RISC-V: Implement existential predicates for CSRs

CSR predicate functions are added to the CSR table.
mstatus.FS and counter enable checks are moved
to predicate functions and two new predicates are
added to check misa.S for s* CSRs and a new PMP
CPU feature for pmp* CSRs.

Processors that don't implement S-mode will trap
on access to s* CSRs and processors that don't
implement PMP will trap on accesses to pmp* CSRs.

PMP checks are disabled in riscv_cpu_handle_mmu_fault
when the PMP CPU feature is not present.

Signed-off-by: Michael Clark <mjc@sifive.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Palmer Dabbelt <palmer@sifive.com>

1 files changed, 93 insertions, 76 deletions

diff --git a/target/riscv/csr.c b/target/riscv/csr.c
index 44ea8b7cb6..5e7e7d16b8 100644
--- a/target/riscv/csr.c
+++ b/target/riscv/csr.c
@@ -42,6 +42,46 @@ void riscv_set_csr_ops(int csrno, riscv_csr_operations *ops)
     csr_ops[csrno & (CSR_TABLE_SIZE - 1)] = *ops;
 }
 
+/* Predicates */
+static int fs(CPURISCVState *env, int csrno)
+{
+#if !defined(CONFIG_USER_ONLY)
+    if (!(env->mstatus & MSTATUS_FS)) {
+        return -1;
+    }
+#endif
+    return 0;
+}
+
+static int ctr(CPURISCVState *env, int csrno)
+{
+#if !defined(CONFIG_USER_ONLY)
+    target_ulong ctr_en = env->priv == PRV_U ? env->scounteren :
+                          env->priv == PRV_S ? env->mcounteren : -1U;
+    if (!(ctr_en & (1 << (csrno & 31)))) {
+        return -1;
+    }
+#endif
+    return 0;
+}
+
+#if !defined(CONFIG_USER_ONLY)
+static int any(CPURISCVState *env, int csrno)
+{
+    return 0;
+}
+
+static int smode(CPURISCVState *env, int csrno)
+{
+    return -!riscv_has_ext(env, RVS);
+}
+
+static int pmp(CPURISCVState *env, int csrno)
+{
+    return -!riscv_feature(env, RISCV_FEATURE_PMP);
+}
+#endif
+
 /* User Floating-Point CSRs */
 static int read_fflags(CPURISCVState *env, int csrno, target_ulong *val)
 {
@@ -115,33 +155,8 @@ static int write_fcsr(CPURISCVState *env, int csrno, target_ulong val)
 }
 
 /* User Timers and Counters */
-static int counter_enabled(CPURISCVState *env, int csrno)
-{
-#ifndef CONFIG_USER_ONLY
-    target_ulong ctr_en = env->priv == PRV_U ? env->scounteren :
-                          env->priv == PRV_S ? env->mcounteren : -1U;
-#else
-    target_ulong ctr_en = -1;
-#endif
-    return (ctr_en >> (csrno & 31)) & 1;
-}
-
-#if !defined(CONFIG_USER_ONLY)
-static int read_zero_counter(CPURISCVState *env, int csrno, target_ulong *val)
-{
-    if (!counter_enabled(env, csrno)) {
-        return -1;
-    }
-    *val = 0;
-    return 0;
-}
-#endif
-
 static int read_instret(CPURISCVState *env, int csrno, target_ulong *val)
 {
-    if (!counter_enabled(env, csrno)) {
-        return -1;
-    }
 #if !defined(CONFIG_USER_ONLY)
     if (use_icount) {
         *val = cpu_get_icount();
@@ -157,9 +172,6 @@ static int read_instret(CPURISCVState *env, int csrno, target_ulong *val)
 #if defined(TARGET_RISCV32)
 static int read_instreth(CPURISCVState *env, int csrno, target_ulong *val)
 {
-    if (!counter_enabled(env, csrno)) {
-        return -1;
-    }
 #if !defined(CONFIG_USER_ONLY)
     if (use_icount) {
         *val = cpu_get_icount() >> 32;
@@ -720,6 +732,11 @@ int riscv_csrrw(CPURISCVState *env, int csrno, target_ulong *ret_value,
     }
 #endif
 
+    /* check predicate */
+    if (!csr_ops[csrno].predicate || csr_ops[csrno].predicate(env, csrno) < 0) {
+        return -1;
+    }
+
     /* execute combined read/write operation if it exists */
     if (csr_ops[csrno].op) {
         return csr_ops[csrno].op(env, csrno, ret_value, new_value, write_mask);
@@ -758,89 +775,89 @@ int riscv_csrrw(CPURISCVState *env, int csrno, target_ulong *ret_value,
 /* Control and Status Register function table */
 static riscv_csr_operations csr_ops[CSR_TABLE_SIZE] = {
     /* User Floating-Point CSRs */
-    [CSR_FFLAGS] =              { read_fflags,      write_fflags      },
-    [CSR_FRM] =                 { read_frm,         write_frm         },
-    [CSR_FCSR] =                { read_fcsr,        write_fcsr        },
+    [CSR_FFLAGS] =              { fs,   read_fflags,      write_fflags      },
+    [CSR_FRM] =                 { fs,   read_frm,         write_frm         },
+    [CSR_FCSR] =                { fs,   read_fcsr,        write_fcsr        },
 
     /* User Timers and Counters */
-    [CSR_CYCLE] =               { read_instret                        },
-    [CSR_INSTRET] =             { read_instret                        },
+    [CSR_CYCLE] =               { ctr,  read_instret                        },
+    [CSR_INSTRET] =             { ctr,  read_instret                        },
 #if defined(TARGET_RISCV32)
-    [CSR_CYCLEH] =              { read_instreth                       },
-    [CSR_INSTRETH] =            { read_instreth                       },
+    [CSR_CYCLEH] =              { ctr,  read_instreth                       },
+    [CSR_INSTRETH] =            { ctr,  read_instreth                       },
 #endif
 
     /* User-level time CSRs are only available in linux-user
      * In privileged mode, the monitor emulates these CSRs */
 #if defined(CONFIG_USER_ONLY)
-    [CSR_TIME] =                { read_time                           },
+    [CSR_TIME] =                { ctr,  read_time                           },
 #if defined(TARGET_RISCV32)
-    [CSR_TIMEH] =               { read_timeh                          },
+    [CSR_TIMEH] =               { ctr,  read_timeh                          },
 #endif
 #endif
 
 #if !defined(CONFIG_USER_ONLY)
     /* Machine Timers and Counters */
-    [CSR_MCYCLE] =              { read_instret                        },
-    [CSR_MINSTRET] =            { read_instret                        },
+    [CSR_MCYCLE] =              { any,  read_instret                        },
+    [CSR_MINSTRET] =            { any,  read_instret                        },
 #if defined(TARGET_RISCV32)
-    [CSR_MCYCLEH] =             { read_instreth                       },
-    [CSR_MINSTRETH] =           { read_instreth                       },
+    [CSR_MCYCLEH] =             { any,  read_instreth                       },
+    [CSR_MINSTRETH] =           { any,  read_instreth                       },
 #endif
 
     /* Machine Information Registers */
-    [CSR_MVENDORID] =           { read_zero                           },
-    [CSR_MARCHID] =             { read_zero                           },
-    [CSR_MIMPID] =              { read_zero                           },
-    [CSR_MHARTID] =             { read_mhartid                        },
+    [CSR_MVENDORID] =           { any,  read_zero                           },
+    [CSR_MARCHID] =             { any,  read_zero                           },
+    [CSR_MIMPID] =              { any,  read_zero                           },
+    [CSR_MHARTID] =             { any,  read_mhartid                        },
 
     /* Machine Trap Setup */
-    [CSR_MSTATUS] =             { read_mstatus,     write_mstatus     },
-    [CSR_MISA] =                { read_misa                           },
-    [CSR_MIDELEG] =             { read_mideleg,     write_mideleg     },
-    [CSR_MEDELEG] =             { read_medeleg,     write_medeleg     },
-    [CSR_MIE] =                 { read_mie,         write_mie         },
-    [CSR_MTVEC] =               { read_mtvec,       write_mtvec       },
-    [CSR_MCOUNTEREN] =          { read_mcounteren,  write_mcounteren  },
+    [CSR_MSTATUS] =             { any,  read_mstatus,     write_mstatus     },
+    [CSR_MISA] =                { any,  read_misa                           },
+    [CSR_MIDELEG] =             { any,  read_mideleg,     write_mideleg     },
+    [CSR_MEDELEG] =             { any,  read_medeleg,     write_medeleg     },
+    [CSR_MIE] =                 { any,  read_mie,         write_mie         },
+    [CSR_MTVEC] =               { any,  read_mtvec,       write_mtvec       },
+    [CSR_MCOUNTEREN] =          { any,  read_mcounteren,  write_mcounteren  },
 
     /* Legacy Counter Setup (priv v1.9.1) */
-    [CSR_MUCOUNTEREN] =         { read_mucounteren, write_mucounteren },
-    [CSR_MSCOUNTEREN] =         { read_mscounteren, write_mscounteren },
+    [CSR_MUCOUNTEREN] =         { any,  read_mucounteren, write_mucounteren },
+    [CSR_MSCOUNTEREN] =         { any,  read_mscounteren, write_mscounteren },
 
     /* Machine Trap Handling */
-    [CSR_MSCRATCH] =            { read_mscratch,    write_mscratch    },
-    [CSR_MEPC] =                { read_mepc,        write_mepc        },
-    [CSR_MCAUSE] =              { read_mcause,      write_mcause      },
-    [CSR_MBADADDR] =            { read_mbadaddr,    write_mbadaddr    },
-    [CSR_MIP] =                 { NULL,     NULL,     rmw_mip         },
+    [CSR_MSCRATCH] =            { any,  read_mscratch,    write_mscratch    },
+    [CSR_MEPC] =                { any,  read_mepc,        write_mepc        },
+    [CSR_MCAUSE] =              { any,  read_mcause,      write_mcause      },
+    [CSR_MBADADDR] =            { any,  read_mbadaddr,    write_mbadaddr    },
+    [CSR_MIP] =                 { any,  NULL,     NULL,     rmw_mip         },
 
     /* Supervisor Trap Setup */
-    [CSR_SSTATUS] =             { read_sstatus,     write_sstatus     },
-    [CSR_SIE] =                 { read_sie,         write_sie         },
-    [CSR_STVEC] =               { read_stvec,       write_stvec       },
-    [CSR_SCOUNTEREN] =          { read_scounteren,  write_scounteren  },
+    [CSR_SSTATUS] =             { smode, read_sstatus,     write_sstatus     },
+    [CSR_SIE] =                 { smode, read_sie,         write_sie         },
+    [CSR_STVEC] =               { smode, read_stvec,       write_stvec       },
+    [CSR_SCOUNTEREN] =          { smode, read_scounteren,  write_scounteren  },
 
     /* Supervisor Trap Handling */
-    [CSR_SSCRATCH] =            { read_sscratch,    write_sscratch    },
-    [CSR_SEPC] =                { read_sepc,        write_sepc        },
-    [CSR_SCAUSE] =              { read_scause,      write_scause      },
-    [CSR_SBADADDR] =            { read_sbadaddr,    write_sbadaddr    },
-    [CSR_SIP] =                 { NULL,     NULL,     rmw_sip         },
+    [CSR_SSCRATCH] =            { smode, read_sscratch,    write_sscratch    },
+    [CSR_SEPC] =                { smode, read_sepc,        write_sepc        },
+    [CSR_SCAUSE] =              { smode, read_scause,      write_scause      },
+    [CSR_SBADADDR] =            { smode, read_sbadaddr,    write_sbadaddr    },
+    [CSR_SIP] =                 { smode, NULL,     NULL,     rmw_sip         },
 
     /* Supervisor Protection and Translation */
-    [CSR_SATP] =                { read_satp,        write_satp        },
+    [CSR_SATP] =                { smode, read_satp,        write_satp        },
 
     /* Physical Memory Protection */
-    [CSR_PMPCFG0  ... CSR_PMPADDR9] =  { read_pmpcfg,  write_pmpcfg   },
-    [CSR_PMPADDR0 ... CSR_PMPADDR15] = { read_pmpaddr, write_pmpaddr  },
+    [CSR_PMPCFG0  ... CSR_PMPADDR9] =  { pmp,   read_pmpcfg,  write_pmpcfg   },
+    [CSR_PMPADDR0 ... CSR_PMPADDR15] = { pmp,   read_pmpaddr, write_pmpaddr  },
 
     /* Performance Counters */
-    [CSR_HPMCOUNTER3   ... CSR_HPMCOUNTER31] =    { read_zero_counter },
-    [CSR_MHPMCOUNTER3  ... CSR_MHPMCOUNTER31] =   { read_zero         },
-    [CSR_MHPMEVENT3    ... CSR_MHPMEVENT31] =     { read_zero         },
+    [CSR_HPMCOUNTER3   ... CSR_HPMCOUNTER31] =    { ctr,  read_zero          },
+    [CSR_MHPMCOUNTER3  ... CSR_MHPMCOUNTER31] =   { any,  read_zero          },
+    [CSR_MHPMEVENT3    ... CSR_MHPMEVENT31] =     { any,  read_zero          },
 #if defined(TARGET_RISCV32)
-    [CSR_HPMCOUNTER3H  ... CSR_HPMCOUNTER31H] =   { read_zero_counter },
-    [CSR_MHPMCOUNTER3H ... CSR_MHPMCOUNTER31H] =  { read_zero         },
+    [CSR_HPMCOUNTER3H  ... CSR_HPMCOUNTER31H] =   { ctr,  read_zero          },
+    [CSR_MHPMCOUNTER3H ... CSR_MHPMCOUNTER31H] =  { any,  read_zero          },
 #endif
 #endif /* !CONFIG_USER_ONLY */
 };