From f80aa59454bd85c3aca1809b1ab3cb481c533a7a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= <bjorn@erlang.org>
Date: Wed, 4 Sep 2024 13:48:28 +0200
Subject: [PATCH] Add code:get_debug_info/1

---
 erts/emulator/beam/atom.names      |  8 ++-
 erts/emulator/beam/beam_bif_load.c | 93 ++++++++++++++++++++++++++++++
 erts/emulator/beam/bif.tab         |  5 ++
 lib/kernel/src/code.erl            | 10 +++-
 4 files changed, 112 insertions(+), 4 deletions(-)

diff --git a/erts/emulator/beam/atom.names b/erts/emulator/beam/atom.names
index 758c84d1c1d7..5c5f9175a4e0 100644
--- a/erts/emulator/beam/atom.names
+++ b/erts/emulator/beam/atom.names
@@ -111,6 +111,7 @@ atom asynchronous
 atom atom
 atom atom_used
 atom attributes
+atom auto
 atom auto_connect
 atom await_exit
 atom await_microstate_accounting_modifications
@@ -217,6 +218,7 @@ atom debug_flags
 atom decentralized_counters
 atom decimals
 atom default
+atom debug_hash_fixed_number_of_locks
 atom delay_trap
 atom demonitor
 atom deterministic
@@ -486,6 +488,7 @@ atom new_processes
 atom new_ports
 atom new_uniq
 atom newline
+atom nifs
 atom no
 atom nomatch
 atom none
@@ -763,10 +766,9 @@ atom warning
 atom warning_msg
 atom wordsize
 atom write_concurrency
+atom x
 atom xor
 atom x86
+atom y
 atom yes
 atom yield
-atom nifs
-atom auto
-atom debug_hash_fixed_number_of_locks
diff --git a/erts/emulator/beam/beam_bif_load.c b/erts/emulator/beam/beam_bif_load.c
index 59bb67ebc6a4..b23fc94aeb85 100644
--- a/erts/emulator/beam/beam_bif_load.c
+++ b/erts/emulator/beam/beam_bif_load.c
@@ -1251,6 +1251,99 @@ any_heap_refs(Eterm* start, Eterm* end, char* mod_start, Uint mod_size)
     return 0;
 }
 
+BIF_RETTYPE code_get_debug_info_1(BIF_ALIST_1)
+{
+#ifdef BEAMASM
+    ErtsCodeIndex code_ix;
+    Module* modp;
+    const BeamCodeHeader* hdr;
+    const BeamDebugTab* debug;
+    Uint i;
+    Uint alloc_size;
+    Eterm result = NIL;
+    Eterm* hp;
+    Eterm* hend;
+
+    if (is_not_atom(BIF_ARG_1)) {
+        BIF_ERROR(BIF_P, BADARG);
+    }
+    code_ix = erts_active_code_ix();
+    modp = erts_get_module(BIF_ARG_1, code_ix);
+    if (modp == NULL) {
+        BIF_ERROR(BIF_P, BADARG);
+    }
+    hdr = modp->curr.code_hdr;
+    if (hdr == NULL) {
+        BIF_ERROR(BIF_P, BADARG);
+    }
+
+    debug = hdr->debug;
+    alloc_size = 0;
+
+    for (i = 0; i < debug->item_count; i++) {
+        /* [ {Index, {FrameSize,[{Name,Value}]} ] */
+        alloc_size += 2 + 3 + 3 + debug->items[i].num_vars * (2 + 3 + 3);
+    }
+
+    hp = HAlloc(BIF_P, alloc_size);
+    hend = hp + alloc_size;
+
+    for (i = debug->item_count-1; i > 0; i--) {
+        BeamDebugItem* items = &debug->items[i];
+        Sint32 frame_size = items->frame_size;
+        Uint num_vars = items->num_vars;
+        Eterm *tp = items->first + 2 * num_vars - 2;
+        Eterm frame_size_term;
+        Eterm var_list = NIL;
+        Eterm tmp;
+
+        if (frame_size < 0) {
+            frame_size_term = am_none;
+        } else {
+            frame_size_term = make_small(frame_size);
+        }
+
+        while (num_vars-- != 0) {
+            Eterm val;
+
+            if (_is_loader_x_reg(tp[1])) {
+                Uint xreg = loader_x_reg_index(tp[1]);
+                val = TUPLE2(hp, am_x, make_small(xreg));
+                hp += 3;
+            } else if (_is_loader_y_reg(tp[1])) {
+                Uint yreg = loader_y_reg_index(tp[1]);
+                val = TUPLE2(hp, am_y, make_small(yreg));
+                hp += 3;
+            } else {
+                val = tp[1];
+            }
+            tmp = TUPLE2(hp, tp[0], val);
+            hp += 3;
+
+            tp -= 2;
+
+            var_list = CONS(hp, tmp, var_list);
+            hp += 2;
+        }
+
+        tmp = TUPLE2(hp, frame_size_term, var_list);
+        hp += 3;
+
+        tmp = TUPLE2(hp, make_small(i), tmp);
+        hp += 3;
+
+        result = CONS(hp, tmp, result);
+        hp += 2;
+    }
+
+    ASSERT(hp <= hend);
+    HRelease(BIF_P, hend, hp);
+    return result;
+#endif
+
+    BIF_ERROR(BIF_P, BADARG);
+}
+
 /*
  * Release of literal areas...
  *
diff --git a/erts/emulator/beam/bif.tab b/erts/emulator/beam/bif.tab
index 798a7418d749..2299abfc37ae 100644
--- a/erts/emulator/beam/bif.tab
+++ b/erts/emulator/beam/bif.tab
@@ -805,3 +805,8 @@ bif erts_internal:trace_pattern/4
 bif erts_internal:trace_info/3
 bif erts_trace_cleaner:check/0
 bif erts_trace_cleaner:send_trace_clean_signal/1
+
+#
+# New in 28.
+#
+bif code:get_debug_info/1
diff --git a/lib/kernel/src/code.erl b/lib/kernel/src/code.erl
index dc8fc44a6a36..7bfa00becc35 100644
--- a/lib/kernel/src/code.erl
+++ b/lib/kernel/src/code.erl
@@ -401,7 +401,8 @@ common reasons.
          module_status/0,
          module_status/1,
          modified_modules/0,
-         get_mode/0]).
+         get_mode/0,
+         get_debug_info/1]).
 
 -removed({rehash,0,"the code path cache feature has been removed"}).
 -removed({is_module_native,1,"HiPE has been removed"}).
@@ -2321,3 +2322,10 @@ _See also:_ [Native Coverage Support](#module-native-coverage-support)
       Supported :: boolean().
 coverage_support() ->
     erlang:nif_error(undefined).
+
+-doc(#{since => <<"OTP 28.0">>}).
+-spec get_debug_info(Module) -> Mode when
+      Module :: module(),
+      Mode :: coverage_mode().
+get_debug_info(_Module) ->
+    erlang:nif_error(undefined).