[PATCH 24/29] accel/tcg: Introduce cpu_unwind_state_data

[Richard Henderson <richard.henderson@linaro.org>]

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

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 include/exec/exec-all.h   | 13 ++++++++
 accel/tcg/translate-all.c | 68 ++++++++++++++++++++++++++-------------
 2 files changed, 58 insertions(+), 23 deletions(-)

diff --git a/include/exec/exec-all.h b/include/exec/exec-all.h
index 300832bd0b..d49cf113dd 100644
--- a/include/exec/exec-all.h
+++ b/include/exec/exec-all.h
@@ -39,6 +39,19 @@ typedef ram_addr_t tb_page_addr_t;
 #define TB_PAGE_ADDR_FMT RAM_ADDR_FMT
 #endif
 
+/**
+ * cpu_unwind_state_data:
+ * @cpu: the vCPU state is to be restore to
+ * @host_pc: the host PC the fault occurred at
+ * @data: output data
+ *
+ * Attempt to load the the unwind state for a host pc occurring in
+ * translated code.  If the searched_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
diff --git a/accel/tcg/translate-all.c b/accel/tcg/translate-all.c
index e4386b3198..c772e3769c 100644
--- a/accel/tcg/translate-all.c
+++ b/accel/tcg/translate-all.c
@@ -320,29 +320,20 @@ 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.
- */
-static 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);
     }
@@ -353,19 +344,40 @@ static int cpu_restore_state_from_tb(CPUState *cpu, TranslationBlock *tb,
         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.
+ */
+static 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);
@@ -375,7 +387,6 @@ static 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)
@@ -408,6 +419,17 @@ 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();
-- 
2.34.1