target-mips: Correct the writes to Status and Cause registers via gdbstub

Make writes to CP0.Status and CP0.Cause have the same effect as
executing corresponding MTC0 instructions would in Kernel Mode.  Also
ignore writes in the user emulation mode.

Currently for requests from the GDB stub we write all the bits across
both registers, ignoring any read-only locations, and do not synchronise
the environment to evaluate side effects.  We also write these registers
in the user emulation mode even though a real kernel presents them as
read only.

Signed-off-by: Maciej W. Rozycki <macro@codesourcery.com>
Signed-off-by: Leon Alrae <leon.alrae@imgtec.com>

1 files changed, 89 insertions, 0 deletions

diff --git a/target-mips/cpu.h b/target-mips/cpu.h
index a08c2c8467..dd72d1ef50 100644
--- a/target-mips/cpu.h
+++ b/target-mips/cpu.h
@@ -904,4 +904,93 @@ static inline void compute_hflags(CPUMIPSState *env)
     }
 }
 
+#ifndef CONFIG_USER_ONLY
+/* Called for updates to CP0_Status.  */
+static inline void sync_c0_status(CPUMIPSState *env, CPUMIPSState *cpu, int tc)
+{
+    int32_t tcstatus, *tcst;
+    uint32_t v = cpu->CP0_Status;
+    uint32_t cu, mx, asid, ksu;
+    uint32_t mask = ((1 << CP0TCSt_TCU3)
+                       | (1 << CP0TCSt_TCU2)
+                       | (1 << CP0TCSt_TCU1)
+                       | (1 << CP0TCSt_TCU0)
+                       | (1 << CP0TCSt_TMX)
+                       | (3 << CP0TCSt_TKSU)
+                       | (0xff << CP0TCSt_TASID));
+
+    cu = (v >> CP0St_CU0) & 0xf;
+    mx = (v >> CP0St_MX) & 0x1;
+    ksu = (v >> CP0St_KSU) & 0x3;
+    asid = env->CP0_EntryHi & 0xff;
+
+    tcstatus = cu << CP0TCSt_TCU0;
+    tcstatus |= mx << CP0TCSt_TMX;
+    tcstatus |= ksu << CP0TCSt_TKSU;
+    tcstatus |= asid;
+
+    if (tc == cpu->current_tc) {
+        tcst = &cpu->active_tc.CP0_TCStatus;
+    } else {
+        tcst = &cpu->tcs[tc].CP0_TCStatus;
+    }
+
+    *tcst &= ~mask;
+    *tcst |= tcstatus;
+    compute_hflags(cpu);
+}
+
+static inline void cpu_mips_store_status(CPUMIPSState *env, target_ulong val)
+{
+    uint32_t mask = env->CP0_Status_rw_bitmask;
+
+    if (env->insn_flags & ISA_MIPS32R6) {
+        bool has_supervisor = extract32(mask, CP0St_KSU, 2) == 0x3;
+
+        if (has_supervisor && extract32(val, CP0St_KSU, 2) == 0x3) {
+            mask &= ~(3 << CP0St_KSU);
+        }
+        mask &= ~(((1 << CP0St_SR) | (1 << CP0St_NMI)) & val);
+    }
+
+    env->CP0_Status = (env->CP0_Status & ~mask) | (val & mask);
+    if (env->CP0_Config3 & (1 << CP0C3_MT)) {
+        sync_c0_status(env, env, env->current_tc);
+    } else {
+        compute_hflags(env);
+    }
+}
+
+static inline void cpu_mips_store_cause(CPUMIPSState *env, target_ulong val)
+{
+    uint32_t mask = 0x00C00300;
+    uint32_t old = env->CP0_Cause;
+    int i;
+
+    if (env->insn_flags & ISA_MIPS32R2) {
+        mask |= 1 << CP0Ca_DC;
+    }
+    if (env->insn_flags & ISA_MIPS32R6) {
+        mask &= ~((1 << CP0Ca_WP) & val);
+    }
+
+    env->CP0_Cause = (env->CP0_Cause & ~mask) | (val & mask);
+
+    if ((old ^ env->CP0_Cause) & (1 << CP0Ca_DC)) {
+        if (env->CP0_Cause & (1 << CP0Ca_DC)) {
+            cpu_mips_stop_count(env);
+        } else {
+            cpu_mips_start_count(env);
+        }
+    }
+
+    /* Set/reset software interrupts */
+    for (i = 0 ; i < 2 ; i++) {
+        if ((old ^ env->CP0_Cause) & (1 << (CP0Ca_IP + i))) {
+            cpu_mips_soft_irq(env, i, env->CP0_Cause & (1 << (CP0Ca_IP + i)));
+        }
+    }
+}
+#endif
+
 #endif /* !defined (__MIPS_CPU_H__) */