Merge remote-tracking branch 'remotes/vivier/tags/m68k-for-6.1-pull-request' into staging

m68k pull request 20210526

implement m68k "any instruction" trace mode

# gpg: Signature made Wed 26 May 2021 20:56:58 BST
# gpg:                using RSA key CD2F75DDC8E3A4DC2E4F5173F30C38BD3F2FBE3C
# gpg:                issuer "laurent@vivier.eu"
# gpg: Good signature from "Laurent Vivier <lvivier@redhat.com>" [full]
# gpg:                 aka "Laurent Vivier <laurent@vivier.eu>" [full]
# gpg:                 aka "Laurent Vivier (Red Hat) <lvivier@redhat.com>" [full]
# Primary key fingerprint: CD2F 75DD C8E3 A4DC 2E4F  5173 F30C 38BD 3F2F BE3C

* remotes/vivier/tags/m68k-for-6.1-pull-request:
  target/m68k: implement m68k "any instruction" trace mode
  target/m68k: introduce gen_singlestep_exception() function
  target/m68k: call gen_raise_exception() directly if single-stepping in gen_jmp_tb()
  target/m68k: introduce is_singlestepping() function

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

2 files changed, 51 insertions, 8 deletions

diff --git a/target/m68k/cpu.h b/target/m68k/cpu.h
index 402c86c876..997d588911 100644
--- a/target/m68k/cpu.h
+++ b/target/m68k/cpu.h
@@ -230,6 +230,9 @@ typedef enum {
 #define SR_T_SHIFT 14
 #define SR_T  0xc000
 
+#define M68K_SR_TRACE(sr) ((sr & SR_T) >> SR_T_SHIFT)
+#define M68K_SR_TRACE_ANY_INS 0x2
+
 #define M68K_SSP    0
 #define M68K_USP    1
 #define M68K_ISP    2
@@ -590,6 +593,8 @@ typedef M68kCPU ArchCPU;
 #define TB_FLAGS_SFC_S          (1 << TB_FLAGS_SFC_S_BIT)
 #define TB_FLAGS_DFC_S_BIT      15
 #define TB_FLAGS_DFC_S          (1 << TB_FLAGS_DFC_S_BIT)
+#define TB_FLAGS_TRACE          16
+#define TB_FLAGS_TRACE_BIT      (1 << TB_FLAGS_TRACE)
 
 static inline void cpu_get_tb_cpu_state(CPUM68KState *env, target_ulong *pc,
                                         target_ulong *cs_base, uint32_t *flags)
@@ -602,6 +607,9 @@ static inline void cpu_get_tb_cpu_state(CPUM68KState *env, target_ulong *pc,
         *flags |= (env->sfc << (TB_FLAGS_SFC_S_BIT - 2)) & TB_FLAGS_SFC_S;
         *flags |= (env->dfc << (TB_FLAGS_DFC_S_BIT - 2)) & TB_FLAGS_DFC_S;
     }
+    if (M68K_SR_TRACE(env->sr) == M68K_SR_TRACE_ANY_INS) {
+        *flags |= TB_FLAGS_TRACE;
+    }
 }
 
 void dump_mmu(CPUM68KState *env);
diff --git a/target/m68k/translate.c b/target/m68k/translate.c
index 200018ae6a..f0c5bf9154 100644
--- a/target/m68k/translate.c
+++ b/target/m68k/translate.c
@@ -124,6 +124,7 @@ typedef struct DisasContext {
 #define MAX_TO_RELEASE 8
     int release_count;
     TCGv release[MAX_TO_RELEASE];
+    bool ss_active;
 } DisasContext;
 
 static void init_release_array(DisasContext *s)
@@ -194,6 +195,18 @@ static void do_writebacks(DisasContext *s)
     }
 }
 
+static bool is_singlestepping(DisasContext *s)
+{
+    /*
+     * Return true if we are singlestepping either because of
+     * architectural singlestep or QEMU gdbstub singlestep. This does
+     * not include the command line '-singlestep' mode which is rather
+     * misnamed as it only means "one instruction per TB" and doesn't
+     * affect the code we generate.
+     */
+    return s->base.singlestep_enabled || s->ss_active;
+}
+
 /* is_jmp field values */
 #define DISAS_JUMP      DISAS_TARGET_0 /* only pc was modified dynamically */
 #define DISAS_EXIT      DISAS_TARGET_1 /* cpu state was modified dynamically */
@@ -308,6 +321,20 @@ static void gen_exception(DisasContext *s, uint32_t dest, int nr)
     s->base.is_jmp = DISAS_NORETURN;
 }
 
+static void gen_singlestep_exception(DisasContext *s)
+{
+    /*
+     * Generate the right kind of exception for singlestep, which is
+     * either the architectural singlestep or EXCP_DEBUG for QEMU's
+     * gdb singlestepping.
+     */
+    if (s->ss_active) {
+        gen_raise_exception(EXCP_TRACE);
+    } else {
+        gen_raise_exception(EXCP_DEBUG);
+    }
+}
+
 static inline void gen_addr_fault(DisasContext *s)
 {
     gen_exception(s, s->base.pc_next, EXCP_ADDRESS);
@@ -1506,8 +1533,10 @@ static inline bool use_goto_tb(DisasContext *s, uint32_t dest)
 /* Generate a jump to an immediate address.  */
 static void gen_jmp_tb(DisasContext *s, int n, uint32_t dest)
 {
-    if (unlikely(s->base.singlestep_enabled)) {
-        gen_exception(s, dest, EXCP_DEBUG);
+    if (unlikely(is_singlestepping(s))) {
+        update_cc_op(s);
+        tcg_gen_movi_i32(QREG_PC, dest);
+        gen_singlestep_exception(s);
     } else if (use_goto_tb(s, dest)) {
         tcg_gen_goto_tb(n);
         tcg_gen_movi_i32(QREG_PC, dest);
@@ -6172,6 +6201,12 @@ static void m68k_tr_init_disas_context(DisasContextBase *dcbase, CPUState *cpu)
     dc->done_mac = 0;
     dc->writeback_mask = 0;
     init_release_array(dc);
+
+    dc->ss_active = (M68K_SR_TRACE(env->sr) == M68K_SR_TRACE_ANY_INS);
+    /* If architectural single step active, limit to 1 */
+    if (is_singlestepping(dc)) {
+        dc->base.max_insns = 1;
+    }
 }
 
 static void m68k_tr_tb_start(DisasContextBase *dcbase, CPUState *cpu)
@@ -6245,17 +6280,17 @@ static void m68k_tr_tb_stop(DisasContextBase *dcbase, CPUState *cpu)
         break;
     case DISAS_TOO_MANY:
         update_cc_op(dc);
-        if (dc->base.singlestep_enabled) {
+        if (is_singlestepping(dc)) {
             tcg_gen_movi_i32(QREG_PC, dc->pc);
-            gen_raise_exception(EXCP_DEBUG);
+            gen_singlestep_exception(dc);
         } else {
             gen_jmp_tb(dc, 0, dc->pc);
         }
         break;
     case DISAS_JUMP:
         /* We updated CC_OP and PC in gen_jmp/gen_jmp_im.  */
-        if (dc->base.singlestep_enabled) {
-            gen_raise_exception(EXCP_DEBUG);
+        if (is_singlestepping(dc)) {
+            gen_singlestep_exception(dc);
         } else {
             tcg_gen_lookup_and_goto_ptr();
         }
@@ -6265,8 +6300,8 @@ static void m68k_tr_tb_stop(DisasContextBase *dcbase, CPUState *cpu)
          * We updated CC_OP and PC in gen_exit_tb, but also modified
          * other state that may require returning to the main loop.
          */
-        if (dc->base.singlestep_enabled) {
-            gen_raise_exception(EXCP_DEBUG);
+        if (is_singlestepping(dc)) {
+            gen_singlestep_exception(dc);
         } else {
             tcg_gen_exit_tb(NULL, 0);
         }