<reg name=\""DBG_REG_T4"\" bitsize=\"32\" type=\"int\"/>"
+"<reg name=\""DBG_REG_T5"\" bitsize=\"32\" type=\"int\"/>"
+"<reg name=\""DBG_REG_T6"\" bitsize=\"32\" type=\"int\"/>"
+"<reg name=\""DBG_REG_EPC"\" bitsize=\"32\" type=\"code_ptr\"/>"
+"<reg name=\""DBG_REG_STATUS"\" bitsize=\"32\" type=\"int\"/>"
+"<reg name=\""DBG_REG_BADADDR"\" bitsize=\"32\" type=\"int\"/>"
+"<reg name=\""DBG_REG_CAUSE"\" bitsize=\"32\" type=\"int\"/>"
+"</feature>";
+#endif
+#endif
diff --git a/arch/riscv/include/asm/kgdb.h b/arch/riscv/include/asm/kgdb.h
index ce5a51bdd6a4..8177a457caff 100644
--- a/arch/riscv/include/asm/kgdb.h
+++ b/arch/riscv/include/asm/kgdb.h
@@ -7,7 +7,7 @@
 
 #define GDB_SIZEOF_REG sizeof(unsigned long)
 
-#define DBG_MAX_REG_NUM (33)
+#define DBG_MAX_REG_NUM (36)
 #define NUMREGBYTES ((DBG_MAX_REG_NUM) * GDB_SIZEOF_REG)
 #define CACHE_FLUSH_IS_SAFE     1
 #define BUFMAX                  2048
@@ -65,6 +65,9 @@ static inline void arch_kgdb_breakpoint(void)
 #define DBG_REG_T5 "t5"
 #define DBG_REG_T6 "t6"
 #define DBG_REG_EPC "pc"
+#define DBG_REG_STATUS "sstatus"
+#define DBG_REG_BADADDR "stval"
+#define DBG_REG_CAUSE "scause"
 
 #define DBG_REG_ZERO_OFF 0
 #define DBG_REG_RA_OFF 1
@@ -102,5 +105,8 @@ static inline void arch_kgdb_breakpoint(void)
 #define DBG_REG_STATUS_OFF 33
 #define DBG_REG_BADADDR_OFF 34
 #define DBG_REG_CAUSE_OFF 35
+
+#include <asm/gdb_xml.h>
+
 #endif
 #endif