target/riscv: Generate the GDB XML file for CSR registers dynamically

At present QEMU RISC-V uses a hardcoded XML to report the feature
"org.gnu.gdb.riscv.csr" [1]. There are two major issues with the
approach being used currently:

- The XML does not specify the "regnum" field of a CSR entry, hence
  consecutive numbers are used by the remote GDB client to access
  CSRs. In QEMU we have to maintain a map table to convert the GDB
  number to the hardware number which is error prone.
- The XML contains some CSRs that QEMU does not implement at all,
  which causes an "E14" response sent to remote GDB client.

Change to generate the CSR register list dynamically, based on the
availability presented in the CSR function table. This new approach
will reflect a correct list of CSRs that QEMU actually implements.

[1] https://sourceware.org/gdb/current/onlinedocs/gdb/RISC_002dV-Features.html#RISC_002dV-Features

Signed-off-by: Bin Meng <bin.meng@windriver.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-id: 20210116054123.5457-2-bmeng.cn@gmail.com
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
index 6aafe4e62c421ce65a093d5d100c7b5c73de780a..27788021eb35be28299b4b0c18b36811e96f0d9e 100644 (file)
--- a/target/riscv/cpu.c
+++ b/target/riscv/cpu.c
@@ -569,6 +569,17 @@ static gchar *riscv_gdb_arch_name(CPUState *cs)
     }
 }
 
+static const char *riscv_gdb_get_dynamic_xml(CPUState *cs, const char *xmlname)
+{
+    RISCVCPU *cpu = RISCV_CPU(cs);
+
+    if (strcmp(xmlname, "riscv-csr.xml") == 0) {
+        return cpu->dyn_csr_xml;
+    }
+
+    return NULL;
+}
+
 static void riscv_cpu_class_init(ObjectClass *c, void *data)
 {
     RISCVCPUClass *mcc = RISCV_CPU_CLASS(c);
@@ -605,6 +616,7 @@ static void riscv_cpu_class_init(ObjectClass *c, void *data)
     cc->vmsd = &vmstate_riscv_cpu;
 #endif
     cc->gdb_arch_name = riscv_gdb_arch_name;
+    cc->gdb_get_dynamic_xml = riscv_gdb_get_dynamic_xml;
 #ifdef CONFIG_TCG
     cc->tcg_initialize = riscv_translate_init;
     cc->tlb_fill = riscv_cpu_tlb_fill;

diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
index 2718617ef4cc2766062b1bfc53cf4276c188438b..02758ae0eb4ac84756b993e135b77d1d175fbe19 100644 (file)
--- a/target/riscv/cpu.h
+++ b/target/riscv/cpu.h
@@ -272,6 +272,8 @@ struct RISCVCPU {
     CPUNegativeOffsetState neg;
     CPURISCVState env;
 
+    char *dyn_csr_xml;
+
     /* Configuration Settings */
     struct {
         bool ext_i;

diff --git a/target/riscv/gdbstub.c b/target/riscv/gdbstub.c
index eba12a86f2ee60db6dce44703d90d95a6dc6e81d..5f96b7ea2a9523b81d3eadb1dd43a1bfc56483b4 100644 (file)
--- a/target/riscv/gdbstub.c
+++ b/target/riscv/gdbstub.c
@@ -20,256 +20,6 @@
 #include "exec/gdbstub.h"
 #include "cpu.h"
 
-/*
- * The GDB CSR xml files list them in documentation order, not numerical order,
- * and are missing entries for unnamed CSRs.  So we need to map the gdb numbers
- * to the hardware numbers.
- */
-
-static int csr_register_map[] = {
-    CSR_USTATUS,
-    CSR_UIE,
-    CSR_UTVEC,
-    CSR_USCRATCH,
-    CSR_UEPC,
-    CSR_UCAUSE,
-    CSR_UTVAL,
-    CSR_UIP,
-    CSR_FFLAGS,
-    CSR_FRM,
-    CSR_FCSR,
-    CSR_CYCLE,
-    CSR_TIME,
-    CSR_INSTRET,
-    CSR_HPMCOUNTER3,
-    CSR_HPMCOUNTER4,
-    CSR_HPMCOUNTER5,
-    CSR_HPMCOUNTER6,
-    CSR_HPMCOUNTER7,
-    CSR_HPMCOUNTER8,
-    CSR_HPMCOUNTER9,
-    CSR_HPMCOUNTER10,
-    CSR_HPMCOUNTER11,
-    CSR_HPMCOUNTER12,
-    CSR_HPMCOUNTER13,
-    CSR_HPMCOUNTER14,
-    CSR_HPMCOUNTER15,
-    CSR_HPMCOUNTER16,
-    CSR_HPMCOUNTER17,
-    CSR_HPMCOUNTER18,
-    CSR_HPMCOUNTER19,
-    CSR_HPMCOUNTER20,
-    CSR_HPMCOUNTER21,
-    CSR_HPMCOUNTER22,
-    CSR_HPMCOUNTER23,
-    CSR_HPMCOUNTER24,
-    CSR_HPMCOUNTER25,
-    CSR_HPMCOUNTER26,
-    CSR_HPMCOUNTER27,
-    CSR_HPMCOUNTER28,
-    CSR_HPMCOUNTER29,
-    CSR_HPMCOUNTER30,
-    CSR_HPMCOUNTER31,
-    CSR_CYCLEH,
-    CSR_TIMEH,
-    CSR_INSTRETH,
-    CSR_HPMCOUNTER3H,
-    CSR_HPMCOUNTER4H,
-    CSR_HPMCOUNTER5H,
-    CSR_HPMCOUNTER6H,
-    CSR_HPMCOUNTER7H,
-    CSR_HPMCOUNTER8H,
-    CSR_HPMCOUNTER9H,
-    CSR_HPMCOUNTER10H,
-    CSR_HPMCOUNTER11H,
-    CSR_HPMCOUNTER12H,
-    CSR_HPMCOUNTER13H,
-    CSR_HPMCOUNTER14H,
-    CSR_HPMCOUNTER15H,
-    CSR_HPMCOUNTER16H,
-    CSR_HPMCOUNTER17H,
-    CSR_HPMCOUNTER18H,
-    CSR_HPMCOUNTER19H,
-    CSR_HPMCOUNTER20H,
-    CSR_HPMCOUNTER21H,
-    CSR_HPMCOUNTER22H,
-    CSR_HPMCOUNTER23H,
-    CSR_HPMCOUNTER24H,
-    CSR_HPMCOUNTER25H,
-    CSR_HPMCOUNTER26H,
-    CSR_HPMCOUNTER27H,
-    CSR_HPMCOUNTER28H,
-    CSR_HPMCOUNTER29H,
-    CSR_HPMCOUNTER30H,
-    CSR_HPMCOUNTER31H,
-    CSR_SSTATUS,
-    CSR_SEDELEG,
-    CSR_SIDELEG,
-    CSR_SIE,
-    CSR_STVEC,
-    CSR_SCOUNTEREN,
-    CSR_SSCRATCH,
-    CSR_SEPC,
-    CSR_SCAUSE,
-    CSR_STVAL,
-    CSR_SIP,
-    CSR_SATP,
-    CSR_MVENDORID,
-    CSR_MARCHID,
-    CSR_MIMPID,
-    CSR_MHARTID,
-    CSR_MSTATUS,
-    CSR_MISA,
-    CSR_MEDELEG,
-    CSR_MIDELEG,
-    CSR_MIE,
-    CSR_MTVEC,
-    CSR_MCOUNTEREN,
-    CSR_MSCRATCH,
-    CSR_MEPC,
-    CSR_MCAUSE,
-    CSR_MTVAL,
-    CSR_MIP,
-    CSR_MTINST,
-    CSR_MTVAL2,
-    CSR_PMPCFG0,
-    CSR_PMPCFG1,
-    CSR_PMPCFG2,
-    CSR_PMPCFG3,
-    CSR_PMPADDR0,
-    CSR_PMPADDR1,
-    CSR_PMPADDR2,
-    CSR_PMPADDR3,
-    CSR_PMPADDR4,
-    CSR_PMPADDR5,
-    CSR_PMPADDR6,
-    CSR_PMPADDR7,
-    CSR_PMPADDR8,
-    CSR_PMPADDR9,
-    CSR_PMPADDR10,
-    CSR_PMPADDR11,
-    CSR_PMPADDR12,
-    CSR_PMPADDR13,
-    CSR_PMPADDR14,
-    CSR_PMPADDR15,
-    CSR_MCYCLE,
-    CSR_MINSTRET,
-    CSR_MHPMCOUNTER3,
-    CSR_MHPMCOUNTER4,
-    CSR_MHPMCOUNTER5,
-    CSR_MHPMCOUNTER6,
-    CSR_MHPMCOUNTER7,
-    CSR_MHPMCOUNTER8,
-    CSR_MHPMCOUNTER9,
-    CSR_MHPMCOUNTER10,
-    CSR_MHPMCOUNTER11,
-    CSR_MHPMCOUNTER12,
-    CSR_MHPMCOUNTER13,
-    CSR_MHPMCOUNTER14,
-    CSR_MHPMCOUNTER15,
-    CSR_MHPMCOUNTER16,
-    CSR_MHPMCOUNTER17,
-    CSR_MHPMCOUNTER18,
-    CSR_MHPMCOUNTER19,
-    CSR_MHPMCOUNTER20,
-    CSR_MHPMCOUNTER21,
-    CSR_MHPMCOUNTER22,
-    CSR_MHPMCOUNTER23,
-    CSR_MHPMCOUNTER24,
-    CSR_MHPMCOUNTER25,
-    CSR_MHPMCOUNTER26,
-    CSR_MHPMCOUNTER27,
-    CSR_MHPMCOUNTER28,
-    CSR_MHPMCOUNTER29,
-    CSR_MHPMCOUNTER30,
-    CSR_MHPMCOUNTER31,
-    CSR_MCYCLEH,
-    CSR_MINSTRETH,
-    CSR_MHPMCOUNTER3H,
-    CSR_MHPMCOUNTER4H,
-    CSR_MHPMCOUNTER5H,
-    CSR_MHPMCOUNTER6H,
-    CSR_MHPMCOUNTER7H,
-    CSR_MHPMCOUNTER8H,
-    CSR_MHPMCOUNTER9H,
-    CSR_MHPMCOUNTER10H,
-    CSR_MHPMCOUNTER11H,
-    CSR_MHPMCOUNTER12H,
-    CSR_MHPMCOUNTER13H,
-    CSR_MHPMCOUNTER14H,
-    CSR_MHPMCOUNTER15H,
-    CSR_MHPMCOUNTER16H,
-    CSR_MHPMCOUNTER17H,
-    CSR_MHPMCOUNTER18H,
-    CSR_MHPMCOUNTER19H,
-    CSR_MHPMCOUNTER20H,
-    CSR_MHPMCOUNTER21H,
-    CSR_MHPMCOUNTER22H,
-    CSR_MHPMCOUNTER23H,
-    CSR_MHPMCOUNTER24H,
-    CSR_MHPMCOUNTER25H,
-    CSR_MHPMCOUNTER26H,
-    CSR_MHPMCOUNTER27H,
-    CSR_MHPMCOUNTER28H,
-    CSR_MHPMCOUNTER29H,
-    CSR_MHPMCOUNTER30H,
-    CSR_MHPMCOUNTER31H,
-    CSR_MHPMEVENT3,
-    CSR_MHPMEVENT4,
-    CSR_MHPMEVENT5,
-    CSR_MHPMEVENT6,
-    CSR_MHPMEVENT7,
-    CSR_MHPMEVENT8,
-    CSR_MHPMEVENT9,
-    CSR_MHPMEVENT10,
-    CSR_MHPMEVENT11,
-    CSR_MHPMEVENT12,
-    CSR_MHPMEVENT13,
-    CSR_MHPMEVENT14,
-    CSR_MHPMEVENT15,
-    CSR_MHPMEVENT16,
-    CSR_MHPMEVENT17,
-    CSR_MHPMEVENT18,
-    CSR_MHPMEVENT19,
-    CSR_MHPMEVENT20,
-    CSR_MHPMEVENT21,
-    CSR_MHPMEVENT22,
-    CSR_MHPMEVENT23,
-    CSR_MHPMEVENT24,
-    CSR_MHPMEVENT25,
-    CSR_MHPMEVENT26,
-    CSR_MHPMEVENT27,
-    CSR_MHPMEVENT28,
-    CSR_MHPMEVENT29,
-    CSR_MHPMEVENT30,
-    CSR_MHPMEVENT31,
-    CSR_TSELECT,
-    CSR_TDATA1,
-    CSR_TDATA2,
-    CSR_TDATA3,
-    CSR_DCSR,
-    CSR_DPC,
-    CSR_DSCRATCH,
-    CSR_HSTATUS,
-    CSR_HEDELEG,
-    CSR_HIDELEG,
-    CSR_HIE,
-    CSR_HCOUNTEREN,
-    CSR_HTVAL,
-    CSR_HIP,
-    CSR_HTINST,
-    CSR_HGATP,
-    CSR_MBASE,
-    CSR_MBOUND,
-    CSR_MIBASE,
-    CSR_MIBOUND,
-    CSR_MDBASE,
-    CSR_MDBOUND,
-    CSR_MUCOUNTEREN,
-    CSR_MSCOUNTEREN,
-    CSR_MHCOUNTEREN,
-};
-
 int riscv_cpu_gdb_read_register(CPUState *cs, GByteArray *mem_buf, int n)
 {
     RISCVCPU *cpu = RISCV_CPU(cs);
@@ -315,11 +65,11 @@ static int riscv_gdb_get_fpu(CPURISCVState *env, GByteArray *buf, int n)
         target_ulong val = 0;
         int result;
         /*
-         * CSR_FFLAGS is at index 8 in csr_register, and gdb says it is FP
+         * CSR_FFLAGS is at index 1 in csr_register, and gdb says it is FP
          * register 33, so we recalculate the map index.
          * This also works for CSR_FRM and CSR_FCSR.
          */
-        result = riscv_csrrw_debug(env, n - 33 + csr_register_map[8], &val,
+        result = riscv_csrrw_debug(env, n - 32, &val,
                                    0, 0);
         if (result == 0) {
             return gdb_get_regl(buf, val);
@@ -338,11 +88,11 @@ static int riscv_gdb_set_fpu(CPURISCVState *env, uint8_t *mem_buf, int n)
         target_ulong val = ldtul_p(mem_buf);
         int result;
         /*
-         * CSR_FFLAGS is at index 8 in csr_register, and gdb says it is FP
+         * CSR_FFLAGS is at index 1 in csr_register, and gdb says it is FP
          * register 33, so we recalculate the map index.
          * This also works for CSR_FRM and CSR_FCSR.
          */
-        result = riscv_csrrw_debug(env, n - 33 + csr_register_map[8], NULL,
+        result = riscv_csrrw_debug(env, n - 32, NULL,
                                    val, -1);
         if (result == 0) {
             return sizeof(target_ulong);
@@ -353,11 +103,11 @@ static int riscv_gdb_set_fpu(CPURISCVState *env, uint8_t *mem_buf, int n)
 
 static int riscv_gdb_get_csr(CPURISCVState *env, GByteArray *buf, int n)
 {
-    if (n < ARRAY_SIZE(csr_register_map)) {
+    if (n < CSR_TABLE_SIZE) {
         target_ulong val = 0;
         int result;
 
-        result = riscv_csrrw_debug(env, csr_register_map[n], &val, 0, 0);
+        result = riscv_csrrw_debug(env, n, &val, 0, 0);
         if (result == 0) {
             return gdb_get_regl(buf, val);
         }
@@ -367,11 +117,11 @@ static int riscv_gdb_get_csr(CPURISCVState *env, GByteArray *buf, int n)
 
 static int riscv_gdb_set_csr(CPURISCVState *env, uint8_t *mem_buf, int n)
 {
-    if (n < ARRAY_SIZE(csr_register_map)) {
+    if (n < CSR_TABLE_SIZE) {
         target_ulong val = ldtul_p(mem_buf);
         int result;
 
-        result = riscv_csrrw_debug(env, csr_register_map[n], NULL, val, -1);
+        result = riscv_csrrw_debug(env, n, NULL, val, -1);
         if (result == 0) {
             return sizeof(target_ulong);
         }
@@ -405,6 +155,38 @@ static int riscv_gdb_set_virtual(CPURISCVState *cs, uint8_t *mem_buf, int n)
     return 0;
 }
 
+static int riscv_gen_dynamic_csr_xml(CPUState *cs, int base_reg)
+{
+    RISCVCPU *cpu = RISCV_CPU(cs);
+    CPURISCVState *env = &cpu->env;
+    GString *s = g_string_new(NULL);
+    riscv_csr_predicate_fn predicate;
+    int bitsize = riscv_cpu_is_32bit(env) ? 32 : 64;
+    int i;
+
+    g_string_printf(s, "<?xml version=\"1.0\"?>");
+    g_string_append_printf(s, "<!DOCTYPE feature SYSTEM \"gdb-target.dtd\">");
+    g_string_append_printf(s, "<feature name=\"org.gnu.gdb.riscv.csr\">");
+
+    for (i = 0; i < CSR_TABLE_SIZE; i++) {
+        predicate = csr_ops[i].predicate;
+        if (predicate && !predicate(env, i)) {
+            if (csr_ops[i].name) {
+                g_string_append_printf(s, "<reg name=\"%s\"", csr_ops[i].name);
+            } else {
+                g_string_append_printf(s, "<reg name=\"csr%03x\"", i);
+            }
+            g_string_append_printf(s, " bitsize=\"%d\"", bitsize);
+            g_string_append_printf(s, " regnum=\"%d\"/>", base_reg + i);
+        }
+    }
+
+    g_string_append_printf(s, "</feature>");
+
+    cpu->dyn_csr_xml = g_string_free(s, false);
+    return CSR_TABLE_SIZE;
+}
+
 void riscv_cpu_register_gdb_regs_for_features(CPUState *cs)
 {
     RISCVCPU *cpu = RISCV_CPU(cs);
@@ -417,16 +199,14 @@ void riscv_cpu_register_gdb_regs_for_features(CPUState *cs)
                                  36, "riscv-32bit-fpu.xml", 0);
     }
 #if defined(TARGET_RISCV32)
-    gdb_register_coprocessor(cs, riscv_gdb_get_csr, riscv_gdb_set_csr,
-                             240, "riscv-32bit-csr.xml", 0);
-
     gdb_register_coprocessor(cs, riscv_gdb_get_virtual, riscv_gdb_set_virtual,
                              1, "riscv-32bit-virtual.xml", 0);
 #elif defined(TARGET_RISCV64)
-    gdb_register_coprocessor(cs, riscv_gdb_get_csr, riscv_gdb_set_csr,
-                             240, "riscv-64bit-csr.xml", 0);
-
     gdb_register_coprocessor(cs, riscv_gdb_get_virtual, riscv_gdb_set_virtual,
                              1, "riscv-64bit-virtual.xml", 0);
 #endif
+
+    gdb_register_coprocessor(cs, riscv_gdb_get_csr, riscv_gdb_set_csr,
+                             riscv_gen_dynamic_csr_xml(cs, cs->gdb_num_regs),
+                             "riscv-csr.xml", 0);
 }