[Qemu-devel] [PATCH v2 8/9] target-mips: add BadInstr and BadInstrP support

[Leon Alrae <leon.alrae@imgtec.com>]

BadInstr Register (CP0 Register 8, Select 1)
The BadInstr register is a read-only register that capture the most recent
instruction which caused an exception.

BadInstrP Register (CP0 Register 8, Select 2)
The BadInstrP register contains the prior branch instruction, when the
faulting instruction is in a branch delay slot.

Using error_code to indicate whether AdEL or TLBL was triggered during
instruction fetch, in this case BadInstr is not updated as valid instruction
word is not available.

Signed-off-by: Leon Alrae <leon.alrae@imgtec.com>
---
 target-mips/cpu.h       |    6 +++
 target-mips/helper.c    |   44 ++++++++++++++++++++++++--
 target-mips/op_helper.c |   17 +++++++++-
 target-mips/translate.c |   80 +++++++++++++++++++++++++++++++++++++++++++---
 4 files changed, 136 insertions(+), 11 deletions(-)

diff --git a/target-mips/cpu.h b/target-mips/cpu.h
index bc52222..656f5ca 100644
--- a/target-mips/cpu.h
+++ b/target-mips/cpu.h
@@ -177,6 +177,8 @@ struct TCState {
     target_ulong CP0_TCScheFBack;
     int32_t CP0_Debug_tcstatus;
     target_ulong CP0_UserLocal;
+    uint32_t CP0_BadInstr;
+    uint32_t CP0_BadInstrP;
 };
 
 typedef struct CPUMIPSState CPUMIPSState;
@@ -383,6 +385,8 @@ struct CPUMIPSState {
 #define CP0C2_SA   0
     int32_t CP0_Config3;
 #define CP0C3_M    31
+#define CP0C3_BP 27
+#define CP0C3_BI 26
 #define CP0C3_ISA_ON_EXC 16
 #define CP0C3_ULRI 13
 #define CP0C3_RXI  12
@@ -453,6 +457,8 @@ struct CPUMIPSState {
     CPUMIPSFPUContext fpus[MIPS_FPU_MAX];
     /* QEMU */
     int error_code;
+#define EXCP_TLB_NOMATCH   0x1
+#define EXCP_INST_NOTAVAIL 0x2 /* No valid instruction word for BadInstr */
     uint32_t hflags;    /* CPU State */
     /* TMASK defines different execution modes */
 #define MIPS_HFLAG_TMASK  0xC07FF
diff --git a/target-mips/helper.c b/target-mips/helper.c
index 5d72438..67fc71d 100644
--- a/target-mips/helper.c
+++ b/target-mips/helper.c
@@ -25,6 +25,7 @@
 
 #include "cpu.h"
 #include "sysemu/kvm.h"
+#include "exec/cpu_ldst.h"
 
 enum {
     TLBRET_XI = -6,
@@ -241,6 +242,10 @@ static void raise_mmu_exception(CPUMIPSState *env, target_ulong address,
     CPUState *cs = CPU(mips_env_get_cpu(env));
     int exception = 0, error_code = 0;
 
+    if (rw == MMU_INST_FETCH) {
+        error_code |= EXCP_INST_NOTAVAIL;
+    }
+
     switch (tlb_error) {
     default:
     case TLBRET_BADADDR:
@@ -259,7 +264,7 @@ static void raise_mmu_exception(CPUMIPSState *env, target_ulong address,
         } else {
             exception = EXCP_TLBL;
         }
-        error_code = 1;
+        error_code |= EXCP_TLB_NOMATCH;
         break;
     case TLBRET_INVALID:
         /* TLB match with no valid bit */
@@ -451,6 +456,20 @@ static void set_hflags_for_handler (CPUMIPSState *env)
                         << MIPS_HFLAG_M16_SHIFT);
     }
 }
+
+static inline void set_badinstr_registers(CPUMIPSState *env)
+{
+    if (env->hflags & MIPS_HFLAG_M16) {
+        /* TODO: add BadInstr support for microMIPS */
+        return;
+    }
+    if (env->CP0_Config3 & (1 << CP0C3_BI)) {
+        env->active_tc.CP0_BadInstr = cpu_ldl_code(env, env->active_tc.PC);
+    }
+    if (env->CP0_Config3 & (1 << CP0C3_BP) && env->hflags & MIPS_HFLAG_BMASK) {
+        env->active_tc.CP0_BadInstrP = cpu_ldl_code(env, env->active_tc.PC - 4);
+    }
+}
 #endif
 
 void mips_cpu_do_interrupt(CPUState *cs)
@@ -458,6 +477,7 @@ void mips_cpu_do_interrupt(CPUState *cs)
 #if !defined(CONFIG_USER_ONLY)
     MIPSCPU *cpu = MIPS_CPU(cs);
     CPUMIPSState *env = &cpu->env;
+    bool update_badinstr = 0;
     target_ulong offset;
     int cause = -1;
     const char *name;
@@ -566,10 +586,13 @@ void mips_cpu_do_interrupt(CPUState *cs)
         goto set_EPC;
     case EXCP_LTLBL:
         cause = 1;
+        update_badinstr = !(env->error_code & EXCP_INST_NOTAVAIL);
         goto set_EPC;
     case EXCP_TLBL:
         cause = 2;
-        if (env->error_code == 1 && !(env->CP0_Status & (1 << CP0St_EXL))) {
+        update_badinstr = !(env->error_code & EXCP_INST_NOTAVAIL);
+        if (env->error_code & EXCP_TLB_NOMATCH &&
+            !(env->CP0_Status & (1 << CP0St_EXL))) {
 #if defined(TARGET_MIPS64)
             int R = env->CP0_BadVAddr >> 62;
             int UX = (env->CP0_Status & (1 << CP0St_UX)) != 0;
@@ -586,7 +609,9 @@ void mips_cpu_do_interrupt(CPUState *cs)
         goto set_EPC;
     case EXCP_TLBS:
         cause = 3;
-        if (env->error_code == 1 && !(env->CP0_Status & (1 << CP0St_EXL))) {
+        update_badinstr = 1;
+        if (env->error_code & EXCP_TLB_NOMATCH &&
+            !(env->CP0_Status & (1 << CP0St_EXL))) {
 #if defined(TARGET_MIPS64)
             int R = env->CP0_BadVAddr >> 62;
             int UX = (env->CP0_Status & (1 << CP0St_UX)) != 0;
@@ -603,9 +628,11 @@ void mips_cpu_do_interrupt(CPUState *cs)
         goto set_EPC;
     case EXCP_AdEL:
         cause = 4;
+        update_badinstr = !(env->error_code & EXCP_INST_NOTAVAIL);
         goto set_EPC;
     case EXCP_AdES:
         cause = 5;
+        update_badinstr = 1;
         goto set_EPC;
     case EXCP_IBE:
         cause = 6;
@@ -615,32 +642,40 @@ void mips_cpu_do_interrupt(CPUState *cs)
         goto set_EPC;
     case EXCP_SYSCALL:
         cause = 8;
+        update_badinstr = 1;
         goto set_EPC;
     case EXCP_BREAK:
         cause = 9;
+        update_badinstr = 1;
         goto set_EPC;
     case EXCP_RI:
         cause = 10;
+        update_badinstr = 1;
         goto set_EPC;
     case EXCP_CpU:
         cause = 11;
+        update_badinstr = 1;
         env->CP0_Cause = (env->CP0_Cause & ~(0x3 << CP0Ca_CE)) |
                          (env->error_code << CP0Ca_CE);
         goto set_EPC;
     case EXCP_OVERFLOW:
         cause = 12;
+        update_badinstr = 1;
         goto set_EPC;
     case EXCP_TRAP:
         cause = 13;
+        update_badinstr = 1;
         goto set_EPC;
     case EXCP_FPE:
         cause = 15;
+        update_badinstr = 1;
         goto set_EPC;
     case EXCP_C2E:
         cause = 18;
         goto set_EPC;
     case EXCP_TLBRI:
         cause = 19;
+        update_badinstr = 1;
         goto set_EPC;
     case EXCP_TLBXI:
         cause = 20;
@@ -671,6 +706,9 @@ void mips_cpu_do_interrupt(CPUState *cs)
  set_EPC:
         if (!(env->CP0_Status & (1 << CP0St_EXL))) {
             env->CP0_EPC = exception_resume_pc(env);
+            if (update_badinstr) {
+                set_badinstr_registers(env);
+            }
             if (env->hflags & MIPS_HFLAG_BMASK) {
                 env->CP0_Cause |= (1U << CP0Ca_BD);
             } else {
diff --git a/target-mips/op_helper.c b/target-mips/op_helper.c
index fa96bb3..431f3a1 100644
--- a/target-mips/op_helper.c
+++ b/target-mips/op_helper.c
@@ -2238,13 +2238,26 @@ void helper_wait(CPUMIPSState *env)
 #if !defined(CONFIG_USER_ONLY)
 
 void mips_cpu_do_unaligned_access(CPUState *cs, vaddr addr,
-                                  int is_write, int is_user, uintptr_t retaddr)
+                                  int access_type, int is_user,
+                                  uintptr_t retaddr)
 {
     MIPSCPU *cpu = MIPS_CPU(cs);
     CPUMIPSState *env = &cpu->env;
+    int error_code = 0;
+    int excp;
 
     env->CP0_BadVAddr = addr;
-    do_raise_exception(env, (is_write == 1) ? EXCP_AdES : EXCP_AdEL, retaddr);
+
+    if (access_type == MMU_DATA_STORE) {
+        excp = EXCP_AdES;
+    } else {
+        excp = EXCP_AdEL;
+        if (access_type == MMU_INST_FETCH) {
+            error_code |= EXCP_INST_NOTAVAIL;
+        }
+    }
+
+    do_raise_exception_err(env, excp, error_code, retaddr);
 }
 
 void tlb_fill(CPUState *cs, target_ulong addr, int is_write, int mmu_idx,
diff --git a/target-mips/translate.c b/target-mips/translate.c
index 4179fea..b931574 100644
--- a/target-mips/translate.c
+++ b/target-mips/translate.c
@@ -1180,6 +1180,8 @@ typedef struct DisasContext {
     int kscrexist;
     bool rxi;
     bool ie;
+    bool bi;
+    bool bp;
 } DisasContext;
 
 enum {
@@ -4872,9 +4874,27 @@ static void gen_mfc0(DisasContext *ctx, TCGv arg, int reg, int sel)
             tcg_gen_ext32s_tl(arg, arg);
             rn = "BadVAddr";
             break;
+        case 1:
+            if (ctx->bi) {
+                gen_mfc0_load32(arg, offsetof(CPUMIPSState,
+                                              active_tc.CP0_BadInstr));
+                rn = "BadInstr";
+            } else {
+                gen_mfc0_unimplemented(ctx, arg);
+            }
+            break;
+        case 2:
+            if (ctx->bp) {
+                gen_mfc0_load32(arg, offsetof(CPUMIPSState,
+                                              active_tc.CP0_BadInstrP));
+                rn = "BadInstrP";
+            } else {
+                gen_mfc0_unimplemented(ctx, arg);
+            }
+            break;
         default:
             goto die;
-       }
+        }
         break;
     case 9:
         switch (sel) {
@@ -5472,8 +5492,22 @@ static void gen_mtc0(DisasContext *ctx, TCGv arg, int reg, int sel)
         }
         break;
     case 8:
-        /* ignored */
-        rn = "BadVAddr";
+        switch (sel) {
+        case 0:
+            /* ignored */
+            rn = "BadVAddr";
+            break;
+        case 1:
+            /* ignored */
+            rn = "BadInstr";
+            break;
+        case 2:
+            /* ignored */
+            rn = "BadInstrP";
+            break;
+        default:
+            goto die;
+        }
         break;
     case 9:
         switch (sel) {
@@ -6098,6 +6132,24 @@ static void gen_dmfc0(DisasContext *ctx, TCGv arg, int reg, int sel)
             tcg_gen_ld_tl(arg, cpu_env, offsetof(CPUMIPSState, CP0_BadVAddr));
             rn = "BadVAddr";
             break;
+        case 1:
+            if (ctx->bi) {
+                gen_mfc0_load32(arg, offsetof(CPUMIPSState,
+                                              active_tc.CP0_BadInstr));
+                rn = "BadInstr";
+            } else {
+                gen_mfc0_unimplemented(ctx, arg);
+            }
+            break;
+        case 2:
+            if (ctx->bp) {
+                gen_mfc0_load32(arg, offsetof(CPUMIPSState,
+                                              active_tc.CP0_BadInstrP));
+                rn = "BadInstrP";
+            } else {
+                gen_mfc0_unimplemented(ctx, arg);
+            }
+            break;
         default:
             goto die;
         }
@@ -6683,8 +6735,22 @@ static void gen_dmtc0(DisasContext *ctx, TCGv arg, int reg, int sel)
         }
         break;
     case 8:
-        /* ignored */
-        rn = "BadVAddr";
+        switch (sel) {
+        case 0:
+            /* ignored */
+            rn = "BadVAddr";
+            break;
+        case 1:
+            /* ignored */
+            rn = "BadInstr";
+            break;
+        case 2:
+            /* ignored */
+            rn = "BadInstrP";
+            break;
+        default:
+            goto die;
+        }
         break;
     case 9:
         switch (sel) {
@@ -16940,7 +17006,7 @@ static void decode_opc (CPUMIPSState *env, DisasContext *ctx)
     /* make sure instructions are on a word boundary */
     if (ctx->pc & 0x3) {
         env->CP0_BadVAddr = ctx->pc;
-        generate_exception(ctx, EXCP_AdEL);
+        generate_exception_err(ctx, EXCP_AdEL, EXCP_INST_NOTAVAIL);
         return;
     }
 
@@ -17576,6 +17642,8 @@ gen_intermediate_code_internal(MIPSCPU *cpu, TranslationBlock *tb,
     ctx.kscrexist = (env->CP0_Config4 >> CP0C4_KScrExist) & 0xff;
     ctx.rxi = (env->CP0_Config3 >> CP0C3_RXI) & 1;
     ctx.ie = (env->CP0_Config4 >> CP0C4_IE) & 1;
+    ctx.bi = (env->CP0_Config3 >> CP0C3_BI) & 1;
+    ctx.bp = (env->CP0_Config3 >> CP0C3_BP) & 1;
     /* Restore delay slot state from the tb context.  */
     ctx.hflags = (uint32_t)tb->flags; /* FIXME: maybe use 64 bits here? */
     ctx.ulri = env->CP0_Config3 & (1 << CP0C3_ULRI);
-- 
1.7.5.4