accel/tcg: Introduce cpu_unwind_state_data

Add a way to examine the unwind data without actually
restoring the data back into env.

Reviewed-by: Claudio Fontana <cfontana@suse.de>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

accel/tcg/internal.h

@@ -106,8 +106,8 @@ void tb_reset_jump(TranslationBlock *tb, int n);
 TranslationBlock *tb_link_page(TranslationBlock *tb, tb_page_addr_t phys_pc,
                                tb_page_addr_t phys_page2);
 bool tb_invalidate_phys_page_unwind(tb_page_addr_t addr, uintptr_t pc);
-int cpu_restore_state_from_tb(CPUState *cpu, TranslationBlock *tb,
-                              uintptr_t searched_pc, bool reset_icount);
+void cpu_restore_state_from_tb(CPUState *cpu, TranslationBlock *tb,
+                               uintptr_t host_pc, bool reset_icount);
 
 /* Return the current PC from CPU, which may be cached in TB. */
 static inline target_ulong log_pc(CPUState *cpu, const TranslationBlock *tb)

accel/tcg/translate-all.c

@@ -247,52 +247,66 @@ static int encode_search(TranslationBlock *tb, uint8_t *block)
     return p - block;
 }
 
-/* The cpu state corresponding to 'searched_pc' is restored.
- * When reset_icount is true, current TB will be interrupted and
- * icount should be recalculated.
- */
-int cpu_restore_state_from_tb(CPUState *cpu, TranslationBlock *tb,
-                              uintptr_t searched_pc, bool reset_icount)
+static int cpu_unwind_data_from_tb(TranslationBlock *tb, uintptr_t host_pc,
+                                   uint64_t *data)
 {
-    uint64_t data[TARGET_INSN_START_WORDS];
-    uintptr_t host_pc = (uintptr_t)tb->tc.ptr;
+    uintptr_t iter_pc = (uintptr_t)tb->tc.ptr;
     const uint8_t *p = tb->tc.ptr + tb->tc.size;
     int i, j, num_insns = tb->icount;
-#ifdef CONFIG_PROFILER
-    TCGProfile *prof = &tcg_ctx->prof;
-    int64_t ti = profile_getclock();
-#endif
 
-    searched_pc -= GETPC_ADJ;
+    host_pc -= GETPC_ADJ;
 
-    if (searched_pc < host_pc) {
+    if (host_pc < iter_pc) {
         return -1;
     }
 
-    memset(data, 0, sizeof(data));
+    memset(data, 0, sizeof(uint64_t) * TARGET_INSN_START_WORDS);
     if (!TARGET_TB_PCREL) {
         data[0] = tb_pc(tb);
     }
 
-    /* Reconstruct the stored insn data while looking for the point at
-       which the end of the insn exceeds the searched_pc.  */
+    /*
+     * Reconstruct the stored insn data while looking for the point
+     * at which the end of the insn exceeds host_pc.
+     */
     for (i = 0; i < num_insns; ++i) {
         for (j = 0; j < TARGET_INSN_START_WORDS; ++j) {
             data[j] += decode_sleb128(&p);
         }
-        host_pc += decode_sleb128(&p);
-        if (host_pc > searched_pc) {
-            goto found;
+        iter_pc += decode_sleb128(&p);
+        if (iter_pc > host_pc) {
+            return num_insns - i;
         }
     }
     return -1;
+}
+
+/*
+ * The cpu state corresponding to 'host_pc' is restored.
+ * When reset_icount is true, current TB will be interrupted and
+ * icount should be recalculated.
+ */
+void cpu_restore_state_from_tb(CPUState *cpu, TranslationBlock *tb,
+                               uintptr_t host_pc, bool reset_icount)
+{
+    uint64_t data[TARGET_INSN_START_WORDS];
+#ifdef CONFIG_PROFILER
+    TCGProfile *prof = &tcg_ctx->prof;
+    int64_t ti = profile_getclock();
+#endif
+    int insns_left = cpu_unwind_data_from_tb(tb, host_pc, data);
+
+    if (insns_left < 0) {
+        return;
+    }
 
- found:
     if (reset_icount && (tb_cflags(tb) & CF_USE_ICOUNT)) {
         assert(icount_enabled());
-        /* Reset the cycle counter to the start of the block
-           and shift if to the number of actually executed instructions */
-        cpu_neg(cpu)->icount_decr.u16.low += num_insns - i;
+        /*
+         * Reset the cycle counter to the start of the block and
+         * shift if to the number of actually executed instructions.
+         */
+        cpu_neg(cpu)->icount_decr.u16.low += insns_left;
     }
 
     cpu->cc->tcg_ops->restore_state_to_opc(cpu, tb, data);
@@ -302,7 +316,6 @@ int cpu_restore_state_from_tb(CPUState *cpu, TranslationBlock *tb,
                 prof->restore_time + profile_getclock() - ti);
     qatomic_set(&prof->restore_count, prof->restore_count + 1);
 #endif
-    return 0;
 }
 
 bool cpu_restore_state(CPUState *cpu, uintptr_t host_pc, bool will_exit)
@@ -335,6 +348,17 @@ bool cpu_restore_state(CPUState *cpu, uintptr_t host_pc, bool will_exit)
     return false;
 }
 
+bool cpu_unwind_state_data(CPUState *cpu, uintptr_t host_pc, uint64_t *data)
+{
+    if (in_code_gen_buffer((const void *)(host_pc - tcg_splitwx_diff))) {
+        TranslationBlock *tb = tcg_tb_lookup(host_pc);
+        if (tb) {
+            return cpu_unwind_data_from_tb(tb, host_pc, data) >= 0;
+        }
+    }
+    return false;
+}
+
 void page_init(void)
 {
     page_size_init();

include/exec/exec-all.h

@@ -39,20 +39,33 @@ typedef ram_addr_t tb_page_addr_t;
 #define TB_PAGE_ADDR_FMT RAM_ADDR_FMT
 #endif
 
+/**
+ * cpu_unwind_state_data:
+ * @cpu: the cpu context
+ * @host_pc: the host pc within the translation
+ * @data: output data
+ *
+ * Attempt to load the the unwind state for a host pc occurring in
+ * translated code.  If @host_pc is not in translated code, the
+ * function returns false; otherwise @data is loaded.
+ * This is the same unwind info as given to restore_state_to_opc.
+ */
+bool cpu_unwind_state_data(CPUState *cpu, uintptr_t host_pc, uint64_t *data);
+
 /**
  * cpu_restore_state:
- * @cpu: the vCPU state is to be restore to
- * @searched_pc: the host PC the fault occurred at
+ * @cpu: the cpu context
+ * @host_pc: the host pc within the translation
  * @will_exit: true if the TB executed will be interrupted after some
                cpu adjustments. Required for maintaining the correct
                icount valus
  * @return: true if state was restored, false otherwise
  *
  * Attempt to restore the state for a fault occurring in translated
- * code. If the searched_pc is not in translated code no state is
+ * code. If @host_pc is not in translated code no state is
  * restored and the function returns false.
  */
-bool cpu_restore_state(CPUState *cpu, uintptr_t searched_pc, bool will_exit);
+bool cpu_restore_state(CPUState *cpu, uintptr_t host_pc, bool will_exit);
 
 G_NORETURN void cpu_loop_exit_noexc(CPUState *cpu);
 G_NORETURN void cpu_loop_exit(CPUState *cpu);