target/riscv: Add initial support for the Sdtrig extension

This adds initial support for the Sdtrig extension via the Trigger
Module, as defined in the RISC-V Debug Specification [1].

Only "Address / Data Match" trigger (type 2) is implemented as of now,
which is mainly used for hardware breakpoint and watchpoint. The number
of type 2 triggers implemented is 2, which is the number that we can
find in the SiFive U54/U74 cores.

[1] https://github.com/riscv/riscv-debug-spec/raw/master/riscv-debug-stable.pdf

Signed-off-by: Bin Meng <bin.meng@windriver.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-Id: <20220315065529.62198-2-bmeng.cn@gmail.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

1 files changed, 339 insertions, 0 deletions

diff --git a/target/riscv/debug.c b/target/riscv/debug.c
new file mode 100644
index 0000000000..c8cec39217
--- /dev/null
+++ b/target/riscv/debug.c
@@ -0,0 +1,339 @@
+/*
+ * QEMU RISC-V Native Debug Support
+ *
+ * Copyright (c) 2022 Wind River Systems, Inc.
+ *
+ * Author:
+ *   Bin Meng <bin.meng@windriver.com>
+ *
+ * This provides the native debug support via the Trigger Module, as defined
+ * in the RISC-V Debug Specification:
+ * https://github.com/riscv/riscv-debug-spec/raw/master/riscv-debug-stable.pdf
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2 or later, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "qemu/osdep.h"
+#include "qemu/log.h"
+#include "qapi/error.h"
+#include "cpu.h"
+#include "trace.h"
+#include "exec/exec-all.h"
+
+/*
+ * The following M-mode trigger CSRs are implemented:
+ *
+ * - tselect
+ * - tdata1
+ * - tdata2
+ * - tdata3
+ *
+ * We don't support writable 'type' field in the tdata1 register, so there is
+ * no need to implement the "tinfo" CSR.
+ *
+ * The following triggers are implemented:
+ *
+ * Index | Type |          tdata mapping | Description
+ * ------+------+------------------------+------------
+ *     0 |    2 |         tdata1, tdata2 | Address / Data Match
+ *     1 |    2 |         tdata1, tdata2 | Address / Data Match
+ */
+
+/* tdata availability of a trigger */
+typedef bool tdata_avail[TDATA_NUM];
+
+static tdata_avail tdata_mapping[TRIGGER_NUM] = {
+    [TRIGGER_TYPE2_IDX_0 ... TRIGGER_TYPE2_IDX_1] = { true, true, false },
+};
+
+/* only breakpoint size 1/2/4/8 supported */
+static int access_size[SIZE_NUM] = {
+    [SIZE_ANY] = 0,
+    [SIZE_1B]  = 1,
+    [SIZE_2B]  = 2,
+    [SIZE_4B]  = 4,
+    [SIZE_6B]  = -1,
+    [SIZE_8B]  = 8,
+    [6 ... 15] = -1,
+};
+
+static inline target_ulong trigger_type(CPURISCVState *env,
+                                        trigger_type_t type)
+{
+    target_ulong tdata1;
+
+    switch (riscv_cpu_mxl(env)) {
+    case MXL_RV32:
+        tdata1 = RV32_TYPE(type);
+        break;
+    case MXL_RV64:
+        tdata1 = RV64_TYPE(type);
+        break;
+    default:
+        g_assert_not_reached();
+    }
+
+    return tdata1;
+}
+
+bool tdata_available(CPURISCVState *env, int tdata_index)
+{
+    if (unlikely(tdata_index >= TDATA_NUM)) {
+        return false;
+    }
+
+    if (unlikely(env->trigger_cur >= TRIGGER_NUM)) {
+        return false;
+    }
+
+    return tdata_mapping[env->trigger_cur][tdata_index];
+}
+
+target_ulong tselect_csr_read(CPURISCVState *env)
+{
+    return env->trigger_cur;
+}
+
+void tselect_csr_write(CPURISCVState *env, target_ulong val)
+{
+    /* all target_ulong bits of tselect are implemented */
+    env->trigger_cur = val;
+}
+
+static target_ulong tdata1_validate(CPURISCVState *env, target_ulong val,
+                                    trigger_type_t t)
+{
+    uint32_t type, dmode;
+    target_ulong tdata1;
+
+    switch (riscv_cpu_mxl(env)) {
+    case MXL_RV32:
+        type = extract32(val, 28, 4);
+        dmode = extract32(val, 27, 1);
+        tdata1 = RV32_TYPE(t);
+        break;
+    case MXL_RV64:
+        type = extract64(val, 60, 4);
+        dmode = extract64(val, 59, 1);
+        tdata1 = RV64_TYPE(t);
+        break;
+    default:
+        g_assert_not_reached();
+    }
+
+    if (type != t) {
+        qemu_log_mask(LOG_GUEST_ERROR,
+                      "ignoring type write to tdata1 register\n");
+    }
+    if (dmode != 0) {
+        qemu_log_mask(LOG_UNIMP, "debug mode is not supported\n");
+    }
+
+    return tdata1;
+}
+
+static inline void warn_always_zero_bit(target_ulong val, target_ulong mask,
+                                        const char *msg)
+{
+    if (val & mask) {
+        qemu_log_mask(LOG_UNIMP, "%s bit is always zero\n", msg);
+    }
+}
+
+static uint32_t type2_breakpoint_size(CPURISCVState *env, target_ulong ctrl)
+{
+    uint32_t size, sizelo, sizehi = 0;
+
+    if (riscv_cpu_mxl(env) == MXL_RV64) {
+        sizehi = extract32(ctrl, 21, 2);
+    }
+    sizelo = extract32(ctrl, 16, 2);
+    size = (sizehi << 2) | sizelo;
+
+    return size;
+}
+
+static inline bool type2_breakpoint_enabled(target_ulong ctrl)
+{
+    bool mode = !!(ctrl & (TYPE2_U | TYPE2_S | TYPE2_M));
+    bool rwx = !!(ctrl & (TYPE2_LOAD | TYPE2_STORE | TYPE2_EXEC));
+
+    return mode && rwx;
+}
+
+static target_ulong type2_mcontrol_validate(CPURISCVState *env,
+                                            target_ulong ctrl)
+{
+    target_ulong val;
+    uint32_t size;
+
+    /* validate the generic part first */
+    val = tdata1_validate(env, ctrl, TRIGGER_TYPE_AD_MATCH);
+
+    /* validate unimplemented (always zero) bits */
+    warn_always_zero_bit(ctrl, TYPE2_MATCH, "match");
+    warn_always_zero_bit(ctrl, TYPE2_CHAIN, "chain");
+    warn_always_zero_bit(ctrl, TYPE2_ACTION, "action");
+    warn_always_zero_bit(ctrl, TYPE2_TIMING, "timing");
+    warn_always_zero_bit(ctrl, TYPE2_SELECT, "select");
+    warn_always_zero_bit(ctrl, TYPE2_HIT, "hit");
+
+    /* validate size encoding */
+    size = type2_breakpoint_size(env, ctrl);
+    if (access_size[size] == -1) {
+        qemu_log_mask(LOG_UNIMP, "access size %d is not supported, using SIZE_ANY\n",
+                      size);
+    } else {
+        val |= (ctrl & TYPE2_SIZELO);
+        if (riscv_cpu_mxl(env) == MXL_RV64) {
+            val |= (ctrl & TYPE2_SIZEHI);
+        }
+    }
+
+    /* keep the mode and attribute bits */
+    val |= (ctrl & (TYPE2_U | TYPE2_S | TYPE2_M |
+                    TYPE2_LOAD | TYPE2_STORE | TYPE2_EXEC));
+
+    return val;
+}
+
+static void type2_breakpoint_insert(CPURISCVState *env, target_ulong index)
+{
+    target_ulong ctrl = env->type2_trig[index].mcontrol;
+    target_ulong addr = env->type2_trig[index].maddress;
+    bool enabled = type2_breakpoint_enabled(ctrl);
+    CPUState *cs = env_cpu(env);
+    int flags = BP_CPU | BP_STOP_BEFORE_ACCESS;
+    uint32_t size;
+
+    if (!enabled) {
+        return;
+    }
+
+    if (ctrl & TYPE2_EXEC) {
+        cpu_breakpoint_insert(cs, addr, flags, &env->type2_trig[index].bp);
+    }
+
+    if (ctrl & TYPE2_LOAD) {
+        flags |= BP_MEM_READ;
+    }
+    if (ctrl & TYPE2_STORE) {
+        flags |= BP_MEM_WRITE;
+    }
+
+    if (flags & BP_MEM_ACCESS) {
+        size = type2_breakpoint_size(env, ctrl);
+        if (size != 0) {
+            cpu_watchpoint_insert(cs, addr, size, flags,
+                                  &env->type2_trig[index].wp);
+        } else {
+            cpu_watchpoint_insert(cs, addr, 8, flags,
+                                  &env->type2_trig[index].wp);
+        }
+    }
+}
+
+static void type2_breakpoint_remove(CPURISCVState *env, target_ulong index)
+{
+    CPUState *cs = env_cpu(env);
+
+    if (env->type2_trig[index].bp) {
+        cpu_breakpoint_remove_by_ref(cs, env->type2_trig[index].bp);
+        env->type2_trig[index].bp = NULL;
+    }
+
+    if (env->type2_trig[index].wp) {
+        cpu_watchpoint_remove_by_ref(cs, env->type2_trig[index].wp);
+        env->type2_trig[index].wp = NULL;
+    }
+}
+
+static target_ulong type2_reg_read(CPURISCVState *env,
+                                   target_ulong trigger_index, int tdata_index)
+{
+    uint32_t index = trigger_index - TRIGGER_TYPE2_IDX_0;
+    target_ulong tdata;
+
+    switch (tdata_index) {
+    case TDATA1:
+        tdata = env->type2_trig[index].mcontrol;
+        break;
+    case TDATA2:
+        tdata = env->type2_trig[index].maddress;
+        break;
+    default:
+        g_assert_not_reached();
+    }
+
+    return tdata;
+}
+
+static void type2_reg_write(CPURISCVState *env, target_ulong trigger_index,
+                            int tdata_index, target_ulong val)
+{
+    uint32_t index = trigger_index - TRIGGER_TYPE2_IDX_0;
+    target_ulong new_val;
+
+    switch (tdata_index) {
+    case TDATA1:
+        new_val = type2_mcontrol_validate(env, val);
+        if (new_val != env->type2_trig[index].mcontrol) {
+            env->type2_trig[index].mcontrol = new_val;
+            type2_breakpoint_remove(env, index);
+            type2_breakpoint_insert(env, index);
+        }
+        break;
+    case TDATA2:
+        if (val != env->type2_trig[index].maddress) {
+            env->type2_trig[index].maddress = val;
+            type2_breakpoint_remove(env, index);
+            type2_breakpoint_insert(env, index);
+        }
+        break;
+    default:
+        g_assert_not_reached();
+    }
+
+    return;
+}
+
+typedef target_ulong (*tdata_read_func)(CPURISCVState *env,
+                                        target_ulong trigger_index,
+                                        int tdata_index);
+
+static tdata_read_func trigger_read_funcs[TRIGGER_NUM] = {
+    [TRIGGER_TYPE2_IDX_0 ... TRIGGER_TYPE2_IDX_1] = type2_reg_read,
+};
+
+typedef void (*tdata_write_func)(CPURISCVState *env,
+                                 target_ulong trigger_index,
+                                 int tdata_index,
+                                 target_ulong val);
+
+static tdata_write_func trigger_write_funcs[TRIGGER_NUM] = {
+    [TRIGGER_TYPE2_IDX_0 ... TRIGGER_TYPE2_IDX_1] = type2_reg_write,
+};
+
+target_ulong tdata_csr_read(CPURISCVState *env, int tdata_index)
+{
+    tdata_read_func read_func = trigger_read_funcs[env->trigger_cur];
+
+    return read_func(env, env->trigger_cur, tdata_index);
+}
+
+void tdata_csr_write(CPURISCVState *env, int tdata_index, target_ulong val)
+{
+    tdata_write_func write_func = trigger_write_funcs[env->trigger_cur];
+
+    return write_func(env, env->trigger_cur, tdata_index, val);
+}